For example, an EPLAN service between 8 sites
requires 56 lightpaths, which can easily lead to lightpath blocking even with 16 or 32
channel DWDM networks.
In summary, EPLAN services will mandate full Layer 2 switching functionality at
the service endpoints. Although some OADM thin-mux blades may offer switching
support, these units cannot generally match the features and price-points of ???best-ofbreed???
Ethernet systems, forcing a difficult compromise. Carriers may also find it costly
and time consuming to integrate these specialized subsystems into their embedded
OSS systems. As a result, the most feasible alternative will be to furnish EPLAN at
the Ethernet/MPLS switching layers and interconnect these devices using underlying
point-to-point EoF or EoWDM EPL services.
Benefits and Shortcomings
Carriers can use a variety of technologies to deliver carrier-grade Ethernet services,
including high-end Ethernet switching, EoS, Ethernet over MPLS (EoMPLS), Ethernet
over RPR (EoRPR), and of course EoF/EoWDM. The related data and control plane protocol
stacks are shown in Figure 8.8 and further details can be found in other chapters
Figure 8.
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