Which statement about voice gateway protocols is accurate?

Which statement about voice gateway protocols is accurate?

• A. TCP/IP is the common application layer protocol used by voice gateways to initiate and maintain connections.
• B. SIP is commonly used for initiating and maintaining sessions in voice networks.
• C. HTTP is required for voice signaling.
• D. UDP is never used for voice signaling.

Answer: (B)

Voice signaling in IP-based voice networks is about starting, managing, and ending calls, separate from how the actual media is transported. The statement that SIP is commonly used for initiating and maintaining sessions captures this role precisely. SIP operates at the application layer and handles the signaling to set up a call, negotiate capabilities (like codecs), and tear it down when finished. It works through a series of requests and responses (for example, an INVITE to start a session, a 200 OK to accept, an ACK to confirm, and BYE to end). The media itself is typically carried separately, often using RTP over UDP. That makes the other options inaccurate: signaling isn’t defined by a single transport like “the TCP/IP suite”—SIP itself is the signaling protocol, and it can run over UDP, TCP, or TLS. HTTP is not required for voice signaling. And UDP is not “never used” for signaling; SIP commonly uses UDP (though it can also use TCP or TLS) and RTP media usually uses UDP.

Voice signaling in IP-based voice networks is about starting, managing, and ending calls, separate from how the actual media is transported. The statement that SIP is commonly used for initiating and maintaining sessions captures this role precisely. SIP operates at the application layer and handles the signaling to set up a call, negotiate capabilities (like codecs), and tear it down when finished. It works through a series of requests and responses (for example, an INVITE to start a session, a 200 OK to accept, an ACK to confirm, and BYE to end). The media itself is typically carried separately, often using RTP over UDP.

That makes the other options inaccurate: signaling isn’t defined by a single transport like “the TCP/IP suite”—SIP itself is the signaling protocol, and it can run over UDP, TCP, or TLS. HTTP is not required for voice signaling. And UDP is not “never used” for signaling; SIP commonly uses UDP (though it can also use TCP or TLS) and RTP media usually uses UDP.