This implementation works in a Peer-to-Peer Environment where a SIP Application or Proxy Server isn’t required. However, a SIP Proxy with TLS support can provide needed Authentication, Confidentiality and Data Encryption.

This implementation works in a Peer-to-Peer Environment where a SIP Application or Proxy Server isn’t required. However, a SIP Proxy with TLS support can provide needed Authentication, Confidentiality and Data Encryption.
While SIP Proxy Server with TLS support offers aforementioned security features, S/MIME is preferred when this service will be used in an inter-domain communication because it offers end-to-end security unlike TLS which offers hop-by-hop security.

While SIP Proxy Server with TLS support offers aforementioned security features, S/MIME is preferred when this service will be used in an inter-domain communication because it offers end-to-end security unlike TLS which offers hop-by-hop security.