Re: [Idr] AD Review of draft-ietf-idr-large-community-09

Jeffrey Haas <jhaas@pfrc.org> Fri, 02 December 2016 17:37 UTC

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From: Jeffrey Haas <jhaas@pfrc.org>
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Date: Fri, 2 Dec 2016 12:37:38 -0500
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To: heasley <heas@shrubbery.net>, "Alvaro Retana (aretana)" <aretana@cisco.com>
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Subject: Re: [Idr] AD Review of draft-ietf-idr-large-community-09
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> On Dec 2, 2016, at 12:14 PM, heasley <heas@shrubbery.net>; wrote:
> 
>> I’m having a hard time with this document “reserving” any value because the number space is not really one where values are assigned (in the typical IANA sense: create a registry, etc. – and I doubt you want to make it that way)…but the contents can be (SHOULD) what is contained in an already existing registry (ASNs) that has distributed control.
> 
> 0 and 4294967295 are reserved ASNs, as is 65535 and 65535 is used by RFC 1997
> communities for well-known communities.  It is the intention to use 65535 if
> in the future it is desirable to define large well-known communities.  The
> other two should not be used because they are invalid ASNs and could lead to
> collision.  This all seems prudent to me.

As I'd unfortunately learned this year, people still operationalize the use of even regular communities in the low and high value (0/65535) global admins in RFC 1997 communities.

Given the huge push for "parity" with 1997, being too restrictive in this document seems unwise. 

We have two audiences that any cautions need to be made to:
- For developers, if you're not cautious about your wording on reserved values, they keep you from configuring stuff in those ranges.
- For operators, you want to tell them "these values either are not globally unique and have the possibility of collisions, or may run afoul of future compatibility mechanisms for well known communities in rfc 1997 space".

-- Jeff