Which statement about TLS handshake in SIP is true?

Which statement about TLS handshake in SIP is true?

• A. The negotiation that establishes an encrypted TLS session and validates certificates
• B. It validates phone numbers
• C. DTMF signaling is negotiated during the handshake
• D. Media codecs are negotiated during the handshake

Answer: (A)

In a SIP TLS handshake, the main goal is to establish a secure signaling channel by negotiating a cipher suite and exchanging certificates so that SIP messages are encrypted and protected from tampering. This process authenticates the peers (via certificate validation) and creates the cryptographic keys used for the session. It happens before any signaling logic like phone number validation or media negotiation. Phone numbers aren’t part of TLS; they’re handled at the signaling layer (SIP URI processing) and aren’t established or verified by the TLS handshake itself. DTMF signaling isn’t negotiated during the TLS handshake either; DTMF is carried separately, typically in RTP payloads or SIP signaling, after the secure channel is in place. Media codecs are negotiated later, usually through SDP during call setup, once the TLS-secured channel exists.

In a SIP TLS handshake, the main goal is to establish a secure signaling channel by negotiating a cipher suite and exchanging certificates so that SIP messages are encrypted and protected from tampering. This process authenticates the peers (via certificate validation) and creates the cryptographic keys used for the session. It happens before any signaling logic like phone number validation or media negotiation.

Phone numbers aren’t part of TLS; they’re handled at the signaling layer (SIP URI processing) and aren’t established or verified by the TLS handshake itself. DTMF signaling isn’t negotiated during the TLS handshake either; DTMF is carried separately, typically in RTP payloads or SIP signaling, after the secure channel is in place. Media codecs are negotiated later, usually through SDP during call setup, once the TLS-secured channel exists.