# Increasing data rate efficiency

When VoIP systems use ThroughPacket instead of RTP to transfer voice data, they substantially reduce the packet header overhead associated with individual data packets. This reduced packet size also leads to a reduced data rate that helps to minimize the costs associated with maintaining a wide area network (WAN). WAN facility costs are generally associated with the network's aggregate data rate, as well as the distance over which systems transfer a given volume of data. Therefore, gateway systems engineered with ThroughPacket can substantially reduce the costs associated with long distance IP-based data transfer.

The following table shows data rate reduction that ThroughPacket can achieve in a gateway system. The TPKT packet data rate efficiency factor column provides a measure of how effectively ThroughPacket reduces bandwidth from a data rate perspective when the system uses different standard VoIP vocoders. As the table shows, gateways reduce bandwidth most significantly when they use low bit rate vocoders.

Vocoder type | Vocoder rate (kbit/s) | Default payload (ms) | Packet rate for 120 RTP streams (packets/sec) | Packet rate for equivalent TPKT stream (packets/sec) | TPKT packet data rate efficiency factor
G.711 | 64.0 | 20 | 9,600.00 | 8640.00 | 1.11
G.726 | 32.0 | 20 | 5,760.00 | 4.320.00 | 1.33
G.723.1 | 6.40 | 30 | 2048.00 | 940.41 | 2.18
G.723.1 | 5.33 | 30 | 1920.00 | 808.42 | 2.37
G.729a | 8.00 | 20 | 2,880.00 | 1,212.63 | 2.38