Which protocol is used for Internet telephony for voice and video calls?

Which protocol is used for Internet telephony for voice and video calls?

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

Answer: (D)

In Internet telephony, the key function is signaling—the process of setting up, managing, and tearing down real-time communication sessions. The protocol designed for this is the Session Initiation Protocol. SIP handles initiating calls, inviting participants, negotiating capabilities, and terminating sessions. Once a session is established, the actual media—voice and video—typically moves over a different protocol like RTP, while SIP takes care of the control and setup. The other protocols serve different purposes: SMTP is for email, FTP is for file transfers, and SSH is for secure remote access. They don’t provide the signaling needed to establish and manage VoIP or video calls, which is why SIP is the correct choice for Internet telephony.

In Internet telephony, the key function is signaling—the process of setting up, managing, and tearing down real-time communication sessions. The protocol designed for this is the Session Initiation Protocol. SIP handles initiating calls, inviting participants, negotiating capabilities, and terminating sessions. Once a session is established, the actual media—voice and video—typically moves over a different protocol like RTP, while SIP takes care of the control and setup.

The other protocols serve different purposes: SMTP is for email, FTP is for file transfers, and SSH is for secure remote access. They don’t provide the signaling needed to establish and manage VoIP or video calls, which is why SIP is the correct choice for Internet telephony.