Data sent over a network. A datagram contains not only user data, but also all the necessary header information for the data to reach its intended destination.


A computer or router that blocks certain types of network datagrams from passing between networks. One example of a firewall is a computer that routes data between a local area network and the Internet, but disallows certain types of direct access from the Internet to computers on the local area network. See also gateway.


A computer or router through which data passes between networks. One example of a gateway is a computer located between a local area network (LAN) and the Internet. See also firewall.


An internal or limited network that uses the basic technologies of the Internet, including Transmission Control Protocol/Internet Protocol (TCP/IP) and World Wide Web servers and browsers. See also local area network, internet, and Internet.


The world-wide network of computers communicating via Internet protocol (IP) datagrams. See also internet.

Internet service provider

Also ISP. An organization or individual who provides the network access for you to connect to the Internet. The ISP relays data from your gateway computer or router to the Internet and vice-versa.

Internet Protocol (IP)

The communication protocol used in combination with TCP to form the standard means (TCP/IP) of communication on the Internet.

IP address

A number that identifies a computer on a TCP/IP network. An IP address is made up of four numbers separated by decimal points, such as Each individual number can be between 0 and 255 (with some exceptions, for example, for reserved IP addresses).

local area network (LAN)

A network of computers local to an organization, typically high speed (such as 10 Base-T Ethernet, FDDI, Token Ring, and so forth), and typically in close proximity. See also intranet.

system console

A character (ASCII) terminal or other computer that is used to communicate with a workstation or server to set up the system, perform system maintenance, operate the system in PROM mode, and display system error messages. See also system console port.

system console port

The serial port to which a system console is attached. On Silicon Graphics workstations and servers, this is the first serial port (port 1).


Transmission control protocol used with the internet protocol. See transmission control protocol.

transmission control protocol

A networking standard, typically used with the Internet Protocol (IP) standard. It forms the basis of an internet as well as the Internet. See also internet protocol.

wide area network (WAN)

A network of computers spanning a wider geographic area than a local area network, and typically using communication technologies designed for longer distances, such as microwave relay and leased (telephone) lines.