Inter-regional Support of Ethernet Services over Any L2 Transport
EoMPLS enables Ethernet to be transported over any Layer 2 transport and over existing
IP/MPLS wide area networks, as discussed previously. Where service providers
want to offer inter-regional Ethernet services with statistical gain, EoMPLS is the
natural choice. Statistical gain is important when offering Ethernet services as most
Ethernet links are very lightly loaded and is even more important in the inter-regional
case where transport costs are relatively high. Where service providers have ???islands???
of Layer 2 Ethernet in major metropolitan areas Ethernet over MPLS may be used to
interconnect those islands, enabling the provider to traffic engineer the wide area links
and to ensure fast protection against failures of those links. The alternative would be
to use Ethernet over SONET/SDH to interconnect the islands. Ethernet over SONET/
SDH could be provisioned with a single GFP-encapsulated VCAT group per pair of
islands, but this, in fact, will tend to cause increased latency and jitter and lower network
utilisation as only a few services would be mapped onto each VCAT group and as
each VCAT group would have a much lower speed than the overall bandwidth demand
per island (lower speed increases serialisation delay as packets are ???clocked??? out onto
the link and also increases jitter for any given level of link loading).
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