The MPLS WG Archive

[Harish Kumtakar <harishk16@yahoo.co.in>]

I've a question on draft
'draft-ietf-mpls-rsvp-lsp-fastreroute-07.txt'
The question is related to the Path message handling
sent over the bypass tunnel (facility backup) for the
protected LSP before/after failure. 

Consider the following example,

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

                Protected LSP : [R1->R2->R3->R4->R5]
                Bypass LSP Tunnel: [R2->R6->R7->R4]

Section 7.4.4 of the draft says,

   More specifically, the PLR MUST:

     - remove all the sub-objects proceeding the first
address belonging
        to the MP.

     - replace this first MP address with an IP
address of the MP.
        (Note that this could be same address that was
just removed.)

So, the ERO of the Path message sent over the bypass
tunnel contains the IP address of MP (i.e R4) as its
sub-object. (My understanding is that, all the
sub-objects that appear before MP's address are
removed from ERO)

Now, when R6 recieves this Path message, as per the
ERO processing rules specified in Section 4.3.4 of RFC
3209:Extensions to RSVP for LSP Tunnels, should it not
return "Bad initial subobject" error to PLR R2? I know
I'm definitely missing something here OR my
understanding of the draft itself is partially
incorrect.

Please clear the grey area,

TIA, Regards,
-Harish


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