Subject: [AVT] RE: new draft on RTCP extention

From: "Haldar, Debashis [PCS]" <[email-masked]>
Date: Mon, 9 Dec 2002 10:22:33 -0600

> Hi all,
> I have posted a draft "Session control through RTCP. An extension to RTCP"
> (draft-ietf-haldar-rtp-sessionl-control-00) in the "individual submission"
> group last month. Later on I subscribed to this group and find my draft
> appropriate to be posted through this group. Can this be considered as a
> potential working group draft? If so, what is the procedure?
> My ietf draft:
> http://www.ietf.org/internet-drafts/draft-haldar-rtp-session-control-00.tx
> t
> thanks,
> -Debashis Haldar
_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

---

From: "Haldar, Debashis [PCS]" <[email-masked]>
Date: Mon, 23 Dec 2002 16:26:05 -0600

I didn't see the comments, since I was not an AVT member when the comments
were made on my draft. Here are my solutions to the issues:
1) Lost packet situation: It is better to handle the transmission loss at
the application layer. This strategy will (i) keep the current RTCP design
(no retransmission) unimpacted and (ii) allow the application to decide
retransmission wait time. To do that, one solution is to create an ACK
message from the receiver to the sender as soon as the receiver receives
this kind of messages. I have to introduce Sequence Number & Timestamp too
in the packet format to recognize duplication/retransmission. The sender
client application will use RTCP timer to wait for an application specified
time before retransmitting the message. Any duplicate message at the
receiver end will be recognized by the sequence number & time stamp combined
checking and would be discarded with the processing of an duplicate ACK
message. I'll include that in the next version of my draft.

2) Congestion control: These messages will be used for call control and will
be infrequent. Also, as a whole, RTCP packets are infrequent compared to RTP
packets. At the Network leyer or Transport layer, we can prioritize RTCP
packets over RTP packets, since Congestion Control for RTP packets can be
done using the statistics from RTCP packets. But, I don't think there is any
need to incorporate Congestion Control for RTCP packets.

3) Interaction with RTCP timer: It is needed for retransmission, as
discussed in the 1st bullet. I'll include it in the next version of my
draft.

Send me more comments on the overall methodology, so that I can find the
rationality of this proposal. 

thanks for the comments,
-Debashis Haldar

-----Original Message-----
From: Stephen Casner [mailto:[email-masked]]
Sent: Monday, December 09, 2002 9:44 PM
To: Haldar, Debashis [PCS]
Cc: [email-masked]'; [email-masked]'; [email-masked]'
Subject: Re: [AVT] new draft on RTCP extention

> potential working group draft? If so, what is the procedure?

It is certainly appropriate to discuss your draft in the AVT working
group, but the question of adopting it as a working group task depends
upon WG agreement that the design makes sense and that this is an
appropriate task.

Two messages attached below were posted to the AVT list after your
draft was announced.  Did you see them?  They are pointing out some
problems with your design.

                                                        -- Steve

---------- Forwarded message ----------
Date: Tue, 26 Nov 2002 17:38:34 -0800
From: John Lazzaro <[email-masked]>
To: [email-masked]
Subject: [AVT] Re: draft-haldar-rtp-session-control-00.txt

A quick read over:

http://www.ietf.org/internet-drafts/draft-haldar-rtp-session-control-00.txt

seems to indicate no provision for handling lost packets, but the
example applications (push-to-talk, mute, ...) would seem to be
brittle in the face of lost packets ...

-------------------------------------------------------------------------
John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu     www.cs.berkeley.edu/~lazzaro
-------------------------------------------------------------------------

---------- Forwarded message ----------
Date: Tue, 26 Nov 2002 22:43:36 -0500
From: Colin Perkins <[email-masked]>
To: John Lazzaro <[email-masked]>
Cc: [email-masked]
Subject: Re: [AVT] Re: draft-haldar-rtp-session-control-00.txt

--> John Lazzaro writes:
>
>A quick read over:
>
>http://www.ietf.org/internet-drafts/draft-haldar-rtp-session-control-00.txt
>
>seems to indicate no provision for handling lost packets, but the
>example applications (push-to-talk, mute, ...) would seem to be
>brittle in the face of lost packets ...

It might also be appropriate to consider congestion control, and
interaction with the RTCP timers.

Colin