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

Geoff Huston <gih@apnic.net> Fri, 04 November 2016 01:21 UTC

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From: Geoff Huston <gih@apnic.net>
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Date: Fri, 4 Nov 2016 12:21:12 +1100
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To: heasley <heas@shrubbery.net>
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Cc: IETF IDR WG <idr@ietf.org>, Susan Hares <shares@ndzh.com>, rtg-dir@ietf.org
Subject: Re: [Idr] Review of draft-ietf-large-community-06.txt
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> On 4 Nov. 2016, at 11:47 am, heasley <heas@shrubbery.net> wrote:
> 
> Fri, Nov 04, 2016 at 11:14:29AM +1100, Geoff Huston:
> 
>> 3. ----------------
>> 
>> "and may apply to an individual route or to a group of routes."
>> 
>> I am confused - surely the attributes in an Update BGP message apply to the
>> collection of routes contained in the Update. It cannot be applied to a 
>> single route when the update itself contains multiple routes. Why not
>> use the text:
>> 
>> "and is applied to all routes contained in a BGP Update Message where
>> the Communities Attribute is included."
> 
> You are correct about a BGP Update msg, obviously, but that text is not
> talking about an update, rather the utility of a community, which may
> apply to a single route or a group of routes - some of which may not be
> in a given BGP Update msg.  Yes?


So there is the mechanism of application (BGP) and the semantics of application.

It seemed to me that the text was implicitly referring to the mechanism
of application and gave the impression that a community value could be selectively
applied to only some routes contained in a single BGP update.

If the text is read as a semantic specification, then yes the same community
value can be applied to any number of routes.

Either way, the text could do with some small clarification, imho.

Geoff