The MPLS WG Archive

[Naiming Shen <naiming@redback.com>]

the trick is for R2 to send the path msg 'directly' to R4 through the
tunnel, not hop-by-hop.

 ] 
 ] 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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 ] 
 ]  
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- Naiming

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