Employing it in Service Provider networks is a different matter. There
are many more endpoints that need to be connected in a typical MAN (thousands of connections)
versus those in a typical LAN (tens of connections). Apart from the scalability to
support so many more customers, failure mechanisms from the LAN such as the Spanning
42 Chapter 1
Tree Protocol (STP) and its variants are ineffectual with such large deployments because
of the long convergence time (the time taken to recover from a failure).
Quality of Service (QoS) As previously mentioned, Ethernet is being considered as
a platform for convergence so that all services are delivered by the carrier over an
Ethernet connection. If this is done, then Ethernet should be able to support a variety
of different applications, including latency sensitive voice and video applications. The
Service Providers would have to ensure a Quality Of Service (QoS) for such services
over Ethernet, something that is generally lacking because Ethernet was mainly confined
to LANs, and in that context, a best effort has been largely acceptable.
Support for TDM Services While Ethernet as a convergent platform makes for operational
simplicity and reduced costs, it is somewhat na??ve to assume that the billionsin-
revenues that TDM services provide will be flash-cut over to packetized services.
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