... , value, and support.Based on the Session Initiation Protocol (SIP), the Cisco SPA942 has been tested to ... call encrypted voice communication support - SIP over Transport Layer Security (TLS), and Secure Real-Time Transport Protocol (SRTP)• Built- ... to 256 bit encryption (HTTP, HTTPS, Trivial File Transfer Protocol [TFTP])• Asynchronous notification of upgrade availability via NOTIFY• Nonintrusive, ...