The Ethernet over MPLS technology is
reasonably complex, and provides benefits in terms of network scaling and statistical
gain which may not be required in all deployments. We will now look at some examples
456 Chapter 14
where alternative technologies may be a better choice than Ethernet over MPLS, as
well as at an example where the technology is sometimes mis-used.
When Access Speed Is Equal to Trunk Speed
Packet switching technologies obtain statistical gain by multiplexing many traffic demands
onto shared facilities that are much larger than any single traffic demand. Where
providers wish to offer point-to-point services of similar speed to that of the trunks in
their network, it is generally best to dedicate facilities to each service to avoid congestion
when multiple services send traffic at full rates simultaneously. For Ethernet services,
this generally implies dedicating a fibre or wavelength to each such service, in which
case, it is much more cost effective for the provider to connect their customer directly
to a transponder than to deploy additional packet switching equipment. For multipoint
services, EoMPLS still makes sense, however, as different flows across the access interface
need to be switched to different destinations on the provider??™s network.
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