Grandstream GXP2000 IP Phone Support SARP/RARP, ICMP, DNS, DHCP, NTP, TFTP protocols Support NAT traversal via STUN & symmetric RTP Support SIP SIMPLE standard for Instant Messaging and Presence Interoperable with various 3rd party SIP end user device, Proxy/Registrar/Server, and gateway products Advanced Digital Signal Processing (DSP) to ensure superb hi-fidelity audio quality