Hi, I am working on windowsce.net4.2. The voip architecture in this OS is based on SIP (RFC2543). I have been trying to register on the Linux SIP server running ser using a Provisioning.xml file which has the details required. I am getting the error " Unable to register, check server settings". I am running the ser-0.8.12 version on the linux box which is based on RFC 3261. Do you think there is a compatibility issue here? Does ser allow clients which are based on older RFC's to register? Any pointers will be greatly appreciated. Thanks, Annie