Cisco Video and TelePresence Architecture Design Guide

Cisco Video and TelePresence Architecture Design Guide
Cisco Video and TelePresence
Architecture Design Guide
March 30, 2012
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Text Part Number: OL-27011-01
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Cisco Video and TelePresence Architecture Design Guide
© 2012 Cisco Systems, Inc. All rights reserved.
CONTENTS
Preface
vii
Revision History
vii
Obtaining Documentation and Submitting a Service Request
Conventions
vii
viii
CHAPTER
1
Introduction
CHAPTER
2
Video Infrastructure Components
1-1
2-1
Cisco TelePresence and Unified Communications
2-1
Video Architecture 2-2
Endpoints 2-3
Video Services 2-4
Conferencing 2-4
Streaming and Recording 2-5
Video Network Services 2-6
Call Control 2-6
Gateways 2-7
Management 2-8
Cisco TelePresence Management Suite 2-8
Cisco TelePresence Manager 2-8
Cisco Prime Collaboration Manager 2-8
Network
CHAPTER
3
2-9
Basic Video Concepts
3-1
Common Terminology in IP Video Solutions 3-1
Video Frame 3-1
Compression in IP Video Solutions 3-1
Lossless 3-2
Lossy 3-2
Intra-Frame 3-2
Inter-Frame 3-2
Codecs in IP Video Solutions 3-3
Video Compression Formats 3-3
Compressed Video Frames 3-4
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Contents
I-Frame 3-5
P-Frame 3-6
B-Frame 3-6
Resolution Format in IP Video Solutions
3-7
Evolution of Cisco IP Video Solutions 3-8
Video over ISDN 3-8
IP Video Telephony 3-9
Desktop Video Conferencing 3-10
Immersive Video Conferencing 3-11
Cloud-Hosted Video Solutions 3-12
Interoperability 3-12
Legacy Multipoint Control Units 3-13
Common Technologies Used in Cisco IP Video Solutions 3-14
Telepresence Interoperability Protocol (TIP) 3-14
ClearPath 3-15
Dynamic Bit Rate Adjustment 3-15
Long-Term Reference Picture 3-15
Video-Aware Forward Error Correction (FEC) 3-15
CHAPTER
4
Call Control Protocols and IPv6 in IP Video Solutions
Call Control Protocols in IP Video Solutions
SCCP 4-1
H.323 4-3
SIP 4-5
4-1
Call Control Protocol Selection in IP Video Solutions
IPv6 in IP Video Solutions
CHAPTER
5
4-1
4-6
4-7
Quality of Service and Call Admission Control
5-1
Quality of Service (QoS) 5-1
Trust Boundary 5-2
Packet Queuing 5-2
Call Admission Control
CHAPTER
6
Dial Plan
5-3
6-1
Dial Plan Dependencies
6-2
Number-Based Dial Plan Networks
URI-Based Dial Plan Networks
6-3
Call Resolution with Dial Plans
6-3
6-2
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Contents
PSTN Access
Transformations
CHAPTER
7
6-3
6-4
Dial Plan Manipulation
6-4
Classes of Restrictions
6-4
Deployment Guidelines for Video Networks
7-1
Planning a Deployment Topology for Video 7-1
Intra-Campus 7-2
Intra-Enterprise 7-3
Inter-Enterprise (Business-to-Business) 7-4
Single-Site Call Processing 7-5
Multi-Site Call Processing 7-5
Hosted Call Processing (Video as a Service) 7-7
Guidelines for Choose a Call Processing Topology and Video Endpoints 7-8
Call Processing Model and Call Processing Agent Selection Guidelines 7-8
Endpoint Selection Guidelines 7-9
Design Considerations for Video Networks 7-9
Allocation of Video Resources 7-10
Centralized Video Resource Allocation
Distributed Video Resource Allocation
7-10
7-13
Creating a Video-Ready Network 7-14
Optimized Video Delivery 7-14
Quality of Service (QoS) 7-14
Content Sharing Technologies 7-15
Reliability 7-16
Security of Video Applications 7-16
Scalability and Performance 7-16
Integration with Standalone Video Networks 7-19
Integration with Standalone H.323 Video Networks 7-19
Integration with Standalone SIP Video Networks 7-20
CHAPTER
8
Collaborative Conferencing
8-1
Conference Type 8-2
Ad-hoc Conference 8-2
Scheduled Conference 8-2
Conferencing Infrastructure 8-2
Conference Multipoint Device 8-3
Transcoding and Switching 8-4
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Contents
Multipoint Deployment Guidelines
Centralized Deployment 8-5
Distributed Deployment 8-6
8-5
Multipoint Solution Selection 8-8
Multipoint Selection Based on Endpoints 8-8
Multipoint Selection Based on Features 8-9
Conference Resource Capacity Planning
CHAPTER
9
Security for Video Communications
8-9
9-1
Network Infrastructure Security 9-2
Separate Auxiliary VLAN 9-3
Device Security 9-3
Secure Management over HTTPS and SSH 9-3
Administrative Passwords 9-4
Device Access 9-4
Signaling and Media Encryption 9-4
Transport Layer Security (TLS) 9-4
Secure Real-Time Transport Protocol (SRTP) and Secure Real-Time Transport Control Protocol
(SRTCP) 9-5
Datagram Transport Layer Security (DTLS) Secure Real-Time Transport Protocol (SRTP) 9-5
Digital Certificates 9-5
Certificate Authority Proxy Function (CAPF) 9-6
The Certificate Trust List (CTL) 9-6
Configuration File Integrity and Encryption 9-7
Media Encryption Details
9-7
Integration with Firewalls and Access Control List Considerations
Firewall Traversal in the DMZ 9-10
9-8
INDEX
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Preface
Revised: March 30, 2012, OL-27011-01
This document describes some of the concepts related to video communications, and it presents
considerations and guidelines for designing a video-enabled network.
This document should be used in conjunction with other documentation available at the following
locations:
•
For Cisco Collaboration and Unified Communications System design documents:
http://www.cisco.com/go/ucsrnd
•
For other Cisco design guides:
http://www.cisco.com/go/designzone
•
For Cisco TelePresence and Video product documentation:
http://www.cisco.com
Revision History
This document may be updated at any time without notice. You can obtain the latest version of this
document online at:
http://www.cisco.com/go/ucsrnd
Visit this Cisco.com website periodically and check for documentation updates by comparing the
revision date of your copy with the revision date of the online document.
The following table lists the revision history for this document.
Revision Date
Document Part Number
Comments
March 30, 2012
OL-27011-01
Initial version of this document.
Obtaining Documentation and Submitting a Service Request
For information on obtaining documentation, submitting a service request, and gathering additional
information, see the monthly What’s New in Cisco Product Documentation, which also lists all new and
revised Cisco technical documentation, at:
http://www.cisco.com/en/US/docs/general/whatsnew/whatsnew.html
Cisco Video and TelePresence Architecture Design Guide
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Preface
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Conventions
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CH A P T E R
1
Introduction
Revised: March 30, 2012, OL-27011-01
This document focuses on the two-way interactive video solutions available from Cisco, including Cisco
TelePresence and Cisco Unified Communications, and it provides an explanation of the overall solution,
technology components, and deployment considerations. With the TelePresence and Unified
Communications product families, Cisco offers a wide range of video solutions from interactive video
applications for large boardrooms down to mobile users. Cisco also offers a comprehensive set of
one-way video applications such as streaming video, digital signage, video surveillance, and even media
transformation, which are not covered in this document.
Each solution, Cisco TelePresence or Cisco Unified Communications, can be deployed as a standalone
solution or together as an integrated solution. Figure 1-1 illustrates an example of a video architecture
that supports both TelePresence and Unified Communications video endpoints. This specific example
also shows access to the PSTN for voice calls, ISDN for legacy video, and the Internet-based video
device.
Cisco Video and TelePresence Architecture Design Guide
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1-1
Chapter 1
Cisco TelePresence and Unified Communications Video Architecture
Legacy H.320
video
EX 90
Jabber
ISDN
PSTN
Internet
H.320
Gateway
Voice
Gateway
VCS
Expressway
Unified CM
Cluster
VCS Control
Cluster
Telepresence
Server
9971
Telepresence
Management
Suite
CTS-1100
CTS-3010
EX 90
Profile
Corporate IP
Network Infrastructure
284652
Figure 1-1
Introduction
This architecture incorporates the endpoints and infrastructure components listed in Table 1-1 and
Table 1-2, respectively.
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Chapter 1
Introduction
Table 1-1
Current Cisco TelePresence and Unified Communications Video Endpoints
Category
Endpoint
TelePresence – Immersive
TX9000 Series
CTS 3000 Series
CTS T Series
TX1300 Series
TelePresence – Multipurpose
CTS MX Series
CTS Profile MXP Series
CTS Profile Series
TelePresence – Desktop
CTS EX Series
CTS MXP Series
TelePresence –Office
CTS 1100
CTS 500
TelePresence – Personal
Cisco Jabber Video for TelePresence (Movi)
TelePresence – Video phone
CTS E20
Unified Communications – Video phone
Cisco Unified IP Phones 9900 Series
Unified Communications – Desktop
Cisco Unified Personal Communicator
Cisco Jabber
Unified Communications – Tablet
Cius
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Chapter 1
Introduction
Table 1-2
Cisco Video Infrastructure Products
Purpose
Product Name
Product Category
Description
Call Control
Cisco Unified Communications
Manager
Unified Communications
and TelePresence
Call control for Unified Communications
and TelePresence devices
Cisco TelePresence Video
Communications Server
Control
Call control for TelePresence and
videoconferencing devices
Conferencing
Gateways
Recording and
Streaming
Management
Cisco Integrated Services Router Unified Communications
G2 Conferencing Services
Multipoint conferencing for all video
endpoints except three-screen immersive
Cisco TelePresence Server
TelePresence
Multipoint Control Unit for all video
endpoints, including three-screen
immersive
Cisco TelePresence Conductor
TelePresence
Policy server for multipoint device
management
Cisco TelePresence Multipoint
Control Unit
TelePresence
Multipoint Control Unit for all video
endpoints except three-screen immersive
Cisco TelePresence Multipoint
Switch
TelePresence
Multipoint switch for CTS, EX, and Profile
series video endpoints
ISDN Gateway
TelePresence
Video gateway allowing connectivity from
H.323 and SIP video endpoints to ISDN
H.320 endpoints
Advanced Media Gateway
TelePresence
Gateway allowing connectivity from
standard H.323 and SIP video endpoints to
Microsoft Lync and Office Communicator
devices
Cisco Telepresence Video
Communications Server
Expressway
TelePresence
Gateway that provides secure
communications between SIP and H.323
video endpoints across the internet
Cisco Unified Border Element
TelePresence
Gateway that provides a secure
demarcation between IP networks
Cisco Intercompany Media
Engine
Unified Communications
Gateway that provides intercompany
connectivity when used with Unified CM
and ASA firewalls
Cisco TelePresence Content
Server
TelePresence
Recording and streaming for all video
endpoints
Cisco TelePresence Recording
Server
TelePresence
Recording server for CTS series video
endpoints
Cisco TelePresence Manager
TelePresence
Scheduling and management platform for
Cisco and third-party video endpoints
Cisco TelePresence
Management Suite
TelePresence
Scheduling and management platform for
Cisco and third-party video endpoints
Cisco Prime Collaboration
Manager
TelePresence
Network and endpoint management for
media flows
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Chapter 1
Introduction
Addressing complex customer requirements is possible due in part to the large number of Cisco
TelePresence and Unified Communications video endpoints and infrastructure components. However, a
large number of options can make choosing the right solution difficult.
As you will see throughout this document, Cisco TelePresence and Cisco Unified Communications
endpoints and infrastructure components share the same protocols, audio and video codecs, and similar
deployment considerations. This document explores deeper into the following areas related to Cisco
TelePresence and Cisco Unified Communications:
•
Video components
Video components consist of devices such as video endpoints, call control, conferencing, gateways,
and management platforms.
•
Basic concepts and terminology of video solutions
TelePresence and video in general introduce a lot of new terminology and concepts that are not
found in other technologies. In just the past few years many new products and features have been
introduced with the advancement of video endpoints, conferencing devices, and error concealment.
•
Call control protocols
Call control protocols handle the setup and processing of media flows across the network. A number
of video call control protocols are used for transporting interactive video over various network
media.
•
Quality of Service (QoS) and call admission control
Interactive video is very sensitive to delay, loss, and jitter. Allowing admission to the network only
when bandwidth is available and guaranteeing media flows that meet Service Level Agreements
(SLAs) are key factors to any successful video deployment.
•
Dial plan
Dial plans provide call routing between video devices and devices external to an enterprise, such as
video intercompany calls over the Internet and the PSTN, as well as PSTN audio-only calls. Dial
plans might need special attention, depending on the method used to address endpoints or to support
advanced feature sets.
•
Deployment scenarios
There are a number of deployment scenarios available for interactive video deployments.
Deployment scenarios are based on a number of factors such as the number and type of endpoints,
and they focus on all aspects of call control, video services, and network design.
•
Business-to-business (B2B)
Business-to-business video communications is becoming more important as video continues to be
deployed and used by more companies. There are a number of ways to allow business-to-business
video communications, depending on the call control platforms and endpoints used in an enterprise.
•
Conferencing
Conferencing allows more than two devices to communicate in a single meeting. There are a number
of options for initiating a conference and a number of different platforms available for conferencing
video endpoints.
•
Security
Security for video calls is a must for many enterprises, especially those using video for
business-to-business communications. There are a number of methods available for encrypting
signaling traffic and media, and a number of factors that must be considered when deploying secured
video communications.
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Chapter 1
Introduction
In addition to this document, a number of design and deployment guides have been written to help users
choose the correct architecture. These guides not only help with video architecture, but in many cases
they also outline the network requirements to ensure proper handling of video calls across the network.
The following design and deployment guides cover the deployment of both Cisco TelePresence and
Cisco Unified Communications video:
•
Cisco Unified Communications System SRND
http://www.cisco.com/go/ucsrnd
•
Cisco TelePresence Network Systems Design Guide
http://www.cisco.com/en/US/solutions/ns340/ns414/ns742/ns819/landing_vid_tPresence.html
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CH A P T E R
2
Video Infrastructure Components
Revised: March 30, 2012, OL-27011-01
Video deployments continue to expand as enterprises focus on decreasing travel, increasing
productivity, and expanding video in Unified Communications platforms. As the Unified
Communications and TelePresence markets continue to grow and mature, the line between the two
markets continues to blur. Both TelePresence and Unified Communications video devices employ many
of the same protocols and codecs, providing full integration and the ability to utilize infrastructure
devices from both solutions.
Both Cisco TelePresence and Cisco Unified Communications solutions have expanded dramatically
with internal development and strategic acquisitions by Cisco.
Cisco TelePresence and Unified Communications
Cisco initially entered the two-way interactive video space in late 1999 through an OEM relationship
with Radvision. The Radvision relationship brought to market a number of Cisco-labeled
videoconferencing infrastructure products, including the Cisco IPVC Multipoint Control Units (MCUs)
and IPVC Gateways. A few years later Cisco added video support to its voice call control agent, Cisco
Unified Communications Manager (Unified CM), and Cisco also added a number of video telephony
products that expanded its video offering to PC-based soft clients and videophones.
In late 2006 Cisco introduced Cisco TelePresence, which added a complete portfolio of high definition
(HD) conferencing products, including endpoints, a multipoint switch, TelePresence management, and
a recording server. Cisco TelePresence took off and rejuvenated the videoconferencing market, making
HD the norm.
With the acquisition of WebEx in 2007, Cisco added more Unified Communications products to its
portfolio, including a new video soft client. Finally, in 2009 Cisco acquired Tandberg. At the time of the
acquisition Tandberg was the number-one videoconferencing vendor in the market, with the most
comprehensive product line in the industry. Combining Cisco TelePresence with the Tandberg portfolio
instantly gave Cisco the best-of-breed TelePresence products from the desktop to the boardroom.
Figure 2-1 illustrates the progression of interactive video within Cisco’s product portfolio.
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Video Infrastructure Components
Video Architecture
Figure 2-1
Progression of Cisco Two-Way Interactive Video Products
Tandberg
WebEx
TelePresence
Video Telephony
1999
2003
2006
2007
2009
284676
IPVC
Video Architecture
All interactive video architectures consist of five categories, as shown in Figure 2-2:
•
Endpoints, page 2-3
•
Video Services, page 2-4
•
Video Network Services, page 2-6
•
Management, page 2-8
•
Network, page 2-9
Each category contains devices that provide a specific function for the video deployment, but devices
from all categories are not required or present in all video deployments.
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Video Infrastructure Components
Video Architecture
Figure 2-2
Video Architecture
Management
Endpoints
Immersive
Multi-purpose
Personal
Video Services
Conferencing
Recording and streaming
Call control
Gateways
Video Network
Infrastructure
Video and
network
Router
Switch
284677
Network
Firewall
Endpoints
An endpoint consists of a screen, microphone, speakers, and one or more video and audio processing
devices called codecs. These components are usually combined into a single unit that can range from a
phone with a screen (at the basic end), to a large TV-like device, to an immersive multi-screen system
with integrated tables and seating. Cisco provides a large number of video endpoints ranging from
video-enabled tablets to multi-screen immersive endpoints.
Different types of video endpoints provide different user experiences and in many cases different feature
sets. Each video endpoint supports multiple resolutions, but not all video endpoints support the same set
of resolutions. For example, a multi-screen immersive endpoint might support high definition
resolutions up to 1080p at 30 frames per second (fps) while a video-enabled tablet might support high
definition resolutions up to only 720p at 30 fps. All video endpoints have a core set of features that
usually consist of the ability to send and receive live audio and video, and send and receive shared
content. Depending on the endpoint type, advanced features such as integrated conferencing or the
ability to support additional video and audio sources may be available.
It is important to remember that higher resolutions consumes more network bandwidth. In most
deployments, customers choose to limit the higher resolutions based on the endpoint type or user type.
Video deployments always start with the type of video endpoints being deployed and the resolutions
being supported. It is not uncommon to see customers create multiple classes of video that directly
correlate with the supported resolution or user type. Classes are often based on a minimum level of
service provided to each endpoint type or user type, and the classes may contain different maximum
resolutions for the same type of endpoint depending on the user. Figure 2-3 shows an example of
possible video classes deployed in an enterprise.
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Video Infrastructure Components
Video Architecture
Figure 2-3
Example of Possible Video Classes
Gold
Silver
Immersive
Endpoints 1080p
Personal
Endpoints 720p
Multi-purpose
Endpoints 720p
Executive
Tablets 720p
Soft Clients
448p
Video Phones
VGA
Tablets w360p
284678
Executive Personal
Endpoints 720p
Bronze
Video Services
Video services consist of two subcategories:
•
Conferencing, page 2-4
•
Streaming and Recording, page 2-5
Video services are not required but are an important part of any video deployment. Almost all video
deployments use one or more of these services.
Conferencing
Conferencing devices allow three or more video devices to participate in a meeting at the same time.
Some conferencing devices can also provide management of conferencing resources, thus allowing
conferencing ports to be used more efficiently. Cisco provides conferencing devices that support
switching and transcoding.
Switching forwards incoming audio and video without manipulating the video media itself. Switching
platforms essentially switch video from one endpoint to another and require all video endpoints in a
meeting to send and receive the same resolution. Switching devices offer a cost-effective and scalable
solution for video deployments supporting video endpoints with the same resolution sets and not
requiring advanced video features such as continuous or active presence.
Transcoding is the encoding and decoding of video media streams between endpoints. Transcoding
devices offer support for video endpoints participating in the same meeting with different resolutions,
continuous or active presence, and other advanced conferencing features. They allow for maximum
conferencing flexibility and feature sets.
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Video Architecture
Cisco provides multiple video conferencing platforms that support both switching and transcoding.
Table 2-1 shows which devices support switching or transcoding.
Table 2-1
Conferencing Platforms for Switching and Transcoding
Conferencing Platform
Switching
Transcoding
Cisco TelePresence Multipoint Switch
Yes
No
Cisco TelePresence Server
No
Yes
Cisco TelePresence MCU 4000 Series and MSE 8000 Series
No
Yes
Cisco Integrated Services Router (ISR) G2
No
Yes
Cisco TelePresence Conductor is a new type of conferencing device that has the capability to manage
conferencing ports intelligently. Cisco TelePresence Conductor serves as the front end for all
conferencing devices and manages the distribution of conferencing requests. Cisco TelePresence
Conductor enables large pools of distributed conferencing resources to be allocated dynamically instead
of being limited to conferencing devices with static configurations.
Streaming and Recording
Streaming and recording devices provide the ability to record, replay, and stream important meetings,
messages, or updates. Meetings can also be streamed to allow a large number of users to participate in
a meeting as view-only participants. Cisco offers one recording and streaming server for TelePresence
and Unified Communications video endpoints, and one recording-only server for TelePresence
endpoints only, as follows:
•
Cisco TelePresence Content Server (TCS)
The Cisco TCS is available as an appliance or a blade for the Cisco TelePresence Media Services
Engine (MSE) chassis. Cisco TCS provides live recording, streaming, and playback of video
meetings with content from any TelePresence or Unified Communications video endpoint. Live
streams and recordings can be viewed with standard QuickTime, RealPlayer, and Windows Media
Players.
•
Cisco TelePresence Recording Server (CTRS)
The CTRS is a server-based platform that provides studio mode and event recording and playback
for Cisco TelePresence System 3x10, 1300, 1100, and 500 endpoints. Recordings can be viewed
in native 1080p or 720p resolution from any Cisco TelePresence System 3x10, 1300, 1100, and 500
endpoints. or with QuickTime, RealPlayer or Windows Media Player in CIF format.
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Video Architecture
Video Network Services
Video network services also consist of two subcategories:
•
Call Control, page 2-6
•
Gateways, page 2-7
Video network services offer essential services such as call routing and access to external video
networks.
Call Control
The main functions of a call control device are endpoint registration, call routing, monitoring, and
maintaining connections. Call control platforms also form the base for network dial plans and options
for call admission control. Cisco offers two main call control platforms for interactive video: Cisco
Unified Communications Manager (Unified CM) and Cisco TelePresence Video Communication Server
(VCS). Unified CM has been used for call control and provisioning for some of the largest IP voice
deployments in the world. Unified CM is also the call control and provisioning platform for the original
Cisco TelePresence and Cisco Unified Communications devices.
Cisco VCS was designed to provide call control for H.323 and Session Initiation Protocol (SIP) video
environments with advanced video features to support large-scale deployments. VCS can be deployed
in either of the following ways:
•
VCS Control — Provides call control for an enterprise video deployment.
•
VCS Expressway— Supports Network Address Translation (NAT) and firewall traversal, extending
video outside the enterprise for business-to-business communication or internet-based remote
workers.
Each call control platform can be deployed independently or as an integrated solution for existing and
new customers. Unified CM supports direct registration for all Unified Communications video
endpoints and most TelePresence endpoints, while VCS supports most TelePresence endpoints but does
not support Unified Communications endpoints. Table 2-2 lists the call control support for each video
endpoint type or series.
Table 2-2
Call Control Support Per Video Endpoint
Endpoint
Unified CM
VCS
TX9000 Series
Yes
No
CTS 3000 Series
Yes
No
CTS T Series
No
Yes
TX1300 Series
Yes
No
CTS MX Series
Yes
Yes
CTS Profile MXP Series
Yes
Yes
CTS Profile Series
Yes
Yes
CTS EX Series
Yes
Yes
CTS MXP Series
No
Yes
CTS 1100
Yes
No
CTS 500
Yes
No
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Video Architecture
Table 2-2
Call Control Support Per Video Endpoint (continued)
Endpoint
Unified CM
VCS
Cisco Jabber Video for TelePresence (Movi)
No
Yes
CTS E20
Yes
Yes
9900 Series
Yes
No
Cisco Unified Personal Communicator
Yes
No
Cisco Jabber
Yes
No
Cius
Yes
No
Gateways
Video gateways provide access from one network to another. Cisco provides the following video
gateways:
•
ISDN gateways
ISDN gateways provide TelePresence and Unified Communications video endpoints with
connectivity to legacy H.320 video endpoints. ISDN gateways are often referred to as H.320
gateways.
•
Advanced media gateways
Advanced media gateways provide communication between Microsoft Office Communications
Server 2007 R2 or Microsoft Lync Server users and standards-based TelePresence and video
conferencing devices.
•
IP-to-IP gateways
Cisco offers the following IP-to-IP gateways that provide business-to-business (B2B) connectivity
as well as support for Internet connectivity for video endpoints:
– Cisco VCS Expressway
VCS Expressway is an appliance that works in conjunction with the VCS Control to provide
firewall traversal using H.460.18, Assent, or SIP protocols. It supports Traversal Using Relay
NAT (TURN) servers. VCS Expressway also provides endpoint registration and signal and
media interworking for SIP and H.323 video devices across the public Internet.
– Cisco Unified Border Element
Cisco Unified Border Element is available on a number of Cisco router platforms and provides
a network-to-network demarcation point for signaling interworking, media interworking,
address and port translations, billing, security, quality of service (QoS), and bandwidth
management. Service provider TelePresence Exchanges often implement Cisco Unified Border
Element as an IP-to-IP gateway because it provides a demarcation point and adds security
between customer networks.
– Cisco Intercompany Media Engine (IME)
The Cisco IME is a server-based platform that provides business-to-business connectivity when
used in conjunction with the Cisco ASA 5500 Series Adaptive Security Appliances and Cisco
Unified CM 8.x or later releases.
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Video Architecture
Management
Video management platforms perform multiple functions such as scheduling, video endpoint and
infrastructure monitoring, and in some cases provisioning or tracing of media flows across the network.
Cisco provides three main management platforms for TelePresence and Unified Communications video:
•
Cisco TelePresence Management Suite, page 2-8
•
Cisco TelePresence Manager, page 2-8
•
Cisco Prime Collaboration Manager, page 2-8
Cisco TelePresence Management Suite
The Cisco TelePresence Management Suite (TMS) is delivered as a management appliance or software
that can be loaded on a server. Cisco TMS provides one-button-to-push (OBTP) call launching,
scheduling, monitoring, and provisioning for TelePresence endpoints registered with the VCS. The TMS
also provides OBTP, scheduling, and statistics for TelePresence endpoints registered to Unified CM.
TMS also extends scheduling and some monitoring features to third-party telepresence and video
endpoints such as Polycom and LifeSize.
The TMS can be integrated with enterprise calendaring systems such as Microsoft Exchange for
scheduling with tools such as Microsoft Outlook. TMS also has a built-in web scheduling interface that
enables users to schedule meetings directly through TMS.
Cisco TelePresence Manager
Cisco TelePresence Manager is a server-based platform that was originally developed to provide OBTP
call launching, scheduling, and management for Cisco TelePresence endpoints. Cisco TelePresence
Manager also performs scheduling for telepresence endpoints, including third-party endpoints that are
not registered to Unified CM.
Cisco TelePresence Manager can be integrated with enterprise calendaring systems such as Microsoft
Exchange for scheduling with tools such as Microsoft Outlook. Unlike TMS, Cisco TelePresence
Manager does not have built-in web-based scheduling.
Cisco Prime Collaboration Manager
Cisco Prime Collaboration Manager is a server-based network management platform that allows
real-time monitoring and analysis of medial flows from Cisco Medianet-enabled devices. Cisco
Medianet devices are routers and switches that support Cisco Mediatrace, which maps the path media
takes through the network and which can be used only with endpoints that contain the Cisco Media
Services Interface (MSI). The MSI is a software component that is embedded in video endpoints and
collaboration applications, and it provides advanced features such as auto-configuration of network
ports and initiation of Mediatrace. Cisco Prime Collaboration Manager also supplies historical reporting
and a view of utilization and problem trends as well as critical outages.
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Network
Network
A properly designed network is a key component of any video design. Using existing network protocols,
features, and tools simplifies video deployments and helps ensure a successful deployment. Interactive
video devices are sensitive to loss, so it is imperative to keep loss to a minimum. Identifying video traffic
on the network and ensuring end-to-end Quality of Service (QoS) provides the most predictable video
experience.
With the use of protocols such as Cisco Discovery Protocol (CDP), which is a Cisco proprietary Data
Link Layer protocol used to share information between network devices, video endpoints can be
identified automatically, thus allowing their QoS markings to be trusted, traffic to be placed in the
appropriate Virtual Local Area Network (VLAN), and packets to be queued appropriately. Additionally,
VLANs can be used to insulate video traffic from other network traffic and to provide additional
security.
Video-aware networks allow for real-time traffic analysis for troubleshooting network issues in real
time. Tracking video flows through the network and identifying the exact point in the network where
loss is occurring is essential in today's networks where video flows between two endpoints can take
different paths across the network, depending on network conditions. Using Cisco Medianet-enabled
devices not only allows for real-time traffic analysis but also provides utilization data that helps avoid
network oversubscription.
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3
Basic Video Concepts
Revised: March 30, 2012, OL-27011-01
This chapter explains some of the fundamental concepts and terminology encountered in video solutions.
Common Terminology in IP Video Solutions
The vocabulary of IP video solutions encompasses a wide range of concepts and terms, from the video
stream formation to how and what devices put the video stream in the wire. This section covers the most
common concepts and terms, explains how they relate to the IP video technologies, and attempts to
de-mystify them.
Video Frame
A video is an action sequence formed by a series of images, and each image in the series succeeds the
previous one in the timeline of the action sequence to be displayed. These still images are called video
frames. The smaller the time difference is between each video frame, the higher the refresh rate is and
the more naturally movement is represented in the video. This is because there are more video frames
generated per second to be displayed as part of the action sequence, therefore changes in the image
between frames are slighter and movement appears smoother.
Compression in IP Video Solutions
Compression of IP video, as the term implies, is a process by which the overall size of the video
information is compacted. Unlike the audio data in an IP telephony stream, which is very light weight,
video data is inherently large in size but irregular in its stream flow. The flow irregularity is due to the
fact that in video there are portions of the information that remain constant (for example, backgrounds)
and portions that are in motion (for example, people). Additionally, motion is not always constant or
from the same object size, therefore transmission of real-time video requires complex mechanisms to
reduce its size and irregularity. Compression reduces the video size so that it can be transmitted more
easily. The primary compression methods for IP video are:
•
Lossless, page 3-2
•
Lossy, page 3-2
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Both of these video compression methods can use the following techniques:
•
Intra-Frame, page 3-2
•
Inter-Frame, page 3-2
Lossless
Lossless IP video compression produces, on the decompression end, an exact copy of the image that was
originally submitted at the input of the compression process. Lossless compression is achieved by
removing statistically redundant information so that the receiving end can reconstruct the perfect video
signal. That is, there is no intentional loss or pruning of video information that occurs as part of the
compression process. Lossless compression is used mostly for archiving purposes because of its inherent
ability to preserve everything about the original image. Lossless video compression is rarely used in IP
video solutions because it creates a large quantity of information that poses difficulties for streaming.
Lossy
Lossy video compression is more common in IP video than its lossless counterpart. Lossy video
compression is based on the premise that not all the video information is relevant or capable of being
perceived by the viewer, therefore some video information is intentionally discarded during the
compression process. An example of this "irrelevant" video information is noise in the case of video that
has undergone analogue to digital conversion. Lossy video compression achieves a very significant
decrease in payload size while maintaining a very high presentation quality, thus making it the
compression method of choice for IP video solutions. It is important to note that video compression is
always a trade-off between video size and quality. Another trade-off is the frame duration or frame rate,
which is measured in frames per second (fps). For example, an image with resolution of 720p at 60 fps
is more appealing than an image with 1080p at 30 fps because of the savings of roughly 10% bandwidth
and better perception of motion.
Intra-Frame
The intra-frame technique consists of compressing the contents of a single video frame at a time, without
considering previous or succeeding video frames. Because every video frame is compressed
individually, no previous or succeeding compressed video frames are needed to decompress a specific
compressed video frame; it is literally as if every compressed video frame is a key frame.
Intra-frame compression alone does not offer many advantages for video streaming or video
conferencing because the compression ratio is not as high as with inter-frame techniques. Therefore,
intra-frame compression is always used in conjunction with the inter-frame compression technique in
video conferencing.
Inter-Frame
Unlike the intra-frame technique, the inter-frame technique uses information from the preceding video
frames to execute the compression. Certain video formats (for example, Advance Video Coding formats
such as H.264) that implement the inter-frame technique also use information from the succeeding video
frames to perform the compression.
The inter-frame technique relies on the fact that parts of the images to be compressed in video are
sometimes not in motion, thus providing the opportunity for the compressor to send only the differences
(what has moved) instead of the entire video frame information. It is important to note that this technique
relies on the concept of a key frame. The key frame is the initial video frame used for reference in the
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compression operation. Therefore, the arrival of the key frame at the decoder becomes critical for the
decompression operation to be successful. For this reason, video formats that employ the inter-frame
technique usually implement recovery mechanisms. Because the key frame is used as a reference in the
inter-frame compression technique, its compressed contents do not depend on any preceding or
succeeding frames.
Codecs in IP Video Solutions
The term codec stands for COmpressor-DECompressor (or COder-DECoder). Video codecs (such as the
Cisco TelePresence System or C-Series codecs) are the hardware or software means by which video is
encoded and decoded. In addition, the term codec is often used to describe the video formats. A video
codec may be able to implement one or more video formats, and these formats may implement lossless
or lossy compression methods using either the intra-frame or inter-frame compression technique. In an
IP video solution, almost all IP video endpoints integrate a codec as part of their basic functions. As
discussed in the section on Compression in IP Video Solutions, page 3-1, compression is necessary
because of the large size of video data to be transmitted in a session. Figure 3-1 shows a codec
performing compression. The codec helps reduce the video stream size and irregularity by applying a
compression operation on it.
A Codec Executing Video Compression
Codec executing
compression
Uncompressed
video
Codec executing
decompression
Compressed
video
Display
of video
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Figure 3-1
Uncompressed
video
Video Compression Formats
As stated in the section on Codecs in IP Video Solutions, page 3-3, video formats are commonly referred
to as codecs and the terms are used interchangeably. Video formats are specifications that state how
compression or encoding of video takes place using a given technique. For instance, H.264 is a widely
used video format that employs the lossy compression method. Video formats are implemented by the
codecs employed in the video endpoints to encode the video. IP video endpoints must negotiate and
agree on the video format to be used during a call. Although some video formats might implement the
same method and technique, they do not necessarily offer the same advantages. How the video format
implements the method and technique determines its strengths and advantages.
Generally speaking, video formats are established by the International Telecommunication Union (ITU)
Telecommunication Standardization Sector (ITU-T) or by the International Organization for
Standardization (ISO) in conjunction with the International Electrotechnical Commission (IEC). Two of
the three most common video formats used in IP video solutions (H.261 and H.263) were established by
ITU-T, while the third (H.264) is a joint effort of ITU-T, ISO, and IEC (the Moving Picture Experts
Group, or MPEG). Table 3-1 compares the features and characteristics of these formats.
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Table 3-1
Comparison of Video Compression Formats
Feature
H.261
H.263
H.264
Bandwidth efficiency
Low
Medium
High
HD support
No
No
Yes
Compressed video
frames supported
I-frame, P-frame
I-frame, B-frame,
P-frame
I-frame, B-frame,
P-frame
Error feedback
mechanism
Error feedback
mechanism
Optimized Virtual
Channel Link (VLC)
tables
Enhanced motion
estimation
Compression and media Error feedback
resiliency features
mechanism
Four optional
negotiation modes
(Annex D, E, F, and G)
Improved entropy
coding
Intra-prediction coding
for I-frames
4x4 Display Channel
Table (DCT)
Network Abstraction
Layer
Gradual Decoder
Refresh (GDR) frame
Long-Term Reference
Picture (LTRP) frame
Currently most Cisco IP Video endpoints utilize H.264 as their default video compression format.
Compressed Video Frames
The compressed video frames are the result of the compression operation (using intra-frame or
inter-frame techniques and using lossy or lossless methods), and they are used instead of the regular
(uncompressed) video frames to reduce the overall size of the video information to be transmitted.
Figure 3-2 depicts a video frame being compressed by a codec, and the resulting compressed video frame
in this example is an I-frame.
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Figure 3-2
Compression at Work
Frame 1 (previous)
Frame 2 (current)
Codec performing
decompression
Frame 1 (previous)
Frame 2 (current)
Difference image
between motion
compensated prediction
and current frame
Codec performing
compression
Frame 2 (current)
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Frame 1 (previous)
There are many different kinds of compressed video frames used in IP video solutions, but the main
types are:
•
I-Frame, page 3-5
•
P-Frame, page 3-6
•
B-Frame, page 3-6
I-Frame
I-frames rely only on their own internal data and they enable decompression or decoding at the start of
the sequence. I-frames are compressed using the intra-frame method. I-frames are also known as key
frames because their content is independent of any other frames and they can be used as a reference for
other frames. As discussed in the inter-frame compression method, a key frame or initial frame is used
at the beginning of the sequence of pictures to be compressed. Instant Decoder Refresh (IDR) frames,
Gradual Decoder Refresh (GDR) frames, and Long-Term Reference Picture (LTRP) frames are well
known I-frames. The main difference between IDR and GDR frames is that a GDR frame can be divided
into smaller frames and sent at smaller time intervals whereas an IDR frame is sent in one packet. The
purpose of using GDR frames is to avoid a significant surge in the data rate that occurs with IDR frames
and to provide a better experience of video quality for the end user. For example, a GDR implementation
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can send 10 individual sections of a complete frame, and each of these sections is itself an IDR encoded
video picture. Because only 1/10 of the frame is gradually changing over a 10-frame window, the user
perception of the video quality is generally very good.
LTRP frames, on the other hand, are part of the media resilience provisions that some codecs implement.
Inevitable network loss and errors of compressed video cause visual errors at the decoder. The errors
would spread across subsequent P-frames. An obvious way to avoid this problem is to have the decoder
request an I-frame from the encoder to flush out the errors (error feedback mechanism). However, a
better way is to employ different reference frames (older, long-term frames). The feedback mechanism,
in conjunction with the known good LTRP frame, helps to repair the lost video data (for example, slices)
and to phase out the bad LTRP frame. In codecs that support this implementation, the LTRP frame is the
last I-frame that arrived at the codec (using either IDR or GDR) The receiving codec then stores this
frame as the LTRP frame. When a new I-frame arrives, it is promoted to LTRP, and so on. If an I-frame
is lost during transmission, the receiving codec attempts to use the LTRP frame to recover.
I-frames are compressed using the intra-frame technique, and this has a direct impact in the bandwidth
consumption of the video stream. The more frequently I-frames are used, the more bandwidth is
required.
P-Frame
Predictive frames (P-frames) are more compressible that I-frames. P-frames are compressed using the
inter-frame encoding technique. P-frames follow I-frames in the video stream, and they store only the
video information that has changed from the preceding I-frame. As mentioned in the discussion of
inter-frame compression, correct decoding of a P-frame is possible only in combination with the most
recent I-frame (key frame).
B-Frame
Although the use of P-frames increase the compression significantly, bidirectional predictive frames
(B-frames) make the overall compression more efficient. B-frames reference the previous I-frames and
subsequent P-frames, and they contain only the image differences between them. However, not all
codecs have the ability to implement B-frames (assuming that the video format utilized in the call
supports B-frames) because the codec needs twice as much memory to provide enough buffer between
the two anchor frames. B-frames also add some delay that is intrinsic to the logic of the B-frame
implementation.
Figure 3-3 depicts the order of the various compressed video frames in a video stream. In this example
the codec is able to implement I-frames, P-frames, and B-frames.
Figure 3-3
Order of Video Display
Order of display
..
I
B
B
B
P
B
B
B
P
B
B
B
P
1
2
3
4
5
6
7
8
9
10
11
12
13
..
Group of Pictures (GOP)
I
P
B
B
B
P
B
B
B
P
B
B
B
1
5
2
3
4
9
6
7
8
13
10
11
12
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Resolution Format in IP Video Solutions
In simplest terms, the resolution format is the image size. However, it is important to note that most
video endpoints today have the ability to scale the image to fit the screen where the video is displayed.
Although this is necessary for the video to be visible from afar, it causes the image to be less crisp.
The video resolution format is formally defined as the scanning method used in combination with the
distinct number of pixels being presented for display. The following list and Figure 3-4 depict some
common video resolution formats in IP video solutions.
Figure 3-4
•
CIF — Common Intermediate Format
•
QCIF — Quarter CIF
•
360p — 360 vertical, progressive scan
•
480p — 480 vertical, progressive scan
•
720p — 720 vertical, progressive scan
•
1080i — 1080 vertical, interlaced video
•
1080p — 1080 vertical, progressive scan
Popular Video Resolutions
QCIF
(176x144)
CIF (352x288)
w288p
(512x266)
360p (640x360)
w448p
448p (576x448) (768x448)
VGA / 480p (640x480)
4CIF (704x576)
w576p
(102x576)
1080p (1020x1080)
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720p (1280x720)
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Evolution of Cisco IP Video Solutions
IP video has largely replaced other video conferencing methods. However, interconnection between
methods is sometimes necessary, therefore a basic understanding of the other methods is useful. This
section briefly highlights the evolution of video conferencing solutions, from video over ISDN media to
the newer cloud-hosted video solutions, and the interoperability between those solutions. The following
video solutions and their interoperability are covered in this section:
•
Video over ISDN, page 3-8
•
IP Video Telephony, page 3-9
•
Desktop Video Conferencing, page 3-10
•
Immersive Video Conferencing, page 3-11
•
Cloud-Hosted Video Solutions, page 3-12
•
Interoperability, page 3-12
This section does not cover these solutions in strict chronological order; some of the solutions overlap
each other or were developed around the same time.
Video over ISDN
Video conferencing was not widely used until the creation of the Integrated Services Digital Network
(ISDN) standard. Therefore, ISDN is often seen as the first technology catalyst that helped to spread
video conferencing. As video conferencing matured, new solutions emerged that offered better
interoperability, resiliency, and video quality. As Cisco entered the video conferencing market, it
became apparent that the ISDN video terminals would need to interoperate with the emerging
technologies. To connect the new IP video networks with existent ISDN video terminals, Cisco IP Video
Solutions integrated the Cisco Unified Videoconferencing 3500 Series products as H.320 gateways.
Since then, Cisco has incorporated a variety of H.320 devices into its portfolio to support the video ISDN
space. These H.320 devices peer to a gatekeeper, Cisco Unified Communications Manager
(Unified CM), or Cisco TelePresence Video Communication Server (VCS) to provide IP video
endpoints with access to ISDN video endpoints residing on the other side of the PSTN cloud.
The H.320 standard defines multimedia (H.221 for video in our case of interest) in ISDN. H.320
originally defined H.261 or H.263 as the video formats to be used when video is used in conjunction
with ISDN, and the last update to the standard added H.264. H.221 defines four modes of transmission:
Px64 kbps, H0 (384 kbps), H11 (1536 kbps), and H12 (1920 kbps). After the video is encoded, the
selected video format (for example, H.261) is multiplexed using the H.221 standard.
ISDN is called a narrow-band visual telephone system because the video resolution formats it supports
are very limited in image size. ISDN supports QCIF, CIF, 4CIF, and 16CIF as video resolution formats.
A distinctive characteristic of this kind of solution is its dependency on a supporting ISDN service
provider, which remains permanently engaged so that the call can work between the different ISDN
terminals, as depicted in Figure 3-5.
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Image 4. Video over ISDN and Protocols Used
H.320 Gateway
and Cisco Unified
CM Peered
ISDN
Central Office
(PSTN) Switch
ISDN Video
Phone
ISDN
ISDN
IP Video
Phone
IP
H.261 using H.221 (ISDN) H0
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Figure 3-5
H.261 over IP
M
Cisco Unified
CM
IP Video Telephony
While video over ISDN was the first video conferencing technology deployed in practice, IP video
telephony brought video conferencing to the enterprise on a much larger scale. IP video telephony
enables video in the enterprise through a variety of approaches. It can enable video on the user's IP phone
through a software client running on a PC, and it can incorporate specialized video endpoints and video
conference bridges to provide a rich media experience. Unlike video over ISDN, IP video telephony
provides better video resolution, resilience, and interoperability.
A call control element is an integral part of every IP video telephony solution. This element is
responsible for the call routing and, in most cases, interoperability and the handling of special features.
In Cisco's first iteration of IP Video Telephony, Cisco Unified Communications Manager (Unified CM)
executed call control. Figure 3-6 depicts a sample topology of Cisco IP Video Telephony.
Figure 3-6
IP Video Telephony
IP Video
Phone
IP Video
Phone
M
Cisco Unified
CM
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H.263 over IP (UDP-RTP) over Ethernet medium
As shown in Figure 3-7, IP Video Telephony improves the video resolution by providing transmission
flexibility in a variety of physical transport media that are not restricted to 2 Mbps as video over ISDN
was (1.54 Mbps in the case of the US). IP (User Datagram Protocol for video) encapsulated packets can
be carried over Ethernet, wireless, Multiprotocol Label Switching (MPLS), and so forth. The synergy
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between the new transmission media (MPLS, Ethernet, optical, and so forth) and IP allows for
transmission of larger compressed video frames for increased resolution. Resiliency is boosted by new
error recovery techniques implemented by new codecs, while backward compatibility is also maintained.
Figure 3-7
IP
(UDP-RTP)
H.264 – Video Payload
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Ethernet
Encapsulation of Compressed Video Frames in IP
Desktop Video Conferencing
Desktop video conferencing involves the consolidation of IP video as the next generation of
communication. Desktop video conferencing started as an add-on to instant messaging programs. In
parallel, IP video telephony technology companies realized its benefits and created software video
clients that would peer with existent IP telephony deployments. Some technologies leveraged current
hardware IP phones and some leveraged software IP phones. Cisco's initial offering for desktop
conferencing was Cisco Unified Video Advantage (VT Advantage), a software video client that enables
video capabilities in both hardware and software IP phones.
Desktop video software clients use the computer's resources to execute software encoding and decoding
of video. The higher the video resolution format and video format complexity, the more computer
resources are needed. As faster and better computers became available and more efficient
encoding-decoding mechanisms were devised, advanced desktop video conferencing clients became
common in the end user space as well. Figure 3-8 shows the typical usage and basic topology of a video
software client during a session.
Figure 3-8
Software Video Clients
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Immersive Video Conferencing
As the quest for new methods of video communications continued, new implementations of IP video
solutions were conceived. Life-size video systems, called telepresence, were created as a means of
communicating more naturally with remote participants. The first telepresence systems suffered from
low adoption rates due to their high cost and dedicated network requirements. In 2006, Cisco entered the
immersive video conferencing market, leveraging its vast networking knowledge to create a true
converged network telepresence product. Eventually, other immersive video conferencing
manufacturers followed Cisco's lead in creating converged network telepresence systems.
Cisco TelePresence shares some aspects in common with regular IP video telephony. Compressed video
frames are encapsulated in User Datagram Protocol (UDP), enabling access to the same kind of media
IP video telephony uses and providing compatibility with video formats used in IP video telephony.
Despite their similarities, though, some elements of Cisco TelePresence differ from IP video telephony.
Cisco TelePresence uses high definition cameras and displays, which are specially fitted in the case of
large participant rooms. Although the call routing in Cisco TelePresence is still handled by a call agent,
the way users interact with the system for call initiation is different than with IP video telephony
Telepresence systems use high definition cameras to capture rich video. After encoding and decoding,
this video is displayed on high definition displays to preserve as much of the experience as possible.
Additionally, special conditioning of conference rooms for a studio-like setting is available to increase
the realism of the meeting. As described earlier, end users interact differently with telepresence systems
for meeting initiation. Telepresence systems typically integrate mechanisms to start meetings at the push
of a button. In the case of Cisco TelePresence, this session initiation feature is call One Button To Push
(OBTP). Figure 3-9 illustrates the flow of media and signaling in a basic point-to-point call for
immersive Cisco TelePresence.
Figure 3-9
Immersive Telepresence
Cisco
Unified CM
M
SIP Signaling
SIP Signaling
IP
IP Phone
used for One
Button to Push
(OBTP)
conference
SIP Signaling
Video RTP Stream
Cisco TelePresence
System 3010 Endpoint
IP
Cisco TelePresence
System 3010 Endpoint
IP Phone
used for One
Button to Push
(OBTP)
conference
284372
SIP Signaling
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Evolution of Cisco IP Video Solutions
Cloud-Hosted Video Solutions
Cloud-hosted video solutions are subscription-based services that provide video communications across
the Internet, making enterprise-grade video collaboration both affordable and accessible.
A notable difference between this solution model and the others is that the customer does not front the
cost of the IP video infrastructure and acquires only the video endpoints (for example, a Cisco
TelePresence System EX90 or a PC). The multiplexing and control of the video endpoints occur off
premises, empowering customers to enter into the video collaboration space without a significant
investment in the infrastructure. This solution model does require an available internet connection and
a subscription from an IP video provide, but the IP video endpoints can be reused if the solutions is
migrated to an on-premises model.
Cloud-hosted video solutions solve the problem of the high cost of an IP video infrastructure by
empowering customers to pay as they go for the IP video service. Examples of this type of video solution
are Cisco Callway and Cisco WebEx, both of which provide video capability and allow customers to
enable video for their users with less administrative overhead and infrastructure investment.
Interoperability
Advancements in technology inevitably create the need for the new technology to interconnect and work
with legacy technologies. Interoperability solves the problem of interconnecting different IP video
technologies, but interoperability is restricted to features that can be implemented in the target
technology. For example, some ISDN terminals are capable of sending text to a participant’s screen
when on a video call because the ISDN standard provides for text transmission. However, it is not
technologically possible to pass this text outside of the ISDN domain (for example, to IP video
telephony) because the standards implemented other technologies do not allow for text transmission.
Interoperability is typically achieved using a product or suite of products to provide the edge element
between the technology islands. Usually the types of products used (either individually or in
combination) to provide interoperability to a video solution include video transcoders, video gateways,
and video conference bridges. Figure 3-10 shows a common interoperability scenario, with
interoperability provided by a Multipoint Control Unit (MCU).
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Evolution of Cisco IP Video Solutions
Figure 3-10
Interoperability in a Video Conferencing System
H.323
Gatekeeper
Cisco
Unified CM
M
H.323
SIP
SIP
IP
SIP Proxy
(Could be VCS)
284373
MCU with
TelePresence
Server
Legacy Multipoint Control Units
Early Multipoint Control Unit (MCU) architectures offered limited services and capabilities. These
legacy MCUs had two main hardware components, a controller blade and a digital signal processor
(DSP) blade. The controller blade was aware of only the local DSP assets and therefore it was impossible
for it to ascertain the assets of a different MCU to cascade them and use them in a video multipoint call.
Furthermore, only certain resolutions were supported, and transrating often was either not supported or
came at the sacrifice of high capability.
Although some legacy MCUs added support for high definition video in their later iterations, the
majority of the legacy MCUs typically offer support only for standard definition video.
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Common Technologies Used in Cisco IP Video Solutions
Common Technologies Used in Cisco IP Video Solutions
Although the list of technologies used in IP video solutions is long, this section discusses the
technologies currently used Cisco IP Video solutions. With these technologies, Cisco has solved
particular problems that otherwise would be left unaddressed. For instance, packet loss, although
avoided as much as possible in every deployment, is sometimes inevitable when control over the
transmission medium is lacking. Cisco ClearPath helps minimize the impact of packet loss. Telepresence
Interoperability Protocol (TIP), on the other hand, addresses several issues, including what video to
display when multiple screen systems are talking. This section describes the following technologies:
•
Telepresence Interoperability Protocol (TIP), page 3-14
•
ClearPath, page 3-15
Telepresence Interoperability Protocol (TIP)
Cisco originally developed the Telepresence Interoperability Protocol (TIP), but Cisco later transferred
it to the International Multimedia Telecommunications Consortium (IMTC) as an open source protocol.
The TIP standard defines how to multiplex multiple screens and audio streams into two Real-Time
Transport Protocol (RTP) flows, one each for video and audio. It enables point-to-point and multipoint
sessions as well as a mix of multi-screen and single-screen endpoints. The TIP specification also defines
how Real-Time Transport Control Protocol (RTCP) application extensions are used to indicate profile
capabilities and per-media flow options as a session is established. It also defines how devices can
provide feedback and trigger resiliency mechanisms during the life of the streams.
As illustrated in Figure 3-11, TIP enables interoperability of multi-vendor, multi-screen IP video
solutions by describing how switching of the screen (and its audio) should occur. TIP is used in video
endpoints, video transcoders, video gateways, and MCUs (video conference bridges).
Figure 3-11
TIP Multiplexing in Action
Cisco TelePresence
System 3010 Series
Cisco TelePresence
System 500 Series
284376
Telepresence Interoperability
Protocol (TIP)
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Basic Video Concepts
Common Technologies Used in Cisco IP Video Solutions
ClearPath
Cisco ClearPath is a technology for removing the negative effects of up to 15% packet loss. It is a
dynamic technology that combines a number of media resilience mechanisms. For example, when using
lossy media, ClearPath helps to counterbalance the effects of the packet loss and thereby to improve the
user experience. ClearPath is enabled by default and is used when it is supported on both ends of the
video communication. The ClearPath mode is set by the xConfiguration Conference
PacketLossResilience Mode command. All the media resilience mechanisms within ClearPath are
H.264 standard-based, and the resulting encoded bit stream is H.264 compliant. ClearPath is designed
to be independent of the call setup protocol, and it can be used by endpoints using H.323, SIP, and
XMPP.
ClearPath uses the following technologies to produce the best possible user experience:
•
Dynamic Bit Rate Adjustment, page 3-15
•
Long-Term Reference Picture, page 3-15
•
Video-Aware Forward Error Correction (FEC), page 3-15
Dynamic Bit Rate Adjustment
Dynamic bit rate adjustments adapt the call rate to the variable bandwidth available, downspeeding or
upspeeding the call based on the packet loss condition. In the case of ClearPath, once the packet loss has
decreased, upspeeding will occur. ClearPath uses a proactive sender approach by utilizing RTCP. In this
case the sender is constantly reviewing the RTCP receiver reports and adjusting its bit rate accordingly.
Long-Term Reference Picture
Long-term reference frame recovery is a method for encoder-decoder resynchronization after a packet
loss without the use of an I-frame. A repair P-frame can be used instead of a traditional I-frame when
packet loss occurs, resulting in approximately 90% less data being transmitted to rebuild the frame.
A Long-Term Reference Picture (LTRP) is an I-frame that is stored in the encoder and decoder until they
receive an explicit signal to do otherwise. For more information on Long-term reference frames or
LTRPs, see the section on I-Frame, page 3-5.
Video-Aware Forward Error Correction (FEC)
Forward error correction (FEC) provides redundancy to the transmitted information by using a
predetermined algorithm. The redundancy allows the receiver to detect and correct a limited number of
errors occurring anywhere in the message, without the need to ask the sender for additional data. FEC
gives the receiver an ability to correct errors without needing a reverse channel to request retransmission
of data, but this advantage is at the cost of a fixed higher forward channel bandwidth. FEC protects the
most important data (typically the repair P-frames) to make sure those frames are being received by the
receiver. The endpoints do not use FEC on bandwidths lower than 768 kbps, and there must also be at
least 1.5% of packet loss before FEC is introduced. ClearPath monitors the effectiveness of FEC, and if
FEC is not efficient, ClearPath makes a decision not to do FEC.
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Common Technologies Used in Cisco IP Video Solutions
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CH A P T E R
4
Call Control Protocols and IPv6 in IP Video
Solutions
Revised: March 30, 2012, OL-27011-01
Protocols provide a complete set of specifications and suite of standards for communications between
devices, This chapter does not discuss all the information available about the protocols but rather focuses
on their most important features and characteristics in the context of handling video communications.
Call Control Protocols in IP Video Solutions
The primary call control protocols used in most IP video solutions today are H.323, Session Initiation
Protocol (SIP), and Skinny Client Control Protocol (SCCP).
SCCP
Skinny Client Control Protocol (SCCP) was first developed by Cisco for IP Telephony applications. As
IP Telephony matured, it integrated video as well and gave rise to Cisco IP Video Telephony. SCCP
defines Transmission Control Protocol (TCP) as the transport protocol and a call agent in an
architectural relationship with the endpoints (also known as a master/slave relationship). The call agent
is the most fundamental difference between SCCP and the rest of the call control protocols discussed in
this section. Because SCCP employs a central call agent, it inherently enables very advanced call
functions for video endpoints that might not be available in other call control protocols.
Because SCCP defines a master/slave (or client/server) relationship between the call agent and the
endpoints, the call agent must always remain available to the endpoint for call features to function.
Therefore, SCCP might not be suitable for certain environments where the endpoints are expected to
function independently from a call agent component.
Figure 4-1 illustrates the role of SCCP call control signaling in a deployment where Cisco Unified
Communications Manager (Unified CM) is the call agent.
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Call Control Protocols in IP Video Solutions
Figure 4-1
SCCP Signaling
Cisco
Unified CM
M
SCCP signaling
remains for the
duration of the call
SCCP signaling
remains for the
duration of the call
284377
Video RTP
Cisco Unified
IP Phone 7985
Cisco Unified
IP Phone 7985
As stated earlier, the SCCP specification provides support for advance call features in a video
environment. Among those features, hold, resume, mute, and conferencing function exactly as they do
for regular audio calls. The features that are most distinctive in SCCP endpoints are ad-hoc video
conferencing and mute. Although support for ad-hoc video conferencing is not exclusive of SCCP,
SCCP and the implementation of reservationless video conferencing in the video endpoints have made
it easier for users to engage in ad-hoc video conferences. When the call control server is coupled with a
compatible SCCP MCU, SCCP video phones are able to launch a conference by having users press a
single key without making a previous conference reservation. This is an important difference from
H.323, in which users must dial an always-on conference destination to establish a reservationless
meeting.
The SCCP mute feature for video also functions differently than in other protocols. Unlike the mute
function in H.323 and SIP, when mute is activated on the SCCP video terminal, both audio and video
are muted simultaneously.
Just as SCCP enables intrinsically advanced call functionality on video endpoints through its phone-like
technology and architecture, it also imposes some legacy phone-like behavior for video. Among the
legacy behavior is the lack of support for uniform resource identifier (URI) dialing and data sharing.
Therefore, when SCCP interoperates with some other protocol in a video deployment, it is important to
consider any architectural limitations of SCCP. Table 4-1 lists other features not implemented in SCCP
that should be considered when interoperating with H.323 or SIP for video.
Table 4-1
Features Not Implemented in SCCP
Feature not available in SCCP
Result
Workaround (if available)
Dynamic addition of video
capability
Cannot promote an audio call to Ensure that video capabilities are
a video call
available and broadcast at the
beginning of the session
Far-end camera control (FECC)
for SCCP endpoints
Cannot adjust remote cameras
Video codec renegotiation
Call session might be terminated Not available
if renegotiation occurs
Not available
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Call Control Protocols in IP Video Solutions
The SCCP messages are encoded in hexadecimal, therefore reading them directly from the transmission
is challenging. However, this encoding mechanism comes with the advantage that SCCP messages are
generally smaller than with other call control protocols. For instance, an SCCP phone averages 256 bps
in unencrypted call control traffic while a SIP phone averages 538 bps.
Another benefit of SCCP when used with video is that it allows authentication and encryption of media
and signaling through Secure Real-time Transport Protocol (SRTP) and Transport Layer Security (TLS),
respectively. When encryption is used, an SCCP video phone averages 415 bps while a SIP phone using
encryption averages 619 bps.
H.323
Unlike SCCP, H.323 is not a single standard or protocol but rather a suite of protocols and
recommendations established by the International Telecommunication Union (ITU) Telecommunication
Standardization Sector (ITU-T). H.323 is very strict in the definition of its features, expected behavior,
and implementation, which puts H.323 in an advantageous position for interoperation between
telecommunication vendors and providers. Because H.323 implementation is so well defined, it leaves
very little room for misinterpretation of what is expected from the vendors when they interoperate.
H.323 uses a peer-to-peer protocol model that supports user-to-user communication without a
centralized call control element. Because of H.323 robustness, it is not uncommon to find call control
elements such as gatekeepers peered with endpoints from different vendors. As described earlier, H.323
is an umbrella protocol. An H.323 peer negotiates call setup and call admission control using H.225 and
media channels using H.245. While H.225 uses User Datagram Protocol (UDP) and TCP as transport
protocols, H.245 uses TCP only. Although this seems inconvenient for firewalls, H.323 is so well
established in the telecommunications industry that most firewall vendors can efficiently inspect H.323
packets.
Figure 4-2 illustrates the use of H.323 with a gatekeeper as the call control element.
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Call Control Protocols in IP Video Solutions
Figure 4-2
H.323 Signaling
Cisco TelePresence
System MXP Series
(H.323 endpoint)
H.323 MCU
(Cisco TelePresence
MSE 8000)
Cisco TelePresence
System MXP Series
(H.323 endpoint)
H.225 (RAS and address location)
H.225 (call setup point-t-point)
H.245 (Media channels negotiation)
Video RTP flows point-t-point
284378
H.323 Gatekeeper
H.323 provides strong support for a wide variety of video conferencing features, the most prominent of
which are application sharing and far-end camera control (FECC). H.323 endpoints use H.224 and H.281
for FECC and H.239 for data sharing. FECC and application sharing in H.323 are key architectural
differences between H.323 and other call control protocols. For instance, while SIP does not define how
application sharing should be implemented, H.323 defines it clearly through Annex Q and its
implementation of H.281 and H.224. With FECC in H.323, the camera control instructions are
embedded into H.281 and later encapsulated in H.224, and RTP therefore provides a robust approach for
transmission of the FECC instructions in the existing network infrastructure.
Application sharing is also very well defined in H.323, which uses H.239 to support it. H.239 defines
how the management and addition of extra video channels must be implemented, and then the
application video is sent over the additional video channel. Moreover, using a token system, H.239
ensures that only one participant at a time utilizes the application sharing functionality in the meeting.
Some features differ greatly between H.323 and other protocols. For example, some H.323 endpoints
implement ad-hoc conferencing, but H.323 does not specify a central call control element in its
architecture to execute conference resource tracking and establish conferences. Therefore, the ad-hoc
conferencing behavior in most H.323 endpoints requires users to dial an always-on conference bridge.
Another example of protocol differences is that H.323 defines media encryption through H.235, but the
definition of signaling encryption is not in the scope of H.323. Therefore, H.323 implementers
commonly use either TLS or Internet Protocol Security (IPsec) when they need to secure the call
signaling. This could potentially cause interoperability problems between endpoints from different
vendors that use different approaches for securing the call signaling.
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Call Control Protocols in IP Video Solutions
Although H.323 is highly evolved in its specification, H.323 features support only video and voice; they
do not extend to instant messaging, presence, or other services. The lack of support in H.323 for new
services should be thoughtfully considered when designing an IP Video network that might later
integrate more communication methods besides voice and video alone.
In addition, H.323 messages are encoded in binary, making it fairly challenging to interpret them without
an appropriate dissector and potentially resulting in little-endian and big-endian errors when
implementing the protocol messages. Although the H.323 messages are smaller than SIP messages, the
difference in bandwidth can be considered negligible.
SIP
Session Initiation Protocol (SIP) is a peer-to-peer protocol. In the simplest implementation, SIP
endpoints do not need a call control entity to contact each other, assuming they know their location.
However, SIP also defines a client/server relationship so that the endpoints can make use of services,
resources, and dialable destinations that are unknown to the endpoints. SIP is defined by the Internet
Engineering Task Force (IETF) and is conglomeration of Requests for Comments (RFCs). Although the
SIP core rules are defined by RFC 3261, the SIP standard includes more than a dozen RFCs.
In most enterprise deployments that use SIP, it is deployed with a call control element (client/server
model) to provide a feature-rich experience, control over the dialable domains, and centralization of call
control. SIP elements consist of two basic categories: user agent client (UAC) and user agent server
(UAS). The element requesting connection to another element is the UAS, while the element receiving
the request is the UAC. During a session, the same end-party can be a UAC for one transaction and a
UAS for another, and the role is limited to a single transaction.
Figure 4-3
SIP Signaling
Cisco TelePresence
Multipoint Switch
(SIP MCU-Conference Bridge)
SIP Call Signaling
Video RTP
Video RTP
Video RTP
Cisco TelePresence
System (SIP endpoint)
Cisco TelePresence
System (SIP endpoint)
Cisco TelePresence
System (SIP endpoint)
SIP Call
Signaling
M
Cisco Unified CM
(as SIP Proxy and
SIP Registrar)
SIP Call
Signaling
284379
SIP Call
Signaling
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Call Control Protocol Selection in IP Video Solutions
In many regards, SIP is better categorized as a communications session signaling protocol than a
telecommunications signaling protocol because SIP enables more than just the establishment of voice
and video communications. SIP can enable instant messaging, presence, and so forth, whereas SCCP and
H.323 are purely telecommunications protocols. Part of the strength of the SIP protocol specification to
support a myriad of services comes from the fact that UAS and UAC elements must ignore what they do
not understand or support. On occasion, however, this strength becomes one of SIP’s disadvantages
because it complicates interoperation between vendors. Furthermore, SIP is less detailed in its
specification than SCCP or H.323, making vendor interoperation somewhat challenging at times. For
example, in SIP there is more than one way to implement some features. If different vendors implement
the same feature in different ways, they would be incompatible.
It is also important to note that some features defined in other call signaling protocols are either not
defined in SIP or function differently than in the other protocols. For instance, before RFC 4353, there
was no standard to define how ad-hoc conferencing should be implemented, and SIP implementers took
different approaches to fill the void. In Cisco IP Video Telephony, ad-hoc conferencing was
implemented by creating a proprietary approach using XML.
Another example of a gray area in SIP is application sharing. Some implementers use the 'm'
(media-type) attribute to specify when application sharing media will be sent and when an additional
video channel will be set up. However, SIP does not clearly define how these features should be
implemented, which makes application sharing between SIP vendors challenging.
SIP is text-based and uses the ISO 10646 character set encoded in 8-bit Unicode Transformation Format
(UTF-8). A SIP phone averages 538 bps for call control traffic in unencrypted mode, while an SCCP
phone averages 256 bps. SIP can use either TCP or UDP. SIP implementations typically use port 5060
but SIP can also be implemented on a different port.
Call Control Protocol Selection in IP Video Solutions
Selecting the right protocol for the design of the IP video solution is crucial to its success. The wrong
choice of protocol could result in scalability issues and/or the inability of users to execute expected
features.
When selecting the call control protocol for an IP video solution or a call leg section, consider the
following factors:
•
What call features are currently needed by the users and what features are planned for the future?
(For example, data sharing, encryption, and so forth)
•
Which transport protocol (TCP or UDP) will be used? Some call control protocols are better suited
to a particular transport protocol.
•
Are network characteristics such as Network Address Translation Traversal (NAT-T) or deep
inspection (security) needed? Sometimes video endpoints might need to be behind a firewall, NAT
support might be required, or payload encryption might form part of the requirements.
•
What interoperability will be needed (for example, with third-party H.323), and what type of
endpoints and MCUs will be used? A particular call leg might include devices that do not support
the protocol selected for the overall design. For example, interoperability might be required with the
IP PBX where the audio deployment resides, and that IP PBX might use H.323.
•
Will business-to-business (B2B) communications be needed? If so, will a B2B vendor be used or
will there be a direct connection to a third-party company? If a B2B vendor is used, what call control
protocol has the B2B vendor implemented?
•
What are the application sharing requirements? For example, will H.239 be required?
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IPv6 in IP Video Solutions
The more information you can gather about the call control protocol usage and roadmap, the better the
decision making process will be. Any additional information that is specific and relevant to you solution
should be included in the criteria for protocol selection.
After gathering all the information needed for protocol selection, you can begin the selection process.
When selecting the protocol, pay particular attention to the following areas:
•
Scalability — Based on the information gathered, how much growth is expected in the IP Video
solution deployment and how will that impact the protocol selected and the call control elements in
the deployment.
•
Use cases — Based on the call flows that are meaningful for the success of the deployment and the
requirements gathered, real-world scenarios should be developed and careful studied to determine
how the protocols affect them. For example, if users are expected to share applications through the
video endpoints without access to laptops, that would reduce the protocol options to H.323 and SIP
only.
•
Customer requirements — Occasionally there might be requirements that do not fall into a clear use
case or scalability area. Depending on the importance of the requirement, it can be assigned a certain
weight for purposes of the protocol selection process.
IPv6 in IP Video Solutions
IP version 4 (IPv4) has by now exhausted all the public IP address assignments. There still is room in
the private address ranges for a large enterprise to be able to increase its operations. Nevertheless,
mobile devices are increasing exponentially the number of IP devices connecting in the enterprise, and
as that trend continues, the implementation of IP version 6 (IPv6) eventually will be necessary to
increase the number of available IP address assignments.
The risks of ignoring IPv6 and not planning ahead could range from inability to connect new devices to
diminished business-to-business capabilities. Those risks, however, are in the mid-to-long-term future,
given the fact that there are currently enough addresses for private usage.
Cisco already supports IPv6 in certain devices, such as the Cisco TelePresence C Series and Video
Communication Server (VCS), while at the same time working on integration of IPv6 into the rest of its
IP video portfolio. However, not many IP video equipment manufacturers support IPv6 at this time.
The best approach is to be prepared, know your network, and track the IP address assignments to
understand when migration to IPv6 will be necessary for your network. When deploying a new IP video
solution, ensure that the manufacturers and products you select have a clear roadmap for IPv6, and
understand how much work the migration will take so that you can plan accordingly.
If your IP video solution requires internetworking of IPv4 and IPv6 devices, the Cisco VCS currently
offers address translation between IPv4 and IPv6. For further information, refer to the documentation at
http://www.cisco.com/en/US/products/ps11337/prod_maintenance_guides_list.html
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CH A P T E R
5
Quality of Service and Call Admission Control
Revised: March 30, 2012, OL-27011-01
Data packets that make up the video streams are transmitted over the network. The packets reach their
destination based on the order in which they are placed into the queue. In a simple network behavior, the
first packet in is the first packet out. For a single LAN switch this process is fairly simple because the
switch will have some ports that are sending the media and some that are receiving it. As the network
grows, the scenario changes from being an ideal world of ordered packets to a mass of unordered
packets, where there are more packets being generated at the same time than can be sent through network
links that do not have sufficient capacity to handle the load. In these real-world scenarios, some methods
are needed to control the flow of packets across the network links.
Quality of Service (QoS)
Quality of Service (QoS) is used to identify certain types of packets that can be processed ahead of
others. The QoS information is inserted into the packets that need a different priority.
QoS can be compared to a freeway system and the vehicles that use it. The network is similar to the
freeway system, which provides the vehicles (data packets in the case of QoS) with a way to travel from
their starting point to their destination. As long as the freeway has sufficient lanes and there is no
incident, traffic flows smoothly in most cases and the travel time is acceptable to most users. However,
during peak traffic times, things might not be as good. Carpool lanes can help. Cars that meet certain
criteria have the privilege to use the carpool lanes and bypass the traffic congestion. In addition,
emergency services such as ambulances have an even higher priority to bypass other traffic. On the other
hand, large or heavily loaded vehicles might use more lanes and can slow down traffic. QoS is similar
in that it allows certain packets to have preferred access to the network and to be transmitted ahead of
other packets in the queue.
Traditionally IP Precedence or Type of Service (ToS) (RFC 791) was specified using three bits in the IP
packet. The Differentiated Services (DiffServ) (RFC 2474 and RFC 2475) model uses six bits and also
maintains the IP Precedence values. The DiffServ model uses assured forwarding (RFC 2597) that
defines various classes of traffic with a drop probability and expedited forwarding (RFC 2598) to
provide for low loss, low latency, and low jitter service. The class in assured forwarding is used to group
different types of traffic, and the drop probability is used to group the traffic that will experience dropped
packets last. The expedited forwarding is used for traffic such as voice that is sensitive to packet drop
and delays.
Each type of traffic can have a different QoS value, and the network then provides preference when it
identifies packets that have a higher QoS value. Table 5-1 lists some of the standard values used for
various types of voice and video traffic.
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Quality of Service (QoS)
Table 5-1
Differentiated Services Code Point (DSCP) Values for Various Types of Traffic
Traffic Type
Layer 2 Class of Service Layer 3 IP Precedence
Layer 3 DSCP
Call signaling
3
3
CS3 (24)
Voice
5
5
EF (46)
Video
4
4
AF41 (34)
TelePresence
4
4
CS4 (32)
Voice calls have only one stream of packets. Video calls have two streams, one for video and another
for voice, and it is important for both streams of the call to have the same QoS marking.
Cisco Unified Communications Manager (Unified CM) supports endpoints that mark QoS for their
media packets. Voice packets are marked as EF (DSCP value 46), while video devices mark media
packets as AF41 (DSCP value 34) and TelePresence endpoints mark their traffic as CS4 (DSCP value
32). All call signaling is marked as CS3 (DSCP value 24).
QoS should be configured on the Cisco TelePresence Video Communication Server (VCS) because it
processes the media and the call signaling. The endpoints that register to the VCS (such as the Cisco
TelePresence System EX Series, C Series, Cisco IP Video Phone E20, or others) should be configured
so that the call signaling uses DSCP CS3 and the media from those endpoints is marked as DSCP AF41.
Trust Boundary
Traffic on the network needs to be marked so that the network can trust it. The network elements such
as the switches can be the trust boundary based on the switch that trusts the packets. It is important to
establish a trust boundary so that the rest of the network does not have to remark packets for QoS. Access
switches can trust IP phones based on association with them. Cisco switches use Cisco Discovery
Protocol (CDP), a Layer 2 protocol, to associate phones with the switches. The switches use CDP to put
IP phones in their respective voice VLANs. Access switches can then trust such phones for marking their
packets with appropriate QoS and thus establish a trust boundary. When IP phones cannot be associated
with the switch or when the trust boundary needs to be the access or distribution switches, the switch
can build the trust boundary by enforcing the marking of packets based on criteria such as the IP
addresses of the devices or the common ports used for signaling or media for calls.
Packet Queuing
While QoS helps the network distinguish different types of traffic and then prioritize it, the network uses
a queuing mechanism to orderly move packets and control their flow. Queuing is widely used for
networks that have low-capacity links between them, such as MAN or WAN networks.
Networks use the following common queuing mechanisms:
•
First In, First Out (FIFO)
This type of queuing is simple and gives the same preference to all packets based on the time they
arrive in the queue. The packets are sent out through the switch or the network in the same order
they arrive. This type of queuing is useful in networks that do not see a large change in the volume
of packets.
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Quality of Service and Call Admission Control
Call Admission Control
•
Priority Queuing (PQ)
This type of queuing gives preference to packets with higher priority over packets with lower
priority. The Priority Queue is commonly used for low-bandwidth traffic that is very sensitive to
delay, such as voice calls.
•
Weighted Fair Queuing (WFQ)
This type of queuing uses multiple queues for priority and non-priority traffic. It provides for
priority traffic without starving lower-priority traffic. This mechanism is used where networks have
traffic that needs priority (such as voice traffic) as well as other important traffic such as business
applications that should not be dropped.
•
Class-Based Weighted Fair Queuing (CBWFQ)
This type of queuing uses different classes to group traffic and then uses the WFQ mechanism while
also providing dedicated bandwidth for some custom queues. This type of mechanism is used widely
for interactive voice and video traffic when combined with business applications. This mechanism
provides the advantage of flexibility for various types of enterprise deployments.
Queuing mechanisms provide Class of Service (CoS) for packets in the organization. The class of service
is used to guarantee latency, jitter, and delay requirements. It also uses the link bandwidth more
efficiently so that organizations can estimate the traffic they can send through their WAN links or plan
their links to support desired traffic.
Policing traffic is important to prevent certain queues from using all the bandwidth. Policing prevents a
certain type of traffic from exceeding its set use limit through a link. Traffic shaping and policing is
needed to avoid packet drops and to allow servicing of non-critical traffic.
With video calls it is important for both the video and voice streams of the call to be sent through the
same queue in order to avoid lip-sync issues. When the video and voice streams use different queues,
one arrives later than the other and causes the video to be shown while the voice associated with that
video may lag, or vice versa.
Call Admission Control
To ensure that the voice and video traffic does not use all the bandwidth in the link and cause other
important data such as business applications to experience dropped packets, organizations can use calls
admission control. Call admission control limits the number of calls allowed through a particular link
between sites.
There are two main methods for limiting the number of calls on a link:
•
Call counting — With this method, the call control agent counts the number of calls allowed
between locations. Only calls of the same type are counted together, so a set voice codec and a set
video codec make counting such calls easy.
•
Bandwidth — This method is similar to call counting, but here the count consists of the amount of
bandwidth used by the calls. The type of voice codec and the type of bandwidth for video calls are
used to count the bandwidth.
Preserving the call quality is important. When calls traverse WAN links, oversubscribing the link can
cause call quality to degrade. Call admission control is important because it can prevent calls from filling
up the link. When routing calls, call control agents know if a call should be allowed or if the link cannot
handle that call. This provides a consistent call experience to users.
Cisco Unified CM supports call admission control using the bandwidth method, so calls with different
codec types and video bandwidth types can be supported on the enterprise network. Unified CM uses the
mechanism of regions to specify per-call parameters for codec and video bandwidth. Unified CM also
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Call Admission Control
uses the mechanism of locations to specify the bandwidth value used to limit voice and video calls for a
particular site. Cisco TelePresence VCS uses similar mechanisms, where Links set the per-call
bandwidth and Pipes set the bandwidth for calls to a site.
Call counting and bandwidth methods for call accounting use static configured values, but the actual call
may use less or more bandwidth. To find the actual bandwidth used for calls, Resource Reservation
Protocol (RSVP) is used. This protocol looks at the actual path used by the media to determine if
sufficient bandwidth is available for a call. When a device in the path does not have the bandwidth to
service the call, that condition gets reported through RSVP and the call might not be allowed.
Cisco Unified CM uses a separate media device called Cisco RSVP Agent to negotiate the network
bandwidth, using RSVP on behalf of the video endpoints. This allows for a more accurate accounting of
calls through it.
TelePresence calls do not use call admission control because the network is designed to allow the needed
traffic so as to guarantee the user experience through such technologies. TelePresence traffic is marked
differently than voice and video; thus, it can be queued separately and can provide low latency and delay,
thereby preserving the user experience.
When there is more than one call control agent in the organization, each agent does its own call
admission control. They work in parallel and do not know about calls through each other. If a call occurs
between two different call control agents at the same site, both agents may count the bandwidth for that
call even though it does not use any WAN bandwidth. Therefore, it is important to have only one call
control agent doing call admission control for the devices in the organization.
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Dial Plan
Revised: March 30, 2012, OL-27011-01
Land-line and cell phone users dial a number to reach each other. Number-based dialing is commonly
known as E.164 or PSTN dialing. PSTN numbers have various components such as country codes, area
codes, and the destination. PSTN service providers then resolve the dialed numbers as local, long
distance, or inter-country numbers and connect the two parties. Similarly, organizations use prefixes
such as 9 or 0 for an outside dial tone to differentiate services. Users dial this prefix and then the number
they wish to call. Dialing internal numbers within an organization may also use prefixes so that users
can dial short numbers and not the entire E.164 number. Some organizations use an abbreviated dial
plan, where users in the organization dial a 4 or 5 digit number to reach their colleagues within the same
company.
This forms the basis of the dial plan that connects various enterprises, mobile networks, and the PSTN
so that people on the respective networks can reach each other. Organizations that are conscious of costs
of long distance or international calls can use a numeric dial plan to restrict calls and allow only certain
users to dial long distance or international. Similarly, organizations need to have the ability to block
unwanted calls such as calls from telemarketing agencies. Organizations should also consider ways to
prevent toll fraud when using a number-based dial plan.
Modern Internet communication has been popular since the introduction of e-mail. E-mail addresses
provide a way for users to be identified uniquely and are now the new identity. This identity can be used
to reach users when they are represented as Uniform Resource Identifiers (URIs). Instant messaging for
people to chat with each other uses URIs, and Voice over IP (VoIP) can also use URIs to send calls. The
format for a URI is <user-id>@<domain-name>. This format is simple for users and generally easier to
remember than a number.
An advanced system is needed to locate the entity represented by the URI, so that calls can be routed to
it or the device using it. The system must be able to identify the domain and the servers that represent
that domain, as well as being able to service calls. At a minimum, external dependencies such as Domain
Name System (DNS) need to be considered. Various VoIP protocols such as H.323 can use Electronic
Numbering (ENUM) for this purpose, but this method is not widely used. SIP has made URI dialing
more popular due to its origins in web technologies. While different types of dialing methods offer users
and enterprises a flexible way to route calls and provide reachability, they require some method to
provide good translations between the systems that provide these different types of dialing experiences
for users.
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Dial Plan
Dial Plan Dependencies
Dial Plan Dependencies
When discussing the wide reach of the PSTN, it is important to understand the dependencies of the dial
plan:
•
E.164-based dial plans can use a variable number of digits. Service providers and telephony systems
should be able to accommodate variable-length dialed numbers, and users should be used to dialing
those numbers. If there are different lengths of dialed numbers, the way the service provider handles
them will be different than how an organization would handle them. Service providers need to
normalize the numbers for caller ID, while the organizations have to normalize the numbers for
direct inward dialing (DID) or for a country-specific dial plan and thus might have to transform the
calling or called numbers.
•
Connecting a voice and video system to the rest of the world requires PSTN or IP connectivity to
call other devices and to be reachable. IP-based systems need connectivity to the external networks
and may use direct peering or some other mechanism to resolve the dial plan through the IP network.
•
IP-based networks need different mechanisms to resolve dial plan between them.
– Electronic Numbering (ENUM) is used for number-based calling. ENUM provides a way to
translate an E.164 number to a corresponding IP address. The service is provided by a ENUM
server. Subscription to the service and network connectivity are needed, and DNS services are
also needed.
– DNS Service (SRV) is used for systems supporting URI dialing. The DNS SRV records provide
domain name information as well as information on call services such as H.323 or SIP protocols
and UDP or TCP types and additional parameters that are useful for call agents. Call agents then
use this information to send calls to hosts.
•
A single user may have more than one endpoint or device. In such cases the dial plan should be able
to reach all of the user’s devices when a single number or URI is dialed. Therefore, number-based
systems should support shared lines and URI-based systems should support alias.
Number-Based Dial Plan Networks
Numeric dial plan systems are more widely deployed. PSTN and H.323 systems use numbers to reach
endpoints. PSTN and IP PBX systems own their dial plan and assign numbers to their endpoints. The
H.323 network gets the dial plan from the endpoints because the endpoints own the dial plan and share
it with the system so that calls can be routed. Exact or most significant match of dialed digits is used to
resolve the dial plan for such systems.
The emergency services network such as the E.911 network in the United States is another type of
system that uses numeric dialing. Numeric dialing is used not only to reach the services but also to reach
the callers, so that additional information associated with the location of the caller can be used to provide
the emergency services.
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Dial Plan
URI-Based Dial Plan Networks
URI-Based Dial Plan Networks
Software-based video endpoints make it easy to dial URIs. Most applications make it even easier by
providing the click-to-call feature. The ease of dialing based on e-mail IDs is very appealing to users.
Most deployments use a common directory service such as Lightweight Directory Access Protocol
(LDAP) to reference a common identity system that provides e-mail IDs for users to dial each other.
Therefore calling outside of the organization’s LDAP system has external dependencies.
DNS provides information on domains so that calls can be routed using domains, similar to instant
messaging systems. DNS is the most common system that is widely used for business-to-business
communications as a common network where information on how to connect to the organizations is
available, so that organizations can make external calls to each other.
Call Resolution with Dial Plans
Call agents use the dialed information to make decisions about how to route calls. Common ways of
processing numbers for calls use the best match for the digits or the most significant match of the routes
that the call agent handles. Endpoints have unique E.164 numbers. Call agents can identify the
country-specific information or the prefix information and then make decisions to send calls to
respective endpoints or to neighbors who service those dialed numbers. Call agents also need to resolve
calls for emergency services and for local calls, so that calls can then be sent to local gateways. In the
case of numeric dialing, the concept of local area codes serves as a way to identify calls that need to be
sent to local resources or to systems that are not local.
Registering devices with URIs also provides uniqueness for users. Call agents can then identify the
destination based on the URI. Multiple servers across multiple locations can service a domain, and
therefore the call agents must be able to resolve the domain and then the server that has the registration
for a given URI. If a destination location is not available, other methods will be needed for making
decisions to resolve calls for emergency services, local IP trunks, or hop-off gateways. In addition, call
agents that need to route with URIs for conferencing services should be capable of choosing the
conference bridge closest to the participants.
PSTN Access
Communicating to the rest of the world means that there should be an interface to the PSTN and the IP
network. Gateways that connect to the PSTN through ISDN provide for voice connectivity to the PSTN.
The gateways provide key functions of normalizing calling and called numbers when interfacing with a
numeric-based PSTN network. Toll fraud prevention should be used for PSTN gateways.
Border elements or IP gateways provide connectivity to an IP-based PSTN either through the service
provider or through the public Internet. The gateways provide topology hiding for the internal IP
networks and normalization for calls. The gateways need to have additional security measures to prevent
denial-of-service attacks and attempts to compromise them.
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Transformations
Transformations
Call agents perform transformations on the dial plan by transparently changing the calling and called
numbers to normalize information of the callers. Transformation is a key function of call agents to
standardize user information for calls. It is also important for relaying information for calls that are not
answered, so that users can then dial back to the callers once they have time to make the calls.
Organizations use transformations to mask their caller IDs or to present callback information to a generic
and standardized format. For PSTN calls, organizations use their public numbers for outgoing calls
rather than expose the internal numbers of their users. URI-based systems use transformations to
normalize calls within their domain and for calls from external organizations.
Some organizations also use DID to oversubscribe internal users to their external ISDN lines. This gives
the organization a way to provide endpoints to all its users while choosing appropriate lines for external
calls. With URI registration, the concept of oversubscription is limited to the capacity used by calls
rather than the number range of the endpoints.
Dial Plan Manipulation
Changing various aspects of the caller or called-party information at various system elements is done to
assist call routing. Caller information needs to be manipulated so that information presented to the caller
or called party is normalized. It also is useful if the call goes unanswered and the user needs to reference
information on missed calls or received calls. In the case of numeric dial plans, these goals are simple
to address; however, for URI dialing the call agent must have mechanisms to achieve the desired goals.
Call agents may manipulate caller information to perform call resolution. Call agents can choose to add
area codes to change numbers to E.164 format and then route them. Providing such manipulation may
require basic pattern matching and replacement functionality. In the case of URI dialing, normalizing
the domain may be used so that call agents can process the URI. To provide searching and replacement
of alphanumeric content, a more elaborate method using regular expressions is needed. Regular
expressions provide greater flexibility for alphanumeric URI formats, but they might not be as simple
as numeric dial plan manipulation.
Classes of Restrictions
Organizations typically want to allowing some users to have access to certain services while denying
other users access to those same services. The most common cases are for long distance and international
dialing restrictions. While restrictions on calls and callers are easy to implement and deploy based on
caller number or called number, those restrictions can be complex for URI dialing. Restrictions can also
be used to prevent calls to toll-free destinations or from telemarketing agencies. Numeric dial plans can
use know number ranges, such as 1-888 collect call numbers, to block calls. With URI dialing, this can
be a challenge because restricting calls based on URIs requires a list of restricted URIs that need to be
configured through the call agent to define a class-of-restriction policy for calls.
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Deployment Guidelines for Video Networks
Revised: March 30, 2012, OL-27011-01
When deploying a video network, it is imperative to design, plan, and implement the video network in
a way that provides the best user experience possible. Video is an application subject to the perceptions
of the various parties during a call. If one of the video users in a meeting or collaboration effort does not
have a satisfying experience, that perception can easily be transferred onto the rest of the attendees.
The following sections offer general guidelines for designing video networks:
•
Planning a Deployment Topology for Video, page 7-1
•
Allocation of Video Resources, page 7-10
•
Creating a Video-Ready Network, page 7-14
•
Integration with Standalone Video Networks, page 7-19
Planning a Deployment Topology for Video
When deploying video applications, it is fundamental to identify and plan the topology or topologies that
are deployed or that should be deployed to cover the needs of the organization. Current video
applications use the following main video deployment topology models:
•
Intra-Campus, page 7-2
•
Intra-Enterprise, page 7-3
•
Inter-Enterprise (Business-to-Business), page 7-4
Video applications also use the following main call processing models:
•
Single-Site Call Processing, page 7-5
•
Multi-Site Call Processing, page 7-5
•
Hosted Call Processing (Video as a Service), page 7-7
The following sections provide an overview of these deployment models as well as guidelines for
choosing a call processing model and topology.
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Planning a Deployment Topology for Video
Intra-Campus
An intra-campus topology for video is limited to offering video throughout a single company site or
campus. This topology model is better suited for companies that require increased meeting effectiveness
and productivity without requiring the users to move throughout the facilities. The intra-campus video
deployment model can be used in conjunction with the intra-enterprise and inter-enterprise topology
models to meet the needs of the organization. Figure 7-1 depicts an intra-campus topology using
single-site call processing.
Figure 7-1
Intra-Campus Deployment with Two Buildings (Everything in One Building Except
Video Endpoints)
Campus Building A
Campus Building B
Video
Endpoint
284810
Video
Endpoint
Campus
Access
Campus
Distribution
Campus
Core
Campus
Distribution
Campus
Access
With respect to call processing, the single-site and hosted call processing models are a better fit for
intra-campus video topology models. Deciding between the two depends greatly on the endpoint density,
planned growth, features required, and cost.
For instance, hosted video call processing deployment models offer a very feature-rich experience with
a low cost investment. However, certain local multipoint call flows might require the media streams to
travel outside of the premises when embedded video resources are not available or when their capacity
is exceeded, and therefore the bandwidth-to-cost relationship becomes a crucial factor as user density
increases.
On the other hand, a single-site call processing model has a higher initial investment because features
require either hardware or software licensing for them to be available. Nevertheless, the single-site call
processing model allows for user growth with a lower cost ratio after it has being deployed.
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Planning a Deployment Topology for Video
Intra-Enterprise
An intra-enterprise topology for video enables more than one site within the same company to use video
applications through the WAN. The intra-enterprise deployment model is suitable for businesses that
often require employees to travel extensively for internal meetings. Deploying video within the
enterprise not only improves productivity by saving travel time and providing feature-rich collaboration,
but it also reduces travel expenses. Furthermore, the overall quality of work and life is often improved
when employees have to travel less.
To enable video across multiple sites, the intra-enterprise topology must make use of high-speed
supporting WAN links to provide a rich video experience. For details about dimensioning the WAN
links, see Scalability and Performance, page 7-16.
Figure 7-2 illustrates an intra-enterprise topology that uses a multi-site call processing deployment
model.
Figure 7-2
Multiple Sites with Distributed Multi-Site Cisco Unified Communications Managers
Remote Campus
Headquarters
Private WAN
MPLS VPN
Video
Endpoint
Metro
Ethernet
284811
Video
Endpoint
Video
Endpoint
Headquarters
Campus
Branch
Intra-enterprise deployments can use either multi-site or hosted call processing deployment models. As
with intra-campus deployments, the same considerations apply when deciding between the two call
processing models.
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Planning a Deployment Topology for Video
Inter-Enterprise (Business-to-Business)
The inter-enterprise network deployment model not only connects video endpoints within an enterprise,
but also allows for video endpoints within one enterprise to call systems within another enterprise. The
inter-enterprise model expands on the intra-campus and intra-enterprise models to include connectivity
between different enterprises. This is also referred to as the business-to-business (B2B) video
deployment model.
The inter-enterprise model offers the most flexibility and is suitable for businesses that often require
employees to travel extensively for both internal and external meetings. In addition to the business
advantages of the intra-enterprise model, the B2B topology deployment model lets employees maintain
high-quality customer relations without the associated costs of travel time and expense.
Figure 7-3 depicts two companies communicating with each other through an inter-enterprise topology
and single-site call processing.
Figure 7-3
Inter-Enterprise (B2B) Deployment with Single-Site Call Processing at Each Company
Company B
Company A
Private WAN
MPLS VPN
Metro
Ethernet
Headquarters
Campus
284812
Video
Endpoint
Video
Endpoint
All three call processing models can work with the inter-enterprise deployment model, and the same
considerations apply as with intra-campus and intra-enterprise deployments.
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Planning a Deployment Topology for Video
Single-Site Call Processing
A single-site call processing model confines call processing to service a single site, and the call
processing agents are in the same location as the serviced endpoints. Whatever the distance is between
the call processing agent and the endpoints, it should be serviced by LAN speed links. The single-site
model is suitable for medium-sized businesses and government operations that reside at one site and that
have basic video call processing needs, but where growth might be explosive or where the user density
is very high, thus making the bandwidth-to-cost ratio of a hosted solution prohibitively expensive.
Figure 7-4 depicts an intra-campus topology using single-site call processing.
Figure 7-4
Intra-Campus Deployment with Two Buildings (Everything in One Building Except
Video Endpoints)
Campus Building A
Campus Building B
Video
Endpoint
284810
Video
Endpoint
Campus
Access
Campus
Distribution
Campus
Core
Campus
Distribution
Campus
Access
Multi-Site Call Processing
In a multi-site call processing model, the call processing agents can all be at the same location
(centralized multi-site call processing) or distributed across various locations where high video user
density exists or where service is critical and a backup is required.
Within the same call processing agent cluster, multi-site call processing can service a variety of
topologies (for example, hub-and-spoke and multiple-hubs-to-spokes topologies) using either a
centralized or distributed multi-site call processing model. Figure 7-5 illustrates a distributed call
processing model where a multi-site call processing deployment services a large central site and multiple
remote or branch sites, with the home office sites or smaller branches depending upon the larger ones
(multiple hubs to spokes) for call processing services.
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Planning a Deployment Topology for Video
Figure 7-5
Distributed Multi-Site Call Processing
Remote Campus
Cluster A
Cluster B
Video
Endpoint
Headquarters
Branch
Private WAN
MPLS VPN
Video
Endpoint
Metro
Ethernet
Video
Endpoint
Video
Endpoint
Branch
Video
Endpoint
Branch
284813
Video
Endpoint
Branch
The multi-site call processing model also includes deployments where clustered call processing agents
interact with other clustered call processing agents through a call processing element deployed for the
sole purpose of aggregating the call routing between the clusters. Deploying an aggregating call
processing entity is advantageous because it eliminates the need to implement full-mesh connectivity
between all the call processing clusters. Instead, the various leaf clusters engage with the aggregating
call processing element when the leaf clusters communicate with each other. If the dial plan is
implemented correctly to provide hierarchy and allow for increasing the capacity of the overall solution,
no dial plan updates are needed in the leaf clusters when new leaf clusters are added.
Figure 7-6 illustrates two examples of multi-site aggregated call processing deployments, one using
Cisco Unified Communications Manager Session Management Edition (SME) the other one using a
Cisco TelePresence Video Communication Server (VCS) as a directory gatekeeper.
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Planning a Deployment Topology for Video
Two Examples of Multi-Site Aggregated Call Processing Deployments
Unified CM
Cluster A
Unified CM
Cluster B
M
M
M
M
Unified CM
Cluster C
M
M
M
M
Note
M
Directory
VCS
M
M
Unified CM
Cluster D
M
VCS B
M
M
Unified CM
SME
M
M
VCS A
M
M
M
M
VCS D
VCS C
284814
Figure 7-6
Although H.323 gatekeepers do allow the concept of a cluster (alternate gatekeeper), a single gatekeeper
is also considered as a clustered call processing agent for purposes of the above discussion because
H.323 gatekeepers are self-deterministic call routing entities.
Hosted Call Processing (Video as a Service)
Hosted deployment models refer to services provided and managed from the cloud. The offering is
compelling because of the lower cost of ownership (low investment) and feature-rich experience it
provides. Hosted video solutions are aimed at mid-sized and smaller businesses, providing them with an
affordable entry point into the world of enterprise-grade video, and some hosted solutions also provide
a migration path that protects the original investment as the business grows.
In this deployment model, more than just the call processing elements are often off-premises, thus
requiring that the video streams travel off premises in some multipoint call flow scenarios. In these
cases, higher user density in a service location will require higher bandwidth to service them.
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Planning a Deployment Topology for Video
Guidelines for Choose a Call Processing Topology and Video Endpoints
Choosing the right elements and deployment models to implement or expand a video network is
instrumental for ensuring that the desired features, performance, and scalability are achieved. Moreover,
choosing the wrong elements and models for the video network can result in costly changes to provide
the functionality that the organization requires.
The following sections provide general guidelines for selecting the elements and deployment models for
a video network:
•
Call Processing Model and Call Processing Agent Selection Guidelines, page 7-8
•
Endpoint Selection Guidelines, page 7-9
•
Design Considerations for Video Networks, page 7-9
For information about call signaling protocol selection, see the chapter on Call Control Protocols and
IPv6 in IP Video Solutions, page 4-1.
Call Processing Model and Call Processing Agent Selection Guidelines
To choose the correct call processing agent and its deployment model and topology, it is important to
consider the following points in addition to the requirements of the organization during the design phase
of the deployment:
•
What features are needed to fulfill the use cases for the success criteria of the deployment? For
example, SIP, SRTP, BFCP, or IPv6 video support.
•
Are any video endpoints already deployed in the network that will have to be serviced? Are there
requirements for previous video endpoints that have to be serviced by the newly selected call agent,
interoperation with a previous video network, and so forth?
•
If there are any previous video elements to be included in the deployment, what protocols do they
use or can they use? For example, multi-protocol endpoints (SIP and H.323) or single-protocol
endpoints.
•
Has the call control protocol been selected? If not, are there any features dependent on a particular
call control protocol? For example, H.239 can be used only in conjunction with H.323.
•
What are the locations that will need video service? What is their user density? How critical will
redundancy be for each particular location? It is advisable to provide a call agent for redundancy
purposes at each site that has a high user density (distributed call processing). A very high user
density will also create challenges (internet bandwidth usage) under certain call flows for hosted call
processing.
•
Will protocol interworking be used? Interworking will significantly influence the placement of the
call agents under certain circumstances because the media stream might have to traverse the call
processing agent in order to reach its destination.
•
What is the maximum number of video calls you expect to service? A single Cisco TelePresence
Video Communication Server (VCS) 7.0 has a limit of 500 non-traversal calls. Beyond that, a
second VCS is needed (in a cluster or standalone) to service the rest of the calls.
The outcome of these considerations, coupled with the customer requirements, product data sheets, and
product release notes, will determine which call processing agent to select and which call processing
model and topology to use. For example, if the requirements include the use of BFCP as an application
sharing technology and service for a maximum of 2000 calls, then a VCS cluster would be the best
choice.
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Planning a Deployment Topology for Video
Endpoint Selection Guidelines
Selecting the right endpoints for the job is just as important as selecting the call processing agent. In
addition to the customer requirements, the following points help determine the selection:
•
What call control protocol will be used, H.323 or SIP?
•
Will embedded video resources be needed for video conferencing? If so, Cisco TelePresence
System EX90 would be a suitable choice.
•
What video resolution formats will be required? For example, HD 720p.
•
What other endpoints will be engaged in a call with the given endpoint(s) being selected? For
example, Cisco Unified IP Phone 9971.
•
What application sharing technologies will be needed? For example, BFCP over UDP.
•
What are the mobility requirements? Will this endpoint be a mobile endpoint (collaboration tablet)?
The outcome of these considerations, coupled with the customer requirements, product data sheets, and
product release notes, will determine which endpoints to select.
Design Considerations for Video Networks
When designing a video network, it is important to consider the implications of interworking. Depending
on the call processing agent selected, the media streams might have to traverse the call agent when
interworking is used. Therefore, interworking might have a negative impact on bandwidth usage if the
call processing agent is remote to the endpoints engaged in the call because the call would not flow point
to point.
Additionally, although DNS SRV records are typically for scalability purposes (the number of SIP
trunks required to integrate a system is reduced when using SRV records), call processing agents behave
differently with regard to endpoint registration and call processing peering when it comes to the use of
DNS SRV records. These differences can create unexpected conditions when integrating different call
agents if the behavioral differences are not understood prior to the integration.
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Allocation of Video Resources
Allocation of Video Resources
Whether servicing one or many physical locations, there are a number of considerations that need to be
weighed to determine the best network locations for the video resources. Video resources can be either
dedicated or embedded. Embedded video resources lie inside of the endpoints and service calls only for
the endpoints that contain those resources. Dedicated video resources, on the other hand, reside in
appliances separate from the endpoints, and they service any endpoints that have access to those
resources.
Correct distribution of the video resources is necessary to achieve the desired level of user experience
and, more often than not, the right level of redundancy and availability. The more factors you take into
consideration, the more reliable your determination will be for the locations of the video resources. The
following factors should be integrated into the decision making process to determine the best allocation
model and locations for the video resources:
•
Branch available bandwidth
•
Bandwidth cost
•
Remote video resource cost
•
Usage patterns at headquarters and remote sites
•
Call agent bridge selection algorithm
•
Type of video resources
The following basic models can be used to allocate dedicated video resources in a deployment:
•
Centralized Video Resource Allocation, page 7-10
•
Distributed Video Resource Allocation, page 7-13
You can also combine embedded video resources with these models for dedicated video resources to
form a hybrid model, if needed, to fit the necessities of your video solution more precisely.
Centralized Video Resource Allocation
Centralized resource allocation should be considered when the combined costs of placing the resources
in the same location are less than distributing them. The feasibility of a centralized resource allocation
should also be considered. For example, not all scenarios will be suitable for a centralized resource
architecture if the concentration of the resources induces an undesirable condition on the endpoints (for
example, unacceptable jitter).
As previously stated, the factors listed in the section on Guidelines for Choose a Call Processing
Topology and Video Endpoints, page 7-8, should be integrated into the decision making process to select
the best approach to fit a given scenario. For instance, consider the scenario depicted in Figure 7-7.
Although at first it might seem less costly to concentrate all the video resources in the headquarters, such
resource concentration would create the side effect of increasing the bandwidth requirements for the
WAN links between the hub and spokes. Furthermore, multipoint conference capacity would be limited
in the remote sites by the bandwidth provided in the WAN links.
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Allocation of Video Resources
Figure 7-7
Hub and Spoke Network with Centralized Dedicated Video Resources (No Embedded
Resources)
Video endpoints
without embedded
resources
VCS
Video endpoints
without embedded
resources
284815
MCU
Video endpoints
without embedded
resources
In general, centralized video resource allocation architectures are better suited for scenarios where not
many remote endpoints exist and their remote location and bandwidth usage does not induce undesirable
effects on the media streams to be transported in the WAN links.
A modification to the previous scenario is presented in the hybrid example in Figure 7-8, in which
embedded video resources are located at the remote sites. In this scenario, the centralized dedicated
video resources would be utilized only when a video conference involves a video endpoint without
embedded resources in the central location or when the number of participants in the video conference
exceeds the capacity that the embedded video resources can handle.
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Allocation of Video Resources
Figure 7-8
Hub and Spoke Network with Centralized Dedicated Video Resources and Embedded
Video Resources at the Remote Sites
Video endpoints
with embedded resources
(for example, EX90)
VCS
Video endpoints
with embedded resources
(for example, EX90)
284816
MCU
Video endpoints
with embedded resources
(for example, EX90)
Many other scenarios are possible, and therefore different strategies and/or restrictions can also apply
to the centralized video resource approach.
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Allocation of Video Resources
Distributed Video Resource Allocation
Distributing the dedicated video resources throughout various locations has several advantages; chief
among them are the WAN link bandwidth savings and less likelihood of inducing undesirable effects on
the media streams (since many of them are locally terminated). However, a distributed allocation also
has some limitations. For example, certain video calls still have to traverse the WAN links, and these
streams are still limited by the WAN link properties.
Cost effectiveness of the solution can be maximized by considering the following points when
determining whether or not to deploy distributed dedicated video resources:
•
What is the expected video call utilization pattern at the location(s) of the video resources?
•
Can the current bandwidth of the WAN link(s) support the expected usage pattern(s) of the remote
location(s) without inducing undesirable effects in the video streams?
•
Will the limitations or effects (if any) of the media transmissions over the WAN links be acceptable
for the intended use cases?
•
Would using distributed embedded video resources satisfy the planned use cases?
•
Will the video solution be able to grow adequately without distributed dedicated video resources,
given the current and planned network topologies?
Additionally, when using a distributed allocation for dedicated video resources, it is important to
understand the bridge selection algorithm of the call control elements in order to decide where best to
locate the video resources. For instance, the dedicated video resources might be reserved based on the
time zones of the endpoints and the resources. Other alternatives involve video resource reservation
based on video location or manual reservation. In any case, the importance of understanding the
selection algorithm derives from the need to understand where the streams are ultimately terminated in
order to distribute the video resources more efficiently.
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Creating a Video-Ready Network
Creating a Video-Ready Network
Video brings significant benefits for businesses, such as superior collaboration, lower travel costs, and
personalized advertisements. However, video applications also introduce additional challenges for the
underlying network infrastructure and IT departments. For instance, how does one configure the network
for video? How should IT departments prioritize and scale video? How do they protect other applications
from being swamped by high-bandwidth video streams? To support these enterprise video applications,
a tightly controlled network foundation providing the following services is required:
•
Optimized Video Delivery, page 7-14
•
Security of Video Applications, page 7-16
•
Scalability and Performance, page 7-16
Optimized Video Delivery
For video to be an efficient collaboration tool, the user experience must be of high quality. To ensure
the user experience quality, the video delivery must be optimized to meet the organization's
requirements. The following sections offer guidelines on how to optimize the video delivery:
•
Quality of Service (QoS), page 7-14
•
Content Sharing Technologies, page 7-15
•
Reliability, page 7-16
Quality of Service (QoS)
The first step in optimizing the delivery of video is to identify the traffic of interest and to apply a
differentiated Quality of Service (QoS). QoS helps the organization to provide application intelligence
to differentiate between business-critical and noncritical video streams, and to keep the latency, jitter,
and loss for selected traffic types within an acceptable range. Furthermore, priority queuing should be
used over other queuing mechanisms whenever possible to provide a better video experience. In the case
of multiple video applications on converged networks (TelePresence and IP video telephony combined
in the same network), Cisco recommends differentiation of QoS classes per application.
Figure 7-9 depicts an example of multiple IP video applications and IP voice converging in the same
network. In this example, immersive video, videoconferencing, video-on-demand, and voice over IP are
identified and assigned the recommended QoS markings to provide the required service level, thus
avoiding over-provisioning or overlap of applications in the queues.
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Creating a Video-Ready Network
Figure 7-9
Recommended QoS Traffic Markings in a Converged Network
Campus
Immersive
video unit
Immersive
video unit
CS4
Video
IP phone
Video Portal
Client
Streaming
Server
Encoder
AF41
AF31
AF31
Video
IP phone
AF31
CS3
IP
IP phone
Web Server/
Content
Repository
EF
IP phone
Pre-recorded Content
Live Content
284817
IP
For more information about QoS in video solutions, refer to the chapter on Quality of Service and Call
Admission Control, page 5-1.
Content Sharing Technologies
Depending on the endpoints being deployed as part of the video solution, it is important to consider the
content sharing standards supported and required by the video endpoints and how they will converge or
interoperate if necessary. There are currently three main content sharing technologies used by IP video
solutions: Binary Floor Control Protocol (BFCP), H.239, and auto-collaborate. H.323 endpoints make
use of the H.239 standard to provide the content sharing functionality, while SIP endpoints may use
auto-collaborate or the newer standard BFCP.
For information about presentation sharing and content sharing technologies, refer to the Cisco
TelePresence Interoperability Deployment Guide, available at
http://www.cisco.com/en/US/products/ps8332/products_device_support_tables_list.html
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Creating a Video-Ready Network
Reliability
The performance and availability of a video-ready campus must be monitored pro-actively and measured
across the network. Alternate paths in the case of failure should also be offered to ensure the reliability
of the video solution. For information about how to design highly available networks, refer to the
Campus Network for High Availability Design Guide, available at
http://www.cisco.com/en/US/solutions/ns340/ns414/ns742/ns815/landing_cHi_availability.html
Security of Video Applications
Whenever possible, a video-ready network should integrate video security to protect against
unauthorized access to video applications. Mitigation of attacks and protection of traffic from snooping
and intrusion by malicious users is essential, and so is preventing malicious users from transmitting
unauthorized video. A variety of techniques can be used to secure a video network, from network
virtualization techniques to segregate video traffic, to the use of Trusted Relay Points (TRP) for software
clients residing in the data VLAN or Session Border Controllers (SBC) for topology hiding from the
exterior world. For information about how to secure video networks, see the chapter on Security for
Video Communications, page 9-1.
Scalability and Performance
Network scalability is critical to supporting increasing bandwidth demands as more video applications
or video users are deployed. To maintain optimal performance, the network should easily accommodate
higher bandwidths, scaling to support high-definition (HD) video streams and in some cases even
multiple HD video streams simultaneously. Therefore, it is crucial to size the network adequately for the
expected traffic generated by the video applications to be deployed.
The first step in sizing the network is to understand the endpoint and user requirements. Next, determine
how the media flows will behave during conferences and point-to-point calls. Then add the
considerations for voice and data traffic and backup measures required for reliability. Figure 7-10
illustrates an example scenario where 20 immersive and desktop video endpoints are located in the
headquarters campus while 15 miscellaneous endpoints are located in the branch. The expected usage
pattern in this example is as follows:
•
Headquarters desktop endpoint users and immersive endpoint users will generate peak usage of
7 calls among each other.
•
Headquarters endpoints will generate and/or receive peak usage of 6 calls to/from the branch office.
•
Calls on headquarters desktop endpoints use 1.3 Mbps while the immersive endpoints use 12 Mbps.
•
Branch video IP phones use 1 Mbps, desktop endpoints use 1.3 Mbps, and immersive endpoints use
12 Mbps.
•
At peak times, branch users will generate a maximum 4 calls among each other and generate or
receive 6 calls (as listed above) to/from the headquarters.
•
Headquarters and branch users need to access 10 Mbps (combined) of data applications between
sites.
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Creating a Video-Ready Network
Figure 7-10
Determining Capacity Requirements for a Video-Ready Network
MCU
Jabber
(x17)
Jabber
(x2)
Video
Phone (x10)
2
Switch A
3
Switch B
4
Router A
5
Router B
Switch C
Immersive
TelePresence (x3)
Immersive
TelePresence (x3)
284818
1
The above requirements are obviously simplistic. A very complex network and deployment would have
a longer set of requirements and applications to support. But with the list of requirements in the example
above, we can determine the following:
•
The maximum expected bandwidth usage is 49 Mbps for the video streams in the uplink between
switch A and switch B (link 1 in Figure 7-10), assuming the worst-case scenario of:
– Seven participants in a local multipoint call of the desktop video endpoints:
7 ∗ (1.3 Mbps) = 9.1 Mbps
– Six participants in a multipoint call of the immersive endpoints, 3 local and 3 remote:
3 ∗ (12 Mbps) = 36 Mbps
– Six participants in a multipoint call of the local desktop endpoints, 3 local and 3 remote video
IP phones:
3 ∗ (1.3 Mbps) = 3.9 Mbps
Note
This bandwidth calculation does not consider the extra bandwidth for data applications or
any other extra bandwidth that is necessary (for call signaling, for example). Before
dimensioning the LAN, you need to include these other bandwidth requirements.
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Creating a Video-Ready Network
•
In a worst-case scenario, the branch WAN link (link 5 in Figure 7-10, but the same considerations
apply for links 3, 4, and 6) would use 43.6 Mbps of bandwidth for video streams, assuming:
– Four participants in a multipoint call between 4 video phones. Because no local Multipoint
Control Unit (MCU) is available, all the streams have to travel to the headquarters for the
multipoint call to occur.
4 ∗ (1 Mbps) = 4 Mbps
– Six participants in a multipoint call between 5 desktop video endpoints and 1 video phone, 3
local endpoints (2 desktop video endpoints and 1 video phone) and 3 remote endpoints:
2 ∗ (1.3 Mbps) + 1 Mbps = 3.6 Mbps
– Six participants in a multipoint call on the immersive endpoints, 3 local and 3 remote:
3 ∗ (12 Mbps) = 36 Mbps
Note
•
This bandwidth calculation does not consider the extra 10 Mbps requested for data
applications or any other extra bandwidth that is necessary (for call signaling, for example).
These requirements also need to be added as part of the sizing process.
Finally, for link 2 servicing the MCU in Figure 7-10, we can anticipate that 92.6 Mbps of video
streams will traverse it at its peak if we consider the two previous bandwidth calculations:
49 Mbps + 43.6 Mbps = 92.6 Mbps
Note
The general rule that has been thoroughly tested and widely used is to over-provision video bandwidth
by 20% in order to accommodate a 10% burst and the Layer 2-to- Layer 4 network overhead.
Furthermore, the above calculations are based on the worst-case scenario for the usage patterns provided
in the example, but they do not consider the case where all video users want to make video calls at the
same time (known as 100% call completion).
In summary, the network capacity and performance design in a video-ready network should allow for
video forwarding without introducing significant latency of the call completion rate desired or the usage
patterns expected. Refer to your endpoint documentation to determine the amount of bandwidth required
per call.
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Integration with Standalone Video Networks
Integration with Standalone Video Networks
Whether replacing a previous video network solution or trying to converge the video network solution
under the same call processing platform elements, integration could pose some challenges for the IT
department. Understanding the options and guidelines for integration will provide a better experience
for the integrator and the user.
The integration approach differs depending upon the call signaling protocol used. The following sections
outline the general guidelines for the two most widely used protocols in video networks today:
•
Integration with Standalone H.323 Video Networks, page 7-19
•
Integration with Standalone SIP Video Networks, page 7-20
Integration with Standalone H.323 Video Networks
H.323 is a very well define protocol, which makes interoperability with H.323 call processing elements
considerably easier than with multi-vendor SIP elements; however, H.323 is not as service-rich as its
counterpart SIP. For example, Cisco has implemented the ability to switch screens depending on who
the active speaker is (smart switching), but this feature is not natively available in H.323 networks.
Whenever possible, use the native interoperability of the video endpoints to connect them directly to the
H.323 network, provided that this does not cause the loss of required features such as smart switching.
Otherwise, if feature retention is critical or if interoperability cannot be obtained point-to-point natively,
then connect the H.323 endpoints through a video transcoder or an interoperability-enabled conference
bridge. A non-overlapping dial plan is also recommended, and different access codes can be used
between the networks to indicate to the call processing agents that a hop to the next video system is
required to complete the call.
Figure 7-11 illustrates the use of a Multipoint Control Unit (MCU) to connect a Cisco TelePresence
System to a third-party H.323 standalone video network.
Figure 7-11
Integrating Standalone H.323 Networks
Media
MCU with
TelePresence
Server Blade
H.323
Standalone Network
7xxxx
284819
Media
Cisco
TelePresence
System
8xxxx
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Integration with Standalone Video Networks
Integration with Standalone SIP Video Networks
SIP video networks are more feature-rich than H.323 networks and can enable very useful features when
all the endpoints support the. However, SIP is not as well defined as H.323, thus making interoperability
with it more challenging.
If an endpoint conforms tightly to the SIP standard, then call agents can make use of the native video
interoperability features available within the call processing agents. Otherwise, video networks can be
bridged to each other with video transcoders or interoperability-ready multipoint control units.
Cisco recommends that you do not use an overlapping dial plan between the video networks, but do use
an access code to indicate to the call processing agents to route between video networks and avoid
inter-digit time-out. If uniform resource identifier (URI) dialing is used for the dial plan, Cisco
recommends using different domains for ease of administration.
Figure 7-12 illustrates integration of a Cisco TelePresence System with a SIP standards-based
third-party system. This example uses native interoperability along with different domains for dialing.
Integrating Standalone SIP Networks
Media
Cisco
TelePresence
System
8xxxx
*.cisco.com
Signaling
Cisco
Unified CM
SIP Standalone
Network
7xxxx
*.tandberg.com
Signaling
284820
Figure 7-12
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8
Collaborative Conferencing
Revised: March 30, 2012, OL-27011-01
When there are three or more participants involved in a call, the call becomes a conference. In
collaborative conferencing, the audio, video and content from some or all of the attendees in a meeting
is mixed into a single stream and the stream is sent back to the attendees. The processing of audio and
video is performed by a Multipoint Control Unit (MCU) or some multipoint devices. Figure 8-1
illustrates a conference involving both internal and external participants, mobile and remote workers, or
even attendees from different organizations.
Figure 8-1
Conceptual View of Collaborative Conferencing
Audio
Video
IP
284272
Content Sharing
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Conference Type
Conference Type
Most conferencing products support two types of conference, ad-hoc and scheduled. Scheduled
conferences require a special tool such as Cisco TelePresence Management Suite (TMS), for example,
that integrate with the calendar applications such as Microsoft Exchange or IBM Domino to provide the
scheduling functionality.
Ad-hoc Conference
In ad-hoc conferences, the conference initiator creates the conference and invites participants to join
without sending any prior notification about the conference information. Typically, the conference
initiator creates the conference by pressing the Conference key on the endpoint and calls the participants
to add them to the conference. Endpoints that do not have the Conference key cannot initiate the
conference but can be invited to join the conference. Resources for an ad-hoc conference cannot be
reserved. The conference can be created only if enough resources are available at the conference creation
time. In this case, the call processing agent (Cisco Unified Communications Manager, for example)
controls the conference.
Scheduled Conference
In this type of conference, the conference organizer schedules the conference using the product
scheduling tool or calendar application that integrated with the conference product scheduling function.
The conference resources are reserved at the time the conference is scheduled. The conference cannot
be scheduled if there are insufficient resources. To join the conference, attendees can dial into the
conference directly or click on the conference link inside the meeting invitation and have the system call
the attendees. In this case, the multipoint device controls the conference and the call processing agent
routes the dialed call to the correct multipoint device.
Conferencing Infrastructure
As shown in Figure 8-2, the call processing agent and multipoint device are the main components in the
conferencing infrastructure. The call processing agent handles the signal and controls the call on the
endpoints. In the case of a scheduled conference, the call processing agent routes the call to the
multipoint device. Cisco Unified Communications Manager (Unified CM) and the Cisco TelePresence
Video Communication Server (VCS) are the most common call processing agents used in the Cisco
video conference products. Unified CM can interconnect with VCS through a SIP trunk so that endpoints
registered to one agent can call or conference in endpoints registered to the other agent.
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Conferencing Infrastructure
Figure 8-2
Conferencing Components
IP
GK
Call Processing
Agent
IP
Unified CM
IP
M
VCS
SIP
H.323
Media
284269
Multipoint
Device
The main function of the multipoint device is to handle the media (audio and video) from the endpoints
during the conference. Typically, the connection between the call processing agent and the multipoint
device is SIP or H.323.
Conference Multipoint Device
The multipoint device is the central component in the conferencing infrastructure and it can be hardware
or software based. The multipoint device processes video streams from all participating endpoints and
transmits a composite image of all participants back to the originating endpoint devices. This composite
view enables all participants to see each other simultaneously. The continuous presence view can display
multiple windows (participants) in a variety of layouts. Each layout offers the ability to make one of the
windows voice-activated, which is useful if there are more participants in the conference than there are
windows to display them all in the composite view.
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Conferencing Infrastructure
Transcoding and Switching
The multipoint platform can be based upon either a transcoding or switching architecture. Both
architectures provide advantages that need to be considered when selecting a multipoint platform for
deployment.
•
Transcoding involves specialized video hardware that decodes the incoming video stream and then
re-encodes it before sending it on. For example, the Cisco TelePresence Server, Cisco Media
Experience Engine (MXE), and Cisco Multipoint Control Unit (MCU) all use the transcoding
architecture.
•
Switching does not require specialized video hardware but uses software instead. The incoming
video and audio streams are copied and redirected to the correct endpoints in the conference, with
no manipulation of the video stream. For example, the Cisco TelePresence Multipoint Switch uses
the switching architecture.
Table 1 describes the advantages and disadvantages of the transcoding and switching architectures of
the multipoint platform.
Table 8-1
Architecture
Transcoding
Switching
Comparison of Transcoding and Switching
Advantages
Disadvantages
1
•
Active presence support
•
Ability for endpoints to connect at
different bandwidth speeds and
resolutions
•
Often endpoints with Far End
Camera Control (FECC) can
customize layouts
•
Ability to scale video (translate)
between endpoints
•
Supports Telepresence
Interoperability Protocol (TIP) and
standards-based endpoints
•
Latency is low (less than 10 ms)
•
Lower cost per port
•
Latency is introduced due to
decoding and re-encoding video
•
Higher cost per port
•
Typically harder to scale
•
Limited to basic full-screen video
switching (No active presence; only
one site is visible on each screen)
•
Endpoints must support and agree on
a single resolution and frame rate2
1. Active presence provides a view of multiple participants on a single display, with the active participant shown in a full screen
while the other participants appear as a picture-in-picture overlaid along the bottom of the display.
2. Beginning with Cisco TelePresence System Release 1.7, Cisco TelePresence System devices using Smart Media can adjust
the video resolution based on the IP network conditions.
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Multipoint Deployment Guidelines
Multipoint Deployment Guidelines
There are two options for deploying any multipoint technology, namely centralized and distributed. It is
important to think through the deployment strategy to optimize the user experience, localize resources,
and ensure reliable multipoint calls. Consider the followings when designing your multipoint solution
deployment:
•
The number of endpoints, which in turn determines the number of multipoint devices required
•
The geographic location of the endpoints
Together these factors determine the multipoint deployment option (centralized or distributed), the
number of multipoint devices, and the physical location of the multipoint devices.
Centralized Deployment
Centralized designs are recommended for multipoint device deployments with a small number of
endpoints, or for larger deployments that cover a limited geographic area.
In centralized deployments, the multipoint device can be located in a regional or headquarters campus
site with the necessary WAN bandwidth available to each of the remote sites (as well as the necessary
LAN bandwidth within the campus). Cisco recommends that you locate the multipoint device centrally
based on the geographic location of the endpoints. (However, this might not be possible in all network
layouts.) Centrally locating the multipoint device prevents unnecessary latency caused by backhauling
calls to a site at the far edge of the network.
Figure 8-3 illustrates a deployment with a small number of endpoints that uses the multipoint device
placed centrally in the headquarters to minimize latency for multipoint meetings.
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Multipoint Deployment Guidelines
Figure 8-3
Centralized Multipoint Deployment
IP
IP
Multipoint
Device
IP
QoS Enabled
WAN
IP
284270
Headquarters
The multipoint device should be located at a site that provides network latency that adheres to the
solution requirements. Also, the site should be provisioned with adequate bandwidth for the number of
endpoints deployed on the network. Bandwidth requirements vary depending on the desired maximum
call rate of endpoints and the number of endpoints connecting to the multipoint device. Provision based
on the maximum bandwidth that a particular endpoint requires for the desired rate and resolution. For
details on network latency and bandwidth requirements, refer to the respective solution deployment or
design guide available at http://www.cisco.com.
Distributed Deployment
Cisco recommends the distributed configuration for large deployments or deployments with a small
number of endpoints in separate geographical regions. As the network grows, it is very advantageous to
localize multipoint devices to minimize latency and save bandwidth.
Figure 8-4 illustrates the deployment where the multipoint devices are placed centrally in each region
(NA and EMEA) but are distributed globally.
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Multipoint Deployment Guidelines
Figure 8-4
Distributed Multipoint Deployment
IP
NA Region
IP
Dallas
EMEA
Region
IP
Multipoint
Device
Multipoint
Device
IP
London
QoS Enabled
WAN
Paris
Boston
284271
New York
Madrid
In the distributed environment, multipoint devices should be located at sites that provide network latency
adhering to solution requirements and adequate bandwidth for the number of endpoints supported by
each site.
The following additional guidelines should be observed when deploying multipoint devices:
•
Build a resilient multipoint solution architecture using multiple multipoint devices. In case one of
the multipoint devices fails, conferences can still be started from the operational device.
•
Cascade multipoint devices to support a larger conference deployment and to minimize bandwidth
consumption. Cisco TelePresence Conductor can be used to cascade multipoint devices.
•
Use Cisco TelePresence Conductor to preferentially select a multipoint device for conferences
based on their properties (for example, geographic location or video quality).
•
Choose a deployment that allows you to build a scalable multipoint solution. For example, if you
have endpoints deployed in multiple geographical regions and expect the number of endpoints to
grow in each regions, use the distributed multipoint deployment
•
Configure a solution so that traffic is load-balanced to the multipoint devices in order to achieve
maximum resource utilization.
•
Cisco recommends using the scheduling option for larger deployments. This would simplify the
conference creation.
•
Wherever possible, Cisco recommends dual-registering (SIP and H.323) the MCU in mixed
environments so that endpoints can connect in their native protocol without interworking.
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Collaborative Conferencing
Multipoint Solution Selection
Multipoint Solution Selection
When deciding on the multipoint solution suitable for your deployment, you need to consider several
factors (such as your organization's current deployment and the intended endpoint combinations) and to
decide which multipoint features have priority. Some common factors to consider when designing the
multipoint solution architecture include:
•
Active presence
•
Scalability
•
Network latency
•
Endpoints support
•
Multi-screen compatibility
•
Collaboration (content sharing)
•
Scheduling
Multipoint Selection Based on Endpoints
When deciding on a multipoint device, start with your endpoints. In some cases, a combination of
endpoints could help eliminate or determine the multipoint device option for the deployment, as in the
following scenarios:
•
In a deployment with heterogeneous endpoints that support different video formats, video codecs,
resolutions, or frame rates, the best option would be multipoint devices that can do both transcoding
and transrating. In this case, the Cisco TelePresence Multipoint Switch would not be a good choice
because it is based on a switching architecture.
•
A deployment that contains both Telepresence Interoperability Protocol (TIP) and standards-based
endpoints would require a video gateway to inter-operate between the protocols. For example, if the
conference environment has a Cisco TelePresence Multipoint Switch and a mix of Cisco
TelePresence System 3200 Series, Cisco IP Video Phone E20, and Cisco TelePresence
System EX90 endpoints registered to Cisco Unified CM, the Cisco Media Experience Engine
(MXE) might be the obvious option to add (from a budget perspective) because it allows
interoperability between endpoints.
However, in most cases there can be more than one option, so you should also consider the features that
you require.
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Collaborative Conferencing
Conference Resource Capacity Planning
Multipoint Selection Based on Features
The multipoint solution options can be further narrowed down by focusing on which features have the
highest priority for your conferencing deployment. The following partial list represents features that
affect the decision of which multipoint solution to choose:
•
Support for Telepresence Interoperability Protocol (TIP), standards-based, or third-party endpoints
•
Multi-screen or single-screen support
•
Support for One Button To Push (OBTP)
•
Active presence or continuous presence
•
Content sharing
•
H.239, Binary Floor Control Protocol (BFCP), or Auto Collaborate content sharing translation
•
WebEx OneTouch integration
•
Layout changes possible from endpoints
•
Switching policy support (room versus speaker switching)
•
SIP and H.323 support
For a complete list of features supported in each multipoint product, refer to the respective product data
sheet available at http://www.cisco.com.
Conference Resource Capacity Planning
There are several factors involved in determining the types and number of video conferences that the
multipoint device can support. These sizing factors are different for different multipoint products.
Multipoint devices can also support higher capacity when using standard definition (SD) as compared
to high definition (HD) for video conference.
Conference capacity depends on the following factors:
•
Type of resolution or video format required for the video conference
•
Total number of ports that the multipoint device can support
•
Number of ports that the multipoint device can dedicate to each protocol
•
Whether the multipoint devices are cascaded
If the video conference utilizes a Cisco High-Density Packet Voice Video Digital Signal Processor
Module (PVDM3) or later model of digital signal processor (DSP) on a Cisco Integrated Services Router
(ISR) as the bridge, use the DSP calculator in the Cisco Unified Communications Sizing Tool to
determine the conference capacity. The Cisco Unified Communications Sizing Tool (Unified CST) is
available to Cisco employees and partners with proper login authentication at
http://tools.cisco.com/cucst.
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Conference Resource Capacity Planning
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CH A P T E R
9
Security for Video Communications
Revised: March 30, 2012, OL-27011-01
Securing video communications over the IP network in an enterprise requires implementing security for
both the Unified Communications components and the network infrastructure that those communication
streams traverse. This chapter focuses on the design and implementation options available within the
Cisco Unified Communications System and the Cisco TelePresence Solution for securing the integrity,
reliability, and confidentiality of video calls within an enterprise IP Telephony network. For more
information on data network security, refer to the Cisco SAFE Blueprint documentation available at
http://www.cisco.com/en/US/netsol/ns744/networking_solutions_program_home.html
To securely implementing voice and video communications, Cisco recommends creating security
policies associated with every network technology deployed within an enterprise (see Figure 9-1). The
security policy defines which data in your network is sensitive so that it can be protected properly when
transported throughout the network. Having a security policy helps define the security levels required
for the types of data traffic that are on a network.
Figure 9-1
Security and Hardening Options in a Cisco Unified Communication System
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Security for Video Communications
Network Infrastructure Security
Hardening the Cisco Unified Communications network involves establishing and maintaining
authenticated communication streams, digitally signing configuration files, and encrypting media
streams and call signaling between various Cisco Unified Communications and Cisco TelePresence
components. All of these security features are not required for every network, but they provide options
for increasing levels of security.
This chapter provides the design guidelines for these features. For the product configuration details,
refer to the following security documentation for your specific version of Cisco Unified
Communications Manager (Unified CM) and Cisco TelePresence:
•
Cisco Unified Communications Manager Security Guide
http://www.cisco.com/en/US/products/sw/voicesw/ps556/prod_maintenance_guides_list.html
•
Cisco Unified Communications System SRND
http://www.cisco.com/go/ucsrnd
•
Cisco TelePresence Design Guide
http://www.cisco.com/en/US/solutions/ns340/ns414/ns742/ns819/landing_vid_tPresence.html
Network Infrastructure Security
Securing video communications requires securing the network that is used for transporting the calls.
This can be achieved by building layers of security, starting at the access port, continuing across the
network and to the Internet edge. Cisco recommends always using firewalls, access control lists,
authentication services, and other Cisco security tools to help protect your network infrastructure
devices from unauthorized access.
Restricting access to the network devices is one of the most important requirements in securing the
infrastructure. A typical enterprise network consists of many components, including routers, switches,
firewalls, and intrusion prevention systems. Attackers are constantly trying to access these devices on
networks. Restricting access to the management interface of each device lowers the opportunities that
attackers have to compromise them. All of the devices on a network should be secured appropriately.
Administrative and operational management of the network devices should be done using secured
protocols such as Secure Shell (SSH) and Hyper-Text Transfer Protocol Secure (HTTPS). Transmission
of passwords and configuration information over clear text, used in protocols such as Telnet, should be
avoided as much as possible.
In addition to securing access to the infrastructure, the services used in the operation of a network also
need to be secured. These include Domain Name System (DNS), Network Time Protocol (NTP),
Dynamic Host Configuration Protocol (DHCP), and signaling protocols such as Session Initiation
Protocol (SIP) and H.323. These services, which are vital to the successful operation of a network, are
also prime targets for an attacker. Disrupting any of these services can cause denial of service and
availability problems for the Unified Communications systems.
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Security for Video Communications
Device Security
Separate Auxiliary VLAN
Cisco recommends implementing separate VLANs for RTP traffic (voice and video) and data traffic in
a Unified Communications environment. In this configuration, all Cisco IP Phones and TelePresence
endpoints are placed in a voice VLAN that is separate from the data VLANs. This implementation
provides the following benefits:
Note
•
It makes it convenient to design VLAN access control lists (VACLs) that can be used to restrict
traffic between voice and data network components. This also allows network administrators to
more effectively implement management access restrictions on the network.
•
It provides address space conservation and voice device protection from external networks. Private
addressing of phones on the voice or auxiliary VLAN ensures address conservation and prevents
phones from being accessible directly through public networks.
•
It enables simplified Quality of Service (QoS) configuration and management. It also allows the
QoS trust boundaries to be extended to voice and video devices without extending the trust and the
QoS features to PCs and other data devices.
•
VLAN access control, 802.1Q, and 802.1p tagging can prevent attempts by data devices to spoof
information and gain access to priority queues through packet tagging.
The Cisco Unified IP Phones and the Cisco TelePresence endpoints have different service requirements,
and placing them together in a single VLAN makes it more complicated to design regular access control
lists.
Device Security
Cisco Unified IP Phones and TelePresence endpoints have multiple configuration options for securing
them against attacks. However, these devices should not be considered hardened by default at the time
of initial configuration. The security features vary among the different endpoints and include:
•
Secure Management over HTTPS and SSH, page 9-3
•
Administrative Passwords, page 9-4
•
Device Access, page 9-4
•
Signaling and Media Encryption, page 9-4
Refer to the endpoint administration guides for information on configuration details for these features.
Also, refer to the phone hardening information in the Cisco Unified Communications Manager Security
Guide, available at
http://www.cisco.com/en/US/products/sw/voicesw/ps556/prod_maintenance_guides_list.html
Secure Management over HTTPS and SSH
Cisco TelePresence endpoints support management through Secure Shell (SSH) and Hyper-Text
Transfer Protocol over Secure Sockets Layer (HTTPs). Access to the endpoints using HTTP, HTTPS,
SSH, or Telnet can be configured in the Network Services setting on the endpoint itself.
Cisco Unified IP Phones can be restricted to use HTTPS only or enabled for both HTTP and HTTPS.
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Security for Video Communications
Device Security
Administrative Passwords
The endpoints ship with default administrative passwords, and Cisco recommends changing the
passwords at the time of installation. Access to management functions should be restricted to authorized
users with administrative privileges.
Device Access
The endpoints can be assigned to users who are given access based on defined roles and privileges.
Passwords and PINs can be specified for these users to enable SSH or Telnet and web-based access. A
credential management policy should be implemented to expire and change passwords periodically and
to time-out logins when idle. This is necessary for limiting access to the devices to verified users.
For information on user authentication and credential management configurations, refer to the following
documentation:
•
Cisco Unified Communication Manager Administration Guide
http://www.cisco.com/en/US/products/sw/voicesw/ps556/prod_maintenance_guides_list.html
•
Securing Cisco TelePresence Products
http://www.cisco.com/en/US/products/ps8332/products_installation_and_configuration_guides_lis
t.html
Signaling and Media Encryption
For supported Cisco Unified Communications devices, signaling and media can be encrypted to prevent
eavesdropping and reconnaissance attacks on active calls and during call establishment. The protocols
and mechanisms used to provide secure communications and signaling within Unified Communications
deployments include the following:
•
Transport Layer Security (TLS), page 9-4, used for encrypting signaling traffic
•
Secure Real-Time Transport Protocol (SRTP) and Secure Real-Time Transport Control Protocol
(SRTCP), page 9-5, used for encrypting media
•
Datagram Transport Layer Security (DTLS) Secure Real-Time Transport Protocol (SRTP),
page 9-5, used for SRTP master key negotiation and/or exchange
•
Digital Certificates, page 9-5
•
Certificate Authority Proxy Function (CAPF), page 9-6
•
The Certificate Trust List (CTL), page 9-6
Transport Layer Security (TLS)
Transport Layer Security (TLS) is a protocol designed to provide authentication, data integrity, and
confidentiality for communications between two applications. TLS is based on Secure Sockets Layer
(SSL) Version 3.0, although the two protocols are not compatible. The latest version, TLS 1.2, is defined
in IETF RFC 5246. TLS operates in a client/server mode, with one side acting as the server and the other
side acting as the client. TLS uses a handshake protocol to allow the client and server to authenticate
each other using public key cryptography (digital certificates). This also enables reliable negotiation of
a compression algorithm, message authentication algorithm, encryption algorithm, and the necessary
cryptographic keys before any application data is sent.
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Device Security
Data authentication and encryption of the SIP signaling between Cisco Unified CM, Cisco Unified IP
Phones, and Cisco TelePresence System components, is implemented using the Transport Layer Security
(TLS) protocol. TLS is also used for the authentication and confidentiality of the web services signaling
between the various Cisco TelePresence components.
The encryption of the signaling protocol is done using the Advanced Encryption Standard (AES)
algorithm, using symmetric keying. Message authentication is done with the HMAC-SHA1 hash
algorithm. The negotiation of keying material is done securely within the TLS Handshake Protocol layer
through the Client and Server Key Exchange messages.
Secure Real-Time Transport Protocol (SRTP) and Secure Real-Time Transport Control Protocol
(SRTCP)
Data authentication and confidentiality of the Real-time Transport Protocol (RTP) voice and video
media flows use Secure Real-time Transport Protocol (SRTP) for both point-to-point and multipoint
TelePresence meetings.
Secure RTP (SRTP) and Secure Real-time Transport Control Protocol (SRTCP) are both defined in IETF
RFC 3711, which details the methods of providing confidentiality and data integrity for both RTP voice
and video media as well as their corresponding RTCP streams.
In SRTP, encryption is applied only to the payload of the RTP packet using an Advanced Encryption
Standard (AES) algorithm with a 128-bit key. SRTP also uses HMAC-SHA1 as the message
authentication hash algorithm. Message authentication is applied to the RTP header as well as the RTP
payload. SRTP protects against replay attacks by applying the message authentication to the RTP
sequence number within the header.
As with SRTP packets, encryption applies only to the payload of the SRTCP packet, when utilized.
Message authentication, however, is applied to both the RTCP header and the RTCP payload.
Datagram Transport Layer Security (DTLS) Secure Real-Time Transport Protocol (SRTP)
The Datagram Transport Layer Security (DTLS) protocol is designed to provide authentication, data
integrity, and confidentiality for communications between two applications, over a datagram transport
protocol such as User Datagram Protocol (UDP). The protocol is defined in IETF RFC 4347. DTLS is
based on TLS, and it includes additional mechanisms such as sequence numbers and retransmission
capability to compensate for the unreliable nature of UDP. DTLS-SRTP is an extension to DTLS for the
negotiation of SRTP keying material within DTLS.
In a Cisco Telepresence solution, the DTLS handshake occurs directly between the TelePresence
endpoints. The DTLS-SRTP session is established between the Cisco TelePresence codecs, within the
RTP media streams between two endpoints, but not with any associated Cisco Unified IP Phone in the
call. In each call, two DTLS-SRTP handshakes occur, one for voice and one for video media, and keys
are negotiated for encryption and authentication of both streams.
Digital Certificates
The Cisco Unified Communications System uses X.509 v3 certificates as part of its Public Key
Infrastructure (PKI) feature for generating public and private keys used for encrypting and decrypting
messages. This PKI implementation generates key pairs that can encrypt messages with the private key
that can be decrypted only with the public key that is exchanged between two devices. The private key
is kept secure within the device and never exposed. The public key is available as an attribute defined
on the X.509 digital certificate. The attributes are established by a Certificate Authority (CA), which
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Security for Video Communications
Device Security
digitally signs the certificate. The digital signature itself is a hash of the message, encrypted using the
private key of the Certificate Authority. The digital signature of the Certificate Authority can be verified
by the recipient using the public key of the Certificate Authority.
A certificate can be either a Manufacturing Installed Certificate (MIC) or a Locally Significant
Certificate (LSC). MICs are pre-installed and LSCs are installed by the Cisco Certificate Authority
Proxy Function (CAPF) on Cisco Unified Communications Manager (Unified CM). The MIC certificate
can provide the credentials used by the endpoints to perform a first-time authentication and enrollment
into Cisco Unified CM's security framework. When MICs are used, the Cisco CA and the Cisco
Manufacturing CA certificates act as the root certificates.
Note
The MIC is also used for establishing Datagram Transport Layer Security (DTLS) sessions between
Cisco TelePresence endpoints.
Certificate Authority Proxy Function (CAPF)
The Cisco Certificate Authority Proxy Function (CAPF) is a software service installed as part of Cisco
Unified CM. CAPF is not enabled by default and needs to be configured after installation. CAPF issues
Locally Significant Certificates (LSCs) for Cisco Unified IP Phones and Cisco TelePresence endpoints.
CAPF self-signs certificates under its own authority. However, it can be used as a proxy to request
certificates from an external Certificate Authority (CA). It supports the signing of certificates by a
third-party certificate authority (CA) using Public-Key Cryptography Standard (PKCS) #10 Certificate
Signing Request (CSR).
When using third-party CAs, the CAPF can be signed by the CA, but the phone LSCs are still generated
by the CAPF. When self-signed LSCs are used, the CAPF certificate is the root certificate. When an
external CA is used, the CAPF acts as the subordinate CA, and the external CA is the root CA.
These certificates are then used to establish secure, authenticated connections for protocols such as SIP
signaling over TLS.
The Certificate Trust List (CTL)
The CTL Provider is another software service, installed as part of Cisco Unified CM, that works together
with a CTL Client to generate a Certificate Trust List (CTL). The CTL Client is a software plug-in that
can be downloaded from the Cisco Unified CM server and run on a separate Windows PC. The
Certificate Trust List itself is a predefined list of trusted certificates stored on the Unified CM server and
downloaded as a file to the Cisco endpoints when they boot up. The CTL indicates the list of Unified CM
servers that the Cisco Unified IP Phones and TelePresence endpoints can trust when they initiate SIP
sessions over TLS for call signaling. In order to provide authentication for the CTL itself, a minimum
of two separate Cisco Universal Serial Bus (USB) hardware security keys (etokens) are required. These
USB keys are not part of the Cisco Unified CM product and must be purchased separately. These
security keys are inserted into the PC running the CTL Client plug-in during the CTL generation process.
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Security for Video Communications
Media Encryption Details
Configuration File Integrity and Encryption
The configuration files for Cisco TelePresence units and Cisco Unified IP Phones are stored within
Cisco Unified CM. These files are downloaded to the endpoints each time they boot up. Configuration
files are also automatically downloaded to a Cisco TelePresence device any time a change in
configuration is made within Unified CM that would affect the endpoint's configuration. A configuration
file download also resets the device.
Device security profiles can be created on Cisco Unified CM that require encryption of the configuration
files. This prevents configuration files from being changed by unauthorized users because they are
digitally signed by Unified CM.
Media Encryption Details
Cisco Unified Communication Manager (Unified CM) supports Secure Real-time Transport Protocol
(SRTP) for the audio portion of a voice call payload but does not support encryption for video media.
Native support for Cisco TelePresence EX Series and C Series endpoints has been added to Cisco
Unified CM 8.6 and later releases, but this does not include support for media encryption. Cisco
TelePresence System and Video Communication Servers support SRTP for endpoints natively registered
to them. Cisco TelePresence endpoints use Datagram Transport Layer Security (DTLS) for private-key
exchange used in establishing SRTP.
Cisco Unified CM, Cisco TelePresence System (CTS), and Cisco Video Communication Servers (VCS)
support secure signaling using TLS for SIP. In implementations where a SIP trunk is used for integrating
Unified CM, VCS, and CTS, end-to-end signaling encryption of SIP protocol is supported using TLS
(see Figure 9-2).
Figure 9-2
Integration of Cisco TelePresence System, Unified CM, and Video Communication
Servers Using TLS
Unified CM
VCS Control
VCS
Expressway
CTS
Internet
Cisco
TelePresence
Multipoint
Switch
E20
E20
EX Series
EX
Series
Movi
C-Series
284809
MCU
EX
Series
Movi
C-Series
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Integration with Firewalls and Access Control List Considerations
Implementing end-to-end SIP signaling encryption requires the configuration of a VCS neighbor zone
to Unified CM to use TLS. This feature requires the installation of the appropriate feature key. In
addition, Unified CM must be able to trust the VCS server's certificate. This can be done either by having
both Unified CM and VCS use certificates from the same Certificate Authority or, if a common root CA
is not used, then by exporting the VCS server certificate and uploading it to the Unified CM trust store
While signaling encryption is achieved using this configuration, this does not secure the media payload.
Encryption of the video calls requires using DTLS between the endpoints for establishing a secure
channel for key exchange. The AES encryption keys that are used for media encryption are then passed
through this channel. This media encryption can be implemented on TelePresence endpoints configured
to support media encryption but will not work on Unified CM IP Phones.
For step-by-step configuration instructions, refer to the Cisco TelePresence Video Communication
Server Cisco Unified Communications Manager Deployment Guide, available at
http://www.cisco.com/en/US/products/ps11337/products_installation_and_configuration_guides_l
ist.html
Integration with Firewalls and Access Control List
Considerations
A secure enterprise network relies on firewalls in conjunction with access control lists (ACLs) to protect
the network from various sorts of malicious threats. ACLs are also frequently used to enforce Quality of
Service (QoS) settings, including marking, shaping, and policing traffic at various places in the network,
such as at the access edge of a local area network (LAN) or at the intersection of a LAN and wide area
network (WAN). Firewalls may also be used for access control within an enterprise campus and between
two or more campus locations.
The servers and endpoints in a Cisco Unified Communications System use a large range of ports and
services; therefore, using firewalls and ACLs to protect them and restrict access to them requires careful
planning. Given the complexities that firewalls introduce into a network design, care is needed in placing
and configuring the firewalls and the devices around the firewalls to allow the traffic that is considered
correct to pass while blocking the traffic that needs to be blocked.
Because of the dynamic nature of the ports used by voice and video devices, having a firewall helps to
control opening up a large range of ports needed for the different services used by the Cisco Unified
Communications System. Application Layer Inspection functionality in firewalls simplifies traffic
filtering by dynamically opening and closing required ports and sockets. It performs deep packet
inspection to obtain the embedded IP addressing information for establishing media streams in a call.
However, for this to function well, the firewall's inspection engine must support the specific protocol
implementation of the Unified Communications components. The Cisco Adaptive Security Appliance
(ASA) 5500 Series firewalls support version-specific implementations of Unified Communications
protocols. This requires that the version of ASA implemented is compatible with the version of the Cisco
Unified Communications solution in the network. Upgrading one might require upgrading the other.
The Cisco ASA 5500 firewalls restrict and allow traffic based on the trust levels assigned to its
interfaces. This establishes different levels of trust within a network. Security levels range from 100,
which is the most secure interface, to 0, which is the least secure interface. These are often referred to
as the "inside" and "outside." By default, traffic initiated from a device on an interface with a higher
security level is allowed to pass to a device on an interface with a lower security level. Return traffic
corresponding to that session is dynamically allowed from the lower interface security level to the
interface with the higher security level. This behavior works well with the Cisco TelePresence endpoints
that use symmetric port numbering in point-to-point calls. However, multipoint TelePresence calls
cannot always use symmetrically numbered ports.
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Integration with Firewalls and Access Control List Considerations
In multipoint TelePresence calls, the audio and video User Datagram Protocol (UDP) streams flow
between the Cisco TelePresence endpoints and the Cisco TelePresence Multipoint Switch. The
endpoints each have one audio and one video call, but because the Multipoint Switch has a single IP
address and has to support multiple UDP audio and video streams from multiple endpoints, the flows are
not necessarily symmetric from a UDP port numbering perspective. This requires configuring
application layer protocol inspection for SIP protocol in order to allow the firewall to open and close the
necessary media ports dynamically.
Firewalls do not allow traffic initiated from a device on an interface with a lower security level to pass
to a device on an interface with a higher security level. This behavior can be modified with an ingress
access control list (ACL) on the lower security interface level. An ingress ACL applied to the interface
with the higher security level may also be used to limit traffic going from higher level security interfaces
to interfaces with lower security levels.
Cisco ASA 5500 Series firewalls can also be allowed to operate with interfaces having equal security
levels. This requires configuring commands that permit same security interface traffic. ACLs can also
be applied on each interface, and static translations can be used to specifically allow access between
certain devices and protocols connected to interfaces with equal security levels.
For a list of TCP and UDP ports that need to be permitted between Cisco TelePresence components, refer
to the Securing Cisco TelePresence Products document, available at
http://www.cisco.com/en/US/products/ps7315/products_installation_and_configuration_guides_lis
t.html
For a list of ports used by Cisco Unified CM, refer to the Cisco Unified Communications Manager TCP
and UDP Port Usage guide, available at
http://www.cisco.com/en/US/products/sw/voicesw/ps556/prod_maintenance_guides_list.html
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Integration with Firewalls and Access Control List Considerations
Firewall Traversal in the DMZ
The Cisco TelePresence Video Communication Server Expressway (VCS Expressway) can establish
video communication calls with devices outside the enterprise network and across the Internet. The
VCS Expressway must be placed outside the private network used by the Cisco Unified
Communications solution to allow external callers to access the device. It can be deployed either on the
public Internet or in a demilitarized zone (DMZ). By default, firewalls block unsolicited incoming
requests, so the firewall must be configured to allow the VCS Expressway to establish a constant
connection with the VCS Control server.
Positioning the VCS Expressway in the DMZ makes this implementation much more secure (see
Figure 9-3). It uses VCS as the dedicated server for handling voice and video traffic, thus making the
firewall configuration less complex. It can limit the management traffic to the VCS Expressway,
restricting it to the internal private traffic and blocking access externally.
Figure 9-3
VCS Expressway in a DMZ
TP
Cisco Unified
Communications
Applications
SIP & Firewall
Traversal
Internet
Video Communication Server
Expressway in a DMZ
284675
SIP & Firewall
Traversal
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GLOSSARY
Revised: March 30, 2012, OL-27011-01
A
AES
Advanced Encryption Standard
ASA
Cisco Adaptive Security Appliance
B
B2B
Business-to-business
BFCP
Binary Floor Control Protocol
bps
Bits per second
C
CA
Certificate Authority
CAPF
Cisco Certificate Authority Proxy Function
CBWFQ
Class-Based Weighted Fair Queuing
CDP
Cisco Discovery Protocol
CIF
Common Intermediate Format
codec
COmpressor-DECompressor (or COder-DECoder)
CSR
Certificate Signing Request
CTL
Certificate Trust List
CTS
Cisco TelePresence System
D
DCT
Display Channel Table
DHCP
Dynamic Host Configuration Protocol
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GL-1
Glossary
DID
Direct inward dialing
DiffServ
Differentiated Services
DMZ
Demilitarized zone
DNS
Domain Name System
DNS SRV
DNS Service
DSCP
Differentiated Services Code Point
DSP
Digital signal processor
DTLS
Datagram Transport Layer Security
E
ENUM
Electronic Numbering
F
FECC
Far-end camera control
FIFO
first in, first out
fps
Frames per second
G
GDR
Gradual Decoder Refresh
H
HD
High definition
HMAC
Hash-based Message Authentication Code
HTTP
Hyper-Text Transfer Protocol
HTTPS
Hyper-Text Transfer Protocol Secure
Cisco Video and TelePresence Architecture Design Guide
GL-2
OL-27011-01
Glossary
I
i
Interlaced video format
IDR
Instant Decoder Refresh
IEC
International Electrotechnical Commission
IETF
Internet Engineering Task Force
IME
Cisco Intercompany Media Engine
IP
Internet Protocol
IPsec
Internet Protocol Security
IPv4
IP version 4
IPv6
IP version 6
ISDN
Integrated Services Digital Network
ISO
International Organization for Standardization
ISR
Cisco Integrated Services Router
ITU
International Telecommunication Union
ITU-T
International Telecommunication Union Telecommunication Standardization Sector
L
LDAP
Lightweight Directory Access Protocol
LSC
Locally Significant Certificate
LTRP
Long-Term Reference Picture
M
MAC
Message Authentication Code
MCU
Multipoint Control Unit
MIC
Manufacturing Installed Certificate
MPEG
Moving Picture Experts Group
MPLS
Multiprotocol Label Switching
MSE
Cisco TelePresence Media Services Engine
Cisco Video and TelePresence Architecture Design Guide
OL-27011-01
GL-3
Glossary
MSI
Cisco Media Services Interface
MXE
Cisco Media Experience Engine
N
NAT
Network Address Translation
NAT-T
Network Address Translation Traversal
NTP
Network Time Protocol
O
OBTP
One Button To Push
P
p
Progressive scan
PKCS
Public-Key Cryptography Standard
PKI
Public Key Infrastructure
PQ
Priority Queuing
PVDM3
Cisco High-Density Packet Voice Video Digital Signal Processor Module
Q
QCIF
Quarter Common Intermediate Format
QoS
Quality of Service
R
RFC
Request for Comments
RSVP
Resource Reservation Protocol
RTCP
Real-time Transport Control Protocol
RTP
Real-time Transport Protocol
Cisco Video and TelePresence Architecture Design Guide
GL-4
OL-27011-01
Glossary
S
SCCP
Skinny Client Control Protocol
SD
Standard definition
SIP
Session Initiation Protocol
SME
Cisco Unified Communications Manager Session Management Edition
SRTCP
Secure Real-time Transport Control Protocol
SRTP
Secure Real-Time Transport Protocol
SSH
Secure Shell
SSL
Secure Sockets Layer
T
TCP
Transmission Control Protocol
TCS
Cisco TelePresence Content Server
TLS
Transport Layer Security
TMS
Cisco TelePresence Management Suite
ToS
Type of Service
TURN
Traversal Using Relay NAT
U
UAC
User agent client
UAS
User agent server
UDP
User Datagram Protocol
Unified CM
Cisco Unified Communications Manager
Unified CST
Cisco Unified Communications Sizing Tool
URI
Uniform resource identifier
USB
Universal Serial Bus
UTF
Unicode Transformation Format
Cisco Video and TelePresence Architecture Design Guide
OL-27011-01
GL-5
Glossary
V
VCL
Virtual Channel Link
VCS
Cisco TelePresence Video Communication Server
VLAN
Virtual Local Area Network
VoIP
Voice over Internet Protocol
W
WFQ
Weighted Fair Queuing
Cisco Video and TelePresence Architecture Design Guide
GL-6
OL-27011-01
INDEX
B-frame
Numerics
3-6
Binary Floor Control Protocol (BFCP)
16CIF
4CIF
3-8
bit rate adjustments
3-8
blocked calls
9-3, 9-8
C
8-8, 8-9
additional information
ad-hoc conference
vii
administrative passwords
9-5
call admission control
9-4
call blocking
5-1, 5-3
advanced media gateways
CA
calculating bandwidth usage
2-7
9-4, 9-5
call control protocols
7-5
allocation of video resources
5-3
aggregated
7-10
1-1, 2-2
auxiliary VLAN
vii
7-5
7-5
7-7
multi-site
assured forwarding
Auto Collaborate
clustered
hosted
9-8
assistance, obtaining
7-5
selection guidelines
5-1
single-site
8-9
call processing agent
9-3
call resolution
CAPF
B2B video deployment model
bandwidth usage
7-15, 8-9
5-3, 7-16
7-4
CDP
7-16
8-9
9-5, 9-6
CBWFQ
4-6
8-2
6-3
capacity planning
B
7-8
7-5
capacity calculations
BFCP
4-1
call processing
aggregated call processing
B2B
5-1, 5-3
2-6
call counting
9-4, 9-5
7-16
6-4
call control
Advanced Encryption Standard (AES)
architecture
9-8
8-2
admission control
7-4
9-3, 9-8
Adaptive Security Appliance (ASA)
ASA
4-6
business-to-business (B2B) video deployment model
active presence
AES
vii
business-to-business (B2B)
access control list (ACL)
ACL
3-15
6-4
bugs, reporting
A
7-15, 8-9
5-2
2-9, 5-2
centralized deployment
8-5
centralized video resource allocation
7-10
Cisco Video and TelePresence Architecture Design Guide
OL-27011-01
IN-1
Index
Certificate Authority (CA)
conferences
9-5
Certificate Authority Proxy Function (CAPF)
Certificate Signing Request (CSR)
Certificate Trust List (CTL)
CIF
ad-hoc
9-5, 9-6
8-2
capacity planning
9-6
endpoints
9-6
8-8
from the desktop
3-7, 3-8
Cisco Adaptive Security Appliance (ASA)
Cisco Certificate Authority Proxy Function (CAPF)
immersive video
9-5,
infrastructure
Cisco Discovery Protocol (CDP)
2-9, 5-2
in general
Cisco High-Density Packet Voice Video Digital Signal
Processor Module (PVDM3) 8-9
Cisco Integrated Services Router (ISR)
Cisco SAFE Blueprint
types
8-2
Cisco TelePresence Conductor
Cisco TelePresence Server
content sharing
vii
7-15, 8-9
Cisco TelePresence System (CTS)
counting calls
9-7
Cisco TelePresence Video Communication Server
(VCS) 3-8
2-7
creating a video-ready network
CSR
9-6
CTL
9-6
CTRS
Cisco Unified Communications Manager Session
Management Edition (SME) 7-5
customer support
CTS
Cisco Unified Communications Sizing Tool
(Unified CST) 8-9
Class-Based Weighted Fair Queuing (CBWFQ)
class restrictions
Data Link Layer
7-14
DCT
6-4
vii
3-4
7-5
8-5
distributed
8-6
7-1
multipoint technology
8-1
3-7
desktop video conferencing
8-5
3-10
device
3-1, 3-3
compressor-decompressor
centralized
for video networks
Common Intermediate Format (CIF)
9-10
deployment models
3-12
3-3
collaborative conferencing
9-5
2-9
demilitarized zone (DMZ)
3-3
compression
9-7
D
3-15
coder-decoder
2-5
Datagram Transport Layer Security (DTLS)
cloud-hosted video solutions
codecs
7-14
5-2
2-3, 6-4
clustered call processing
viii
5-3
Cisco Unified Communications Manager
(Unified CM) 3-8, 5-2, 8-2
classification of traffic
8-9
conventions used in this document
8-4
Cisco Unified Border Element
9-7
continuous presence
2-4
8-3
8-2
configuration files
9-1
Cisco Technical Assistance Center (TAC)
classes of service
8-2
8-1
scheduled
8-4, 8-8
2-4
3-11
multipoint device
8-9
Cisco Media Experience Engine (MXE)
3-10
hardware platforms
9-8
9-6
ClearPath
8-9
3-3
access
security
9-4
9-3, 9-7
Cisco Video and TelePresence Architecture Design Guide
IN-2
OL-27011-01
Index
DHCP
dial plan
DID
Expressway
9-2
6-1
6-2
Differentiated Services (DiffServ)
DiffServ
F
5-1
Differentiated Services Code Point (DSCP)
5-2
far-end camera control (FECC)
5-1
FEC
digital certificates
9-5
direct inward dialing (DID)
8-9
Display Channel Table (DCT)
distributed deployment
FIFO
3-4
9-10
DNS
6-1, 9-2
3-1, 3-4
G
feedback
vii
gatekeeper
obtaining
vii
gateways
vii, 1-6
GDR
Domain Name System (DNS)
dropped packets
DSP
6-1, 9-2
4-3
2-7
3-4, 3-5
glossary
5-1
1-1
Gradual Decoder Refresh (GDR)
5-2
3-4, 3-5
guidelines
8-9
DTLS
3-15
6-2, 7-9
documentation
related
5-2
forward error correction (FEC)
frame
DNS Service (SRV)
9-8, 9-10
first in, first out (FIFO)
7-13
vii
5-2
firewalls
8-6
distributed video resource allocation
DMZ
4-2, 4-4, 8-4
feedback on this document
6-2
4-2, 4-4, 8-4
3-15
FECC
digital signal processor (DSP)
DSCP
2-6, 2-7, 9-10
for call processing
9-5
7-8
for endpoint selection
dynamic bit rate adjustment
7-9
3-15
Dynamic Host Configuration Protocol (DHCP)
9-2
H
H.323
E
4-3
H.323 standalone video networks
E.164
6-1
hardening the network
Electronic Numbering (ENUM)
embedded video resources
encryption
endpoints
ENUM
6-1
7-10
8-9
High-Density Packet Voice Video Digital Signal Processor
Module (PVDM3) 8-9
1-3, 2-3, 2-6, 7-9, 8-8, 9-7
history of
6-1
7-16
revisions
vii
this document
9-6
evolution of video solutions
expedited forwarding
9-1
8-9
high definition (HD)
9-4, 9-7
equations for calculating bandwidth usage
etokens
HD
7-19
5-1
3-8
video solutions
HMAC-SHA1
vii
3-8
9-4, 9-5
Cisco Video and TelePresence Architecture Design Guide
OL-27011-01
IN-3
Index
hosted call processing
HTTPS
7-7
9-2, 9-3
Hyper-Text Transfer Protocol Secure (HTTPS)
9-2, 9-3
IP version 6 (IPv6)
4-1, 4-7
IP video telephony
3-9
ISDN
3-8
ISDN gateways
I
ISO
3-3
ISR
8-9
3-3, 4-3
IDR
3-5
ITU
IEC
3-3
ITU-T
IETF
3-5
J
2-7
immersive video conferencing
infrastructure components
Jabber
3-11
Integrated Services Router (ISR)
3-8
L
8-9
Intercompany Media Engine (IME)
2-7
inter-enterprise video deployment model
interlaced video
latency
7-4
LDAP
3-2
6-3
9-8
Lightweight Directory Access Protocol (LDAP)
International Electrotechnical Commission (IEC)
3-3
International Organization for Standardization (ISO)
International Telecommunication Union (ITU)
Links
3-3
3-3, 4-3
International Telecommunication Union
Telecommunication Standardization Sector (ITU-T)
Internet Engineering Task Force (IETF)
Internet Protocol Security (IPsec)
4-5, 9-4
4-4
lip-sync
intra-campus video topology
intra-enterprise video topology
intra-frame compression
5-2
Locally Significant Certificate (LSC)
7-2
lossless compression
lossy compression
LTRP
9-5
5-3
Long-Term Reference Picture (LTRP)
LSC
3-12
6-3
5-3
locations
3-3,
4-3
introduction
5-1
levels of security
3-7
interoperability
5-1
3-5
Integrated Services Digital Network (ISDN)
inter-frame compression
1-3, 2-6
jitter
1-4, 2-1
Instant Decoder Refresh (IDR)
3-4, 3-5, 3-15
3-2
3-2
9-5
3-4, 3-5, 3-15
7-3
3-2
M
1-1
IP Precedence
IPsec
3-3, 4-3
4-5, 9-4
I-frame
IME
2-7
management of video networks
5-1
2-8
manipulation of caller information
4-4
IP-to-IP gateways
2-7
Manufacturing Installed Certificate (MIC)
IPv4
4-7
MCU
2-1, 3-13, 8-1, 8-4
IPv6
4-1, 4-7
media
9-4
IP version 4 (IPv4)
4-7
6-4
media encryption
9-5
9-7
Cisco Video and TelePresence Architecture Design Guide
IN-4
OL-27011-01
Index
Media Experience Engine (MXE)
Media Services Engine (MSE)
OBTP
2-8
optimizing video delivery
1-3, 2-6
Moving Picture Experts Group (MPEG)
MPEG
3-3
MPLS
3-9
MSE
multipoint device
loss of
2-1, 3-13, 8-1, 8-4
passwords
deployment guidelines
endpoints
P-frame
Pipes
8-8
Multiprotocol Label Switching (MPLS)
multi-site call processing
9-4
7-16
3-6
5-3
PKCS #10 Certificate Signing Request (CSR)
3-9
PKI
7-5
ports
PQ
N
5-2
preface
native support for endpoints
5-1
vii
presence
9-7
8-8, 8-9
Prime Collaboration Manager
4-6
Network Address Translation (NAT)
Network Address Translation Traversal (NAT-T)
network infrastructure
network management
4-6
problems, reporting
progressive scan
2-1, 2-9
2-8
5-2
vii
3-7
protocols
2-8
Network Time Protocol (NTP)
9-2
BFCP
7-15, 8-9
call control
5-1
notational conventions
Priority Queuing (PQ)
2-6, 4-6
2-4
9-8
precedence
2-6, 4-6
9-6
9-5
platforms for switching and transcoding
8-4, 8-8
network traffic
5-2
performance
8-5
8-8
selection criteria
5-1
queuing
8-3, 8-8
multipoint solution
NTP
2-9
packets
Multipoint Control Unit (MCU)
NAT-T
7-14
P
2-8
NAT
2-8, 8-9
oversubscription of network bandwidth
3-3
2-5
MXE
2-8, 8-9
One Button To Push (OBTP)
9-5
Movi
MSI
O
2-5
Media Services Interface (MSI)
MIC
8-4, 8-8
viii
9-2
CDP
4-1
2-9
DHCP
9-2
number-based dial plans
6-2
DTLS
9-5
number transformations
6-4
H.323
4-3, 9-2
HTTPS
in general
IPv4
4-7
IPv6
4-7
9-2, 9-3
4-1
Cisco Video and TelePresence Architecture Design Guide
OL-27011-01
IN-5
Index
LDAP
6-3
RFC 4347
9-5
9-4
NTP
9-2
RFC 5246
RTP
9-5
RSVP
SCCP
SIP
RSVP Agent
4-1
RTP
2-6, 4-5, 9-2
SRTCP
4-3, 9-5, 9-7
9-5
S
4-1
TIP
3-14, 8-4, 8-8, 8-9
SAFE Blueprint
TLS
4-3, 9-4
scalability
UDP
3-9, 4-3, 9-5, 9-8
SCCP
PSTN access
6-3
9-1
7-16
4-1
scheduled conferences
Public Key Infrastructure (PKI)
PVDM3
5-3
9-5
SRTP
TCP
5-3
9-5
SD
8-9
8-2
8-9
Secure Real-time Transport Control Protocol
(SRTCP) 9-5
Secure Real-time Transport Protocol (SRTP)
Q
Secure Shell (SSH)
QCIF
QoS
security
2-9, 5-1, 7-14, 9-3, 9-8
quality of a call
9-3
Session Initiation Protocol (SIP)
2-9, 5-1, 7-14, 9-3, 9-8
Quarter Common Intermediate Format (QCIF)
3-7
signaling
SIP
9-4
recording
regions
SME
5-3
related documentation
vii
7-16
Request for Comments (RFC)
resolution
3-7
restrictions to calling services
revision history
5-3
6-4
vii
4-5
RFC 3711
7-20
9-5
4-1
7-5
sockets
9-8
SRTCP
9-5
SRTP
4-5
Resource Reservation Protocol (RSVP)
RFC
2-6, 4-5, 9-2
Skinny Client Control Protocol (SCCP)
2-5
reliability
7-5
SIP standalone video networks
9-5
7-5
7-15
single-site call processing
R
2-6, 4-5, 9-2
Session Management Edition (SME)
sharing content
5-2
Real-time Transport Protocol (RTP)
9-4
4-3, 7-16, 9-1
separate VLANs
5-3
Quality of Service (QoS)
queuing
9-2, 9-3
Secure Sockets Layer (SSL)
3-7, 3-8
4-3, 9-5, 9-7
4-3, 9-5, 9-7
SSH
9-2, 9-3
SSL
9-4
standalone video networks
standard definition (SD)
streaming
2-5
switching
2-4, 8-4
symmetric port numbering
7-19
8-9
9-8
Cisco Video and TelePresence Architecture Design Guide
IN-6
OL-27011-01
Index
system architecture
UDP
1-1
3-9, 4-3, 9-5, 9-8
Unicode Transformation Format (UTF)
Unified Border Element
T
Unified CM
4-6
2-7
3-8, 5-2, 8-2
TAC
vii
Unified Communications
TCP
4-1
Unified Communications Manager (Unified CM)
TCS
2-5
Unified Communications Manager Session Management
Edition (SME) 7-5
technical assistance
vii
Technical Assistance Center (TAC)
telepresence
Unified CST
Universal Serial Bus (USB)
2-5
Telepresence Interoperability Protocol (TIP)
3-14, 8-4, 8-8,
URI
TelePresence Management Suite (TMS)
TelePresence Manager
2-8
TelePresence Recording Server
TIP
2-8, 8-2
2-5
TLS
6-3
9-6
user agent client (UAC)
4-5
user agent server (UAS)
4-5
3-9, 4-3, 9-5, 9-8
4-6
2-8, 8-2
topology for video networks
ToS
USB
UTF
4-3, 9-4
TMS
9-6
User Datagram Protocol (UDP)
3-14, 8-4, 8-8, 8-9
4-1, 6-1
4-1, 6-1
URI-based dial plans
8-9
8-9
8-9
uniform resource identifier (URI)
2-4
TelePresence Content Server (TCS)
3-8, 8-2
Unified Communications Sizing Tool (Unified CST)
vii
1-1, 2-1, 3-11
TelePresence Conductor
1-1, 2-1
7-1
V
5-1
traffic
VCS
classification
VCS Control
7-14
on the network
transformations of dialed numbers
6-4
Transmission Control Protocol (TCP)
Transport Layer Security (TLS)
TURN
2-7
architecture
2-2
as a service
7-7
classes of service
5-1
2-3
cloud-hosted solutions
3-12
compression
3-1
conferencing
3-10, 3-11, 8-1
endpoints
2-7
Type of Service (ToS)
4-1
4-3, 9-4
Traversal Using Relay NAT (TURN)
5-2
2-6, 2-7, 9-10
video
5-2
2-4, 8-4
trust boundary
2-6, 9-10
VCS Expressway
5-1
shaping and policing
transcoding
2-6, 3-8, 4-7, 5-2, 8-2, 9-7
frame
1-3, 2-3, 2-6
3-1, 3-4
history of solutions
3-8
infrastructure components
U
introduction
1-4, 2-1
1-1
UAC
4-5
network management
UAS
4-5
optimizing delivery
2-8
7-14
Cisco Video and TelePresence Architecture Design Guide
OL-27011-01
IN-7
Index
over ISDN
products
3-8
2-1
recording
2-5
resolution
3-7
resource allocation
7-10
standalone networks
streaming
2-5
telephony
3-9
7-19
Video Communication Server (VCS)
2-6, 3-8, 4-7, 5-2, 8-2,
9-7
Video Communication Server Expressway
(VCS Expressway) 9-10
Virtual Channel Link (VLC)
3-4
Virtual Local Area Network (VLAN)
VLAN
VLC
2-9, 9-3
3-4
Voice over IP (VoIP)
VoIP
2-9
6-1
6-1
W
WebEx OneTouch integration
Weighted Fair Queuing (WFQ)
WFQ
8-9
5-2
5-2
X
X.509 v3 certificates
9-5
Cisco Video and TelePresence Architecture Design Guide
IN-8
OL-27011-01
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