The MPLS WG Archive

["Quan Sun" <qnsun@hotmail.com>]

A dumb question, but still a bit confusing for me when reading the RSVP TE 
draft: when you receive a Path message, (a) you immediately allocate a label 
for the upstream link and save it for later use (this label will be later 
put to the RESV message coming from the downstream node), or (b)the label is 
only allocated after a RESV message has come.

If you read RSVP draft Section 4.1.1 (Handling Label Objects in Resv 
Messages), you understand the above (b) is the case. When you read Section 
4.2.4 (Handling of LABEL_REQUEST), you have a feel that the label is 
attempted to be allocated when you receive the Path message (The draft says: 
"A node that recognizes a LABEL_REQUEST object, but that is unable to 
support it (possibly because of a failure to allocate labels) SHOULD send a 
PathErr...). At least, I know of a MPLS vendor who uses the above case (a).

Or, this is an implementation specific issue?

Quan




that later this label will be put to the LABEL object in the RESV message, 
for puting to the RESV message  Consider the following simple topology:

--- LER1 --- LSR --- LER2 ---

(1) LER1 first sends a Path message to LSR


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