So, while some Carrier Ethernet services are ???best
effort,??? some important customer applications (digital video delivery is one example) require Carrier
Ethernet services where all the bandwidth is dedicated. For these dedicated-bandwidth Carrier Ethernet
services, SONET protection is no more or less efficient than packet-based protection schemes.
310 Chapter 11
complete optical networking layer beneath the packet layer??”and one that, from
the perspective of the packet layer, provides perfect QoS. Ethernet frames that are
mapped within an STS path will traverse the SONET portion of the network with
no contention for network resources??”and therefore no packet loss, no packet jitter
(delay variation), and only minimal additional latency (typically tens of microseconds
per SONET node traversed, plus speed of light delays on transmission links).
An EoS solution that combines robust Ethernet-level QoS control and judicious use
of the underlying SONET network can provide unparalleled Carrier Ethernet QoS.
?– Standardized services This attribute, too, depends a great deal on the packet level
functions of a Carrier Ethernet solution.
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