Short for Network Address Translation.
IP trick used to hide the details of a host or network behind a front-end machine, typically a firewall.
Also used to multiplex a single IP address (provided by an internet service provide), allowing the IP address to be shared by a small network (such as a home network or small business network). Some ISPs charge a lot more to dedicate a range of IP addresses instead of a single one, and NAT lets you get by with just a single one.
PJSIP : Tcl interface to the pjsiptcl client library. PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. It combines signaling protocol (SIP) with rich multimedia framework and NAT traversal functionality into high level API.