[SIPForum-discussion] Branch parameter v/s CSeq as transactionidentifier

[sunilkumar.verma at wipro.com]

Hi,
 
I think dinesh answerd it correcty but its not just the branch parameter
that is used to match the transaction.
 
As per RFC 3261: Section 17.2.3
 
  The request matches a transaction if:

      1. the branch parameter in the request is equal to the one in the
         top Via header field of the request that created the
         transaction, and

      2. the sent-by value in the top Via of the request is equal to the
         one in the request that created the transaction, and

      3. the method of the request matches the one that created the
         transaction, except for ACK, where the method of the request
         that created the transaction is INVITE.

   This matching rule applies to both INVITE and non-INVITE transactions
   alike.

      The sent-by value is used as part of the matching process because
      there could be accidental or malicious duplication of branch
      parameters from different clients.
 
 
Regards
Sunil Verma


________________________________

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of dinesh gupta
Sent: Tuesday, February 02, 2010 2:45 PM
To: SIP Babie
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Branch parameter v/s CSeq as
transactionidentifier


Hello,
 
Branch:  The branch parameter is a transaction identifier. Responses
relating to this
request can be correlated because they will contain this same
transaction
identifier.

CSeq: The remote CSeq storage is necessary to distinguish
between a re-INVITE and a retransmission. A re-INVITE is used to
change the session parameters of an existing or pending call. It uses
the
same Call-ID, but the CSeq is incremented because it is a new request. A
retransmitted INVITE will contain the same Call-ID and CSeq as a
previous
INVITE. 
 
 
As Vijay said that is true.
 
 


 
On Fri, Jan 29, 2010 at 2:39 PM, SIP Babie <sipbabie at gmail.com> wrote:


	Hi All,
	
	I would like to know why and how is a branch parameter in Via
header able to identify a transaction, and if so, why do we need CSeq
header to identify a transaction?
	
	If possible please explain with an example.  
	
	Regards
	sipBabie
	
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-- 
Thanks & Regards,

Dinesh Gupta
+91-9999863622

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