Subject: [conex] Benoit Claise's No Objection on draft-ietf-conex-destopt-09: (with COMMENT)

From: "Benoit Claise" <[email-masked]>
Date: Thu, 01 Oct 2015 03:13:43 -0700

Benoit Claise has entered the following ballot position for
draft-ietf-conex-destopt-09: No Objection

When responding, please keep the subject line intact and reply to all
email addresses included in the To and CC lines. (Feel free to cut this
introductory paragraph, however.)

Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
for more information about IESG DISCUSS and COMMENT positions.

The document, along with other ballot positions, can be found here:
https://datatracker.ietf.org/doc/draft-ietf-conex-destopt/

----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------

As mentiond by Scott in his OPS-DIR review:

As an experiment this should have few operational concerns for any
network not involved in the experiment but if the 
technology becomes standardized at some later time it will add somewhat
to the complexity of configuring network 
devices (i.e. routers).

Bottom line, technology-wise this ID seems ready to publish.

But I do have some comments on the use of rfc 2119 terminology in the
ID.

I do not think I’ve seen a case where a document says SHOULD NOT and MAY
in the same paragraph referring to the same thing:

   As with any destination option, an ingress tunnel endpoint will not
   natively copy the CDO when adding an encapsulating outer IP header.
   In general an ingress tunnel SHOULD NOT copy the CDO to the outer
   header as this would changed the number of bytes that would be
   counted.  However, it MAY copy the CDO to the outer header in order
   to facilitate visibility by subsequent on-path ConEx functions if the
   configuration of the tunnel ingress and the ConEx nodes is co-
   ordinated.  This trades off the performance of ConEx functions
   against that of tunnel processing.

I suggest that this be reworded to say something like “SHOULD NOT unless
xxx, in which case it MAY xxx”

The next paragraph says

   An egress tunnel endpoint SHOULD ignore any CDO on decapsulation of
   an outer IP header.  The information in any inner CDO will always be
   considered correct, even if it differs from any outer CDO.
   Therefore, the decapsulator can strip the outer CDO without
   comparison to the inner.

Why is this a SHOULD rather than a MUST?

imo, SHOULDs should only be used when there is a known reason that an
otherwise MUST behavior 
might not be followed – in that case the reason should be explained