Configuring POTS Entity 2269Configuring DTMFTransmissionDTMF transmissionIn conversation, DTMF digits can be transparently transmitted between theoriginating and terminating gateways in inband or out-of-band mode:■ Inband transmission: DTMF digits are encapsulated in RTP voice packets fortransmission.■ Out-of-band transmission: Corresponding information is extracted from DTMFdigits and is then encapsulated in H.245 or H.225 packets or RTP packets (RFC2883) for transmission. The transmission of DTMF digits in RTP packets is alsocalled as named telephone event (NTE) mode.Configure out-of-band DTMF transmissionFollow these steps to configure out-of-band DTMF transmission:n ■ Both H.323 and SIP support NTE. For H.323, the NTE transmission mode andthe same payload type value must be set on the originating and terminatingsides. If the NTE transmission mode is adopted on one side and the inbandtransmission mode on the other side, or the inband transmission mode on bothsides, NTE negotiations may fail and even users may not hear DTMF, dependingon the implementation of the communicating routers. For SIP, the NTEtransmission mode is required and the same payload type value is stronglyrecommended on the originating and terminating sides. H3C routers supportdifferent payload type values for communication. Since the implementations ofdifferent manufacturers may differ, different payload type values may result inan NTE negotiation failure. Therefore, the same payload type value isrecommended when the device is communicating with other manufacturers’routers.■ It is forbidden to set the NTE payload type field to "98", which has alreadybeen used to identify nonstandard T.38 fax packets.■ When the device is connected with other manufacturers’ routers forcommunication, you cannot set the payload type field to any forbidden bythese routers. Otherwise, an NTE negotiation failure may occur.Enabling VAD The voice activity detection (VAD) discriminates between silence and speech on avoice connection according to their energies. VAD reduces the bandwidthrequirements of a voice connection by not generating traffic during periods ofsilence in an active voice connection. Speech signals are generated andTo do... Use the command... RemarksEnter system view system-view -Enter voice view voice-setup -Enter voice dial program view dial-program -Create a POTS entity andenter POTS entity viewentity entity-number pots -Configure out-of-band DTMFtransmissionoutband { h225 | h245 |nte }OptionalBy default, the inband DTMFtransmission is configured.Configure the value of thepayload type used by NTErtp payload-type nte value Optional101 by default.
