Address Resolution Protocol (ARP)

An Internet protocol for resolving an IP address into a physical layer address (such as an Ethernet media access control address). See also Physical Layer, Internet Protocol.

Advanced Research Projects Agency Network (ARPANET)

Predecessor to the Internet that was developed by the Department of Defense in the late 1960s.

AppleTalk

The built-in (to firmware) suite of network protocols that Macintosh computers use. Windows NT Server uses AppleTalk to service Macintosh clients by simulating an Apple server. Sec also Macintosh, Network Protocol.

Administrators

Users who are part of the Administrators group. This group has the ultimate set of security permissions. See also Administrator Account, Permissions, Groups.

Encryption

The process of obscuring information by modifying it according to a mathematical function known only to the intended recipient. Encryption secures information being transmitted over non- secure or untrusted media. See also Security.

Home Directory

A directory that stores a user's personal files.

Directories

 In a file system, directories are containers that store files or other directories. Mass storage devices have a root directory that contains all other directories, thus creating a hierarchy of directories sometimes referred to as a directory tree. See also File, File System.

Bridge

A device that connects two networks of the same data link protocol by forwarding those packets destined for computers on the other side of the bridge. See also Router, Data Link Layer.

Bridge

A device that connects two networks of the same data link protocol by forwarding those packets destined for computers on the other side of the bridge. See also Router, Data Link Layer.

Compression

A space-optimization scheme that reduces the size (length) of a data set by exploiting the fact that most useful data contains a great deal of redundancy. Compression reduces redundancy by creating symbols smaller than the data they represent and an index that defines the value of the symbols for each compressed set of data.

Components

Interchangeable elements of a complex software or hardware system. See also Module.

Hardware Profile,

Used to manage portable computers that have different configurations based on their location.

Dynamic Host Configuration Protocol (DHCP)

A method of automatically assigning IP addresses to client computers on a network.

Groups

Security entities to which users can be assigned membership for the purpose of applying the broad set of group permissions to the user. By managing permissions for groups and assigning users to groups, rather than assigning permissions to users, security administrators con keep coherent control of very large security environments. See also Permissions, Accounts, Security Local Group, Global Group.

Disk Administrator

Graphical utility used to manage disks.

Bottlenecks

Components operating at their peak capacity that restrict the flow of information through a system. Used singularly, the term indicates the single most restrictive component in a system.

Hypertext Transfer Protocol (HTTP)

Hypertext transfer protocol is an Internet protocol that transfers HTML documents over the Internet and responds to context changes that happen when a user clicks a hypertext link. See also Hypertext Markup Language, World Wide Web

Fiber Distributed Data Interface (FDDI)

A data link layer that implements two counter- rotating token rings at 100 megabits per second. FDDI has been a popular standard for interconnecting campus and metropolitan area networks because it allows distant digital connections at high speed, but ATM is replacing FDDI in many sites. See also Asynchronous Transfer Mode, Data Link Layer.