Re: [trill] Alvaro Retana's Discuss on draft-ietf-trill-channel-tunnel-10: (with DISCUSS and COMMENT)

[Donald Eastlake <[e-mail]>]

Hi Alvaro,

Thanks for you comments, See below.

On Wed, Jul 6, 2016 at 9:53 PM, Alvaro Retana <[e-mail]> wrote:
> Alvaro Retana has entered the following ballot position for
> draft-ietf-trill-channel-tunnel-10: Discuss
>
> ...
>
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
>
> Even though the IANA Considerations section was just updated (in version
> -10), I am putting in this DISCUSS because it is still
> incomplete/incorrect.
>
> 1. Guidance for managing the SubERR namespace should be included.  Note
> that this document only specifies values for ERR 6, but guidance should
> be given to IANA for the other ERR values as well.

No IANA registry is created for any SubERR values so I'm not sure why
there needs to be IANA guidance. The draft can be made clearer that
for all values of ERR other than 6, SubErr should be sent as zero and
ignored on receipt. If you want, a registry could be added. I would
think IETF Review was the appropriate registration procedure.

> 2. Section 6.2.1 (RBridge Channel Error Codes Subregistry) requests the
> creation of a new registry ("RBridge Channel Error Codes”), but that
> registry was already created by RFC7178.  This document should then split
> the requests in two parts: assignment of the vales 6-8, and the change to
> the registration procedure.

You are correct. Sorry for the oversight.

However, I actually think the registration procedure should stay as
Standards Action for new ERR codes as provided in the current IANA
registry. New major error codes can cause substantial problems with
older implementations that do not know what they mean. (I do not think
this is a problem with SubErr since implementations can take a default
action based on the major ERR code.)

> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
> >From Section 2. (RBridge Channel Header Extension Format), is the RESV4
> field a space that is reserved for potential future use?  Why isn’t it
> ignored on receipt (similar to the RESV field in Section 4.3)?  If there
> is potential for use of this space (RESV is defined as 4 bits, which
> makes me think about potential bit-level allocations), then there should
> be some guidance in the IANA Considerations.

Earlier versions of this document added three features to RBridge
Channel. As well as the payload feature and security feature in the
current document, which are invoked by non-zero values of the PType
and SType nibbles,
     if you look at the -01 or -00 version you will see a "Scope"
feature invoked by non-zero values of the Scope nibble. RBridge
Channel supports messages between RBridges in the same TRILL campus
and between an end station and an RBridge on the same link. The Scope
feature extended this to support, for example, messages between an end
station and an RBridge not on the same link. However, the scope
feature added significant complexity and there was no immediate
requirement for it so it was dropped and the Scope nibble was
relabeled RESV4.
    Those bits are deliberately made "critical" so the Scope feature
could be revived in the future and Scope-ignorant RBridges would know
to reject Extended RBridge Channel messages that are using the Scope
feature which changes the format a little. Any attempt to re-instate
the Scope feature or to make other use of these four bits will require
a Standards Track document in any case. I don't understand why there
needs to be any guidance in the IANA Considerations about this. What
would it say other than that any non-zero value is treated as an
error? which is a technical specification already present in the body
of the document and not an IANA Consideration.

Thanks,
Donald
===============================
 Donald E. Eastlake 3rd   [phone] (cell)
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