Which protocol is used for session establishment between computers, especially for initiating calls?

Which protocol is used for session establishment between computers, especially for initiating calls?

• A. Session Initiation Protocol
• B. Simple Mail Transfer Protocol
• C. File Transfer Protocol
• D. Domain Name System

Answer: (A)

Session establishment and call signaling in real-time communications is handled by a protocol expressly designed to initiate, modify, and terminate multimedia sessions between endpoints. This protocol is Session Initiation Protocol. It operates by exchanging text-based requests and responses to set up a call, refine the session parameters, and end the call. For example, an INVITE request begins the setup, responses confirm or negotiate details, and messages like BYE terminate the session. It often works with other protocols to carry the actual media (voice, video) and can use transport methods such as UDP or TCP, with TLS for security when needed. This signaling role—finding endpoints, registering devices, negotiating session details, and managing the lifecycle of the call—is precisely what this protocol handles in VoIP and video conferencing. In contrast, Simple Mail Transfer Protocol is used to move email between servers, File Transfer Protocol is for transferring files, and Domain Name System translates domain names to IP addresses. None of these provide the dedicated signaling and session-control functions required to establish and manage a call between computers.

Session establishment and call signaling in real-time communications is handled by a protocol expressly designed to initiate, modify, and terminate multimedia sessions between endpoints. This protocol is Session Initiation Protocol. It operates by exchanging text-based requests and responses to set up a call, refine the session parameters, and end the call. For example, an INVITE request begins the setup, responses confirm or negotiate details, and messages like BYE terminate the session. It often works with other protocols to carry the actual media (voice, video) and can use transport methods such as UDP or TCP, with TLS for security when needed. This signaling role—finding endpoints, registering devices, negotiating session details, and managing the lifecycle of the call—is precisely what this protocol handles in VoIP and video conferencing.

In contrast, Simple Mail Transfer Protocol is used to move email between servers, File Transfer Protocol is for transferring files, and Domain Name System translates domain names to IP addresses. None of these provide the dedicated signaling and session-control functions required to establish and manage a call between computers.