Subject: [ippm] comments on draft-ietf-ippm-twamp-01.txt

From: Matthew J Zekauskas <[email-masked]>
Date: Wed, 08 Nov 2006 00:27:22 -0500

I mentioned in the meeting that I had some comments about how we might
harmonize this draft with the OWAMP RFC, and in particular ensure that
modifications to OWAMP are seen as modifications that do not affect the
security and privacy of either the control or test protocols, since
those aspects required a lot of consultation with the security area to
get correct.  I don't want this document hung up needing a detailed
security review.

So here goes my first set of not-fully-baked comments, to spur discussion.

--Matt

-=-=-
In reading the document, I wonder if we shouldn't have created an IANA
registry for owamp-control message types... but this is the only likely
protocol that would modify what exists.

RFC 2119 is not in the references, but standards language is included.

My basic idea is to see if we can minimize the changes to being
straightforward deltas from the OWAMP spec, so that a detailed security
review is not required.  Note that the RFC changes section numbers, so
the references are now wrong, and that some of the protocol has changed
as well (in particular using HMAC instead of IZP).  Most of these are
brought over by reference, except for the twamp-test packet format and
content section.

Here's one thought, just focusing on TWAMP-control for now:

4. TWAMP Control
   The TWAMP control protocol is exactly the OWAMP control protocol,
   with two modifications:

   1. The Request-Session for a two-way test has the value of 5
      as the first octet, instead of 1.  All other fields and
      values are as specified in the OWAMP Request-Session message.

      [behavior, though, is different?]
      [reaction to value 1: reject if one-way not supported?] (2nd para
below)

   2. The purpose of TWAMP is measurement of two-way metrics.  Two-way
    measurements do not rely on packet level data collected by the
    Session-Reflector such as sequence number, timestamp, and TTL.   As
    such the protocol does not require the retrieval of packet level
    data from the Server and the Fetch-Session command is optionally
    supported by the Server.

    However, TWAMP can be used as an extension to OWAMP [OWAMP] where
    both one-way and two-way measurements are measured in the same
    session.  In this case the Server MAY support the Fetch-Session
    command as defined in section 3.9 of OWAMP [OWAMP].  The
    Session-Reflector will reject the Fetch-Session request if either
    it does not support the Fetch-Session command or Session-Reflector
    cannot provide the required data.  In this case the server MUST
    respond with a Fetch-Ack message with Accept value of 3.

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