IETF solutions work very well for E-Line EVCs or for a modest number of
E-LAN EVCs. As the number of E-LANs grows, interconnecting virtual provider
bridges via MPLS pseudowires becomes feasible.
?– When a provider??™s physical plant consists primarily of non-Ethernet (technology
???xyz, perhaps ATM) links, and when much of the traffic on that network is not carried
as Ethernet over xyz, then it may (or may not) be more practical to use another
technology (e.g., Ethernet over MPLS over xyz).
?– If the provider??™s physical plant consists primarily of rings of devices, rather than
a mesh topology, nonstandard solutions are not acceptable, physical redundancy
is required for robustness against failures, and 1 to 2 sec convergence times are
not acceptable, a bridge-based solution does not exist. There are nonstandard solutions
to the ring problem, however, and the new 802.1aq standard should solve the
problem.
?– ???Network religion??? and/or the ability to clearly differentiate one??™s offerings from a
competitor??™s can play an important role in a provider??™s rejection of an implementation
technology.
Benefits and Shortcomings
When compared to the alternatives, bridged Carrier Ethernet networks have both
benefits and shortcomings.
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