Hi,

              Please refer inline

Hi, all

We meet a question when implementing VPLS using MS-PW, pls see the following figure.

CE1---T-PE1----------S-PE----------T-PE2---CE2
                      |
                     CE3

Configure a static multi-segment Pseudo Wire between T-PE1 and T-PE2, consisted by S-PW1 and S-PW2. If S-PE is also a T-PE and need to setup a PW between S-PE and T-PE2, named PW3. CE1, CE2 and CE3 are in the same VPLS.

Then what's the relationship between S-PW2 and PW3 ?

There are two cases:
1. S-PW2 and PW3 are independent PWs, then the path from CE1 to CE3 is T-PE1->S-PE->T-PE2->S-PE. It is not the best path. And if PWs belonging to the same VPLS need same PWID. Then to identify them individually, PW need to implement certain extension, for PW identification cannot be based-upon Source+Destination+Pwid mechnism.

You would use generalized PWID for MS-PW signaling. So apart from PWID the SAII, TAII would differentiate the Pseudo wires. Please refer to draft

http://www.ietf.org/internet-drafts/draft-ietf-pwe3-dynamic-ms-pw-02.txt for details.

2. S-PW2 and PW3 are the same PW, then Multi-segment PW is not needed, hub & spoke PWs are setup between T-PE1, S-PE and T-PE2. This case can solve this problem.

Which cases do you guys prefer?

Hope this helps,

Pranjal

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