Hi All, I had been trying to register the PJSIP with the IMS for sometime but proved futile. I figured a way out and thought I could share it with you in case someone else runs into the same problem. It seems impossible to register with the IMS when someone lists his paramaters via the command line. I was only able to register when I used a config file. I tried using the parameters below via the command line but I got varying errors. The error depends on the order of the parameters, so I can't list all. Examples are "address in use" and "too many hops". I used these parameters: micadeyeye at micadeyeye:/opt/pjproject-0.8.0/pjsip-apps/bin$ ./pjsua-i686-pc-linux-gnu --id sip:alice at open-ims.test --registrar sip:open-ims.test --proxy sip:pcscf.open-ims.test:4060;lr --realm open-ims.test --username alice at open-ims.test --password alice --use-ims --local-port 5066 I hope this helps and will want it possibly fixed. I use Linux(Ubuntu) while Sasah and Benny reported that it works fine. I found out that they used Windows when testing it and I want to assume that they also used the config file. Michael.