• SIP version 2 (RFC 3261, 3262, 3263, 3264) • SPCP with the Cisco Unified Communications 500 Series • SIP proxy redundancy: dynamic via DNS SRV, A records • Reregistration with primary SIP proxy server • SIP support in NAT networks (including STUN) • SIPFrag (RFC 3420) • Secure (encrypted) calling via SRTP • Codec name assignment • Voice algorithms: • G.711 (A-law and μ-law) • G.726 (16/24/32/40 kbps) • G.729 A • G.722 • Dynamic payload support • Adjustable audio frames per packet • Dual-tone multifrequency (DTMF), in-band and out-of-band (RFC 2833) (SIP INFO) • Flexible dial plan support with interdigit timers • IP address/URI dialing support • Call progress tone generation • Jitter buffer: adaptive • Frame loss concealment • Comfort Noise Generation (CNG) • Voice activity detection (VAD) with silence suppression • Attenuation/gain adjustments • Message waiting indicator (MWI) tones • VMWI via NOTIFY, SUBSCRIBE • Caller ID support (name and number) • Third-party call control (RFC 3725) |