Subject: [sipcore] About RFC3911(Join header)'s potential error:

From: [email-masked]
Date: Sun, 26 Sep 2010 10:27:11 +0800

Hi,

By section 4 of RFC3911(User Agent Server Behavior: Receiving a Join 
Header), UAS always create mixing or conferencing resources for authorized 
INVITE with Join header:

If authorization is successful, the UA attempts to accept the new INVITE, 
and assign any mixing or conferencing resources necessary to complete the 
join.

But I think it is not necessary, while it should depend on SDP's send and 
recv attribute.

Let's consider a use case for IPTV system or VoD system:
User_A connects to a vedio channel/file;
User_A want to share this vedio with User_B synchronous, and shared the 
dialog information with User_B;
User_B send INVITE with Join header to Join in the vedio 
broadcast/multicast;

In fact, User_A and User_B all just have downlink media for the stream. 
So, the media server needn't create  any mixing or conferencing resources. 
The server just need to duplicate the media stream to User_B.

Thanks,

Gao

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---

From: Paul Kyzivat <[email-masked]>
Date: Mon, 27 Sep 2010 09:35:32 -0400

Gao,

I think the works you are concerned about already are consistent with 
the scenario you raise. Specifically,

> and assign any mixing or conferencing resources necessary to complete the join

includes the case where no mixing or conferencing resources are necessary.

	Thanks,
	Paul

On 9/25/2010 10:27 PM, [email-masked] wrote:
> Header), UAS always create mixing or conferencing resources for
> authorized INVITE with Join header:
>
> If authorization is successful, the UA attempts to accept the new
> INVITE, and assign any mixing or conferencing resources necessary to
> complete the join.
>
> But I think it is not necessary, while it should depend on SDP's send
> and recv attribute.
>
> So, the media server needn't create any mixing or conferencing
> resources. The server just need to duplicate the media stream to User_B.
>
> Thanks,
>
> Gao
>
> _______________________________________________
> sipcore mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/sipcore

---

From: [email-masked]
Date: Mon, 27 Sep 2010 23:30:10 +0800

Paul,

IMO, no matter the original concept of RFC3911 is always create mixing or 
conferencing resources, or it depends on SDP attributes(as I showed in the 
IPTV scenario), the UAS's behavior for INVITE with Join header is not quit 
correct/clear by current text in RFC3911.

The UAS's behavior in the IPTV scenario is my understanding. It seems that 
you have the similar understanding(that's nice). 

But there's people said that this is not defined in the RFC3911, once in 
one discussion. Though I think my/our understanding is reasonable, but I 
admit that RFC3911 really hasn't do such definition.

And if the Join INVITE with less or more media streams(m= lines), how 
would the UAS behave as? I think this also not clear now.

Thanks,

Gao

Paul Kyzivat <[email-masked]> 
2010-09-27 21:35

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Re: [sipcore] About RFC3911(Join header)'s potential error:

Gao,

                 Thanks,
                 Paul

On 9/25/2010 10:27 PM, [email-masked] wrote:
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---

From: "Worley, Dale R (Dale)" <[email-masked]>
Date: Thu, 30 Sep 2010 16:23:18 -0400

________________________________________
From: [email-masked] [[email-masked]] On Behalf Of Paul Kyzivat [[email-masked]]

I think that Paul is correct here.  If two dialogs go to a server and are joined at the server, and both dialogs are sendonly at the server, then "mixing" is very simple: the one source (generated by the server) is duplicated as RTP to each dialog's remote end.

In practice, one might say that this "does not allocate mixing resources".  OTOH, for some implementations, this duplication of the media stream may require the allocation of a mixing resource, if no other component of the server can perform the duplication.

I do not see this as a problem that needs to be solved.

Dale