Critism on So Long a Letter

LAN

Local Area Network or LAN, in computer science, a group of computers and other devices dispersed over a relatively limited area and connected by a communications link that enables any device to interact with any other on the network. LANs commonly include microcomputers and shared (often expensive) resources such as laser printers and large hard disks. Most (modern) LANs can support a wide variety of computers and other devices. Each device must use the proper physical and data-link protocols for the particular LAN, and all devices that want to communicate with each other on the LAN must use the same upper-level communications protocol. Although single LANs are geographically limited (to a department or an office building, for example), separate LANs can be connected to form larger networks. Similar LANs are linked by bridges, which act as transfer points between networks; dissimilar LANs are linked by gateways, which both transfer data and convert it according to the protocols used by the receiving network.

The devices on a LAN are known as nodes, and the nodes are connected by cabling through which messages are transmitted. Types of cables include twisted-pair wiring, coaxial cable, or fibre-optic cable. Nodes on a LAN can be wired together in any of three basic topologies, known as bus, ring, and star. As implied by their names, a bus network is more or less linear, a ring network forms a loop, and a star network radiates from a central hub.

To avoid potential collisions when two or more nodes attempt to transmit at the same time, LANs use either contention and collision detection or token passing to regulate traffic.

WAN

It is a computer network that covers a wide geographical area, usually over telephone lines, as compared to a local area network, which operates in a single company or institution. The Internet is an interconnected web of WANs.

MAN

Short for Metropolitan Area Network, a data network designed for a town or city. In terms of geographic breadth, MANs are larger than local-area networks (LANs), but smaller than wide-area networks (WANs). MANs are usually characterized by very high-speed connections using fiber optical cable or other digital media.

HAN

Short for home-area network. It is network contained within a user's home that connects a person's digital devices.

CAN

Short for campus-area network. Here, the computers are within a limited geographic area, such as a campus or military base.

VPN

Short for virtual private network, a network that is constructed by using public wires to connect nodes. For example, there are a number of systems that enable you to create networks using the Internet as the medium for transporting data. These systems use encryption and other security mechanisms to ensure that only authorized users can access the network and that the data cannot be intercepted.

Server and Client and Distributed Processing

Client/Server Architecture, in computer science, an arrangement used on local area networks that makes use of "distributed intelligence" to treat both the server