Which protocol is used to establish and manage video calls over IP networks?

• A. File Transfer Protocol (FTP)
• B. Hypertext Transfer Protocol (HTTP)
• C. Simple Mail Transfer Protocol (SMTP)
• D. Session Initiation Protocol (SIP)

Answer: (D)

Video calls over IP rely on signaling to set up and manage the session. The protocol designed for this is SIP, which handles locating participants, inviting them to a session, negotiating the media parameters (such as audio and video codecs and ports), and supporting changes during the call (hold, transfer, end). The actual media streams are typically carried over a protocol like RTP, while SIP takes care of the call control and session management. The other protocols serve different purposes: FTP is for transferring files, HTTP is for retrieving web resources, and SMTP is for delivering email. So SIP is the one that establishes and manages video calls over IP networks.