Lesson 4 Computer Networks]

local area network (LAN)

A LAN is a computer network limited to a small area such as an office building, university, or even a residential home. Most mid to large-sized businesses today use LANs, which makes it easy for employees to share information. Currently, the most common type of LANs are Ethernet-based and use software from Novell or Oracle. However, with the emergence of wireless networking, wireless LANs have become a popular alternative.

mainframe

A mainframe is an ultra high-performance computer made for high-volume, processor-intensive computing. They are typically used by large businesses and for scientific purposes. You probably won't find a mainframe in any household. In the hierarchy of computers, mainframes are right below supercomputers, the most powerful computers in the world. (Which is why they are aptly named "supercomputers.") Yet a mainframe can usually execute many programs simultaneously at a high speed, whereas supercomputers are designed for a single process. Currently, the largest manufacturers of mainframes are IBM and Unisys.

metropolitan area network (MAN)

A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN).

network topology

A network topology describes the arrangement of systems on a computer network. It defines how the computers, or nodes, within the network are arranged and connected to each other. Some common network topologies include star, ring, line, bus, and tree configurations.

personal area network (PAN)

A personal area network (PAN) is a computer network used for data transmission amongst devices such as computers, telephones, tablets and personal digital assistants.

virtual private network (VPN)

A virtual private network is "tunneled" through a wide area network WAN such as the Internet. This means the network does not have to be located in one physical location like a LAN. However, by using encryption and other security measures, a VPN can scramble all the data sent through the wide area network, so the network is "virtually" private.

extranet

An extranet actually combines both the Internet and an intranet. It extends an intranet, or internal network, to other users over the Internet. Most extranets can be accessed via a Web interface using a Web browser. Since secure or confidential information is often accessible within an intranet, extranets typically require authentication for users to access them.

intranet

An intranet is a private network that can only be accessed by authorized users. The prefix "intra" means "internal" and therefore implies an intranet is designed for internal communications. "Inter" (as in Internet) means "between" or "among."

peer-to-peer (P2P)

In a P2P network, the "peers" are computer systems which are connected to each other via the Internet. Files can be shared directly between systems on the network without the need of a central server. In other words, each computer on a P2P network becomes a file server as well as a client.

server

In computing, a server is a computer program or a device that provides functionality for other programs or devices, called "clients". This architecture is called the client-server model, and a single overall computation is distributed across multiple processes or devices.

network protocol

Network protocols are formal standards and policies comprised of rules, procedures and formats that define communication between two or more devices over a network. Network protocols govern the end-to-end processes of timely, secure and managed data or network communication.

network hardware

Networking hardware, also known as network equipment or computer networking devices, are physical devices which are required for communication and interaction between devices on a computer network. Specifically, they mediate data in a computer network.

TCP/IP

Stands for "Transmission Control Protocol/Internet Protocol." These two protocols were developed in the early days of the Internet by the U.S. military. The purpose was to allow computers to communicate over long distance networks. The TCP part has to do with the verifying delivery of the packets. The IP part refers to the moving of data packets between nodes. TCP/IP has since then become the foundation of the Internet. Therefore, TCP/IP software is built into all major operating systems, such as Unix, Windows, and the Mac OS.

client

The "client-server" architecture is common in both local and wide area networks. For example, if an office has a server that stores the company's database on it, the other computers in the office that can access the database are "clients" of the server.

OSI model

The OSI (Open Systems Interconnection) model was created by the ISO to help standardize communication between computer systems. It divides communications into seven different layers, which each include multiple hardware standards, protocols, or other types of services.

wide area network (WAN)

Unlike LANs, WANs are not limited to a single location. Many wide area networks span long distances via telephone lines, fiber optic cables, or satellite links. They can also be composed of smaller LANs that are interconnected. The Internet could be described as the biggest WAN in the world.

computer network

When you have two or more computers connected to each other, you have a network. The purpose of a network is to enable the sharing of files and information between multiple systems. The Internet could be described as a global network of networks. Computer networks can be connected through cables, such as Ethernet cables or phone lines, or wirelessly, using wireless networking cards that send and receive data through the air.