RTP Multiplexing table. RTP Multiplexing: In IP telephony system, the addition of packet headers, including IP, UDP and RTP headers, increases the header overhead, decreasing efficient transmission. Also, because of large numbers of short voice packets flowing into the network, Internet load increases, eventually resulting in large delay and packet loss. RTP Multiplexing is a way to send multiple RTP packets between a pair of Gateways, with a single IP frame. This will reduces the header overhead and decreases delay by enabling voice transmission with fewer packets.