What is a "SIP Invite transaction"?

A "SIP Invite transaction" refers specifically to the process surrounding the sending and acknowledgment of an INVITE request within the Session Initiation Protocol (SIP). The INVITE request is crucial for initiating a communication session between two parties, as it establishes the parameters of the session, including the type of media and the participants involved.

When a user agent calls another, it sends an INVITE request to the intended recipient. For this transaction to be successful, the recipient must not only receive the INVITE but also send back a response indicating acceptance (or rejection) of the invitation. This process involves a series of signaling exchanges that confirm the session establishment, making the acknowledgment of the initial INVITE request a key component of the transaction.

Understanding this process is essential because it illustrates how SIP orchestrates the initiation of calls over IP networks, facilitating real-time communication, such as voice and video calls. The other options do not accurately capture the specific role of the SIP Invite transaction, focusing instead on broader or different aspects of SIP or communication session management.