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Re: [Isis-wg] Ben Campbell's No Objection on draft-ietf-isis-rfc4971bis-03: (with COMMENT)

"Les Ginsberg (ginsberg)" <ginsberg@cisco.com> Tue, 16 August 2016 20:31 UTC

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From: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
To: Ben Campbell <ben@nostrum.com>, The IESG <iesg@ietf.org>
Thread-Topic: Ben Campbell's No Objection on draft-ietf-isis-rfc4971bis-03: (with COMMENT)
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Date: Tue, 16 Aug 2016 20:31:51 +0000
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Subject: Re: [Isis-wg] Ben Campbell's No Objection on draft-ietf-isis-rfc4971bis-03: (with COMMENT)
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Ben -

> -----Original Message-----
> From: Ben Campbell [mailto:ben@nostrum.com]
> Sent: Tuesday, August 16, 2016 12:58 PM
> To: The IESG
> Cc: draft-ietf-isis-rfc4971bis@ietf.org; Christian Hopps; isis-chairs@ietf.org;
> chopps@chopps.org; isis-wg@ietf.org
> Subject: Ben Campbell's No Objection on draft-ietf-isis-rfc4971bis-03: (with
> COMMENT)
> 
> Ben Campbell has entered the following ballot position for
> draft-ietf-isis-rfc4971bis-03: No Objection
> 
> When responding, please keep the subject line intact and reply to all email
> addresses included in the To and CC lines. (Feel free to cut this introductory
> paragraph, however.)
> 
> 
> Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
> for more information about IESG DISCUSS and COMMENT positions.
> 
> 
> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-isis-rfc4971bis/
> 
> 
> 
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
> 
> The first sentence in section 4 says:
> 
>    Routers that do not support the Router CAPABILITY TLV MUST silently
>    ignore the TLV(s) and continue processing other TLVs in the same LSP.
> 
> Is this the authoritative text for a new requirement, or is that preexisting
> behavior defined elsewhere? If the former, why would we expect an
> implementation that does not implement this spec (perhaps the
> implementors haven't read it) to honor this requirement? If the latter, then
> please state it descriptively (i.e. without 2119 keywords), preferably with a
> citation.
> 
[Les:] Repeating my previous reply to Alexey who had a similar comment:

"Ignoring TLVs/sub-TLVs that are not understood is fundamental to the IS-IS protocol and defined in the base spec ISO 10589 (which is referenced). Repeating this is strictly speaking unnecessary - but was done in the original RFC as a point of emphasis."

Normative language is quite appropriate here. It is what guarantees backwards compatibility when new TLVs are introduced.

   Les

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