This content is no longer actively maintained. It is provided as is, for anyone who may still be using these technologies, with no warranties or claims of accuracy with regard to the most recent product version or service release.
A telephone session is an audio session that is created using either a server-based endpoint instance or a proxy endpoint instance. The proxy endpoint is used when the local user is making or receiving calls using a PBX telephone handset. When the local user has a USB telephone such as a Unified Communications-enabled telephone or just a laptop microphone, the server-based endpoint instance is used. Whether using a proxy endpoint instance or server-based endpoint instance, the audio session used to interact with a remote user is primarily the same. The real difference between a proxy endpoint-based session and a server endpoint-based session is that you cannot add video to the proxy endpoint session. In addition, your organization PBX may not support all of the call control functionality available to a server-based endpoint session.