This object
may be sent in an LDP notification message to inform the remote PE of pseudowire
status changes, instead of withdrawing the PW label. The notification message includes
both the status TLV, which carries a code indicating the reason for the PW fault,
and an FEC 128 or 129 TLV to identify the pseudowire, or pseudowires, for which the
change in status is being relayed.
440 Chapter 14
Although control plane??“based OAM techniques are sufficient in the absence of software
or hardware bugs, there may also be a requirement for forwarding plane??“based
OAM, especially in cases where pseudowires are established manually. The forwarding
plane OAM technique for pseudowires is known as Virtual Circuit Connectivity
Verification (VCCV) and creates an OAM control channel along which LSP ping or BFD
packets can be transported. VCCV supports three control channel types:
?– The PW Associated Channel is defined in RFC 4385, and is known as inband VCCV.
The PW Associated Channel may only be used on pseudowires that carry a control
word and is identified by a 32-bit header starting with the bits ???0001??? (to distinguish
it from the control word).
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