246 V6100 and V7122 User GuideIn this configuration, T.30 faxes use Relay mode (T.38) while V.34 fax uses Bypass mode.In order to use V.34 fax in Relay mode (T.38), you must configure:FaxTransportMode = 1 (Relay)V34ModemTransportType = 0 (Transparent)V32ModemTransportType = 0V23ModemTransportType = 0V22ModemTransportType = 0This configuration forces the V.34 fax machine to work in T.30 mode.ThroughPacket™The gateway supports a proprietary method to aggregate RTP streams from severalchannels to reduce the bandwidth overhead caused by the attached Ethernet, IP, UDP andRTP headers, and to reduce the packet / data transmission rate. This option reduces theload on network routers and can typically save 50% (e.g., for G.723) on IP bandwidth.ThroughPacket™ is accomplished by aggregating payloads from several channels that aresent to the same destination IP address into a single IP packet.ThroughPacket™ can be applied to the entire gateway or, using IP Profile, to specific IPdestinations (see IP Profile Settings). Note that ThroughPacket™ must be enabled on bothgateways.To enable ThroughPacket™ set the parameter ‘RemoteBaseUDPPort’ to a nonzero value.Note that the value of ‘RemoteBaseUDPPort’ on the local gateway must equal the value of‘BaseUDPPort’ of the remote gateway. The gateway uses these parameters to identify anddistribute the payloads from the received multiplexed IP packet to the relevant channels.In ThroughPacket™ mode, the gateway uses a single UDP port for all incoming multiplexedpackets and a different port for outgoing packets. These ports are configured using theparameters ‘L1L1ComplexTxUDPPort’ and ‘L1L1ComplexRxUDPPort’.When ThroughPacket™ is used, Call statistics aren’t available (since there is no RTCP flow).Dynamic Jitter Buffer OperationVoice frames are transmitted at a fixed rate. If the frames arrive at the other end at the samerate, voice quality is perceived as good. In many cases, however, some frames can arriveslightly faster or slower than the other frames. This is called jitter (delay variation), anddegrades the perceived voice quality. To minimize this problem, the gateway uses a jitterbuffer. The jitter buffer collects voice packets, stores them and sends them to the voiceprocessor in evenly spaced intervals.
