Subject: Re: RSVP-TE

From: Sachin Kalra <[email-masked]>
Date: Wed, 14 Nov 2001 12:09:29 -0500

Even if [R4] is using GLA (Global Label Allocation) then

When and how is Backup tunnel signaled and established?

(Because some papers talk about "Un signaled Backup tunnels" and some talk 
about "signaling backup tunnels" & labels being swapped in LSRs along this 
tunnel. So how do these LSRs along the Backup Tunnel decide upon their 
Label operations if there is no signaling for backup Tunnel?)

Thanks,
Sachin Kalra

>Date: Tue, 13 Nov 2001 18:02:31 -0500
>To: [email-masked]
>From: Sachin Kalra <[email-masked]>
>Subject: RSVP-TE
>
>Dear All:
>
>I have some questions about RSVP-TE Backup LSPs (Bypass tunnels). Any help 
>is greatly appreciated.
>
>Please let me know if the draft (draft-swallow-rsvp-bypass-label-01) is 
>too old to discuss in the list. (So that I just don't keep waiting for the 
>mails :-)  )
>
>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