Re: draft-kompella-l2vpn-vpls-multihoming-01

[Bhupesh Kothari <[e-mail]>]

HENDERICKX Wim <[e-mail]> wrote:

> During the session I expressed concerns regarding 2 dual homes CE(s)
> on 2 PE(s) with multi-homing. Here is the scenario I had in mind.
> 
>                             (VE1, VE2)
>                 ____ PE1………………..
>               /  ____/  :                               :
>         __/   /         :                                PE3
> CE1 __   /          :                                 :
>             \ /             :                              :
>              / \_____ PE2 ………………
>        __/               /  (VE1, VE2)
> CE2 _________/
> 

> PE3 picks a designated forwarder lets say PE1 for both CE1 and
> CE2. After discussion what I understood is that when CE1 fails PE3
> reelects the designated forwarder for both CE1 and CE2 and PE3 also
> flushes the Mac table.

When CE1--PE1 link fails, all PEs will reelect who is the designated
PE for VE1 (assuming VE1 is for CE1).  Since the designated PE in this
case will move from PE1 to PE2, PE3 needs to flush the MACs learned
from PE1.

> 
> This should be addressed as an impact on CE1 should not impact other
> CE(s) according to me.
> 

In VPLS, there is only one PW between a pair of PEs as the ACs are not
tied to particular remote neighbors as in the case of P2P L2VPNs.
Since PWs are not tied to ACs, when a AC goes down there is no way to
flush just the MACs associated with a particular AC other than
explicitly sending a list of MACs to be flushed.  In your example, PE1
can send a list of MACs (learned from CE1) to be flushed to PE3.  The
capability to send a list of MACs to be flushed is not yet there, but
can be added.


> Cheers,
> Wim


Thanks
Bhupesh