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

From: "HENDERICKX Wim" <[email-masked]>
Date: Thu, 31 Jul 2008 08:51:17 +0200

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.

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

Cheers,
Wim

---

From: "BALUS Florin" <[email-masked]>
Date: Thu, 31 Jul 2008 15:01:22 -0500

I have some other comments, questions I want to raise on this draft:

-          Let's assume PE1 is chosen by PE3 over PE2 in the diagram
below

-          The distribution model for BGP VPLS information (through BGP)
is one to many with no individual p2p communication between PE2-PE3. 

-          How does PE2 know that he was not chosen by PE3? PE3 needs to
know that to bring down its own data plane towards PE2 or otherwise I
see some problems (e.g. PE3 sending BUM traffic to PE2 wasting bandwidth
in the core, even confusion at PE3 for the PHP case when receiving
traffic from both PE2 and PE1 from the same VE ID).

Adding to the comments raised below by Wim

-          I think the case of a single homed CE mixed with the
dual-homed ones seems even more problematic: i.e. the single-homed CE
could be left hanging, isolated from the other VPLS sites. 

-          I was under the impression this could be done by assigning
separate VE IDs & label blocks for each dual-homed CEs/single-homed CE
group (a complex solution, wasting a lot of label block resources).  I
understood from hallway discussions that the authors said the separate
VE IDs are not anyhow the solution. Can we get a confirmation about how
this is addressed? 

Thanks,

Florin

From: [email-masked] [mailto:[email-masked]] On Behalf
Of HENDERICKX Wim
Sent: Wednesday, July 30, 2008 11:51 PM
To: [email-masked]
Subject: draft-kompella-l2vpn-vpls-multihoming-01

                            (VE1, VE2) 

Cheers, 
Wim

---

From: "BALUS Florin" <[email-masked]>
Date: Thu, 31 Jul 2008 15:08:11 -0500

I had an error in my email below - PE3 got switched with PE2. Here is
the correct paragraph should have been:

-How does PE2 know that he was not chosen by PE3? PE2 needs to know that
to bring down its own data plane towards PE3 or otherwise I see some
problems (e.g. PE2 sending BUM traffic to PE3 wasting bandwidth in the
core, confusion can be created at PE3 for the PHP case when receiving
traffic from both PE2 and PE1 from the same VE ID)."

Sorry about that,

Florin

From: [email-masked] [mailto:[email-masked]] On Behalf
Of BALUS Florin
Sent: Thursday, July 31, 2008 1:01 PM
To: HENDERICKX Wim; [email-masked]
Subject: RE: draft-kompella-l2vpn-vpls-multihoming-01

Thanks,

Florin

                            (VE1, VE2) 

Cheers, 
Wim

---

From: "Kaliraj Vairavakkalai" <[email-masked]>
Date: Fri, 1 Aug 2008 12:14:48 +0530

> -How does PE2 know that he was not chosen by PE3?

I'll try answering this; experts can correct/clarify where required:

PE1, PE2 and PE3 will run the BGP-selection-process for the
Layer2-BGP-NLRI (VE-id VE1) routes announced by PE1 and PE2, and will
arrive at the same result - that either PE2 or PE1 is the
designated-forwarder for site "VE1". 

When PE2 determines that it-is-not the designated-forwarder-PE for VE1,
it tears-down any PW(dataplane) it may have to the other PEs - with VE1
as the local-endpoint. 

When PE1 determines that it-is the designated-forwarder-PE for VE1, it
initiates a PW to other PEs (in this case only PE3, supposing PE3 is
housing a layer2-site VE3) as appropriate - where VE1 will be the
local-endpoint of PW, and VE3 the remote-endpoint. 

PE3 on determining the designated-forwarder-PE for VE1(as PE1 in current
example), will tear-down any PW with PE1 w/ remote-endpoint-as-VE1, and
initiate a PW with PE1 - where VE3 will be the local-endpoint of the PW,
and VE1 the remote-endpoint. 

After discussion what I understood is that when CE1 fails PE3 reelects
the designated forwarder for both CE1 and CE2

As I understand, when PE3 re-elects PE2 as the designated-forwarder for
site VE1(because CE1-PE1 link failed), PE3 may still elect PE1 as the
designated-forwarder for site VE2 provided CE2 is still connected to PE2
and everything else is fine between PE2-PE3. The designated-forwarder
selection is done per-Site-Id (VE-id), so the results for VE1 would not
necessarily affect the results for VE2.

Thanks,

Kaliraj 

________________________________

From: [email-masked] [mailto:[email-masked]] On Behalf
Of BALUS Florin
Sent: Friday, August 01, 2008 1:38 AM
To: BALUS Florin; HENDERICKX Wim; [email-masked]
Subject: RE: draft-kompella-l2vpn-vpls-multihoming-01

Sorry about that,

Florin

-      Let's assume PE1 is chosen by PE3 over PE2 in the diagram below

-      The distribution model for BGP VPLS information (through BGP) is
one to many with no individual p2p communication between PE2-PE3. 

-      I think the case of a single homed CE mixed with the dual-homed
ones seems even more problematic: i.e. the single-homed CE could be left
hanging, isolated from the other VPLS sites. 

Thanks,

Florin

                            (VE1, VE2) 

Cheers, 
Wim