Dear All, I have integrated Kamailio (Version 4.0.1) with Asterisk (Version 11.4.0 rc1) server. I should have get VoIP features(call, SMS) with this integrated server. But when i tried to call other end SIP client through this integrated server, I'm getting this '*481 dialog/transaction does not exists*' error (please find the attachment 'call.pcap' below). SMS is through with the kamailio server without any problem (Find the attachment 'SMS.pcap' below). But when it comes to Calling feature, something is wrong and i am unable to find it. So please help me in resolving this issue. My system configuration is as follows: Host Architecture: i686 OS : Ubuntu 12.04 LTS Clients: Wi-Fi enabled VoIP phones. Also find the attachments below for the kamailio configuration file and tcpdump based trace files for Calling and SMSing process, to give a more complete picture. Any help will greatly appreciate. *Thank you and Best regards,* *R Ravindra **Gowda***