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

Job Snijders <job@ntt.net> Tue, 21 March 2017 15:24 UTC

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Date: Tue, 21 Mar 2017 16:24:01 +0100
From: Job Snijders <job@ntt.net>
To: Jeffrey Haas <jhaas@pfrc.org>
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Subject: Re: [Idr] Early allocation for draft-ietf-idr-bgp-gr-notification
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On Mon, Mar 20, 2017 at 04:41:25PM -0400, Jeffrey Haas wrote:
> On Mon, Mar 20, 2017 at 09:14:55PM +0100, Job Snijders wrote:
> [session culling]
> > > I haven't yet read this draft, so take my further comments with
> > > that under consideration.
> > 
> > ack. Please read the draft. We may have a fundamental problem on our
> > hands here.
> 
> I read it. It's a weird hack, but it works. :-)
> 
> > 1/ To emphasize the congruency issue here: BGP Hold Timer expiration
> > often (from the Operator's perspective) an unplanned event. BGP Hold
> > Timers usually expire because there is an issue with the lower layer
> > network. If there is an issue with the lower layer network, we
> > should not continue to forward traffic over that path. If I
> > understand draft-ietf-idr-bgp-gr-notification correctly, that is
> > what would happen if both sides through capabilities negotation
> > understand they both support draft-ietf-idr-bgp-gr-notification.
> 
> I suspect the point you've overlooked is the N-bit is intended to
> indicate support for this on a per AFI-SAFI basis.  This is something
> you have to explicitly ask for.

Yes, but since a number of days or even weeks, can pass between when you
ask for it at OPEN, and when a NOTIFICATION event actually occurs,
circumstances might have changed.

> It also isn't something that makes sense in many scenarios, especially
> Internet.

I'm happy to read that we're finding common understanding on the
applicability of GR Notification. Perhaps a note to that point would be
useful?

> > 3/ If I may ask, why isn't BGP Cease NOTIFICATION message subcode 4
> > "Administrative Reset" used to perform the 'hard reset' function, and
> > isn't subcode 9 (the suggested value) requested as a new feature called
> > 'soft reset'? This way we don't break people's preconceptions about what
> > it means to type in "clear neighbor 1.2.3.4"..
> 
> It will depend on whether you want to trigger this behavior or not.  The
> semantics change from simply "I typed clear bgp" to "this session must not
> go through this mechanism if you've configured it".

ack.

> > By declaring "subcode 9" to be a hard clear, it appears to me the
> > meaning of 'Administrative Reset (subcode 4)' is redefined, and
> > redefining existing constructs might not be an easy task.
> 
> Naming things is one of the two traditionally hard problems of computer
> science. 

mmm, regardless, since there is code in the wild we may already have
passed the naming station.

Kind regards,

Job