Re: [Idr] Review of draft-ietf-large-community-06.txt

"Jakob Heitz (jheitz)" <jheitz@cisco.com> Fri, 04 November 2016 13:50 UTC

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From: "Jakob Heitz (jheitz)" <jheitz@cisco.com>
To: Jeffrey Haas <jhaas@pfrc.org>
Thread-Topic: [Idr] Review of draft-ietf-large-community-06.txt
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Date: Fri, 4 Nov 2016 13:50:32 +0000
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Cc: IETF IDR WG <idr@ietf.org>, Sue Hares <shares@ndzh.com>, "rtg-dir@ietf.org" <rtg-dir@ietf.org>
Subject: Re: [Idr] Review of draft-ietf-large-community-06.txt
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The text in RFCs 1997 and 4360 is not a constraint:


If a range of routes is to be aggregated and the resultant aggregates
   attribute section does not carry the ATOMIC_AGGREGATE attribute, then
   the resulting aggregate should have a COMMUNITIES path attribute
   which contains all communities from all of the aggregated routes.


It does not describe how to aggregate if ATOMIC_AGGREGATE is present. The text is more constrained if ATOMIC_AGGREGATE is left out of it.

Thanks,
Jakob.


On Nov 4, 2016, at 4:24 AM, Jeffrey Haas <jhaas@pfrc.org<mailto:jhaas@pfrc.org>> wrote:


On Nov 4, 2016, at 4:59 AM, Geoff Huston <gih@apnic.net<mailto:gih@apnic.net>> wrote:

I just noted that RFC1997 and RFC4360 had these constraints.

It seems strange to me that an implementation would handle aggregation differently, treating communities and extended communities one way and large communities in a subtly different manner.

Frankly I would prefer to see a consistent treatment of communities in the case of aggregation, and reproducxing the RFC4360 text kinda makes that clear (at least to me)

Omitting it invites different handling and that would be not good

The relevant point from the thread is that the atomic-aggregate attribute is largely protocol noise.  It's a vestigial organ from the BGP-3 to BGP-4 transition, and a poorly specified one at that.  We shouldn't include its use in specifications, particularly where discussing aggregation.

The only place its discussion would be relevant is as part of *de-*aggregation of a prefix.

-- Jeff