The MPLS WG Archive

[Randolph Chung <rc42@yahoo.com>]

Hi all,

Have some questions about how the following situation
should be handled according to the LDP RFC.....

Suppose you have two LSRs Lu and Ld. 

Ld advertises some FEC with label l1 to Lu
Some time later, the route for that FEC is gone on Ld,
so it sends a label withdraw message to Lu. According
to the RFC, after this Ld would expect to receive a
label release message for that FEC, so it needs to
"remember" to there is an outstanding "unacknowledged"
label withdraw.

What should the LSR Ld do if, before it receives a
label release message from Lu, the route for the same
FEC is learned, and Ld wishes to advertise that FEC to
Lu? If it does send a label map before the release
message is received, then when a release message
finally arrives Ld needs to determine if the release
is for the withdraw or the map....

Also, is there any recovery mechanism (I don't see
anything in the RFC w.r.t timers and such) if the
upstream router does not send back a label release
message in response to a label withdraw?

thanks,
randolph

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