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

Job Snijders <job@ntt.net> Fri, 04 November 2016 17:18 UTC

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Date: Fri, 4 Nov 2016 18:18:34 +0100
From: Job Snijders <job@ntt.net>
To: Geoff Huston <gih@apnic.net>
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Subject: Re: [Idr] Review of draft-ietf-large-community-06.txt
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On Fri, Nov 04, 2016 at 08:04:47PM +1100, Geoff Huston wrote:
> >> 4.  Canonical Representation
> >> 
> >> I am confused here - this section used an example with TWO
> >> canonical representations:
> >> 
> >>   "For example: 64496:4294967295:2, 64496:0:0, or (64496, 111, 222)."
> >> Conventionally, it's better to use a single canonical
> >> representation, so the authors should pick either a colon-delimited
> >> list, or a bracketed comma+space separated object.
> 
> > On 4 Nov. 2016, at 3:05 pm, Jakob Heitz (jheitz) <jheitz@cisco.com> wrote:
> > 
> > To explain this one, it was originally "Textual Representation" and
> > it was with colons only. Then we discovered that Bird uses commas as
> > a separator. Since that does not degrade the utility, we allowed it.
> > The real point is that it has to be exactly 3 positive decimal
> > integers. If some implementations only offered hexadecimal or used 6
> > int16's then it would become very difficult for ISPs to communicate
> > community settings to customers.  I can change it to a single
> > representation and detail the allowed deviations from it.
> 
> if you make a canonical a SHOULD not a MUST then you can permit
> variation without breaking the standard.
> 
> So what you are saying is that the canonical representation of a
> single Large Community value is three unsigned decimal integer values,
> separated by a ‘:’ (colon) character, representing the value as a
> triplet of unsigned 32-bit integer values. Implementations SHOULD
> accept this representation as a valid form of representation of the
> value of a Large Community.

It appears the word "canonical" is maybe triggering something. The key
element is that its three separate values. Nobody cares whether it is a
colon, comma or a hypen.

Does removing the word "canonical" address the raised remark?

"""
4.  Representation

   Large BGP Communities MUST be represented as three separate unsigned
   integers in decimal notation in the following order: Global
   Administrator, Local Data 1, Local Data 2.  Numbers MUST NOT contain
   leading zeros; a zero value MUST be represented with a single zero.
   For example: 64496:4294967295:2, 64496:0:0, or (64496, 111, 222).
"""

Kind regards,

Job