The IEEE 802.3ah was ratified in 2004 and was expected to complement existing protocols
such as SNMP that were otherwise being employed for management purposes.
The EFM OAM also uses Ethernet frames (albeit with a specific destination MAC
address and the Ethernet type/length field to identify EFM-related frames uniquely
(PDUs). It is also an in-band protocol (i.e., it uses the same bandwidth as the data
frames) and is characterized as a slow protocol; it is not required for normal operation
and typically uses about 10 frames per second.
The EFM OAM addresses some fundamental aspects necessary when deploying
Ethernet over the first/last mile:
?– Link monitoring Gives the Service Provider visibility of the first mile physical
connection through periodic heartbeat messages. In case of any issues on this link,
the Service Provider is immediately notified with pertinent information.
?– Fault signaling Enables a device to convey to its peer at the remote location
that severe conditions such as link failure (noted because it can no longer receive
any signal) or a dying gasp (when the remote device is about to be powered down
and operationally unavailable) have occurred.
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