Likewise, an MPLS solution
inherently offers QoS and can scale as required of Carrier Ethernet solutions. Most of
these solutions are, in fact, feasible because they possess some of the attributes dictated
by Carrier Ethernet and can carry Ethernet frames, albeit some more efficiently
than others. Some of these solutions, in their attempt to be relevant in the long-term,
are also being actively augmented with additional (Carrier Ethernet) attributes for
optimizing Ethernet delivery.
504 Chapter 16
NOTE These delivery solutions usually provide the Carrier Ethernet attributes in the
TRAN layer, not necessarily in the ETH layer. Because these attributes are only being
defined in the ETH layer by the MEF4 and, in most cases, are far from being standardized
(refer to Chapter 2 for more information), these TRAN-layer capabilities are often
the only realistic??”and obviously acceptable??”recourse.
Different Parts of the Network Each of these solutions is usually deployed in different
parts of the network, based on their technical and economic feasibility. Some, such as
copper and WiMax are typically used only in the access portion of the network??”between
the customer premise and Service Provider??™s Point Of Presence (POP)??”whereas others
such as SONET and WDM are often used in the Service Provider??™s MANs and WANs
(these can also be employed in the access MAN as well and in fact are when the economics
work out).
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