Any erratic behavior in
these messages could enable preemptively addressing any emerging issues.
?– Link trace messages These messages are used by a Service Provider to track
a specific path between two pieces of equipment/devices traversing through the
intervening devices. This hop-by-hop approach is useful in identifying whether a
data path exists or not.
?– Loopback messages These allow a Service Provider to validate connectivity
(either on a service or a circuit basis) to a particular maintenance point to
Carrier Ethernet 91
determine whether it is reachable or not, without particularly worrying about the
intermediate nodes.
?– Alarm indication signal (AIS) messages These messages are used to indicate
that there is a fault in the network.
ITU Y.1731 The ITU Standards Group (SG) 13, in Recommendation Y.1731, identifies
the OAM functions in an Ethernet network that are needed to allow fault management
and performance monitoring. Fault management is closely aligned with the fault
management capability of the IEEE 802.1ag (and hence includes capabilities such as
discovery, continuity checks, loopbacks, link trace, etc.). However, the Y.
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