Re: [Gen-art] review of draft-ietf-teas-lsp-attribute-ro-02.txt

[Elwyn Davies <[e-mail]>]

Hi.

In the process of doing the gen-art review of 
draft-ietf-teas-rsvp-te-li-lb for IETF last call, I needed to look at  
draft-ietf-teas-lsp-attribute-ro-02 in connection with some comments 
about ordering of subobjects in the loopback draft.

I thought that the text in the first paragraph of s2.3:
>     As described in [RFC3209  <https://tools.ietf.org/html/rfc3209>] and [RFC3473  <https://tools.ietf.org/html/rfc3473>] the ERO is managed as a list
>     where each hop information starts with a subobject identifying an
>     abstract node or link.  The ERO Hop Attributes subobject MAY be
>     appended after any of the existing subobjects defined in [RFC3209  <https://tools.ietf.org/html/rfc3209>],
>     [RFC3473  <https://tools.ietf.org/html/rfc3473>], [RFC3477  <https://tools.ietf.org/html/rfc3477>], [RFC4873  <https://tools.ietf.org/html/rfc4873>], [RFC4874  <https://tools.ietf.org/html/rfc4874>], [RFC5520  <https://tools.ietf.org/html/rfc5520>] and [RFC5553  <https://tools.ietf.org/html/rfc5553>].
>     Several ERO Hop Attributes subobject MAY be present, for each hop.
was not very clear: The use of 'appended' was slightly confusing.  I 
felt it needed something a bit closer to the "Presence Rules" that are 
given for RRO subobjects in RFC 5420, s7.3.1 to make it quite clear what 
is going on.

I am not totally clear what would happen in the case of (say) an IPv4 
address subobject followed by two Label subobjects.  The wording seems 
to indicate that Hop attributes can be inserted anywhere in the sequence 
of three subobjects - but would they specifically apply to one or other 
Label if they were inserted after a Label or would they always apply 
generically to the hop terminated at the IPv4 address entity?

My suggestion for rewording, based on the assumption that the hop 
attributes apply to the hop rather than any of the labels, would be:

    As described in [RFC3209] the ERO is managed as a list of subobjects
    each identifying a specific entity, an abstract node or a link. 
Identifying
    subobjects of various types are defined in [RFC3209], [RFC3477], 
[RFC4873],
    [RFC4874], [RFC5520] and [RFC5553].  [RFC3473] modified the ERO list by
    allowing one or two Label subobjects to be interposed in the list 
after a
    subobject identifying an entity by its IP address or interface 
identifier.   One
    or more ERO Hop attributes subobjects applicable to a particular hop 
MAY
    be inserted after any of the existing identifying subobjects defined in
    [RFC3209],  [RFC3477], [RFC4873], [RFC4874], [RFC5520] and [RFC5553].
    If any Label subobjects are present for a hop, the ERO Hop attributes
    subobject(s) MUST be inserted after the Label subobjects.

The last two sentences would need to be altered if Hop attributes were 
applicable to Labels rather than just to the hop as a whole.

Regards,
Elwyn