Re: [Isis-wg] Alexey Melnikov's Discuss on draft-ietf-isis-rfc4971bis-03: (with DISCUSS and COMMENT)

["Les Ginsberg (ginsberg)" <[e-mail]>]

Alexey -

> -----Original Message-----
> From: Alexey Melnikov [mailto:[e-mail]]
> Sent: Tuesday, August 16, 2016 8:43 AM
> To: The IESG
> Cc: [e-mail]; Christian Hopps; [e-mail];
> [e-mail]; [e-mail]
> Subject: Alexey Melnikov's Discuss on draft-ietf-isis-rfc4971bis-03: (with
> DISCUSS and COMMENT)
> 
> Alexey Melnikov has entered the following ballot position for
> draft-ietf-isis-rfc4971bis-03: Discuss
> 
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> 
> Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
> for more information about IESG DISCUSS and COMMENT positions.
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> 
> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-isis-rfc4971bis/
> 
> 
> 
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
> 
> I would like to get clarification on the following points before recommending
> approval of this document:
> 
> 1) How do multiple CAPABILITY TLVs from the same source treated, if they
> have the same S and D flags, but different subTLV? Are the cumulative? Or
> this is not allowed?
> I am sorry if I missed where this was described, let me know if I did.

[Les:] Section 2 states:

" The Router CAPABILITY TLV is OPTIONAL.  As specified in Section 3,
   more than one Router CAPABILITY TLV from the same source MAY be
   present."

The only problematic case is when you have two TLVs from the same source which have different settings for the same attribute i.e. same sub-TLV but different values. This case is discussed in detail in Section 3. Different sub-TLVs presents no issue of course.
Note this text is unchanged from the existing RFC.

> 
> 2) In Section 4, 1st sentence: how can this specification have requirements
> on implementation that don't support this extension? If this behaviour is
> already prescribed by another specification, then you should not use RFC
> 2118 keyword and you should reference the relevant specification.
> 

[Les:] 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.

> 
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
> 
> Should subTLVs have an IANA registry? Or is there an existing one already?
> 

[Les:] http://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-codepoints.xhtml#isis-tlv-codepoints-242
It has already been noted that the registry should be updated to point to the new RFC once it is published.

   Les