SIP over TLS

SIP over TLS is the use of Transport Layer Security to protect Session Initiation Protocol signalling on a network connection. SIP messages establish, modify and terminate calls. They may contain routing information, session descriptions and other call metadata. TLS helps protect those messages against observation or modification while they travel between the endpoints of the secured connection.

This protection applies to signalling rather than to the audio itself. Media encryption requires a separate mechanism, commonly SRTP. TLS also depends on correct certificate validation and configuration; simply choosing a secure port is not enough to establish the intended trust relationship. In a multi-network call, each connection and intermediary needs its own security assessment. Teams should distinguish transport protection from end-to-end encryption, and review how endpoints authenticate each other. When diagnosing a setup failure, certificate expiry, hostname mismatches and incompatible TLS settings are different problems from codec negotiation or media routing.