Nevertheless, given the ongoing deployment and
expansion of metro-area DWDM infrastructures, particularly ROADM, it is widely expected
that EoWDM will emerge as the preferred native-mode EPL-over-fiber solution.
Ethernet Private LAN Services (EPLAN)
EPLAN is a multipoint-to-multipoint (any-to-any) service designed to support Ethernet
transparent LAN and Ethernet virtual private networks (Layer 2 VPN) applications
[14]. Similarly, EVPLAN is a further enhancement that allows for multiple EPLAN
entities to share a single port. These services basically interconnect multiple customer
sites, making them appear linked by a LAN segment. These services require some form
220 Chapter 8
of packet broadcasting over WAN/MAN domains, which is very difficult to achieve at the
optical layer. Perhaps the only means of implementing EPLAN at the optical layer (e.g.,
via EoF or EoWDM) is to establish direct connectivity between all source-destination
pairs (e.g., dark fiber or WDM lightpath mesh). In the EoF case, this approach is too
exorbitant and will quickly lead to fiber-exhaust. Similarly, in the EoWDM case, it will
lead to wavelength exhaust (unscalable).
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