Secure SIP signalling
Transport Layer Security (TLS) is a cryptographic protocol that provides message security. As it relates to SIP, TLS protects SIP messages sent by your PBX or softphone with encryption. SIP headers contain your called and calling numbers and other authentication data. With TLS properly configured, these messages become impossible for the attacker or eavesdropper in the middle, to read or modify.
In addition to message security, with TLS turned on, VoIP can be unlocked on many mobile networks around the world that normally block SIP. Switching to TLS also solves some of the NAT issues inherent to internet access over 3G/LTE. In many non-deregulated, restrictive jurisdictions such as the Gulf states, use of TLS over non-standard port can unlock SIP calling in a heavily censored environment.