[SIPForum-discussion] SIP uses UDP

AMIT ANAND amiit.anand at gmail.com
Fri May 30 14:38:13 UTC 2008

Hi Ashish,

SIP use UDP for the following reasons,

TCP header is of 20 Bytes and UDP header is of 8 Bytes so if you use TCP it
gives extra burden of 12 Bytes per packet.

TCP works on ACK and three packets for hand shake so this increase number of
packets in sesions

Although TCP is reliable but SIP has its own retransmission technique which
cover up this unreliability of UDP.

On Thu, May 29, 2008 at 7:30 PM, Ashis Jena <jenaashis at gmail.com> wrote:

> why does SIP uses UDP eve though UDP is non relaible , connectionless
> protcol?
> what happens if the message is lost in the way?
> what happens to the call set up time if the message is lost and sending
> port goes on retransmitting the message?
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