Linux VoIP: Installation and Security

For the most part, VoIP is transmitted by UDP/RTP (Real Time Protocol) packets. There is a good reason for this. TCP provides verification of packet delivery. This sounds like a good thing, but in the VoIP world, it's not. With TCP, if a packet is dropped, the remote side will retransmit the packet at the receivers request. By the time the voice packet is retransmitted, it's to late to put it in our audio stream! If we don't receive the packet within the allotted time it's useless to us. This is why network latency is such a issue with VoIP.