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Computer NEtwork ► A computer network, often simply referred to as a network, is a collection of computers and devices connected by communications channels that facilitates communications among users and allows users to share resources with other users. ► Networks may be classified according to a wide variety of characteristics. ► This article provides a general overview of types and categories and also presents the basic components of a network.

Purpose ► Facilitating communications. Using a network, people can communicate efficiently and easily via , instant messaging, chat rooms, telephony, video telephone calls, and videoconferencing. ► Sharing hardware. In a networked environment, each computer on a network can access and use hardware on the network. Suppose several personal computers on a network each require the use of a laser printer. If the personal computers and a laser printer are connected to a network, each user can then access the laser printer on the network, as they need it. ►

► Sharing files, data, and information. In a network environment, any authorized user can access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks. ► Sharing software. Users connected to a network can access application programs on the network.

Network classification ► Connection method ► Computer networks can be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as optical fiber, Ethernet, Wireless LAN, HomePNA, Power line communication ► Wired technologies ► Twisted pair, Coaxial cable, Optical fiber Twisted pairCoaxial cableOptical fiber Twisted pairCoaxial cableOptical fiber ► Wireless technologies  Terrestrial Microwave – Microwave  Communications Satellites Satellites  Cellular and PCS Systems –  Wireless LANs –  Bluetooth –  The Wireless Web – ► Scale ► Functional relationship (network architecture)  Network topology

Scale ► Networks are often classified as ► local area network (LAN), ► wide area network (WAN), ► metropolitan area network (MAN), ► personal area network (PAN), ► virtual private network (VPN), ► campus area network (CAN), ► storage area network (SAN), ► and others, ► depending on their scale, scope and purpose. Usage, trust level, and access right often differ between these types of network. For example, LANs tend to be designed for internal use by an organization's internal systems and employees in individual physical locations (such as a building), while WANs may connect physically separate parts of an organization and may include connections to third parties.

► LAN - Local Area Network ► WLAN - Wireless Local Area Network ► WAN - Wide Area Network ► MAN - Metropolitan Area Network ► SAN - Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network ► CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network ► PAN - Personal Area Network ► DAN - Desk Area Network

► LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution.

► Other Types of Area Networks ► While LAN and WAN are by far the most popular network types mentioned, you may also commonly see references to these others: ► Wireless Local Area Network - a LAN based on WiFi wireless network technology WiFi ► Metropolitan Area Network - a network spanning a physical area larger than a LAN but smaller than a WAN, such as a city. A MAN is typically owned an operated by a single entity such as a government body or large corporation. ► Campus Area Network - a network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus. ► Storage Area Network - connects servers to data storage devices through a technology like Fibre Channel. Fibre ChannelFibre Channel ► System Area Network - links high-performance computers with high-speed connections in a cluster configuration. Also known as Cluster Area Network.

► Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., active networking, client- server and peer-to-peer (workgroup) architecture. active networkingclient- serverpeer-to-peeractive networkingclient- serverpeer-to-peer

Types of networks ► Personal area network ► Local area network ► Home area network ► Campus area network ► Metropolitan area network ► Wide area network ► Global area network ► Virtual private network ► Internetwork ► Internet ► Intranets and extranets

Basic hardware components ► Network interface cards ► Repeaters ► Hubs ► Bridges ► Switches ► Routers