The MPLS WG Archive

[Sachin Kalra <skalra@opnet.com>]

Hi:

I have few questions about "Bypass Tunnels". Any help is appreciated.

In following figure Primary LSP traverses from (R1->R2->R3->R4->R5) and 
Bypass tunnel from (R2->R6->R7->R8->-R4). Bypass is denoted by double lines.

	
	 [R0]
	     \
[R1]---------[R2]------------------[R3]-----------------[R4]-----------------[R5] 

	          \\                                        //     \
	           \\			  //	 \
		[R6]======[R7]======[R8]        [R9]


If R4 is using Interface specific Label Space. (i.e. it does not use Global 
Label Space). Then we need to signal LSP through "Bypass Tunnel" path to 
obtain label assigned out of the label space used by R4 on the interface 
terminating the link from R8 (Which will later be used by R2 for label 
swapping before stacking the label for Bypass Tunnel)

In this case my understanding is that once R2 has the "required label" from 
R4, then R6, R7, R8 do not need to maintain any state for the signaled LSP, 
nor do they need any NHLFEs for that LSP. Because traffic will be sent 
through the "Bypass Tunnel".

1. Is this correct?

2. How do we handle this scenario?

3. Does LSPs signaled through Bypass Tunnel need NHLFEs on transit nodes?

Thanks for your time,
Sachin Kalra