Summary:ASTERISK-02417: Parking calls with blind transfer phones like GrandStream does not read digits
Reporter:cshaw59 (cshaw59)Labels:
Date Opened:2004-09-15 17:59:26Date Closed:2011-06-07 14:05:12
Versions:Frequency of
Description:When parking calls with a "Dumb" SIP device like the GrandStream BT10X for example, the parking slot announcement is not heard because asterisk (Correctly) sends 202 and then 200 OK. When the GrandStream receives the 200 OK, and thinking this is just another blind transfer simply sends a BYE and disconnects...

What I propose and please tell me if I'm on the wrong track here or if this has already been thought of or what. Is to add an option in sip.conf in the user section where you define SIP devices that's something like BLINDTRANSFERSONLY=YES or something to that effect that would change the behavior of parking so that it sends a 100 TRYING then if successful a 183 SESSION PROGRESS with the parking slot digits and then a 200 OK which will cause the phone to disconnect on success...
Comments:By: Mark Spencer (markster) 2004-09-15 18:08:42

We're not permitted to send 100 Trying to anything but INVITE (and maybe REGISTER?) because the other operations are expected to be atomic.  183 cannot be used either.

Unfortunately, there is no way that you can do park with only blind transfer.  However if you support supervised transfer then it can be done, even with SIP by calling the parking extension and then after listening to the number completing the supervised transfer.

How about supplying a SIP debug of what happens now.  That will tell us if the grandstream is doing blind or supervised.

By: cshaw59 (cshaw59) 2004-09-15 18:25:01

Wow! thanks for writing so quickly!

I know it's blind because * will correctly send a 202, then a 200, then immediately the grandstream will send back a BYE because once we get a 200 OK, everything's good and we can disconnect...

I'm at work right now and don't have access to my GS unfortunately but I WILL send a debug output for completeness, maybe it will give you some ideas? :)

So basically what this means is that if we're using a blind-only phone, not even a blind-only phone but a phone that supports some wierd proprietary semi-attended transfer like I think some of the Cisco phones do, you can never hear the digits? Stupid SIP, that's lame...

I guess the current implementation DOES work, but it's kind of a hack since you MUST have * in the media stream and cannot use reinvites... :(


By: Mark Spencer (markster) 2004-09-16 23:46:53

Did you get a chance to get that trace?

By: Mark Spencer (markster) 2004-10-01 23:14:20

User seems to have lost interest.  In any case you can use # transfer.