We are trying to work through an issue where SIP trunking calls are answered live, parked and then retrieved from another extension. When the call is picked out of park there is one-way audio. Here's my theory of what's happening, but any input from others who have worked with this problem would be appreciated.
1) Call rings in to handset. Handset profile allows codec G.729.
2) G.729 is the negotiated codec for the RTP stream.
3) Call is placed in Park.
4) Music on Hold on the Allworx is G.711 only. (Allworx PBX supports G.711 only. This would include voicemail, AA, MOH etc.)
5) The call that was running a G.729 RTP stream is now forced to renegotiate to G.711 and during this process the RTP port is changed.
6) Caller Picks up the parked call and experiences one-way audio due to the RTP port mismatch.

It is my opinion that Allworx needs have the PBX support the same codec sets that the handsets support so that SIP reinvites can be stopped when parking calls. SIP reinvites are a bad practice because they increase the possibility of Call Control problems and further more, there is no need to reinvite when a call is parked.

Just curious. What version software are you using?? Your logic seems to be intact.

Have you run this by anyone at Allworx?

Let us know what happens.

aw...?? shouldn't there be another sip invite when the call goes from park to the talk path of the handset since it's going back to a G.729 handset profile? Just curious.

...bob...

It's been several days now. Since setting several of our customers using SIP trunking to a handset profile of G.711 only, we haven't had a single report of dropped calls. It's a work around. Allworx listen up! You need to have the PBX support the same codec set as the handsets and then turn off SIP reinvites to the ITSP when calls are parked/unparked.

Software versions vary by customer site anywhere from pre 7.0 to 7.4.9.x The problem seems to pop up when the back end carrier handling the call is Level 3.