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TECHNICAL
REPORT
ISO/IEC
TR
12860
First edition
2009-04-15
Information technology —
Telecommunications and information
exchange between systems — Next
Generation Corporate Networks
(NGCN) — General
Technologies de l'information — Télécommunications et échange
d'information entre systèmes — Réseaux d'entreprise de prochaine
génération (NGCN) — Généralités
Reference number
ISO/IEC TR 12860:2009(E)
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ISO/IEC TR 12860:2009(E)
Contents
Page
Foreword............................................................................................................................................................. v
Introduction ....................................................................................................................................................... vi
1
Scope ..................................................................................................................................................... 1
2
Normative references ........................................................................................................................... 1
3
Terms and definitions........................................................................................................................... 2
4
Abbreviated terms ................................................................................................................................ 4
5
Background ........................................................................................................................................... 5
6
6.1
6.2
6.2.1
6.2.2
6.2.3
6.3
6.4
6.4.1
6.4.2
6.5
6.5.1
6.5.2
6.5.3
6.5.4
General concepts.................................................................................................................................. 6
Basic communication architecture ..................................................................................................... 6
Session level architecture ................................................................................................................... 8
Signalling using SIP ............................................................................................................................. 8
Media path ........................................................................................................................................... 10
Example ............................................................................................................................................... 10
Domains ............................................................................................................................................... 10
Mobility ................................................................................................................................................ 11
Roaming of enterprise users outside their home domain.............................................................. 12
Accommodating guest users on an NGCN ...................................................................................... 13
The hosting concept........................................................................................................................... 13
Dedicated NGCN ................................................................................................................................. 14
Enterprise hosted by a single public network infrastructure......................................................... 15
Enterprise hosted by multiple public network infrastructures ...................................................... 15
Enterprise hosted by a combination of enterprise infrastructure and a public network
infrastructure....................................................................................................................................... 16
Private network traffic and public network traffic ........................................................................... 16
Other technical considerations ......................................................................................................... 17
6.6
6.7
7
7.1
7.2
7.2.1
7.2.2
7.2.3
7.2.4
7.2.5
7.2.6
7.3
7.3.1
7.3.2
7.3.3
7.3.4
7.3.5
7.4
7.4.1
7.4.2
Scenarios for session-based communications ............................................................................... 17
Session-based intra-domain communications................................................................................ 18
Session-based inter-domain communications within a single enterprise network .................... 19
Communication between domains supported by the same infrastructure .................................. 20
Communications between domains of an NGCN via a TSP ........................................................... 21
Communications between domains of an NGCN using private network traffic through a
hosting NGN ........................................................................................................................................ 21
Communications between domains of an NGCN using public network traffic through a
public SSP such as an NGN .............................................................................................................. 22
Communications between a dedicated NGCN domain and a domain hosted by an NGN .......... 22
Communications between a dedicated NGCN domain and a domain hosted by an NGN as
private network traffic via an intermediate NGN domain................................................................ 22
Session-based communication between two enterprises ............................................................. 23
Extension of enterprise network to include partner networks ...................................................... 23
Direct peering...................................................................................................................................... 23
Indirect peering ................................................................................................................................... 24
Third party assistance........................................................................................................................ 25
Direct peering between two enterprises hosted by the same hosting enterprise
infrastructure....................................................................................................................................... 26
Session-based communication with users of public networks..................................................... 26
Communication between an NGCN user and an NGN public network user................................. 26
Communication between an NGCN user and an NGN public network user with break-in or
break-out function in the NGN........................................................................................................... 27
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7.4.3
7.4.4
7.5.3
7.5.4
7.5.5
7.5.6
Communication between an NGCN user and a public network user of a remote NGN............... 28
Communication between an NGCN user and a public network user of a remote NGN with
break-in or break-out function in the local NGN .............................................................................. 28
Communication between an NGCN user and a public network user of a remote NGN with
break-in or break-out function in the remote NGN .......................................................................... 28
Communication between an NGCN user and a PSTN/ISDN user via an NGN .............................. 29
Communication between an enterprise user hosted by a public network infrastructure
and a public network user of that same infrastructure................................................................... 30
Session-based roaming...................................................................................................................... 30
An NGCN user at a visited sub-domain of the NGCN ..................................................................... 30
An NGCN user at a visited sub-domain of the NGCN using private network traffic through
an NGN ................................................................................................................................................. 31
An NGCN user at a visited NGN......................................................................................................... 31
An NGCN user at a visited NGN using indirect roaming ................................................................ 31
An NGN-hosted enterprise user at a visited NGN............................................................................ 32
An NGN-hosted enterprise user at a visited NGCN ......................................................................... 32
8
8.1
8.1.1
8.1.2
8.1.3
8.2
8.2.1
8.2.2
8.2.3
NGN considerations............................................................................................................................ 32
Summary of scenarios involving NGN.............................................................................................. 32
Scenarios involving NGN as a TSP ................................................................................................... 32
Scenarios involving NGN as a SSP ................................................................................................... 33
Roaming scenarios involving NGN as a SSP................................................................................... 33
Interfacing NGCN to NGN................................................................................................................... 33
Subscription-based business trunking ............................................................................................ 33
Peering-based business trunking ..................................................................................................... 34
Roaming ............................................................................................................................................... 34
9
Application considerations ................................................................................................................ 34
10
10.1
10.2
10.3
10.4
10.5
Current standards and standardisation efforts ............................................................................... 36
IETF Real-time Applications and Infrastructure (RAI) area ............................................................ 36
SIP Forum ............................................................................................................................................ 36
ETSI TISPAN ........................................................................................................................................ 36
3GPP..................................................................................................................................................... 37
ITU-T Study Group 13 ......................................................................................................................... 37
7.4.5
7.4.6
7.4.7
7.5
7.5.1
7.5.2
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Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC TR 12860 was prepared by Ecma International (as ECMA TR/95) and was adopted, under a special
“fast-track procedure”, by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel with
its approval by national bodies of ISO and IEC.
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ISO/IEC TR 12860:2009(E)
Introduction
This Technical Report is the first of a series of publications that explore IP-based enterprise communication
involving Corporate telecommunication Networks (CNs) (also known as enterprise networks) and in particular
Next Generation Corporate Networks (NGCN). The series particularly focuses on inter-domain
communication, including communication between parts of the same enterprise, between enterprises and
between enterprises and carriers. This particular Technical Report provides general information on the subject,
defines some architectural concepts, identifies various communication scenarios, and provides a framework in
support of other publications that provide greater detail on particular topics.
This Technical Report is based upon the practical experience of Ecma member companies and the results of
their active and continuous participation in the work of ISO/IEC JTC 1, ITU-T, ETSI, IETF and other
international and national standardization bodies. It represents a pragmatic and widely based consensus. In
particular, Ecma acknowledges valuable input from experts in ETSI TISPAN.
vi
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TECHNICAL REPORT
ISO/IEC TR 12860:2009(E)
Information technology — Telecommunications and information
exchange between systems — Next Generation Corporate
Networks (NGCN) — General
1
Scope
This Technical Report is part of a series of publications that provides an overview of IP-based enterprise
communication involving Corporate telecommunication Networks (CNs) (also known as enterprise networks)
and in particular Next Generation Corporate Networks (NGCN). The series particularly focuses on session
level communication based on the Session Initiation Protocol (SIP) [6], with an emphasis on inter-domain
communication. This includes communication between parts of the same enterprise (on dedicated
infrastructures and/or hosted), between enterprises and between enterprises and public networks. Key
technical issues are investigated, current standardisation work and gaps in this area are identified and a
number of requirements are stated.
This particular Technical Report provides general information on the subject, defines some architectural
concepts, identifies various communication scenarios, and provides a framework in support of other
publications that provide greater detail on particular topics. At the time of publication of this Technical Report,
one further document in the series has been published, on the subject of identification and routing [3].
The scope of this Technical Report is limited to communications with a real-time element, including voice,
video, real-time text and instant messaging.
Further details on mobility in an NGCN environment are to be found in ISO/IEC TR 26927 [2].
2
Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
[1] ISO/IEC 18051:2007, Information technology — Telecommunications and information exchange
between systems — Services for Computer Supported Telecommunications Applications (CSTA)
Phase III
[2] ISO/IEC TR 26927:2006, Information technology — Telecommunications and information exchange
between systems — Corporate Telecommunication Networks — Mobility for Enterprise
Communications
[3] ISO/IEC TR 12861:2009, Information technology — Telecommunications and information exchange
between systems — Next Generation Corporate Networks (NGCN) — Identification and routing
[4] ITU-T Recommendation H.248, Gateway control protocol
[5] ITU-T Recommendation H.323, Packet-based multimedia communications systems
[6] IETF RFC 3261, SIP: Session Initiation Protocol
[7] IETF RFC 3550, RTP: A Transport Protocol for Real-Time Applications
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[8] IETF RFC 4566, SDP: Session Description Protocol
[9] SIP Forum sf-adopted-twg-IP_PBX_SP_Interop-sibley-sipconnect “IP-PBX / Service Provider
Interoperability - SIPConnect 1.0 Technical Recommendation”
[10] ETSI EG 201 017, Corporate Telecommunication Networks (CN); Standardization plan
[11] ETSI TR 180 000, Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Terminology
[12] IEEE 802.1x, Port Based Network Access Control
3
Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
Corporate telecommunication Network (CN) (ETSI EG 201 017 [10])
Telecommunication network serving a corporation, i.e. a single organization, an extended enterprise, or an
industry application group as defined by the International Chamber of Commerce (ICC).
NOTE
Sets of equipment [Customer Premises Equipment (CPE) and/or Customer Premises Networks (CPN)] are
typically located at geographically dispersed locations and are interconnected to provide networking services to a defined
group of users. A CN can employ connection-oriented and connectionless technology.
3.2
Domain
Session level capabilities within a single administrative area.
NOTE
A domain may or may not correspond to a DNS domain.
3.3
Enterprise network
A CN comprising session level capabilities and optionally application layer capabilities hosted on one or more
infrastructures.
NOTE
Infrastructures can include the enterprise's own infrastructure (dedicated NGCN), the infrastructure of one or
more hosting NGNs, the infrastructure of one or more hosting NGCNs or any combination of these.
3.4
Home server
For a given user, as identified by a SIP address of record, the SIP intermediary that contains registrar and
proxy functionality in support of that user.
NOTE
It is therefore the SIP intermediary with which the user's UAs register.
3.5
Transport service provider (TSP)
A business or organisation separate from an enterprise that provides services for transporting data based on
the use of IP at the network layer, thereby allowing the enterprise to communicate with entities outside the
enterprise or with geographically dispersed parts of the enterprise.
NOTE 1
Communication can but need not be via the public Internet.
NOTE 2
A TSP should not intervene above the transport layer. This does not preclude a business or organisation that
acts as a TSP also acting as the provider of higher level services, e.g., as an SSP.
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3.6
Medium
A given type of payload transported between session users (e.g., audio, video, text), separate from any
signalling used for session establishment.
3.7
Next Generation CN (NGCN)
That part of an enterprise network that is not based on public network infrastructure, that is designed to take
advantage of emerging IP-based communications solutions and that can have its own applications and
service provisioning.
NOTE
An NGCN can be an entire enterprise network if none of that network is based on public network infrastructure.
3.8
Next Generation Network (NGN)
The definition in ETSI TR 180 000 applies.
NOTE
This defines an NGN as follows: “A Next Generation Network is a packet-based network able to provide
services including Telecommunication Services and able to make use of multiple broadband, QoS-enabled transport
technologies and in which service-related functions are independent from underlying transport-related technologies. It
offers unrestricted access by users to different service providers. It supports generalized mobility which will allow
consistent and ubiquitous provision of services to users.” It also goes on to list some fundamental aspects that
characterise NGN.
3.9
Private network traffic
Signalling for session level communications that is handled according to rules specific to an enterprise
network.
3.10
Public network traffic
Signalling for session level communications that is handled according to rules for public networks.
3.11
Roaming
The use of session capabilities of a visited domain to allow a user to access session level services at his
home domain.
NOTE 1
This usually requires a roaming agreement between the operators of the domains concerned.
NOTE 2
This definition of roaming reflects the concept of roaming as found in mobile telephone networks, for example.
It does not encompass certain other common uses of the term, e.g., concerning transport service provision.
3.12
Roaming hub
A network or other entity with which an enterprise domain has a roaming agreement, allowing enterprise users
to visit other domains that have a roaming agreement with the roaming hub but not directly with the enterprise
domain.
3.13
Session service provider (SSP)
A business or organisation separate from an enterprise that provides communication capabilities at the
session layer using SIP and thereby allows the enterprise to communicate using SIP with entities outside the
enterprise or with geographically dispersed parts of the enterprise.
3.14
SIP intermediary
Any intermediate entity involved either actively or passively in SIP signalling between two UAs, including but
not limited to proxies, Back-to-Back User Agents (B2BUAs), Application Layer Gateways (ALGs) and Session
Border Controllers (SBCs).
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Abbreviated terms
ALG
Application Layer Gateway
B2BUA
Back-to-Back User Agent
CN
Corporate telecommunication Network
DNS
Domain Name System
IP
Internet Protocol
IPPBX
IP Private Branch eXchange
IPSEC
Internet Protocol Security
ISDN
Integrated Services Digital Network
LAN
Local Area Network
NAT
Network Address Translator
NGCN
Next Generation Corporate Network
NGN
Next Generation Network
PSTN
Public Switched Telephone Network
QoS
Quality of Service
RTP
Real Time Protocol
SBC
Session Border Controller
SDP
Session Description Protocol
SIP
Session Initiation Protocol
SRTP
Secure Real Time Protocol
SSP
Session Service Provider
TLS
Transport Layer Security
TSP
Transport Service Provider
UA
User Agent
UAC
User Agent Client
UAS
User Agent Server
URI
Universal Resource Identifier
WAN
Wide Area Network
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5
Background
Many enterprises and other organisations require their own telecommunications capabilities to support their
own internal communications as well as supporting communications with the outside world. This avoids
incurring unnecessary charges and provides added value in terms of services and features available,
integration with other enterprise applications, etc. These capabilities are provided through enterprise
telecommunication networks (or corporate telecommunication networks, CN, or simply enterprise networks).
Many administrations do not apply the same licensing conditions or regulation to enterprise networks and their
internal traffic as they do to public networks and their public network traffic. Many public networks also offer
optional services to corporate customers, such as hosted (Centrex) services and the leasing and maintenance
of customer premises equipment.
There has been a major evolution in enterprise telecommunications during the last few years. Prior to that,
enterprise network were based on 64 kbit/s circuit-switched technology, which had synergy with
corresponding technology deployed in public Integrated Services Digital Networks (ISDN) and traditional
analogue services. Those enterprise networks primarily delivered a voice or telephony service to their users,
although in principle they were capable of other services too, including video and various types of data service.
For communication outside the enterprise, enterprise networks were able to interwork with public ISDNs
across standardized interfaces (at the T-Reference Point). The T reference point formed the demarcation
point between standards and regulations applicable to public networks and standards and regulations
applicable to enterprise networks and their PBXs.
With the advent of technologies for transmitting voice and other real-time media over the Internet Protocol (IP)
(e.g., based on Real Time Protocol (RTP) [7]) and corresponding new signalling protocols (e.g., H.323 [5], the
Session Initiation Protocol (SIP) [6]), there was potential for providing telephony and other real-time person-toperson services in the public Internet. Moreover, such services also became possible in the IP-based
“intranets” already deployed in enterprises for data services such as corporate email, file transfer, corporate
web services and access to the world wide web. Enterprises saw advantages such as savings on
infrastructure costs (e.g., one wire to the desk) and the introduction of innovative services that exploited the
convergence of real-time and data communication. The traditional PBX (Private Branch Exchange) was
replaced by or evolved to an “IP-PBX” or “soft switch” that supported IP connectivity to the desktop and IP
connectivity between nodes. Direct IP-based transmission of multimedia between endpoints meant that
switching capabilities were no longer required, except gateways for interworking with “legacy” circuit-switched
networks and media servers for conference bridging, announcements, etc. The “IP-PBX” or “soft switch” was
just required to handle signalling.
IP-based enterprise networks are continuing to evolve, to support additional services, improved security,
improved Quality of Service (QoS), etc. Moreover, SIP has become the dominant signalling protocol. An
enterprise network that fully embraces IP technology and uses SIP as the signalling protocol is referred to
here as a Next Generation CN (NGCN). An NGCN could still contain some components that are not based on
IP (e.g., traditional PISN components) or that use signalling other than SIP (e.g., H.323 [5], H.248 [4]), but it
would also include SIP components and be able to interface externally using SIP.
Until recently, NGCNs generally fell back to legacy circuit-switched techniques for standardised
communication outside the enterprise, e.g., using public ISDN or circuit-switching over leased lines. Gateways
provided the necessary interworking of signalling and media. This was sometimes the case also for
communication between different parts of the same enterprise.
We are now witnessing a period when NGCNs are extending IP-based communication externally by
interfacing to public IP-based networks. This permits IP-based communication between:
•
enterprise users supported by different NGCNs (i.e., different enterprises),
•
enterprise users supported by different parts of the same NGCN at geographically dispersed locations
(different sites);
•
enterprise users supported by NGCN and users supported by hosted enterprise services provided on
public network infrastructure;
•
enterprise users supported by NGCNs and individual users of public networks (fixed or mobile); and
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