[Asterisk-Dev] About contact field in ACK request header

[phu at bevertec.com]

Hi, guys:

I'm using sip-communicator as softphone to talk to x-lite phone using
Asterisk as PBX. Whoever sponsors a call, only x-lite can hear the other
endpoint, no voice on sip-communicator.

I notice that Asterisk send ACK containing Contact field, and
sip-communicator does not. Actually, in RFC3261, ACK Request doesn't
include Contact field.

Why does Asterisk ACK request include Contact field? Is it possible that
Asterisk does need Contact field mandatorily? Is the problem with my
situation because of this issue?

Astersik:

ACK sip:2000 at 192.168.221.56:5060 SIP/2.0
Via: SIP/2.0/UDP 192.168.221.22:5060;branch=z9hG4bK62ac799b;rport
From: <sip:2002 at 192.168.221.22>;tag=as6ed3cf28
To: number2000 <sip:2000 at 192.168.221.22>;tag=2880422889
Contact: <sip:2002 at 192.168.221.22>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Call-ID: E31E12D2-07EE-40F9-AC4B-4CB684C970C3 at 192.168.221.56
CSeq: 102 ACK
User-Agent: Asterisk PBX
Content-Length: 0

---------------
sip-communicator:

ACK sip:2002 at 192.168.221.22 SIP/2.0
Call-ID: 08cb327ce9dfd5b5814350003ebf6c02 at 192.168.221.56
CSeq: 1 ACK
From: "Laptop" <sip:2000 at 192.168.221.22:5060;transport=udp>;tag=176713
To: <sip:2002 at 192.168.221.22>;tag=as74245c4e
Via: SIP/2.0/UDP
192.168.221.56:5060;branch=z9hG4bKa3b481ee78e5de29bf01f2b1c3cc2bd8
Max-Forwards: 70
Content-Length: 0


Thanks for any of your helps

Paul