[asterisk-dev] REFER and NOTIFY behavior

[Klaus Darilion]

Am 15.09.2010 22:00, schrieb Russell Bryant:
> On Wed, 2010-09-15 at 11:51 +0200, Klaus Darilion wrote:
>> Hi!
>>
>> I just tested blind transfer notification with Asterisk (1.6.2.9) and it
>> seems to be wrong:
>>
>> Asterisk does:
>>
>> U1(SIP)          Asterisk         U2(SIP)             U3(ISDN)
>>     |                  |              |                    |
>>     |----INVITE------->|              |                    |
>>     |                  |---INVITE---->|                    |
>>     |                  |<--200 OK-----|                    |
>>     |                  |---ACK------->|                    |
>>     |<------200 OK.----|              |                    |
>>     |----ACK---------->|              |                    |
>>     |                  |              |                    |
>>     |---REFER--------->|              |                    |
>>     |<--202 Accepted---|              |                    |
>>     |                  |              |                    |
>>     |                  |              |                    |
>>     |<--NOTIFY---------|              |                    |
>>     |  w/ 183 Ringing  |              |                    |
>>     |                  |              |                    |
>>     |<--NOTIFY---------|              |                    |
>>     |  w/ 200 OK       |              |                    |
>>     |                  |              |                    |
>>     |                  |----------------SETUP------------->|
>>     |                  |              |                    |
>>
>> So Asterisk notifies the transferer that the blind transfer is ringing
>> and was performed successfully although it does not even have tried to
>> contact the target. I would expect that NOTIFY with sipfrag 183/200 is
>> only sent when the PROGRESS/CONNECT is received from the transfer target.
>>
>> Just as shown in  http://tools.ietf.org/html/rfc5359#section-2.4
>
> I think this is expected behavior for Asterisk.  The reason is that the
> transfer really is "complete" as far as Asterisk is concerned.  The
> target of the transfer isn't U3, it's the Asterisk dialplan.  Asterisk
> has successfully completed the transfer of U2 to a specified dialplan
> location which will now executed (and may happen to make a new outbound
> call, who knows).

OK, I see. So from chan_sip's point of view the transfer is successful. 
But from transferer's point of view the transfer is only successful if 
U3 is reached.

Currently implementation of transfer notification is useless - it only 
indicates if the transfer targets number exists in the dialplan - 
nothing more.

Are there any plans/wills to make the notifications more useful?

regards
Klaus