IGMP
A network control protocol running on top of the IP protocol. It is used by Internet hosts to maintain information related to multicast. All machines that want to use the multicast have to have the IGMP implemented

IMAP
(Internet Messaging Access Protocol) A standard mail server expected to be widely used on the Internet. It provides a message store that holds incoming e-mail until users log on and download it. IMAP4 is the latest version. IMAP is more sophisticated than the Post Office Protocol (POP3) mail server.

Messages can be archived in folders, mailboxes can be shared, and a user can access multiple mail servers. There is also better integration with MIME, which is used to attach files. For example, users can read only the headers in the message without having to automatically accept and wait for attached files to download that they don't want. Both IMAP and POP accept SMTP-formatted messages that have been routed across the Internet.

Index Server
Index Server indexes the contents and properties of documents on an Internet or intranet Web site served by IIS 4.0. Index Server enables Web clients with any browser to search a Web site by filling in the fields of an HTML query form.

Internet
The vast collection of inter-connected networks that all use the TCP/IP protocols and that evolved from the ARPANET of the late 60's and early 70's. The Internet now (July 1995) connects roughly 60,000 independent networks into a vast global internet.

Internet backbone
An extremely fast network that connects major cities. Most often it utilizes T3 or OC3 circuits and provides the bandwidth of 45Mbps.

InterNIC
InterNIC (now known as Network Solutions) once held an exclusive contract with the U.S. government to assign domain names ending with a .com, net, and .org. Since their contract expired, the U.S. government has opened the monopoly once held by Network Solutions and now there are many different registrars who can register these domain names.

Intranet
A private network inside a company or organization that uses the same kinds of software that you would find on the public Internet, but that is only for internal use.

As the Internet has become more popular many of the tools used on the Internet are being used in private networks, for example, many companies have web servers that are available only to employees.

IP Number
Internet Protocol Number. Sometimes called a dotted quad. A unique number consisting of 4 parts separated by dots, e.g. 65.13.135.65

Every machine that is on the Internet has a unique IP number - if a machine does not have an IP number, it is not really on the Internet. Most machines also have one or more Domain Names that are easier for people to remember.

IPX
Internet Packet Exchange. A Novell's proprietary network protocol.

IRC
Internet Relay Chat. Basically a huge multi-user live chat facility. There are a number of major IRC servers around the world which are linked to each other. Anyone can create a channel and anything that anyone types in a given channel is seen by all others in the channel. Private channels can (and are) created for multi-person conference calls.

ISDN
Integrated Services Digital Network. An international standard that governs the transmission of both voice and data. It uses a digital circuits and has speed of 64Kbps. It can be used for normal telephone service as well as data transmission.

ISO
International Organisation for Standardisation. An Geneva-based international organization that develops and publishes various international standards.

ISP
A company that provides access to the Internet, such as AOL, Prodigy, etc. Allows users to dial up through a modem, DSL, or cable connection to view the information on the internet.

ITU
International Telecommunication Union. (Formerly CCITT). Another international standards body concerned with telecommunications.