Re: [Isis-wg] New Version Notification for draft-ginsberg-isis-sbfd-discriminator-00.txt

"Nobo Akiya (nobo)" <nobo@cisco.com> Wed, 14 May 2014 15:48 UTC

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From: "Nobo Akiya (nobo)" <nobo@cisco.com>
To: Jeffrey Haas <jhaas@pfrc.org>, Hannes Gredler <hannes@juniper.net>
Thread-Topic: [Isis-wg] New Version Notification for draft-ginsberg-isis-sbfd-discriminator-00.txt
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Date: Wed, 14 May 2014 15:48:10 +0000
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Cc: "Les Ginsberg \(ginsberg\)" <ginsberg@cisco.com>, "rtg-bfd@ietf.org" <rtg-bfd@ietf.org>, "isis-wg@ietf.org" <isis-wg@ietf.org>
Subject: Re: [Isis-wg] New Version Notification for draft-ginsberg-isis-sbfd-discriminator-00.txt
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Hi Jeff,

> On Wed, May 14, 2014 at 05:26:52PM +0200, Hannes Gredler wrote:
> > On May 14, 2014, at 5:22 PM, Les Ginsberg (ginsberg) wrote:
> > > Thanx for the comments.
> > > I don't see how your proposal solves the problem you are attempting to
> address. The sender of the S-BFD packet has no control over what interface
> is used to receive the packet on the target node. Associating it with a prefix
> will not help in that regard.
> >
> > well it would help first endpoint discovery and pinning down BFD traffic to
> particular line card.
> 
> Indeed.  In the SPRING related case (or even some MPLS scenarios), traffic
> may be heavily steered to a given interface.  This interface may not even be
> to a router, but may be an ingress for a SFC device and that ingress is critical
> for the execution of the chain.

In those cases, one should be sending S-BFD packet in-band, which would go through the specific interface/LC to reach the reflector session on the target node (i.e. outage will be detected regardless of the discriminator used). So having separate reflector discriminator won't be adding further benefit.

Flip side is, if a reflector is hosted on LC 1 and traffic engineered tunnel is terminating on LC2, then outage of LC1 can cause the "no S-BFD response" on the tunnel terminating on LC2. However, I would think this is a limitation with implementation.
 
-Nobo