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

[Vijay Tiwari]

Hello

are you right that branch parameter in via header use as transaction
identifier but CSeq not used for transaction identifier it use for
relationship between request and there response.

every new request have new CSeq number like if you send invite message two
time then you have two different Cseq but same
branch parameter in vai header

INVITE sip:12127773456 at x.x.x.x:5060 SIP/2.0
Via: SIP/2.0/UDP x.x.x.x:5061;branch=z9hG4bK-7942-1-0
From: 17778880307 <sip:17778880307 at 192.168.5.3:5061>;tag=1
To: off-net <sip:12127773456 at x.x.x.x:5060>
Call-ID: 1-7942 at 122.160.83.154
CSeq: 1 INVITE
Contact: <sip:sipp at 122.160.83.154:5061>
Max-Forwards: 70
Subject: Performance Test
Allow: INVITE,ACK,CANCEL,BYE,UPDATE
Content-Type: application/sdp
Content-Length:   140
v=0
o=user1 53655765 2353687637 IN IP4 122.160.83.154
s=-
c=IN IP4 122.160.83.154
t=0 0
m=audio 2000 RTP/AVP 0 18
a=rtpmap:0 PCMU/8000


SIP/2.0 100 Trying
Via: SIP/2.0/UDP 122.160.83.154:5061;branch=z9hG4bK-7942-1-0
To: off-net <sip:12127773456 at x.x.x.x:5060>
From: 17778880307 <sip:17778880307 at 192.168.5.3:5061>;tag=1
Call-ID: 1-7942 at 122.160.83.154
CSeq: 1 INVITE
Server: Sansay-SIP/8.0
Content-Length: 0

SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 122.160.83.154:5061;branch=z9hG4bK-7942-1-0
To: off-net <sip:12127773456 at x.x.x.x:5060>;tag=5419592-tdb3
From: 17778880307 <sip:17778880307 at 192.168.5.3:5061>;tag=1
Call-ID: 1-7942 at 122.160.83.154
CSeq: 1 INVITE
Server: Sansay-SIP/8.0
WWW-Authenticate: Digest
realm="172.16.23.216",nonce="b2a031b1be776f5e21a744a871ccdbffb5f0"
Content-Length: 0

INVITE sip:12127773456 at x.x.x.x:5060 SIP/2.0
Via: SIP/2.0/UDP 122.160.83.154:5061;branch=z9hG4bK-7942-1-4
From: 17778880307 <sip:17778880307 at 192.168.5.3:5061>;tag=1
To: off-net <sip:12127773456 at x.x.xx:5060>
Call-ID: 1-7942 at 122.160.83.154
CSeq: 2 INVITE
Contact: <sip:sipp at 122.160.83.154:5061>
Max-Forwards: 70
Subject: Performance Test
User-Agent: SIPp
Authorization: Digest
username="7",realm="172.16.23.216",uri="sip:x.x.x.x:5060",nonce="b2a031b1be776f5e21a744a871ccdbffb5f0",response="585c122458eda63f8bcc5200aea362ef",algorithm=MD5
Content-Type: application/sdp
Content-Length:   140
v=0
o=user1 53655765 2353687637 IN IP4 122.160.83.154
s=-
c=IN IP4 122.160.83.154
t=0 0
m=audio 2000 RTP/AVP 0 18
a=rtpmap:0 PCMU/8000

you can saw the red marked,  that branch id is same in all the message but
Cseq change into same transaction.


Thanks
Vijay

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
>
> _______________________________________________
> This is the SIP Forum discussion mailing list
> TO UNSUBSCRIBE, or edit your delivery options, please visit
> http://sipforum.org/mailman/listinfo/discussion
> Post to the list at discussion at sipforum.org
>
>


-- 
They can because they think they can.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sipforum.org/pipermail/discussion/attachments/20100131/0b08e70c/attachment-0002.html>