... VoIP Phone Description: ZP502 VoIP Phone is ZYCOO business IP phone terminal which adopts SIP and IAX2 protocols.With ... basic, MD5), DNS name of server,Peer to Peer/ IP callDTMF:Support SIP info, DTMF Relay, RFC2833Advanced Application FeaturesLarge dot ... DMZSupport DNS Relay, SNTP Client, FirewallSupport VPN (L2TP/UDP TUNNEL) , Open VPN/TLS, SRTP security protocolQoS with DiffServNetwork tools ...