Introduction to Networking Topologies and Definitions

Network Topology and Definitions
• Definitions and icons
• Network topologies
• PoP topologies
• Interconnections and IXPs
Introduction to Networking
• IP Addressing
ISP/IXP Workshops
Cisco ISP
Workshops
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• Gluing it all together
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Cisco ISP
Workshops
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Some Icons…
Router
(layer 3, IP datagram forwarding)
ATM or Frame Relay switch
(layer 2, frame or cell forwarding)
Topologies and Definitions
Ethernet switch
(layer 2, packet forwarding)
What does all the jargon mean?
Network Cloud
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Network Topologies
Network Topologies
Routed backbone
Switched backbone
• Routers are the
infrastructure
• frame relay or ATM
switches in the core
surrounded by routers
• Physical circuits run
between routers
• Physical circuits run
between switches
• Easy routing
configuration, operation
and troubleshooting
Virtual circuits run between
routers
• more complex routing and
debugging
• The dominant topology
used in the Internet
today
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Workshops
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• “traffic management”
• Virtually obsolete today
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1
Definitions
PoP Topologies
• Core routers
• PoP – Point of Presence
high speed trunk connections
Physical location of ISP’s equipment
• Distribution routers
higher port density, aggregating network edge to the network
core
Sometimes called a “node”
• vPoP – virtual PoP
• Access routers
To the end user, it looks like an ISP location
high port density, connecting the end users to the network
• Border routers
In reality a back hauled access point
connections to other providers
Used mainly for consumer access networks
• Service routers
• Hub/SuperPoP – large central PoP
hosting and servers
Links to many PoPs
Cisco ISP
Workshops
• Some functions might be handled by a single router
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Cisco ISP
Workshops
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Definitions
PoP Topologies
service
other
PoPs
core
to other provider
or interconnects
• Transit
carrying traffic across a network, usually for
a fee
border
• Peering
distribution
access
exchanging routing information and traffic
access
• Default
where to send traffic when there is no
explicit match in the routing table
Customer Premises Routers/Hosts
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Workshops
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Peering and Transit example
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Private Interconnect
Autonomous System 334
provider A
IXP-West
IXPEast
network B
Backbone
Provider D
border
border
network A
provider B
provider C
A and B can peer, but need transit
arrangements with D to get packets
to/from C
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Workshops
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Autonomous System 99
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Workshops
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2
Public Interconnect Point
Public Interconnect Point
• Centralised (in one facility)
• A location or facility where several ISPs are
present and connect to each other over a
common shared media
• Distributed (connected via WAN links)
• Shared, switched or routed interconnect
• Why?
Router (Layer 3) or Ethernet (Layer 2)
Technologies such as FDDI, ATM, Frame relay, SMDS,
have been used in the past
To save money, reduce latency, improve performance
• IXP – Internet eXchange Point
• Each provider establishes peering relationship
with other providers at IXP
• NAP – Network Access Point
ISP border router peers with all other provider border
routers
Cisco ISP
Workshops
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Public Interconnect
ISP 1
ISP 2
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Route Server
• Purpose:
ISP 4
IXP
Cisco ISP
Workshops
Collects all the routes heard from ISPs at the IXP and
sends them to all ISPs at the IXP
• Advantages:
ISP 5
reduces resource burden on border routers (CPU, memory,
configuration complexity)
reduces administrative burden on providers
ISP 3
• Disadvantages:
ISP 6
must rely on a third party (for management, configuration,
software updates, maintenance, etc)
each of these represents a border router in a different autonomous system
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Workshops
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Route Collector
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Workshops
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Route Server/Collector
• Purpose:
ISP 1
Collects all the routes heard from ISPs at the IXP
ISP 4
• Advantages
Allows IXP participants to see destinations available at the
IXP
ISP 2
Useful for troubleshooting, information, “IXP Marketing”
IXP
ISP 5
• Disadvantages
Needs to be maintained, but not critical to IXP operation
Information is only as good as that which ISPs send to it
ISP 3
• Basically a Route Server without the ability to send
routing information to participant ISPs
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Workshops
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ISP 6
Route Server/Collector
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3
IP Addressing
• Internet is classless
• Concept of Class A, class B or class C is no more
engineers talk in terms of prefix length, for example the
class B 158.43 is now called 158.43/16.
Cisco ISP
Workshops
IP Addressing
• All routers must be CIDR capable
Where to get address space and who from
RFC1812 – Router Requirements
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Classless InterDomain Routing
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IP Addressing
Cisco ISP
Workshops
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IP Addressing
• Pre-CIDR (<1994)
• IPv4 Address space is a resource shared amongst all
Internet users
big networks got a class A
medium networks got a class B
Regional Internet Registries delegated allocation
responsibility by the IANA
small networks got a class C
AfriNIC, APNIC, ARIN, LACNIC & RIPE NCC are the five RIRs
RIRs allocate address space to ISPs and Local Internet
Registries
• Nowadays
allocations/assignments made according to
demonstrated need – CLASSLESS
ISPs/LIRs assign address space to end customers or other
ISPs
• 67% of usable IPv4 address space has been allocated
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Workshops
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Definitions
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Workshops
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Definitions
• Non-portable – ‘provider aggregatable’ (PA)
Customer uses RIR member’s address space while
connected to Internet
• Portable – ‘provider independent’ (PI)
Aids control of size of Internet routing table
Customer gets or has address space
independent of ISP
May fragment provider block when multihoming
Customer keeps addresses when changing ISP
Customer has to renumber to change ISP
• PA space is allocated to the RIR member with the
requirement that all assignments made by the
RIR member to end sites are announced as an
aggregate to the rest of the Internet
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Workshops
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Considered bad for size of Internet routing table
PI space is rarely distributed by the RIRs
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Workshops
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4
Default Free Zone
The default free zone is made up
of Internet routers which have
explicit routing information about
the rest of the Internet, and
therefore do not need to use a
default route.
Internet Hierarchy
The pecking order
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Workshops
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Workshops
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High Level View of the Global Internet
Categorising ISPs
Tier 1 NSP
Default Free Zone
$
$
$
$
$
$
$
$
$
$
$
$
$
$
$
Backbone
Provider 2
Local NAP or IXP
Access
Providers 2
Customer Networks
Cisco ISP
Workshops
Tier 1 NSP
Default Free Zone
Backbone
Provider 1
Access
R4 1
Providers
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Tier 1 NSP
Tier 1 NSP
Tier 2 ISP
Tier 2 ISP
Tier 2 ISP
Tier 2 ISP
IXP
Tier 3 ISP
IXP
Tier 3 ISP
Tier 3 ISP
Cisco ISP
Workshops
Tier 3 ISP
Tier 3 ISP
Tier 3 ISP
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Inter-provider relationships
• Peering between equivalent sizes of service
providers (e.g. Tier 2 to Tier 2)
shared cost private interconnection, equal traffic flows
“no cost peering”
• Peering across exchange points
Gluing it together
if convenient, of mutual benefit, technically feasible
• Fee based peering
unequal traffic flows, “market position”
Cisco ISP
Workshops
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Cisco ISP
Workshops
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5
Gluing it together
Engineers keep talking to each other...
• North America
• Who runs the Internet?
NANOG (North American Network Operators Group)
No one
NANOG meetings and mailing list
• How does it keep working?
www.nanog.org
Inter-provider business relationships and the need for
customer reachability ensures that the Internet by and
large functions for the common good
To subscribe: majordomo@merit.edu
subscribe nanog-post xxxx@yyyy.zzzz
• Any facilities to help keep it working?
subscribe nanog xxxx@yyyy.zzzz
Not really. But…
• Latin America
Engineers keep talking to each other!
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Workshops
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Foro de Redes
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Engineers keep talking to each other...
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Workshops
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Engineers keep talking to each other...
• Asia & Pacific
• Europe
APRICOT annual conference
www.apricot.net
RIPE meetings, working groups and mailing
lists
APOPS & APNIC-TALK mailing lists
mailman.apnic.net/mailman/listinfo/apops
Routing WG:
www.ripe.net/mailman/listinfo/routing-wg
mailman.apnic.net/mailman/listinfo/apnic-talk
PacNOG (Pacific NOG)
EOF (European Operators Forum)
mailman.apnic.net/mailman/listinfo/pacnog
www.ripe.net/mailman/listinfo/eof-list
SANOG (South Asia NOG)
E-mail to sanog-request@sanog.org
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Engineers keep talking to each other...
Cisco ISP
Workshops
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Summary
• Africa
• Network Topologies and Definitions
AfNOG meetings and mailing list
• IP Addressing
listserv2.cfi.co.ug/mailman/listinfo/afnog
PI versus PA address space
• And many in-country ISP associations and
NOGs
• Gluing it all together
• IETF meetings and mailing lists
Engineers co-operate
www.ietf.org
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Workshops
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Cisco ISP
Workshops
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6
Introduction to Networking
ISP/IXP Workshops
Cisco ISP
Workshops
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37
7
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