We have a customer that has an Adtran 908e having an issue with when an incoming calls comes in it connects to the adtran and toshiba system but when the call connects and you hear the auto attendant you are unable to select any options to talk to someone "0 for operator, 1 leave a message" the auto attendant just keeps playing. We have contacted our service provider on this and they are showing that when the call comes in it is using RTP and the Adtran accepts the call, then the Adtran sends our service provider a re-invite and there is no SDP being sent, at this point it strips away the DTMF tones making it unable to make a selection when you are at the auto attendant. The customer is able to dial internally and make outbound calls without issue. This Adtran has been in place for 8 years with no configuration changes and as a side note we have two other locations ( with adtran 924e 2nd gen ) that is experiencing the same issue. Any help/insight is greatly appreciated! Below is the response from our service provider engineers. We are a VoIP company that resells a pbx solution. Thank you!
"I spoke more with my engineer to get a bit more of an in-depth analysis of what we are seeing as it is a bit confusing to me. The essential breakdown of the issue is that we send an invite, your adtran acknowledge and accepts and established and RTP stream and then send a "re-Invite" packet with no SDP.
This means that you are essentially inviting our servers to a call that has already been established, but on the re-invite you have no information as to which RFC parameter is used, what codecs are acceptable and about all information the carriers look for when establishing the calls.
My engineer is continuing to dig on our end but has recommended that you follow up with Adtran to see if they have any insight as to why you are sending a re-invite to us after the call is established."