SIP (Session Initiation Protocol)
A protocol used to set up voice and video calls over the Internet, e.g.
VOIP (Voice Over Internet Protocol)
and instant messaging. It can run over TCP/IP (Transmission Control Protocol/Internet Protocol),
UDP (User Datagram Protocol)
or SCTP (Stream Control Transmission Protocol). SIP
headers look very much like HTTP (Hypertext Transfer Protocol)
headers, with an ASCII (American Standard Code for Information Interchange)
keyword:value per line.