Subject: [AVT] I-D Action:draft-ietf-avt-rtcp-port-for-ssm-00.txt

From: [email-masked]
Date: Thu, 17 Jun 2010 00:30:02 -0700 (PDT)

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Audio/Video Transport Working Group of the IETF.

	Title           : RTP Control Protocol (RTCP) Port for Multicast Sessions
	Author(s)       : A. Begen
	Filename        : draft-ietf-avt-rtcp-port-for-ssm-00.txt
	Pages           : 7
	Date            : 2010-06-16

The Session Description Protocol (SDP) has an attribute that allows
RTP applications to specify an address and a port associated with the
RTP Control Protocol (RTCP) traffic.  In RTP-based source-specific
multicast (SSM) sessions, the same attribute is used to designate the
address and the RTCP port of the Feedback Target in the SDP
description.  However, the RTCP port associated with the SSM session
itself cannot be specified by the same attribute to avoid ambiguity,
and thus, is required to be derived from the "m=" line of the media
description.  Similarly, in any-source multicast (ASM) sessions,
there is no explicit way to specify the destination RTCP port.
Deriving the RTCP port from the "m=" line imposes an unnecessary
restriction.  This document removes this restriction by introducing a
new SDP attribute.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtcp-port-for-ssm-00.txt

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

Below is the data which will enable a MIME compliant mail reader
implementation to automatically retrieve the ASCII version of the
Internet-Draft.

---

From: Peter Musgrave <[email-masked]>
Date: Thu, 17 Jun 2010 05:12:49 -0400

HI Ali,

The one thing that jumps out at me is there are two attributes which
define an RTCP port. One gives <port> <protocol> <protocol version>
<ip> and the extension defined just gives <port>.

I assume the IP is implicitly the one in the c=line for the session
(and not the IP in the rtcp attribute)?

Is there any value in defining the extension in the same format as the
existing rtcp attribute?

Regards,

Peter Musgrave

On Thu, Jun 17, 2010 at 3:30 AM,  <[email-masked]> wrote:
> _______________________________________________
> Audio/Video Transport Working Group
> [email-masked]
> https://www.ietf.org/mailman/listinfo/avt
>
>

---

From: "Ali C. Begen (abegen)" <[email-masked]>
Date: Thu, 17 Jun 2010 07:38:19 -0700

Hi Peter,

           a=rtcp:43000 IN IP4 192.0.2.1

defines the port and address of the Feedback Target (RFC 5760). The "IN IP4" part says that the FT has an IPv4 address of 192.0.2.1.

Whereas,
           a=multicast-rtcp:42000

defines the destination port the SSM Sender sends its RTCP reports to (So, this is a port on the receiver side). Since the line below already specified that the RTP packets would be multicast to the group with IPv4 address of 233.252.0.2, it is implied that the SSM Sender sends its RTCP reports to the same multicast group.

           a=source-filter:incl IN IP4 233.252.0.2 198.51.100.1

So, to me, there is no need to specify an additional address (and type) in the "multicast-rtcp: line. But, I am open to suggestions. Do you consider a scenario where RTCP could be multicast in a different multicast group? Is there any use case for it? If so, we should add that support here.

Thanks,
-acbegen

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of Peter Musgrave
> Sent: Thursday, June 17, 2010 5:13 AM
> To: [email-masked]
> Cc: [email-masked]; [email-masked]
> Subject: Re: [AVT] I-D Action:draft-ietf-avt-rtcp-port-for-ssm-00.txt
> 
> HI Ali,
>

---

From: Peter Musgrave <[email-masked]>
Date: Fri, 18 Jun 2010 06:46:11 -0400

Hi Ali,

I think since this draft is specific to SSM all that is really is
needed is the port. I re-read parts of RFC5760 as a penance for
hitting send too quickly :-)

Peter