[SIPForum-discussion] proper time to establish stream

[Ravi Siebel]

Hi All,
 
Yes Herve is right. I also have observed in case where we are trying to Outbound PSTN call through the  VOIP Gateway, where Gateway respond with 183 and also starts Media towards the Originating parties and said "The Number you are dailing has been changed and new number is ".
 
Once the session or dialog has been created with success final repsonse , the media 
streaming can start even without waiting for ACK to reached the other end safely.
 
Regards,
Ravi 

--- On Fri, 8/29/08, Herve Jourdain <herve.jourdain at mstarsemi.com> wrote:

From: Herve Jourdain <herve.jourdain at mstarsemi.com>
Subject: Re: [SIPForum-discussion] proper time to establish stream
To: "'雨 陈'" <chen.yu26 at yahoo.com.cn>, discussion at sipforum.org, "'Vivek Batra'" <vivek7683 at gmail.com>
Date: Friday, August 29, 2008, 5:21 AM








Hi Nora,
 
As far as I understand, your concern is about when caller can start sending RTP, right ?
If it’s so, then it’s only after receiving the 200 OK.
But the callee can send you “early media” by providing you SDP information in a 18X response – usually 183, but I’ve seen in 180 as well. This can carry “announcements” (tones, voice prompts, etc…).
So I think that the caller can start to “listen” to the “early media” flow as soon as it’s announced by the callee (provided it supports the codec used). But send only after receiving 200 OK (because only then does it know the codecs to use…).
 
Regards,
 
Herve




From: 雨 陈 [mailto:chen.yu26 at yahoo.com.cn] 
Sent: vendredi 29 août 2008 11:57
To: discussion at sipforum.org; Vivek Batra; Jourdain Herve
Subject: proper time to establish stream
 

Hi,

 

There is another question: What is the real time that the media stream begin to set up?

 

I think in the two common offer/answer models: INVITE/200 and 200/ACK, they can set up the stream after the SDP answer with 200 and ACK respectively, But what is the matter in the reliable response ? I mean the model INVITE/ 180(183). 

 

My 2 cents is even though the 180(183) with SDP answer was accepted by the offer entity , the media stream CAN NOT STRAT until the 200 OK for INVITE is received. Because during the early-dialog, the caller may send a CANCEL to break down the call. 

 

Please correct me if I am wrong. Thanks in advance!

 

Regards

 

Nora :)


 

 
  



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