5??? details some scenarios).
Many customers may request lower-priced fractional (subrate) EPL services with
speeds ranging from 50 Mbps to 1.0 Gbps. This is particularly true of small and medium
enterprises (SME) clients. This poses a clear fiber/wavelength efficiency problem
for EoF and EoWDM, which can only provision full-rate channels. In a related concern,
EVPL support (via EoF or EoWDM) is also difficult as port partitioning requires
Ethernet switching functionality at the endpoints. Because many DWDM OADM nodes
can come with Ethernet thin-mux blades (see ???Reconfigurable Add-Drop Rings???), in the
practical sense some form of fractional EPL and/or EVPL can be achieved. Alternatively,
carriers can use point-to-point EoF/EoWDM to interconnect Layer 2 Ethernet/MPLS
switching nodes that are equipped with 1310 nm or 1550 nm SFP interfaces. In this
case, EoF/EoWDM basically serves as an underlying compliment to EVPL switching
devices supporting full VLAN stacking and QoS.
Overall, many carriers are already offering EPL services today using a variety of technologies,
see the comparison in ???Benefits & Shortcomings??? Within this market, EoF and
EoWDM-based services currently comprise a decent portion, about 20 percent, with EoF
being the more prevalent type [12].
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