1. PW Group Protection draft-zhang-pwe3-gid-app-00.txt Yang Yang

2. Why PW Group Protection?
It’s possible that multiple PWs are transmitted over one physical media. Therefore when one PW fail, other PWs may fail as well. Under this circumstance, it’s more effective to do group protection instead of one by one PW protection.

3. Why not just tunnel protection?
There are cases of multiple PWs in one tunnel some of which need protection while the others don’t. That’s why tunnel protection couldn’t replace group protection.
4 PWs are trasmitted along a tunnel. Only the blue PWs need to be protected.
This tunnel provides backup PWs.

4. Why not just tunnel protection? __Cont.
Tunnel protection only limits to a single domain/network and couldn’t provide E2E protection for MS-PW. PW protection could work in this scenario but it consumes more bandwidth for continuity monitoring.

5. What’s the benefit of PW Group Protection?
Faster Protection Switching
When the path is failure, the PW group will switching to protection PW group. The PWs will be treated as a whole.
Lower bandwidth consumer of OAM traffic:
To monitor the continuity, only one OAM control channel is needed while every PW one OAM control channel if PW group protection isn’t used.

6. Consideration for MS-PW Scenario --Tunnel Switching Mode
In tunnel switching mode, all of the PWs of a tunnel will be switched to another tunnel.
Customer_X
TPE_C
Customer_Y
TPE_B
SPE
TPE_A
Customer_X
If miss-cross connect happens in the intermediate router, all PWs are miss connected. The PW group only need one control channel for miss-cross connect detecting.

7. Consideration for MS-PW Scenario --PW Switching Mode
If PW is switched in S-PE, there maybe miss-cross connect errors.
Customer_Y
Customer_X
TPE_C
TPE_B
SPE
TPE_A
Customer_X
If miss-cross connect happens in the intermediate router, maybe only some of the PWs are miss connected. It’s suggested that each PWs in the group should perform miss-cross connect detecting.

8. Your suggestions and/or comments are appreciated!
Thank you!
Your suggestions and/or comments are appreciated!