Subject: Re: [Idr] Fwd: I-D Action: draft-chen-bfd-unsolicited-00.txt

From: Nick Hilliard <[email-masked]>
Date: Tue, 01 Aug 2017 14:55:29 +0100

Enke Chen wrote:
> Here is a proposal for "unsolicited bfd".  We (the authors) believe that
> "add-path + unsolicited bfd" is a simper solution to the nexthop liveness
> issue at the IXP with Route Servers.

This is interesting.

I wonder about the wisdom of lots of routers sending unsolicited bfd
control packets.  At the least, there ought to be a back-off mechanism
in place to slow things down where the non-Active router is ignoring
packets.  Also, it would be good to have an explicit reject mechanism,
to stop streams of unsolicited bfd control packets completely.

IXP participants will want some mechanism of never receiving BFD
solicitations.

Active/passive session collision may be a problem.

This proposal slightly goes to the other side of the KISS principal:
"keep it as simple as possible, but no simpler". It may be too simple.

Nick

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From: Jeffrey Haas <[email-masked]>
Date: Tue, 1 Aug 2017 10:33:59 -0400

> to stop streams of unsolicited bfd control packets completely.

The BFD protocol, by default, backs off to 1pps when not in the Up state.

> IXP participants will want some mechanism of never receiving BFD

This would require protocol signaling, or provisioning.

> Active/passive session collision may be a problem.

I don't understand this.  BFD already handles demux between common endpoints
when in active/active.  If a session comes up, it simply means that there's
no reason to initiate another session when the previously passive side now
has an active interest.

-- Jeff