Subject: [AVT] Concurrent RTP streams and SSRC

From: "Jorge Canas" <[email-masked]>
Date: Mon, 11 Dec 2006 17:00:53 -0500

Hello,

Does RFC 3550 allow two bi-directional RTP streams to exist between the same 
origination and destination IP_Addr:Port combination, and only 
differentiated by SSRCs?

For example:  Node A starts a bi-directional RTP stream (over UDP) between 
it and Node B.  Node A's stream source address is 1.2.3.4:40000 and the 
destination address (node B) is 2.3.4.5:50000.  The SSRC for node A is A1, 
and for node B it is B1.   While this stream is active, does RFC 3550 allow 
for Node A to start a second stream from 1.2.3.4:40000 to 2.3.4.5:50000, but 
this time with a's SSRC being A2 and B's being B2 and does the RFC allow 
both streams to remain active concurrently?

Thanks!

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

---

From: Colin Perkins <[email-masked]>
Date: Tue, 12 Dec 2006 14:10:47 +0000

On 11 Dec 2006, at 22:00, Jorge Canas wrote:
> Does RFC 3550 allow two bi-directional RTP streams to exist between  
> the same origination and destination IP_Addr:Port combination, and  
> only differentiated by SSRCs?
>
> For example:  Node A starts a bi-directional RTP stream (over UDP)  
> between it and Node B.  Node A's stream source address is  
> 1.2.3.4:40000 and the destination address (node B) is  
> 2.3.4.5:50000.  The SSRC for node A is A1, and for node B it is  
> B1.   While this stream is active, does RFC 3550 allow for Node A  
> to start a second stream from 1.2.3.4:40000 to 2.3.4.5:50000, but  
> this time with a's SSRC being A2 and B's being B2 and does the RFC  
> allow both streams to remain active concurrently?

Yes, provided they're the same type of media, and for the same  
session. For example, if Node A had two video cameras, SSRC A1 would  
represent the first camera, SSRC A2 the second camera (e.g. for two  
different views of the same scene). You cannot use this to multiplex  
unrelated RTP sessions (e.g. two different phone calls), nor to  
multiplex audio and video on a single port.

Colin