Which protocol is used to establish sessions for real-time communications such as voice and video?

• A. Session Initiation Protocol (SIP)
• B. Secure Shell (SSH)
• C. Simple Mail Transfer Protocol (SMTP)
• D. File Transfer Protocol (FTP)

Answer: (A)

The main idea here is signaling for real-time multimedia sessions. Session Initiation Protocol is designed to establish, modify, and terminate those sessions, making it the exact tool used to set up voice and video calls, invite participants, negotiate codecs and capabilities, and manage session state. The actual voice or video data usually travels separately over a media transport like RTP, while SIP handles the control signaling that starts and ends the communication.

The other protocols serve different purposes: Secure Shell provides secure remote login and command execution, SMTP handles email transfer, and FTP is for transferring files. They don’t manage the setup and control of real-time multimedia sessions.