SIP in higher education

[Nimal Ratnayake <>]

Apologies for duplicates. previously posted on 
.

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Hi,

When a call between a SIP phone and a PBX extension is transfered
by the SIP phone to another SIP phone, the SIP gateway does not
seem to handle the REFER correctly.  I am using a Cisco 3640 router
running IOS 12.3(12).  The call flow is as shown below ( I have
omitted the proxy in this picture)


SIP                             PBX-GW
IP=A.B.C.D                      IP=P.Q.R.S
1602                            3423

-------------INVITE--------------->
<------------TRYING----------------
<------SESSION PROGRESS------------
<--------------OK------------------
--------------ACK----------------->
----INVITE c=IN IP4 0.0.0.0------->
<-----OK c=IN IP4 P.Q.R.S----------
--------------ACK----------------->
-------REFER Refer-To: 1600------->
<-----------Accepted---------------
<------------NOTIFY OK-------------
-------------- OK----------------->


Shouldn't the gateway do an invite to 1600 after receiving REFER
*before* sending NOTIFY?

Any help or pointers to solve the problem would be appreciated.

Thanks.

Nimal Ratnayake