... (none, basic, MD5), DNS name of server,Peer to Peer/ IP callDTMF:Support SIP info, DTMF Relay, RFC2833Advanced ... pickup/ join call/ redial andunredial/ click to dial/ vport/secondary dialing automatically/ push to talkCall control features: flexible dial map, hotline ... , SNTP Client, FirewallSupport VPN (L2TP/UDP TUNNEL) , Open VPN/TLS, SRTP security protocolQoS with DiffServNetwork tools in telnet ...