A much more scalable and efficient EPL approach is to map native optical Ethernet
interfaces onto WDM lightpaths??”Ethernet over WDM (EoWDM)??”as shown in Figure 8.6.
The economics of this collapsed ???transparent??? solution are very compelling, especially
for carriers with existing DWDM infrastructures. For example, an Ethernet packet can
leave a server via a Gigabit Ethernet DWDM interface, move across a metro ROADM
ring, and be received on a workstation??”all without costly intermediate SONET/SDH
or ATM/Frame Relay electronics. From the data-plane perspective, EoWDM (like EoF)
can also provide highly stringent circuit-like QoS guarantees. Nevertheless, its geographic
coverage is much greater than EoF, as amplified DWDM networks can readily
span over 1000 km. Moreover, EoWDM is vastly more bandwidth scalable than
EoF??”by almost two orders of magnitude??”and new third-generation DWDM ROADM
nodes can provide much faster service velocity (minutes and hours).
EoWDM can also leverage the full range of WDM survivability schemes (see Figure 8.5)
to offer multiple tiered (i.e., differentiated and value-added) EPL packages. Some examples
are shown in Table 8.
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