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

"Nobo Akiya (nobo)" <nobo@cisco.com> Wed, 14 May 2014 16:15 UTC

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From: "Nobo Akiya (nobo)" <nobo@cisco.com>
To: 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 16:15:43 +0000
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Cc: Jeffrey Haas <jhaas@pfrc.org>, "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 Hannes,

Please see in-line.

> -----Original Message-----
> From: Hannes Gredler [mailto:hannes@juniper.net]
> Sent: Wednesday, May 14, 2014 11:58 AM
> To: Nobo Akiya (nobo)
> Cc: Jeffrey Haas; Les Ginsberg (ginsberg); rtg-bfd@ietf.org; isis-wg@ietf.org
> Subject: Re: [Isis-wg] New Version Notification for draft-ginsberg-isis-sbfd-
> discriminator-00.txt
> 
> On Wed, May 14, 2014 at 03:48:10PM +0000, Nobo Akiya (nobo) wrote:
> | 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.
> 
> what about AF discovery ? - how would a receiver know what AF a S-BFD
> session to bring up with ?

I was under the impression that IP header (i.e version) can distinguish the AF if implementations required demux'ing received S-BFD packet based on AF. If I missed your point/question, do clarify.

-Nobo