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How users access packet
networks?
Example -1 – Access
Multiplexing
* The diagram
above shows an access network with a point to point topology where computer in
homes are connected to an access multiplexer located in service provider
network.
* The main
purpose of the access multiplexer is to combine the bursty traffic flows from
individual computers into aggregated flows.
* Eg1. DSL
traffic multiplexed at DSL Access Mux
* Eg2. Cable
modem traffic multiplexed at Cable Modem Termination System
* Private IP
addresses in Home is done using Network Address Translation (NAT).
Example -2-
Campus Network
• LANs are interconnected through use of LAN switches identified by
letter ‘S’ in the figure.
• Resources such as servers and databases that are primarily use are
kept within the subnet. This reduces delay in accessing resources.
• Subnet has access to rest of organization through router R that
access campus backbone network.
• Subnet uses campus backbone to reach outside world such as Internet
through a border router.
• Servers containing critical resources that are required by entire
organization are located in a data center where it can be easily maintained and
security can be enforced
• Critical Servers maybe provided with redundant paths to campus
backbone network
• The routers in the campus network are interconnected to form the
campus backbone network.
Example -3 Connecting
to Internet Service Provider
• Domain: the routers running the same routing protocol
• Autonomous System: one or more domains under the single
administration.
• The campus network maybe connected to internet service provider
(ISP) through one or more border routers.
• To communicate with other networks, the autonomous system must provide
information about its network routes in border routers.
• The border router communicates on an interdomain level, whereas
other routers operate at an intradomain level.
Example -4:-
Internet Backbone
• National ISP provides points of presence (POPs) where customer can
connect to their network
• The ISP has its own national backbone network for interconnecting
its POPs
• The ISPs exchange traffic at public peering points called network
access points (NAPs)
• NAP is a collocated set of high-speed routers through which the
routers from different ISPs exchange traffic.
• Private peering points can be used to connect ISPs to exchange
traffic directly with agreement routing polices.
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