Subject: Re: [Sip] m= lines with multiple ports

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 08 Jan 2002 14:27:54 -0500

Christer Holmberg wrote:

> Hi,
> 
> More on the SIP media handling discussion.
> 
> At the moment, I think most people agree that the number of m= lines in
> the request and response MUST match.
> 
> Now, SDP allows the including of multiple ports (so called port pairs)
> in a single m= line, so the UAC may send:
> 
> m=audio 2000/2 RTP/AVP 31

This is for hierarchically layered video, typically used with multicast. 
I don't think there is any use for unicast.

> 
> Now, there are a few scenarios:
> 
> 1. The UAS only supports the stream on one port. In that case, it could
> indicate that by sending:
> 
> m=audio 3000 RTP/AVP 31
> m=audio 0 RTP/AVP 31
> 
> However, this breaks the matching rule...

Christer, you are inventing problems. The response to this would mirror 
the same m line since its multicast.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.            72 Eagle Rock Avenue
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