Support SIP (RFC3261), TCP/IP/UDP, RTP/RTCP, HTTP, ARP, ICMP, DNS (A record and SRV), PPPoE, TFTP, NTP, DHCP (client only) Support NAT traversal (STUN, etc), server fail-over, SIP presence (SIMPLE), and more Multiline support of up to 11 lines indicators (expandable to 112 lines through expansion key-module) Graphical LCD to display up to 8 lines and 22 characters per line Dual 10/100Mbps Ethernet ports 2.5mm headset jack (versions 0.3 and 0.4 - 3.5mm headset jack) Support Caller ID display or block, per call or permanent Call waiting, hold, mute, transfer (blind or attended),forward, and more 3-way conferencing Integrated Power-over-Ethernet (802.3af) And many more enterprise grade features