Microsoft Windows Small Business Server 2003 Administrators Companion (Pro-Administrators Companion)

An international communications standard for sending voice, video, and data over regular or digital telephone wires. ISDN supports data transfer rates of 64 Kbps (64,000 bits per second).

The Microsoft implementation of Remote Authentication Dial-In User Service (RADIUS), an authentication and accounting system used by many Internet Service Providers (ISPs). When a user connects to an ISP using a user name and password, the information is passed to a RADIUS server, which checks that the information is correct, and then authorizes access to the ISP system.

A protocol used to report problems encountered with the delivery of data, such as unreachable hosts or unavailable ports. ICMP is also used to send a request packet to determine whether a host is available. The receiving host sends back a packet if it is available and functioning. See ping.

The inter-network layer protocol used as a basis of the Internet. IP enables information to be routed from one network to another in packets and then reassembled when they reach their destination.

An Internet Engineering Task Force (IETF) standard for creating Virtual Private Networks (VPNs).

In IPv4, a four-part number separated by periods (for example, 165.113.245.2) that uniquely identifies a machine on the Internet. Every machine on the Internet has a unique IP number.