Re: [Idr] Early allocation for draft-ietf-idr-bgp-gr-notification

Jeffrey Haas <jhaas@pfrc.org> Mon, 20 March 2017 19:37 UTC

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Date: Mon, 20 Mar 2017 15:44:14 -0400
From: Jeffrey Haas <jhaas@pfrc.org>
To: Job Snijders <job@ntt.net>
Cc: "Jakob Heitz (jheitz)" <jheitz@cisco.com>, "idr-chairs@ietf.org" <idr-chairs@ietf.org>, "idr@ietf.org" <idr@ietf.org>
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Subject: Re: [Idr] Early allocation for draft-ietf-idr-bgp-gr-notification
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Job,

On Sat, Mar 18, 2017 at 10:53:53AM +0000, Job Snijders wrote:
> Given the 50+ years of combined IETF experience the authors of this draft
> possess, I'm somewhat surprised to see a suggested value in the IANA
> considerations instead of "TBD". See the last major bullet point here:
> https://trac.ietf.org/trac/idr/wiki/Checklist%20for%20writing%20a%20BGP-related%20draft

Unfortunately it's not an uncommon practice, and one we're moving out of
thankfully.  If you look around other working groups, even other BGP working
groups like bess, it's not uncommon.

> Furthermore, shouldn't the "Hard Reset" be called "Really Really Really
> Reset"? I am skeptical whether the principles of graceful restart should be
> applied to the notification mechanism. In
> https://tools.ietf.org/html/draft-iops-grow-bgp-session-culling-00 we are
> describing a procedure that strongly relies on the currently understood
> semantics of expiration of BGP Hold Timers and the Administrative Shutdown:
> "STOP sending traffic".

I haven't yet read this draft, so take my further comments with that under
consideration.

> I find it hard to reconcile how we can have both "My control-plane
> temporarily going away, but keep sending traffic" and "data-plane is
> broken, bgp subsequently dies, don't send traffic". The exact failure
> scenario which triggers the expiration of the BGP Hold Timers cannot be
> known at OPEN when the capabilities are exchanged. The GR NOTIFICATION
> seems to distort the congruency between data-plane and control-plane.
> 
> Perhaps there should be an implementation guideline which encourages
> vendors to by default, disable this mechanism on non-RFC3021/RFC6164 links?
> 
> Has draft-idr-bgp-gr-notification been vetted in the wild? What were the
> results and under which circumstances is the mechanism useful? Am I missing
> something?

The non-obvious connection is it's a requirement of
draft-uttaro-idr-bgp-persistence (long-lived graceful restart).  There's
code shipping for this feature.  I *believe* that it's another vendor as
well, but can't confirm from memory.  

There has been some discussion that LLGR needs to be resurrected from zombie
draft state.

-- Jeff