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• SIP v2, RFC 3216
• Sending SIP messages via User Datagram Protocol (UDP)/TCP
• G.711a, G.711u, G.729, G.726 codecs
• G.711 pass-through
• Echo cancellation (G.167 and G.168)
• Dynamic jitter buffer
• Simple traversal of UDP through Network Address Translation (NAT) (Serial Tunnel [STUN], RFC 3489)
• Session Description Protocol (SDP), RFC 2327
• Real Time Protocol (RTP)/Real Time Control Protocol (RTCP) over UDP
• Three-way conferencing
• Remote firmware upgrade
• Dual-tone multifrequency (DTMF) tone detection and generation
• Voice activity detection (VAD)
• Silence suppression
• Comfort noise generation (CNG)
• Caller ID generation and detecting (frequency shift keying [FSK] and DTMF)
• Media loopback
• SIP Transport Layer Security (TLS)
• SIP channels support both UDP and TCP transport
• Support for 2 simultaneous T.38 or G.729 calls
• T.38 fax relay, including V.17, V.21, V.27ter, and V.29 and fax pass-through (pulse code modulation [PCM})
• T.38 support is dependent on fax machine and network/transport resilience*
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