Subject: RSVP-TE

From: Sachin Kalra <[email-masked]>
Date: Wed, 14 Nov 2001 12:24:18 -0500

Dear All:

I have some questions about RSVP-TE Backup LSPs (Bypass tunnels). Any help 
is greatly appreciated.

The draft draft-swallow-rsvp-bypass-label-01.txt states that (Pg 4, Line 11)

"...if R4 does not use a global label space then a label must be assigned 
out of the label space used by R4 on the interface terminating the link 
from R7. if, however, R4 has a global label space then the label which R2 
uses during the backup could be the same label value which is used by R3."

For the following topology

	[R8]
	     \
[R1]---------[R2]----[R3]----[R4]-----------------[R5]
	         \\               //    \
	          [R6]===[R7]      [R9]

My questions are that if R4 does not use global label space (i.e. it has 
multiple label spaces, specific to particular interfaces) then
	1> WHEN should the label be assigned out of label space used by R4 on the 
interface terminating the link from R7?
		a> Does it happens at the time when Primary LSP is signaled?
			If Yes, then how is [R2] informed about this label?
		b> Or does it happens at time when primary LSP fails and backup takeover?
			If Yes, then does this means that signaling for Backup LSP takes place?
		c> How does [R6] and [R7] decide in this case upon their labels to be 
used and when to swap and when to pop? Or in other words how is the Bypass 
Tunnel established? Is it statically configured?

Please, give some pointers to other readings related to this topic.
Thanks,
Sachin Kalra