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Document: draft-ietf-ccamp-rsvp-te-bandwidth-availability-13
Reviewer: Paul Kyzivat
Review Date: 2019-01-23
IETF LC End Date: 2019-01-31
IESG Telechat date: ?

Summary:

This draft is on the right track but has open issues, described in the 
review.

Issues:

Major: 0
Minor: 1
Nits:  1

1) NIT:

Section 3.1 includes the following:

    ... The Ethernet SENDER_TSPEC object
    MAY include more than one Availability TLV. The Availability TLV has
    the following format:

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Index      |                 Reserved                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          Availability                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

I find it confusing that this is described as a TLV yet it shows neither 
a type nor a length. Apparently it is only showing the value portion of 
the TLV. The type portion is only mentioned in the IANA considerations 
section, and isn't explicitly linked to this element. I would expect 
this to be shown something like:

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Type=4                     | Length=96                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Index      |                 Reserved                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          Availability                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

(But the type value needs to be keyed to the IANA assigned value, since 
there is no guarantee that IANA will assign 4 for this.)

2) MINOR:

Section 3.2 includes the following:

    When a node does not support the Availability TLV, it SHOULD
    generate PathErr message with the error code "Extended Class-Type
    Error" and the error value "Class-Type mismatch" (see [RFC2205]).

I have a question about this: Is this the default behavior that is 
prescribed for any unknown TLV type found in an Ethernet SENDER_TSPEC 
object, or is this behavior specific to the "availability" TLV? It is a 
problem if this is not the default behavior.

And is there a reason for SHOULD (rather than MUST) here? If so, please 
describe the situations where this need not be done.