The challenges, of course, have been in scaling up an enterprise network into a provider
network. It is the opinion of an increasing number of vendors and providers that
these challenges are being met.
When Does This Solution Fit?
As (the author hopes) this chapter has made clear, there are a number of scenarios
where an IEEE 802.1 bridge-based solution performs most effectively:
?– Bridges are not just useful for constructing multipoint-to-multipoint (E-LAN) or
point-to-multipoint EVCs, they define the model for such services. Wherever a provider
is offering a significant number of ports connected to such E-LAN EVCs, compared
to the number of ports connected to E-Line EVCs, bridges are a viable choice.
Keep in mind, when making this determination, that if 10 percent of the EVCs are
E-LANs, they may easily constitute 50 percent of the total number of UNIs.
?– Where the links used to interconnect the nodes of the provider??™s network are
Ethernet links and where a large portion of the frames on those links is Carrier
Ethernet traffic, it is straightforward, economical, and sensible to make those nodes
412 Chapter 13
bridges and let them do what they do best.
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