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How to resolve DTMF issue on AS5400 gw

If remote end is 3rd. party and terminating side is AS5400 it is a chance that DTMF send from remote end not understood via terminating side.

LegacyPBX == ISDN == AS5400 ---- H323 --- BTS10200 --- H323 --- Quintum -- FXS

Here Quintum is originating , AS5400 is terminating side.

NSEs are the Cisco-proprietary version of named telephony events (NTEs), which are defined in IETF RFC 2833.

NSEs and NTEs are used to communicate telephony signaling events that are normally indicated by the presence of tones, such as dual-tone multifrequency (DTMF) or fax transmissions.

NSEs and NTEs do not transmit audible signaling tones across the network, but instead work by sending a binary code that is later used to recreate the tone. NSEs use different values to represent events and tones than NTEs use.

NSEs and NTEs are passed in the media stream. They consist of Real-Time Transport Protocol (RTP) packets that have the same source and destination

IP addresses and User Datagram Protocol (UDP) ports as the rest of the media stream. However, NSE and NTE packets use different RTP payload types than the rest of the media stream so that they can stand apart from the audio packets in the stream. NSEs are normally sent with RTP payload type 100.

If remote gateway is and terminating gateway is CiscoAS5400 to understand what NTE type is send from remote end open following debug

debug voip rtp session named

You will see such a trace.

<<<Rcv> Pt:98     Evt:1       Pkt:0B 01 90
         s=VoIP d=DSP payload 0x62 ssrc 0xxxxxxx sequence 0xD2FA timestamp 0x3714B00

Since NTE type is 98 you have to change it 3rd LEG of AS5400

dial-peer voice 6798 voip
  incoming called-number .

   rtp payload-type nte 98

That's all.