http://tcllib.sourceforge.net/doc/tcllib_ip.html

The Internet Protocol (described in RFC 791 [1]), which controls how machines talk to and address each other. Usually you have TCP or UDP layered over the top to provide port-based addressing and checksums...

The most common version of IP at the moment is version 4, though you may well also see version 6 about from time to time (mostly at very large ISPs though.)

The currently used checksum in IPV4 as described in RFC 791 [2] is known as the Internet Checksum.

[Need more info on the difference between IPv4 and IPv6...]

If you need to manipulate internet addresses, read Handling internet addresses. You may also be interested in the DNS page for turning hostnames into addresses.

See also A Little CIDR Calculator

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