[SIPForum-discussion] The process sequence

[Mark R Lindsey]

I don't think you can infer that a 183 means the called party is not  
aware. It may mean the called party MAY NOT be aware, but it may also  
be used when the called party's phone is ringing.

If you said, "When caller receives 183 session progress, it means  
callee is not NECESSARILY aware about incoming call," then I'd agree.

In the case of calls terminated through SS7 PSTN gateways, the 183  
response usually means in-band audio is available.  When the called  
party's phone is alerting, the ringback is streamed through RTP toward  
the calling party. By convention (but not by RFC) a 183 is sent when  
the terminating (called) device begins to stream RTP with the ringback  
audio. By RFC, the terminating (called) may send RTP to the calling  
party who has provided an SDP offer.

On Jun 19, 2009, at 4:58 AM, NEERAJ JAIN wrote:

> Hi,
>
> Purpose of 183 and 180 is totally different. When caller received  
> 183 session progress, it means callee is not aware about incomming  
> call. while caller received 180 ringing, it means that callee is  
> started alerting and now callee can accept or reject the call.
>
>
>
>
> ------- Original Message -------
> Sender : Karthik Ramiya<Karthik_Ramiya at infosys.com>
> Date : Jun 19, 2009 17:42 (GMT+09:00)
> Title : RE: [SIPForum-discussion] The process sequence
>
> Hi,
>
>    But is 180 ringing really needed when we get a 183 in the  
> firstplace??
>
> Cheers,
> Karthik
>
> ________________________________
> From: discussion-bounces at sipforum.org [discussion- 
> bounces at sipforum.org] On Behalf Of NEERAJ JAIN [neeraj.jain at samsung.com 
> ]
> Sent: Friday, June 19, 2009 11:48 AM
> To: Mike Jiang; discussion at sipforum.org
> Subject: Re: [SIPForum-discussion] The process sequence
>
> Hi MIke,
>
> 183 session progress is generaly used when user is intrested in  
> resource reservation according to 3GPP spec. Genrally 183 and PRACK  
> is used to do the media negotiation before user is alerted. So it  
> always comes before 180 ringing.
>
>
>
> Thanks,
>
> Neeraj
>
>
>
>
>
>
> ------- Original Message -------
> Sender : Mike Jiang<mike.jiang at andersontaylor.com>
> Date : Jun 19, 2009 02:35 (GMT+09:00)
> Title : [SIPForum-discussion] The process sequence
>
> Hi All,
>       One quick question: I was wondering if the Ringing (180) is  
> always occurring ahead of the Session Progress (183).
>       In my case, the 183 response always happened before the 180  
> happened.
>
>       Thanks,
>
>       Mike J.
>
>
>
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