Alcatel-Lucent 7750 SR OS Interface Configuration Manual page 41

An FR SAP configured on an MLFR bundle can be part of a VLL, VPLS, IES, or VPRN service.
MLFR Bundle Link Integrity Protocol
FRF.16.1 defines a MLFR Bundle Link Integrity Protocol which verifies the serviceability of a
member link. If a problem is found on the member link the link integrity protocol will identify the
problem, flag the link as unusable, and adjust the Bundle's available bandwidth. For MLFR
Bundles the link integrity protocol is always enabled.
For each member link of a bundle the link integrity protocol will do the following:
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Specifically, the MLFR Bundle Link Integrity Protocol defines the following control messages:
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7750 SR OS Interface Configuration Guide
Confirm frame processing capabilities of each member link.
Verify membership of a link to a specific remote bundle.
Report to the remote end of the member link the bundle to which the link belongs
Detect loopbacks on the member link. This is always enabled on the 7750 SR. The near-
end monitors the magic number Information Element (IE) sent by the far-end and if its
value matches the one it transmitted in ten consecutive control messages, it sends a
remove_link message to the far-end and brings the link down. The near-end will attempt
to add the link until it succeeds.
Estimate propagation delay on the member link. The differential delay is calculated as
follows in the 7750 SR implementation. Every time the near-end sends an add_link or
Hello message to the far-end, it includes the Timestamp Information Element (IE) with
the local time the packet was sent. FRF16.1 standard requires that the remote equipment
includes the timestamp IE and copies the received timestamp value unchanged if the
sender included this IE. When the far-end node sends back the ACK for these messages,
the near-end calculates the round trip time. The 7750 SR implementation maintains a
history of the last "N" round-trip-times that were received. It takes the fastest of these
samples for each member link to find out the member link with the fastest RTT. Then for
each link it calculates the difference between the fastest links RTT, and the RTT for the
current link. The user has the option to coordinate link removal between the local and
remote equipment. Note, however, that in the 7750 implementation, the addition of a link
will be hitless but the removing a link is not.
ADD_LINK
ADD_LINK_ACK
ADD_LINK_REJ
HELLO
HELLO_ACK
REMOVE_LINK
REMOVE_LINK_ACK
Interface Configuration
Page 41