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List:       sip-implementors
Subject:    Re: [Sip-implementors] Call Transfer using 3pcc
From:       OKUMURA Shinji <shinji.okumura () softfront ! jp>
Date:       2011-09-13 10:15:41
Message-ID: A2CC71FE173E6Ashinji.okumura () softfront ! jp
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Hi,

The typical flow may be shown as follows.

sathish kumar chevuru <satish.chevuru@gmail.com>
Sat, 10 Sep 2011 17:36:38 +0530
>Thanks to your responses.
>
>Below is the scenario .
>
>
>Caller             3pcc               Callee        Transfer Target
>|                   |                   |                   |
>|---INVITE--------->|---INVITE--------->|                   |
>|                   |                   |                   |
>|<---------200 OK---|<---------200 OK---|                   |
>|                   |                   |                   |
>|---Ack------------>|---Ack------------>|                   |
>|                   |                   |                   |
>|<-----------------RTP----------------->|                   |
>|                   |                   |                   |
>|                   |<----------REFER---|                   |
 |                   |---202------------>|                   |
 |                   |---NOTIFY--------->|                   |
 |                   |<------------200---|                   |
 |<-------reINVITE---|                   |                   |
 |---200 OK(SDP1)--->|                   |                   |
 |                   |---INVITE(SDP1)----------------------->|
 |                   |<-----------------------200 OK(SDP2)---|
 |<-----ACK(SDP2')---|                   |                   |
 |                   |---ACK-------------------------------->|
 |                   |                   |                   |
 |<===========================RTP===========================>|
 |                   |                   |                   |
 |                   |---NOTIFY--------->|                   |
 |                   |<------------200---|                   |
 |                   |<------------BYE---|                   |
 |                   |---200------------>|                   |
 |                   |                   |                   |


>The 3pcc is a B2BUA.
>
>The Callee sent REFER, such that 3pcc establish the call between Caller and
>Transfer Target.
>
>Once the 3pcc receives REFER, Is it must that it should put Caller and
>Callee on Hold ?

It is not mandatory for Callee to put Caller on hold.
If it is required as a voice service, Callee may play MoH
in RTP packets.

>If the 3pcc, Initiates a dialog with Transfer Target (URI in Refer-To ) in
>REFER message, What happens to the existing RTP path ?

Finally, the existing RTP path between Callee and Caller
should be terminated.

Regards,
Shinji

>Thanks,
>Sathish
>
>On Fri, Sep 9, 2011 at 12:18 AM, Paul Kyzivat <pkyzivat@alum.mit.edu> wrote:
>
>> On 9/6/11 5:02 PM, sathish kumar chevuru wrote:
>> > Hi,
>> >
>> > In case of Call Transfer using 3pcc and REFER , If the Callee sends out
>> > REFER without sending INVITE HOLD, What should be the behaviour of 3pcc.
>> >
>> > Does 3pcc sends out INVITE HOLD's to Caller and Callee , before
>> > initiating the call to Transfer Target ? Are the INVITE HOLD's to Caller and
>> > Callee MUST in this case ?
>> >
>> > If 3pcc doesn't send INVITE HOLD's to Caller and Callee, What happens to
>> > the existing RTP path between Caller and Callee ?
>> >
>> > Where do i find this information.
>>
>> To be specific, we really need more info about what you are trying to do
>> and what assumptions you are making about the capabilities of the
>> various devices.
>>
>> Based on what you have said, I guess you have the following situation:
>>
>>    A ------------- B ---------------- C
>>                    |
>>    D ............. |
>>
>> where you have an existing call between the A (caller) and C (callee)
>> through a B2BUA (B). Apparently C understands REFER and is using it to
>> request a transfer from A to D.
>>
>> If so, then it is up to B to carry out the REFER correctly as seen by C.
>> On the other side it can do a variety of things. One of those is a "3pcc
>> transfer", by sending an INVITE to D, and then splicing it into the
>> referred call with C.
>>
>> As Dale said, this is not standardized behavior. Its left for the reader
>> to figure out. If you have a call flow in mind, post it and people will
>> comment on it for you.
>>
>>        Good Luck,
>>        Paul

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