Subject: [rbridge] Redundancy for appointed VLAN forwarder

From: Sambath Kumar Balasubramanian <[email-masked]>
Date: Mon, 4 Oct 2010 09:50:06 -0700 (PDT)

Hi,

  I am going through the TRILL draft and I see that the failure of 
appointed VLAN forwarder has implications on the traffic network
wide which will result in flooding of traffic and also traffic loss till
the DRB appoints a new forwarder for the VLAN. Am I interpreting
the draft correctly?

If the above is true is there any work on adding redundancy features
for appointed VLAN forwarder? From the view of the problem TRILL 
is trying to solve do we needthis redundancy?

 Regards,
Sambath

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From: Donald Eastlake <[email-masked]>
Date: Mon, 4 Oct 2010 13:59:55 -0400

Hi Sambath,

Yes, if an RBridge fails, you want to detect that failure quickly and
change the routing and, if relevant, forwarder appointment to adjust
to the failure. You can lose traffic until you have adjusted to the
failure. I'm not sure why their would be "flooding". What sort of
scenario are you thinking of?

If an end station has a point-to-point connection to an RBridge, you
don't have any alternative. So I assume you are thinking of something
like end stations connected to a bridge that is multi-homed to two or
more RBridges...

Thanks,
Donald

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From: Sambath Kumar Balasubramanian <[email-masked]>
Date: Mon, 4 Oct 2010 13:38:46 -0700 (PDT)

Hi Donald,

  Thanks for your response. Yes I am thinking of end stations 
multihomed to two or more bridges. What I meant in terms of 
flooding is that all the Rbridges in the campus will have to remote 
the remote entries learnt through the failed appointed forwarder 
and till that time they relearn the MAC (assuming ESADI is not 
implemented), the unknown macs gets to all Rbridges. I have 
not thought of a complete solution, but I am thinking more in 
lines with VRRP where two Rbridges share the same nickname 
and provide redundancy to the end stations and also to the
remote Rbridges so that when the appointed forwarder fails,
the backup can takeover without any disruption.

There are issues with this especially if the link consists of bridges
since the appointed vlan forwarded is essentially proxying the remote
mac addresses (bridges in the link learn the remote mac address
as though they are located on the appointed forwarder), but before
putting effort into defining a solution I wanted to check if this is
a relevant problem to solve or does existing TRILL specification solves
this already (Maybe I missing something)

 Regards,
Sambath

----- Original Message ----
From: Donald Eastlake <[email-masked]>
To: Sambath Kumar Balasubramanian <[email-masked]>
Cc: [email-masked]
Sent: Mon, October 4, 2010 10:59:55 AM
Subject: Re: [rbridge] Redundancy for appointed VLAN forwarder

Hi Sambath,

Thanks,
Donald

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From: Donald Eastlake <[email-masked]>
Date: Mon, 11 Oct 2010 21:39:46 -0400

Hi Sambath,

Sorry for the delay in response. I've been traveling...

On Mon, Oct 4, 2010 at 4:38 PM, Sambath Kumar Balasubramanian
<[email-masked]> wrote:
> implemented), the unknown macs gets to all Rbridges.

Well, all RBridges in that VLAN. But, generally speaking, RBridges
implemented according to the base protocol specification act the same
way as Bridges and would have the same amount of flooding, etc., if
they depend on the mandatory to implement data plane learning.

> I have

Yes, something along these lines would also help.

> this already (Maybe I missing something)

I think an extension to the TRILL protocol to address this would be useful.

> Sambath

Thanks,
Donald
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