Re: [Idr] Capability Advertisement in draft-ietf-idr-bgp-extended-messages

Jeffrey Haas <jhaas@pfrc.org> Wed, 31 July 2019 21:14 UTC

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Date: Wed, 31 Jul 2019 17:16:02 -0400
From: Jeffrey Haas <jhaas@pfrc.org>
To: Alvaro Retana <aretana.ietf@gmail.com>
Cc: "idr@ietf. org" <idr@ietf.org>, idr-chairs@ietf.org, draft-ietf-idr-bgp-extended-messages@ietf.org, Susan Hares <shares@ndzh.com>
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Subject: Re: [Idr] Capability Advertisement in draft-ietf-idr-bgp-extended-messages
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On Wed, Jul 31, 2019 at 01:06:04PM -0700, Alvaro Retana wrote:
> During the IESG Evaluation, Sue pointed out that we removed the piece of
> text below:
> 
> Just to let you know that the text below:
> 
> “A peer which does not advertise this capability MUST NOT send BGP
>    Extended Messages, and BGP Extended Messages MUST NOT be sent to it.”
> 
> was added due to comments on the IDR WG list from reviewers and operators.
> 
> Given that Extended Messages is a very important extension to BGP, and even
> though I didn’t see objections in the thread mentioned above, I want to
> confirm one more time that the current text is ok with the WG. 

I am fine with the current text, although my opinion is nuanced.

By requiring bi-directional advertisement of the capability, UPDATEs sent
from one can have NOTIFICATIONs of similar size.  This avoids some ugly edge
conditions that would result from uni-directional advertisement of the
capability.

The converse argument, which I'm not supporting, is that uni-directional
advertisement intentionally lets peers opt-out of receiving extended
messages, even it understands them.

Let the bi-directional requirement stand.

Note that RFC 6793 (4-byte ASes) require bi-directional advertisement.

-- Jeff