[SIPForum-discussion] SIP uses UDP

[Yuantao Zhang]

Hi Ashis

 

TCP is too slow for real time voice or video communication. The three way handshake and retransmission mechanism makes TCP not suitable. 

 

The application layer should take care reliable transmission if you really care and the transmission layer is not reliable. Such as the SIP 200OK message or PRACK messages has ACK function. And the application layer should keep timer.

 

Best regards

Steven

 

From: Ashis Jena [mailto:jenaashis at gmail.com] 
Sent: 2008年5月29日 22:01
To: discussion at sipforum.org
Subject: [SIPForum-discussion] SIP uses UDP

 

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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