Subject: Re: [AVT] Working group last call:draft-ietf-avt-rtp-framing-contrans-04.txt

From: lazzaro <[email-masked]>
Date: Wed, 05 Jan 2005 11:31:46 -0800

Hi Magnus,

	Thanks for the comments ... most of these are not
controversial, I'll put them in ... everyone, please read
the potentially controversial ones below, some of you
may wish to comment ...

> I would also like to point out that due to comedia it doesn't seem 
> that this framing method can be used in any non Offer/Answer usage. Or 
> have I missed something in the comedia draft?

Appears to be so -- anyone disagree?  Assuming,
of course, the application uses SDP-based session
management at all, perhaps it uses RTP AVP and
does session management by other, non-SDP based
means.

> 5. Section 4, second last paragraph:
> "The RTP stream MUST have an unbroken sequence number order.  RTCP 
> stream packets MUST appear as defined in [2], with no lost or 
> re-ordered
> packets.  IETF standards-track documents MAY loosen these restrictions
> on packet loss and packet ordering."
>
> This paragraph is in contradiction with a statement in section 3.

There's a misunderstanding here, I'll rewrite Section 3 to
clarify.  Sections 2-3 define the framing in the most general
of terms, so that other documents can reference Sections 2-3
and add their own restrictions.  Section 3 specifically describes
what is NOT specified by the framing method, and thus what is
left up to other documents to define as they wish.  Thus, this
section from Section 3:

    Packet loss and reordering.

       The reliable nature of a connection does not imply that a
       framed RTP stream has a contiguous sequence number ordering.
       For example, if the connection is used to tunnel a UDP stream
       through a network middlebox that only passes TCP, the sequence
       numbers in the framed stream reflect any packet loss or
       reordering on the UDP portion of the end-to-end flow.

Is saying "the framing method definition is agnostic -- it doesn't
care.  Any document referencing Section 2-3 is free to apply a
restriction or not, as it wishes" -- and Section 4 is, in effect, one of
those documents.

>  I also think that it is wrong to make this requirement on the packets 
> entering the TCP connection.

I can't find documentation at the moment, but someone specifically
requested this requirement -- I'm thinking that it was Colin, but I
can't find email to back up that memory.  Does anyone remember
requesting an unbroken sequence numbering requirement?
Please chime in ...

> 6. What is meant with the following sentence in section 4:
> "The out-of-band semantics for the connection MUST comply with [3]." I 
> don't think it is clear what is meant with out-of-band semantics.

I'll use a different phrase, or just drop it -- I meant all of the
"when to open a connection", "when to terminate it" semantics
of comedia ...

---
John Lazzaro
http://www.cs.berkeley.edu/~lazzaro
lazzaro [at] cs [dot] berkeley [dot] edu
---

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

---

From: lazzaro <[email-masked]>
Date: Thu, 06 Jan 2005 09:34:48 -0800

On 13 Dec 2004, at 16:47, Colin Perkins wrote:
> This working group last call period ended yesterday. Magnus raised a 
> number of technical issues. Accordingly, the draft will not be 
> advanced until they have been addressed.

OK, I'll probably execute the changes I described on the list
posting yesterday quite soon -- so, if anyone has an issues
with those changes, please send them along ASAP.  Thanks!

---
John Lazzaro