[asterisk-dev] SIP: INFO before answer causes disconnect

[Kevin P. Fleming]

Alan Ferrency wrote:

> This seemed to happen only randomly, but I figured out how to reproduce
> it. We are using SIP INFO for DTMF. The problem occurs if the PRI caller
> enters a DTMF tone after the SIP invite was sent to the SIP phone, but
> before the SIP phone answers.
> 
> In this case, the SIP phone responds to the INFO packet immediately,
> before the call is answered. Then, when the call is answered, the phone
> responds to the initial INVITE, and Asterisk sends an ACK for the INVITE.
> 
> However, the phone never receives an ACK for the INFO response it sent.
> The phone doesn't care much about this lack of ACK, but it looks like
> Asterisk didn't see the INFO response. It reports:

This does appear to be an Asterisk bug; please make sure there are no
other reports of this already open in the bug tracker, and if not, open
a new one with your debug log and description attached.

In the meantime, you can easily avoid this problem by using RFC2833 for
DTMF transport instead :-)