Why Does RTP use UDP instead of TCP?

networking udp protocols voip rtp
Namratha Patil picture Namratha Patil · Dec 12, 2008 · Viewed 77.5k times · Source

I wanted to know why UDP is used in RTP rather than TCP ?. Major VoIP Tools used only UDP as i hacked some of the VoIP OSS.

Answer

Stobor picture Stobor · Dec 12, 2008

As DJ pointed out, TCP is about getting a reliable data stream, and will slow down transmission, and re-transmit corrupted packets, in order to achieve that.

UDP does not care about reliability of the communication, and will not slow down or re-transmit data.

If your application needs a reliable data stream, for example, to retrieve a file from a webserver, you choose TCP.

If your application doesn't care about corrupted or lost packets, and you don't need to incur the additional overhead to provide the additional reliability, you can choose UDP instead.

VOIP is not significantly improved by reliable packet transmission, and in fact, in some cases things in TCP like retransmission and exponential backoff can actually hurt VOIP quality. Therefore, UDP was a better choice.

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