Which SIP function assesses if an endpoint is available for a call?

The function that assesses if an endpoint is available for a call is vital in the Session Initiation Protocol (SIP) architecture, as it ensures that communication can occur between endpoints without any interruptions. This involves sending specific requests to check whether the particular endpoint can accept calls at that moment.

This assessment typically occurs through mechanisms like the SIP OPTIONS method, which allows one endpoint to query another about its capabilities and current state. If the endpoint responds positively, it indicates that it is available to engage in communication, allowing the call to be established smoothly.

The processes of establishing call parameters, handling call termination, and routing the call are important aspects of SIP functionality, but they do not provide the direct evaluation of availability. They pertain more to the management of the call itself rather than confirming endpoint readiness.