Related specifications
RFC 3261, SIP: Session Initiation Protocol, available at http://www.ietf.org/
draft-ietf-sip-sips-06.txt, The use of the SIPS URI Scheme in the Session Initiation Protocol (SIP), available at http://www.ietf.org/
RFC 3711, The Secure Real-time Transport Protocol (SRTP), available at http://www.ietf.org/
RFC 4568, Session Description Protocol (SDP) Security Descriptions for Media Streams, available at http://www.ietf.org/
RFC 3263, Session Initiation Protocol (SIP): Locating SIP Servers, available at http://www.ietf.org/
RFC 3263, Session Initiation Protocol (SIP): Locating SIP Servers, available at http://www.ietf.org/
RFC 2782, A DNS RR for specifying the location of services (DNS SRV), available at http://www.ietf.org/
RFC 2915, The Naming Authority Pointer (NAPTR) DNS Resource Record, available at http://www.ietf.org/
Implementation notes
Supports SIPS scheme only in all headers
TLS transport URI parameter is not supported (as defined in draft-ietf-sip-sips-06.txt)
Re-direction from secure to unsecure is not allowed. No user query is made in such a case.
Security preconditions are not supported.
Support is available for the following fallback logic with MO calls:
If the destination address is a SIPS URI: A secure call is attempted without fallback.
If secure call is mandated in the provisioned VoIP settings: A secure call is attempted without fallback.
If secure call is preferred in the provisioned VoIP settings: A secure call is attempted first. If it fails, a fallback to non-secure call is attempted.
If non-secure call is preferred in the provisioned VoIP settings: A non-secure call is attempted first. If the network or the remote endpoint rejects the call attempt with a ‘480 (Temporarily Unavailable)’ response with a Warning header with warn-code ‘381 SIPS Required‘, a fallback to secure call is attempted.