g., to Internet Service Provider)
Local
Access
Loop
Local
Access
Loop
10s of miles 100/1000s of miles 10s of miles
Ethernet: From LAN to the WAN 25
Carriers and across different regions of the world and to a large extent are dictated by local
and national regulatory constraints, the figure represents a reasonable generalization.
As Figure 1.9 illustrates, enterprise customers are usually connected to the Service
Provider infrastructure employing a TDM access circuit such as DS-0, T-1 (or DS-1), and
OC-3 to connect to a Service Provider??“owned SONET-based Multi-Service Provisioning
Platform (MSPP) at its closest Point-Of-Presence/Central Office. The MSPPs are generally
deployed in a ring topology (since this topology is physically supportive of a more
resilient architecture) across a metro area and are used as collector rings. If traffic is
TABLE 1.3 Comparing LANs to MANs/WANs
Local Area Network (LAN) Metro/Wide Area Network (MAN/WAN)
Geographic coverage Usually a few hundred meters
but typically less than a mile
10s, 100s, or even 1000s of miles
Service delivery model Enterprise owns and operates
the LAN and delivers
applications over it.
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