CREST Practitioner Security Analyst (CPSA) Practice 2025 - Free CPSA Practice Questions and Study Guide

The correct answer is INVITE, as it is one of the core SIP (Session Initiation Protocol) request methods used to initiate a session between two or more parties. The INVITE request is sent from a user agent client to a user agent server to establish a session and can include details such as codecs, ports, and other session management parameters. This method is crucial in establishing voice or video calls over IP networks.

The other options, while related to SIP or have uses in networking, do not represent standard SIP request methods. CONNECT is used in HTTP to establish a tunnel to the server identified by a given URI, primarily for secure communications. REGISTRATION typically refers to the process of a user agent registering its location with a SIP registrar but is not an official request method in SIP itself. UPDATE is a method used in SIP for modifying session parameters without affecting the session itself; however, its main purpose is not as foundational as INVITE.