TCP/IP

TCP/IP (Transmission Control Protocol / Internet Protocol) is the central protocol of the Internet (or actually two protocols, but they're tightly connected and usually discussed together). These protocols form the heart of the Internet protocol stack, which has, in all, between four and seven layers depending on how you count (doesn't Taco Bell have a burrito like that?). IP addresses computers on the Internet by means of IP addresses, which currently come in two varieties, IPv4 addresses (consisting of four bytes worth of numbers generally expressed as a dotted series like 123.45.67.89; this address space is running out due to the vast expansion of the Internet) and IPv6 addresses (long enough to give every person in the world trillions of addresses, which could be needed for all the nanomachines of the future). The address expansion of IPv6 is a useful thing, but it is still taking many years to complete the transition, and most current Internet activity is still in the old address space.

Links

 * Wikipedia: Internet protocol suite
 * Introduction to the Internet protocols (from 1987)
 * RFC 675 - 1974 version of TCP, predecessor of TCP/IP
 * RFC 1180 - TCP/IP tutorial
 * TCP/IP State Transition Diagram