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Re: [Idr] Bug in RFC 7911 (add-paths) and tie-breaking

Robert Raszuk <robert@raszuk.net> Sat, 26 June 2021 14:41 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Sat, 26 Jun 2021 16:41:33 +0200
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To: Jeffrey Haas <jhaas@pfrc.org>
Cc: John Scudder <jgs=40juniper.net@dmarc.ietf.org>, "dwalton76@gmail.com" <dwalton76@gmail.com>, "idr@ietf. org" <idr@ietf.org>
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Subject: Re: [Idr] Bug in RFC 7911 (add-paths) and tie-breaking
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Jeff,

If there are common scenarios where a given BGP speaker will locally
> originate multiple paths without having gotten them from somewhere else,
> I'm
> not currently aware of it.


I think it is pretty common to connect PE (for simplicity assume non VPN
case) to two customer CEs.

Those CEs are over static + bfd.

Further those may be connected with different link bw.

So if you redistribute those two static routes to different CE's next hops
you will likely end up with two paths in BGP. Normally sending one will be
cool as you set next hop self, normally repair any failure, locally load
balance across links to CEs etc ... life is good.

But the moment you enable add-paths, adventure (not to say pollution)
starts.

I think this could be a pretty common case this discussion could get
triggered off.

And thx for bringing up the  conn-restore draft. I guess it matured
sufficiently to perhaps refresh it and start WG adoption call ? Either
Pradosh or myself should have the latest xml for it.

Thx,
R.

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