1.3.1 The Basic Internet Protocols

IP

The Internet Protocol. This protocol is almost never used directly by applications. It provides the basic packet delivery and routing infrastructure of the Internet. Much like the phone company's switching centers or the Post Office's trucks, it is not of much day-to-day interest to the regular user (or programmer). It happens to be a best effort datagram protocol.

UDP

The User Datagram Protocol. This is a best effort datagram protocol. It provides a small amount of extra reliability over IP, and adds the notion of ports, described in TCP and UDP Ports.

TCP

The Transmission Control Protocol. This is a duplex, reliable, sequenced byte-stream protocol, again layered on top of IP, and also providing the notion of ports. This is the protocol that you will most likely use when using gawk for network programming.

All other user-level protocols use either TCP or UDP to do their basic communications. Examples are SMTP (Simple Mail Transfer Protocol), FTP (File Transfer Protocol), and HTTP (HyperText Transfer Protocol).