252 V7122 GatewayUser Guidec=IN IP4 m=audio A> RTP/AVP 18 0a=ptime:10a=rtpmap:96 PCMU/8000a=gpmd: 96 vbd=yesIn the example above, V.152 implementation is supported (using the dynamic payload type96 and G.711 mu-law as the VBD codec) as well as the voice codecs G.711 mu-law andG.729.Instead of using VBD transport mode, the V.152 implementation can use alternative relay faxtransport methods (for example, fax relay over IP using T.38). The preferred V.152 transportmethod is indicated by the SDP ‘pmft’ attribute. Omission of this attribute in the SDP contentmeans that VBD mode is the preferred transport mechanism for voice-band data.Event Notification using X-Detect HeaderThe gateway supports the sending of notifications to a remote party notifying the occurrence(or detection) of certain events on the media stream. Event detection and notifications isperformed using the X-Detect SIP message header, and only when establishing a SIPdialog.For supporting some events, certain gateway configurations need to be performed. The tablebelow lists the support event types (and subtypes) and the corresponding gatewayconfigurations, if required:Table 50 Supported X-Detect Event TypesEvents Required Gateway ConfigurationType SubtypeAMD voiceautomatasilenceunknownEnableDSPIPMDetectors = 1AMDTimeout = 2000 (msec)CPT SIT SITDetectorEnable = 1UserDefinedToneDetectorEnable = 1Note: Differentiation of SIT is not supported in 5.0.FAX CED (IsFaxUsed ≠ 0) or (IsFaxUsed = 0 and FaxTransportMode ≠ 0)modem VxxModemTransportType = 3PTT voice-startvoice-endEnableDSPIPMDetectors = 1
