SIP Trunking: 3300 send another invite out after receiving 486 Busy

[wyeee]

This is not happening all the time but when it happens, it is quite annoying.

Extension off 3300 calls an external number on Asterisk (using SIP Trunking).
When 486 Busy is returned (with no retry-after header), 3300 sends another INVITE (within a second, with different callid) to the same number and gets 486 again. And it goes on and on:

INVITE, 486; INVITE, 486... Until the caller hangs up. In Mitel internal trace I notice some timer is fired and that seems to kick off another call.

There must be a flag to turn this behavior off (through COS, SIP Peer Profile, ...)

Does anyone know how to do it?

Thanks

[brantn]

There is not really a timer to effect this I believe it is how it is sending the headers. PM me your SIP Peer Profile and I might be able to suggest some changes.