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

[Samir Patni]

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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