Computer network

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"Computer networks" redirects here. For the periodical, see Computer Networks.

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Internet map. The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide.

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Distributed processing

A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information.^[1] Where at least one process in one device is able to send/receive data to/from at least one process residing in a remote device, then the two devices are said to be in a network.
Networks may be classified according to a wide variety of characteristics such as the medium used to transport the data, communications protocol used, scale, topology, and organizational scope.
Communications protocols define the rules and data formats for exchanging information in a computer network, and provide the basis for network programming. Well-known communications protocols are Ethernet, a hardware and link layer standard that is ubiquitous in local area networks, and the internet protocol suite, which defines a set of protocols for internetworking, i.e. for data communication between multiple networks, as well as host-to-host data transfer, and application-specific data transmission formats.
Computer networking is sometimes considered a sub-discipline of electrical engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of these disciplines.

Contents 1 History 2 Properties 3 Communication media 3.1 Wired technologies 3.2 Wireless technologies 3.3 Exotic technologies 4 Communications protocols and network programming 4.1 Ethernet 4.2 Internet Protocol Suite 4.3 SONET/SDH 4.4 Asynchronous Transfer Mode 4.5 Network programming 5 Scale 5.1 Personal area network 5.2 Local area network 5.3 Home area network 5.4 Storage area network 5.5 Campus area network 5.6 Backbone network 5.7 Metropolitan area network 5.8 Wide area network 5.9 Enterprise private network 5.10 Virtual private network 5.11 Internetwork 6 Organizational scope 6.1 Intranets and extranets 6.2 Internet 7 Network topology 7.1 Common layouts 7.2 Overlay network 8 Basic hardware components 8.1 Network interface cards 8.2 Repeaters and hubs 8.3 Bridges 8.4 Switches 8.5 Routers 8.6 Firewalls 9 Network performance 10 Network security 11 Network resilience 12 Views of networks 13 See also 14 References 15 Further reading 16 External links

History

This section requires expansion.

Before the advent of computer networks that were based upon some type of telecommunications system, communication between calculation machines and early computers was performed by human users by carrying instructions between them. Many of the social behaviors seen in today's Internet were demonstrably present in the 19th century and arguably in even earlier networks using visual signals.

• In September 1940, George Stibitz used a Teletype machine to send instructions for a problem set from his Model at Dartmouth College to his Complex Number Calculator in New York and received results back by the same means. Linking output systems like teletypewriters to computers was an interest at the Advanced Research Projects Agency (ARPA) when, in 1962, J.C.R. Licklider was hired and developed a working group he called the "Intergalactic Network", a precursor to the ARPANET.
• Early networks of communicating computers included the military radar system Semi-Automatic Ground Environment (SAGE), started in the late 1950s.
• The commercial airline reservation system semi-automatic business research environment (SABRE) went online with two connected mainframes in 1960.^[2][3]
• In 1964, researchers at Dartmouth developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at Massachusetts Institute of Technology, a research group supported by General Electric and Bell Labs used a computer to route and manage telephone connections.
• Throughout the 1960s Leonard Kleinrock, Paul Baran and Donald Davies independently conceptualized and developed network systems which used packets that could be used in a network between computer systems.
• 1965 Thomas Merrill and Lawrence G. Roberts created the first wide area network (WAN).
• The first widely used telephone switch that used true computer control was introduced by Western Electric in 1965.
• In 1969 the University of California at Los Angeles, the Stanford Research Institute, University of California at Santa Barbara, and the University of Utah were connected as the beginning of the ARPANET network using 50 kbit/s circuits.^[4]
• Commercial services using X.25 were deployed in 1972, and later used as an underlying infrastructure for expanding TCP/IP networks.

Today, computer networks are the core of modern communication. All modern aspects of the public switched telephone network (PSTN) are computer-controlled, and telephony increasingly runs over the Internet Protocol, although not necessarily the public Internet. The scope of communication has increased significantly in the past decade, and this boom in communications would not have been possible without the progressively advancing computer network. Computer networks, and the technologies needed to connect and communicate through and between them, continue to drive computer hardware, software, and peripherals industries. This expansion is mirrored by growth in the numbers and types of users of networks, from the researcher to the home user.
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Server Roles

The term server refers to a machine that is providing a service for other machines, e.g. A computer which shares files on the network would be classed as a file server. For example, A Domain Controller is classed as a server because it is providing a service for the rest of the clients on the network. Windows 2003 can take several different server roles. These are as follows:

File Server

A File Server stores files and folders that are used by other machines on the network. It can hold applications, text documents, or a user’s My Documents Folder.  For security, many shared folders are housed on file servers. A distributed file system is housed on more than one file server for the sake of fault-tolerance and ease of access.

A Windows XP Professional machine may act as a limited File Server.

A Windows Server 2003 Computer can also act as a file server for different operating systems, e.g. Apple Macintosh.

Print Server

A Print Server is a computer that has a printer attached to it and shares the printer for use on the network.

A Windows XP Professional Machine can be a reasonably capable Print Server.

Application Server

Besides being a Domain Controller, Windows Server 2003 can also be a host to many different services e.g. as a Database Server and a Terminal Server.

Some Common Microsoft Servers:

Microsoft Exchange allows you to setup an e-mail server and also allows you setup a messaging and collaboration system for your company’s network.

Microsoft SQL Server enables you to setup up powerful database servers for your company’s network.

Microsoft ISA Server allows you to setup an Internet Gateway/Proxy Server for your company’s network.

These applications require Windows Server 2003. Their integration with Active Directory allows for tighter security and easier administration.

A Database Server holds a database! This is not just a list of information. It is structured, and dynamic. It needs to be managed, updated, extended and secure, while at the same time being accessible to users.  A dedicated server is required for this.

Remote Administration enables an administrator to manage a server from almost any workstation on the network using Terminal Services. Terminal Services lets workstations use powerful applications housed at the server as if they were installed at that workstation.

Web Servers

A Web Server hosts and manages websites for the Internet or an intranet. Because of the need to manage heavy and burst-mode traffic while maintaining security, a dedicated server is recommended.

Windows 2003 can function as a web server using the Internet Information Services (IIS) service

Windows XP Professional ships with a limited version of IIS which allows a workstation to host a single website.