A snapshot of the current distribution of services by enterprise spending is shown in
Figure 1.18 and vividly illustrates54 that Ethernet currently forms a very small portion
(3 percent) of the total. It is implausible to assume that the other 97 percent will
migrate to Ethernet in a short period of time. For one thing, end users (and Service
Providers) have spent a considerable amount of effort and cost stabilizing their TDMbased
services, and there is invariably some real-and perceived risk involved in moving
to an Ethernet-based service. For end users who have grown comfortable with TDM
(or ATM or Frame Relay) services for their mission-critical applications, moving to
Ethernet is, therefore, not compelling??”particularly if there is no short-term growth in
bandwidth or new packet-based applications being introduced.
It is realistic to assume that demand for TDM (and other incumbent) services will not
dramatically reduce for a while longer. This offers a new challenge for Service Providers
that, in an attempt to optimize their delivery infrastructure, are migrating to a packetbased
(Ethernet) infrastructure; they should be able to support the delivery of TDM
(and other packet and non-packet-based) services over an Ethernet infrastructure using
some kind of emulation techniques
Operations, Administration, and Maintenance (OAM) Finally, managing these Ethernet
services in a MAN/WAN imposes significant new challenges.
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