Traffic Engineering By using RSVP-TE, carriers are able to pin the primary and secondary
paths for any given service to specific links in their network and to optimise
use of physical resources. Although this is possible with some alternative techniques
(such as Ethernet over SDH/SONET or over ATM), there are other techniques (such as
802.1ah Provider Backbone Bridging) that are unable to do so. The benefits of traffic
engineering are sufficiently clear to operators that technologies which lack the capability
are often extended to include it (for example the PBB-TE effort in IEEE).
Shortcomings of Ethernet over MPLS
The shortcomings of Ethernet over MPLS may be divided into two classes: shortcomings
of Ethernet itself and shortcomings of the Ethernet over MPLS architecture.
Ethernet Shortcomings Ethernet over MPLS services are still Ethernet services and
don??™t enhance the Ethernet UNI. Enhancements in the UNI are being standardised
by the Metro Ethernet Forum and are required for Ethernet services to offer the same
carrier-class features that already exist in protocols such as ATM.
VPLS services emulate Ethernet LANs. As discussed, Ethernet LANs are inherently
unscalable.
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