Re: [Idr] draft-spaghetti-idr-bgp-sendholdtimer - Feedback requested

Job Snijders <job@fastly.com> Fri, 23 April 2021 12:43 UTC

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Date: Fri, 23 Apr 2021 14:43:02 +0200
From: Job Snijders <job@fastly.com>
To: "Jakob Heitz (jheitz)" <jheitz=40cisco.com@dmarc.ietf.org>
Cc: Ben Cox <ben=40benjojo.co.uk@dmarc.ietf.org>, "idr@ietf.org" <idr@ietf.org>
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Subject: Re: [Idr] draft-spaghetti-idr-bgp-sendholdtimer - Feedback requested
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Hi Jakob, group,

Thanks for the feedback, a -02 has been submitted.

On Fri, Apr 23, 2021 at 12:56:40AM +0000, Jakob Heitz (jheitz) wrote:
> I propose to add this text:
> 
> It is possible that a BGP speaker presents a TCP zero receive window
> after receiving a large batch of updates. Resetting the session to
> such a speaker may just repeat the large batch, whereas waiting a little
> longer may have given it a chance to recover. The possibility of this
> occurrence makes it difficult to determine a good value for the
> timer. The default value of the timer is therefore recommended
> to be 15 minutes.

In this email John Scudder appears to suggest using a separate new
timer, and populate the timer with the default HoldTimer value (and the
-02 draft attempts to describe exactly that).
https://mailarchive.ietf.org/arch/msg/idr/E5pqxIObPS7e9A2IqIApTHVSfig/

you propose 15 minutes; so it seems there is some convergent thinking in
the group the proposed timers at hand is in the order of 'multiple
minutes'.

How long should a BGP speaker be willing to buffer on behalf of another
BGP speaker's inability to progress message processing?

If the oldest message in the queue is a KEEPALIVE message, and its been
stuck there for more than HoldTimer, wouldn't we have expected the
remote side to have killed the BGP session anyway? 

Would you mind sharing your thinking on why a default of 15 minutes is
better than for example 180 seconds? What do others think?

Kind regards,

Job