g., aggregation of multiple emulated T1 lines into a single T3 or OC-3 link), creating
a Multipoint-to-Point or even a Multipoint-to-Multipoint configuration, as shown in
Figure 2.19.
The service multiplexing is carried out using standard TDM multiplexing techniques
and is considered part of the TSP block, rather than the CES inter-working function.
The TDM interface at the input of the CES inter-working function is the same as the
output from the CES IWF at the opposite end of the emulated link. It is the TSP that
may be used to multiplex (or de-multiplex) that TDM service into the actual TDM service
provided to the customer. This allows a TDM service to a customer to be provided as
a collection of emulated services at lower rates.
There are, therefore, three modes of operation: unstructured emulation, structured
emulation, and multiplexing mode; in all three modes, the delivery of the TDM service
employs Ethernet Virtual Connections (EVCs) as shown in the Figure 2.19.
In unstructured emulation, the service is Point-to-Point and will have the identical
TDM handoff on either end. The CES capability should maintain integrity across the
network.
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