[SIPForum-discussion] confussion about use of tcp/udp

[Francois Audet]

It pretty much doesn't work like this in real life.
 
You pick either TCP or UDP and in the case of UDP, pray that you won't get fragmentation problems.


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	From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Samir Patni
	Sent: Monday, June 09, 2008 04:48
	To: 'Neill Wilkinsonj'; khalikh at yahoo.com; discussion at sipforum.com
	Cc: 'kranti kumar'
	Subject: Re: [SIPForum-discussion] confussion about use of tcp/udp
	
	

	 

	Hi All, 

	 

	Can a call contain both TCP and UDP messages. 

	 

	From section 18.1.1 from rfc 3261 

	"If a request is within 200 bytes of the path MTU, or if it is larger
	than 1300 bytes and the path MTU is unknown, the request MUST be sent
	using an RFC 2914 [43] congestion controlled transport protocol, such

	as TCP."

	 

	Consider a scenario in which Invite is sent over UDP and for some other subsequent request/response  (say  A).

	 Within the same call the Request length is more then 1300 bytes. Should this request A be sent over 

	TCP? 

	 

	Has someone seen two transport layer protocols used in the same call?  

	 

	Thanks, 

	Samir Patni

	
________________________________


	From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Neill Wilkinsonj
	Sent: Monday, June 09, 2008 12:45 PM
	To: khalikh at yahoo.com; discussion at sipforum.com
	Cc: 'kranti kumar'
	Subject: Re: [SIPForum-discussion] confussion about use of tcp/udp

	 

	RTP (voice) is always carried over UDP. There is one notable exception and I believe Skype can sometimes use TCP to carry voice. TCP generally has some undesirable properties (Head-of-Line blocking and long timers related to connection state), which make it unsuitable for carry realtime traffic such as voice.

	 

	SIP signalling can travel over UDP or TCP, generally the UA(C) will choose one or the other at the start of the interaction and the UA(S) will respond using the same for the complete dialogue. That is my observation in Practice.

	 

	Someone else on the list more conversant with RFC which to confirm or clarify?

	 

	 Neill....;o)

	From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of khalikh uddin
	Sent: 09 June 2008 07:18
	To: discussion at sipforum.com
	Cc: kranti kumar
	Subject: [SIPForum-discussion] confussion about use of tcp/udp

	 

hai all
can anybody tell me 
 *when a sip enabled end device opens a TCP connection and when it uses UDP to send *REQ/RESPONSES to proxy or other UA.
*can it use both in a  aparticular diloge i.e to send INVITE use TCP and to send ACK use       
  UDP.
*Can we force it to use TCP/UDP.
*For media transmission SIP uses only tcp.Is this true.



	 

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