IP by itself is something like the postal system. It allows you to address a package and drop it in the system, but there's no direct link between you and the recipient. TCP/IP, on the other hand, establishes a connection between two hosts so that they can send messages back and forth for a period of time.

The current version of IP is IPv4. A new version, called IPv6 or IPng, is under development.

Telecommunications Training - Telecom, datacom, networking, IP, MPLS, VoIP and wireless training for non-engineers. Seminars, DVD video courses, CBT, textbooks, free tutorials.

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InterNIC's home page 
Features information on InterNIC's directory and database services, tools and resources for the Internet community, Scout report and net-happenings publications, and domain name registration and IP network number assignment services.

Protocols.com 
Contains a comprehensive directory of some 200+ protocols with links to protocol standards and other protocol related Internet sites. Protocols listed include: ATM UNI, ATM signalling, Frame Relay, Ethernet, ISDN, PNNI, PPP, TCP/IP and many more.

Yahoo!'s IP information and documentation page
Yahoo!'s directory IP information and documentation.