Subject: About the label operation in FRR(Relevant to Y.17fw)

From: lidefeng <[email-masked]>
Date: Thu, 28 Aug 2003 09:43:05 +0800

In Draft Recommendation Y.17fw (MPLS management framework) TD 26 Rev.1 (WP
3/13) at the meeting of Geneva, 21 July - 1 August 2003,it described the FRR
process procedure when a failure occurs along a protected LSP,but I am not
very clear about it in detail.

As to the Figure A2.1 (See attachment) in Appendix 2,it states that "When a
failure occurs along a protected LSP, the Point of Local Repair (PLR)
redirects traffic into the appropriate bypass LSP. For instance if node R3
fails in figure 6.1, R2 will switch traffic received from R1 on the
protected LSP onto the Bypass LSP1 toward link [R2-R6]; the label will be
switched from one which will be understood by R4 to indicate the protected
LSP and then the bypass LSP's label will be pushed onto the label stack of
the redirected packets. "

what is the detail label operation in R2 when R2 switch traffic received
from R1 on the protected LSP onto the Bypass LSP1 toward link [R2-R6],in my
understanding,R2 has the label L3(which R3 distributed to R2),but has no
label which R4 distributed to R2,so R2 has no label which will understood by
R4(as indicated in the above paragraph).

And R2 needn't switch the label in the packet received from upstream with
the label L3( the label R3  distributed to R2), just need to switch the
label in the packet received from upstream with the label L6(the label R6
distributed to R2).

Did I catch it?

Sincerely Yours

Defeng Li
Huawei Technologies
+86-10-82882343
[email-masked]

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From: Jean Philippe Vasseur <[email-masked]>
Date: Thu, 28 Aug 2003 20:10:03 -0400

Hi,

>very clear about it in detail.

For the details on FRR, please refer to 
draft-ietf-mpls-rsvp-lsp-fastreroute-03.txt

>R4(as indicated in the above paragraph).

R2 learns the label expected by the MP R4 via the RRO object carried in the 
Resv message of the protected TE LSP.

>label in the packet received from upstream with the label L6(the label R6

no, it needs to swap the label used between R1 and R2 to the label 
distributed by R4 to R3, push an additional label corresponding to the 
bypass tunnel and redirect the traffic to the R2-R6 intefrace.

Again see the draft above.

JP.