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
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