Yes, Dale, it is retransmission by observing same branch in both Via header
of these two INVITES.

I found this issue when I am using eyebeam to talk to SIPX ......

Regards,

Jun


-----Original Message-----
From: Dale Worley [mailto:[email protected]] 
Sent: Thursday, December 03, 2009 5:45 AM
To: Wen Jun
Cc: [email protected]
Subject: Re: [sipx-users] Why there are 2 SIP INVITE in a call to
calledparty

On Tue, 2009-12-01 at 17:48 +0800, Wen Jun wrote:
> Hi, I have no idea why there are 2 SIP INVITE from SIPX to called 
> party in a call. Is there any specific reason for that ?

Retransmissions can cause a duplicated INVITE.  (You can verify this by
seeing that the "branch" value in the top-most "Via" header is the same in
the two INVITEs.)  Another possibility is that the call is getting routed to
the phone twice.  (Usually the phone will give a 482 response to the second
INVITE in this case, so it won't cause the phone to ring a second time.)  To
tell what is going on, obtain a trace of one of these calls and examine the
messages.

Dale



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