• 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)
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