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Encyclopedia > Computer network

A computer network is an interconnected group of computers. Networks may be classified by the network layer at which they operate according to basic reference models considered as standards in the industry, such as the five-layer Internet Protocol Suite model. While the seven-layer Open Systems Interconnection (OSI) reference model is better known in academia, the majority of networks use the Internet Protocol Suite (IP). The tower of a personal computer. ... The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet and most commercial networks run. ... The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design. ...

Contents

By scale

Computer networks may be classified according to the scale: Personal area network (PAN), Local Area Network (LAN), Campus Area Network (CAN), Metropolitan area network (MAN), or Wide area network (WAN). A personal area network (PAN) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person. ... LAN redirects here. ... In the case of a university campus-based campus area network the network is likely to link a variety of campus buildings including academic departments, the university library and student residence halls. ... Metropolitan area networks, or MANs, are large computer networks usually spanning a city. ... Wide Area Network (WAN) is a computer network that covers a broad area (i. ...


As Ethernet increasingly is the standard interface for networks, these distinctions are more important to the network administrator than the user. Network administrators may have to tune the network, to correct delay issues and achieve the desired performance level.


By connection method

Computer networks can also be classified according to the hardware technology that is used to connect the individual devices in the network such as Optical fibre, Ethernet, Wireless LAN, HomePNA, or Power line communication. Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... The notebook is connected to the wireless access point using a PC card wireless card. ... The HomePNA seeks to establish standards for home networking over regular coax and phone lines within the home - for compatibility between telecom, computer and network products. ... For other uses, see Power band. ...


Ethernets use physical wiring to connect devices. Often they employ hubs, switches, bridges, and/or routers.


Wireless LAN technology is built to connect devices without wiring. These devices use a radio frequency to connect.


By functional relationship (Network Architectures)

Computer networks may be classified according to the functional relationships which exist between the elements of the network, e.g., Active Networking, Client-server and Peer-to-peer (workgroup) architecture. Active networking is a communication paradigm that allows packets flowing through a communication network to dynamically modify the operation of the network. ... Client/Server is a network application architecture which separates the client (usually the graphical user interface) from the server. ... A peer-to-peer (or P2P) computer network is a network that relies on the computing power and bandwidth of the participants in the network rather than concentrating it in a relatively few servers. ...


By network topology

Main article: Network Topology

Computer networks may be classified according to the network topology upon which the network is based, such as Bus network, Star network, Ring network, Mesh network, Star-bus network, Tree or Hierarchical topology network, etc. For other uses of topology, see topology (disambiguation). ... For other uses of topology, see topology (disambiguation). ... Image showing bus network layout A bus network Topology is a network architecture in which a set of clients are connected via a shared communications line, called a bus. ... Bold text Star network layout Star networks are one of the most common computer network topologies. ... Image showing ring network layout A ring network is a network topology in which each node connects to exactly two other nodes, forming a circular pathway for signals: a ring. ... Mesh networking is a way to route data, voice and instructions between nodes. ... A star-bus network is a combination of a star network and a bus network. ... This article does not cite any references or sources. ...


Network Topology signifies the way in which intelligent devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network. Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, the network has a Star topology, rather than a Bus Topology. In this regard the visual and operational characteristics of a network are distinct; the logical network topology is not necessarily the same as the physical layout.


By protocol

Computer networks may be classified according to the communications protocol that is being used on the network. See the articles on List of network protocol stacks and List of network protocols for more information. For a development of the foundations of protocol design see Srikant 2004[1] and Meyn 2007[2] This article concerns communication between pairs of electronic devices. ... Computer networks may be implemented using a variety of protocol stack architectures, computer buses or combinations of media and protocol layers, incorporating one or more of: ARCNET AppleTalk ATM Bluetooth DECnet Ethernet FDDI Frame relay HIPPI IEEE 1394 aka FireWire, iLink IEEE 802. ... This is an incomplete list of individual network protocols, categorized by their nearest OSI model layers. ...


Types of networks:

Below is a list of the most common types of computer networks in order of scale.


Personal Area Network (PAN)

Main article: Personal area network

A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that are used in a PAN are printers, fax machines, telephones, PDAs or scanners. The reach of a PAN is typically within about 20-30 feet (approximately 6-9 metres). A personal area network (PAN) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person. ...


Personal area networks may be wired with computer buses such as USB[3] and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA and Bluetooth. USB redirects here. ... The 6-pin and 4-pin FireWire 400 Connectors The alternative ethernet-style cabling used by 1394c FireWire is Apple Inc. ... This article is about an Infrared communications protocol. ... Bluetooth logo This article is about the electronic protocol named after Harald Bluetooth Gormson. ...


Local Area Network (LAN)

Main article: Local Area Network

A network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library will have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet. All of the PCs in the library are connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnection devices and eventually connect to the internet. The cables to the servers are on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbit/s. LAN redirects here. ... Cat5 patch cable Category 5 cable, commonly known as Cat 5, is a twisted pair cable type designed for high signal integrity. ...


The staff computers (bright green in the figure) can get to the color printer, checkout records, and the academic network and the Internet. All user computers can get to the Internet and the card catalog. Each workgroup can get to its local printer. Note that the printers are not accessible from outside their workgroup.

Typical library network, in a branching tree topology and controlled access to resources
Typical library network, in a branching tree topology and controlled access to resources

All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers. The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ...


The defining characteristics of LANs, in contrast to WANs (wide area networks), include their higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 100 Gbit/s, and possibly 40 Gbit/s. IEEE 802. ... The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ...


Campus Area Network (CAN)

Main article: Campus Area Network

A network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, or a military base. A CAN may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN. This term is most often used to discuss the implementation of networks for a contiguous area. This should not be confused with a Controller Area Network In the case of a university campus-based campus area network the network is likely to link a variety of campus buildings including academic departments, the university library and student residence halls. ... Controller Area Network (CAN or CAN-bus) is a computer network protocol and bus standard designed to allow microcontrollers and devices to communicate with each other and without a host computer. ...


Metropolitan Area Network (MAN)

A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town, city, or metropolitan area. Multiple routers, switches & hubs are connected to create a MAN. Metropolitan area networks, or MANs, are large computer networks usually spanning a city. ...


Wide Area Network (WAN)

Main article: Wide Area Network

A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer. Wide Area Network (WAN) is a computer network that covers a broad area (i. ... The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design. ... This article does not cite any references or sources. ... The data link layer is layer two of the seven-layer OSI model as well as of the five-layer TCP/IP reference model. ... The network layer is third layer out of seven in OSI model and it is the third layer out of five in TCP/IP model. ...


Global Area Network (GAN)

Main article: Global Area Network

Global area networks (GAN) specifications are in development by several groups, and there is no common definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is "handing off" the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial Wireless local area networks (WLAN).[4] The global area network standard has been proposed as IEEE 802. ... The notebook is connected to the wireless access point using a PC card wireless card. ...


Internetwork

Main article: Internetwork

Two or more networks or network segments connected using devices that operate at layer 3 (the 'network' layer) of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork. This article is about the Internet An internet is a more general term for any set of interconnected computer networks that are connected by internetworking Graphic representation of the WWW information network structure around Wikipedia, as represented by hyperlinks The Internet, or simply the Net, is the publicly available worldwide...


In modern practice, the interconnected networks use the Internet Protocol. There are at least three variants of internetwork, depending on who administers and who participates in them:

  • Intranet
  • Extranet
  • Internet

Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.


Intranet

Main article: Intranet

An intranet is a set of interconnected networks, using the Internet Protocol and uses IP-based tools such as web browsers and ftp tools, that is under the control of a single administrative entity. That administrative entity closes the intranet to the rest of the world, and allows only specific users. Most commonly, an intranet is the internal network of a company or other enterprise. A large intranet will typically have its own web server to provide users with browseable information. An intranet is a private computer network that uses Internet protocols, network connectivity to securely share part of an organizations information or operations with its employees. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ...


Extranet

Main article: Extranet

An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities (e.g. a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint). Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network. An extranet is a private network that uses Internet protocols, network connectivity, and possibly the public telecommunication system to securely share part of an organizations information or operations with suppliers, vendors, partners, customers or other businesses. ...


Internet

Main article: Internet

A specific internetwork, consisting of a worldwide interconnection of governmental, academic, public, and private networks based upon the Advanced Research Projects Agency Network (ARPANET) developed by ARPA of the U.S. Department of Defense – also home to the World Wide Web (WWW) and referred to as the 'Internet' with a capital 'I' to distinguish it from other generic internetworks. ARPANET logical map, March 1977. ... The Defense Advanced Research Projects Agency (DARPA) is an agency of the United States Department of Defense responsible for the development of new technology for use by the military. ... The United States Department of Defense (DOD or DoD) is the federal department charged with coordinating and supervising all agencies and functions of the government relating directly to national security and the military. ... The World Wide Web and WWW redirect here. ...


Participants in the Internet, or their service providers, use IP Addresses obtained from address registries that control assignments. Service providers and large enterprises also exchange information on the reachability of their address ranges through the Border Gateway Protocol (BGP). An IP address (or Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, a computer address. ... The Border Gateway Protocol (BGP) is the core routing protocol of the Internet. ...


Basic Hardware Components

All networks are made up of basic hardware building blocks to interconnect network nodes, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers. In addition, some method of connecting these building blocks is required, usually in the form of galvanic cable (most commonly Category 5 cable). Less common are microwave links (as in IEEE 802.11) or optical cable ("optical fiber"). Node(Latin nodus ‘knot’) is critical element of any computer network. ... Cat5 patch cable Category 5 cable, commonly known as Cat 5, is a twisted pair cable type designed for high signal integrity. ... IEEE 802. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. ...


Network Interface Cards

Main article: Network card

A network card, network adapter or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of MAC addresses. It allows users to connect to each other either by using cables or wirelessly. Every NIC in the world has a unique MAC address. A network card, network adapter or NIC (network interface controller) is a piece of computer hardware designed to allow computers to communicate over a computer network. ... Computer hardware is the physical part of a computer, including its digital circuitry, as distinguished from the computer software that executes within the hardware. ... In computer networking a Media Access Control address (MAC address) or Ethernet Hardware Address (EHA) or hardware address or adapter address is a quasi-unique identifier attached to most network adapters (NICs). ...


Repeaters

Main article: Repeater

A repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair ethernet configurations, repeaters are required for cable runs longer than 100 meters. For other uses, see Repeater (disambiguation). ... Surface mount electronic components Electronics is the study of the flow of charge through various materials and devices such as semiconductors, resistors, inductors, capacitors, nano-structures and vacuum tubes. ... In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... Retransmission might refer to: Retransmission (data networks), the resending of packets which have been damaged or lost Replication of a signal at a repeater This is a disambiguation page, a list of pages that otherwise might share the same title. ...


Hubs

Main article: Network hub

A hub contains multiple ports. When a packet arrives at one port, it is copied to all the ports of the hub. When the packets are copied, the destination address in the frame does not change to a broadcast address. It does this in a rudimentary way, it simply copies the data to all of the Nodes connected to the hub.[5] In general, a hub is a centre point: a wheels hub, which is the center of the wheel with spokes radiating out from it. ...


Bridges

Main article: Network bridge

A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges do not promiscuously copy traffic to all ports, as hubs do, but learns which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received. A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. ... A network segment is a portion of a computer network wherein every device communicates using the same physical layer. ... The data link layer is layer two of the seven-layer OSI model as well as of the five-layer TCP/IP reference model. ... The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design. ... In computer networking a Media Access Control address (MAC address) or Ethernet Hardware Address (EHA) or hardware address or adapter address is a quasi-unique identifier attached to most network adapters (NICs). ...


Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived.


Bridges come in three basic types:

  1. Local bridges: Directly connect local area networks (LANs)
  2. Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced by routers.
  3. Wireless bridges: Can be used to join LANs or connect remote stations to LANs.

Switches

Main article: Network switch

A switch is a device that performs switching. Specifically, it forwards and filters OSI layer 2 datagrams (chunk of data communication) between ports (connected cables) based on the Mac-Addresses in the packets.[6] This is distinct from a hub in that it only forwards the datagrams to the ports involved in the communications rather than all ports connected. Strictly speaking, a switch is not capable of routing traffic based on IP address (layer 3) which is necessary for communicating between network segments or within a large or complex LAN. Some switches are capable of routing based on IP addresses but are still called switches as a marketing term. A switch normally has numerous ports with the intention that most or all of the network be connected directly to a switch, or another switch that is in turn connected to a switch.[7] For other uses, see Switch (disambiguation). ...


Switches is a marketing term that encompasses routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier). Switches may operate at one or more OSI layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch. // Uniform Resource Locator (URL) formerly known as Universal Resource Locator, is a technical, Web-related term used in two distinct meanings: In popular usage and many technical documents, it is a synonym for Uniform Resource Identifier (URI); Strictly, the idea of a uniform syntax for global identifiers of network-retrievable... OSI is primarily used as an abbreviation and has many meanings: OSI Pharmaceuticals, an American pharmaceutical company OSI Restaurant Partners, the restaurant and entertainment group that includes Outback Steakhouse OSI Systems a company that manufactures security scanners and medical equipment based in California Olomouc Summer Institute, an educational program for... This article does not cite any references or sources. ... The data link layer is layer two of the seven-layer OSI model as well as of the five-layer TCP/IP reference model. ... The network layer is third layer out of seven in OSI model and it is the third layer out of five in TCP/IP model. ... In computing and telecommunications, the transport layer is the second highest layer in the four and five layer TCP/IP reference models, where it responds to service requests from the application layer and issues service requests to the Internet layer. ... It has been suggested that layer 4 router be merged into this article or section. ...


Overemphasizing the ill-defined term "switch" often leads to confusion when first trying to understand networking. Many experienced network designers and operators recommend starting with the logic of devices dealing with only one protocol level, not all of which are covered by OSI. Multilayer device selection is an advanced topic that may lead to selecting particular implementations, but multilayer switching is simply not a real-world design concept.


Routers

Main article: Router

Routers are networking devices that forward data packets between networks using headers and forwarding tables to determine the best path to forward the packets. Routers work at the network layer of the TCP/IP model or layer 3 of the OSI model. Routers also provide interconnectivity between like and unlike media (RFC 1812). This is accomplished by examining the Header of a data packet, and making a decision on the next hop to which it should be sent (RFC 1812) They use preconfigured static routes, status of their hardware interfaces, and routing protocols to select the best route between any two subnets. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Some DSL and cable modems, for home (and even office) use, have been integrated with routers to allow multiple home/office computers to access the Internet through the same connection. Many of these new devices also consist of wireless access points (waps) or wireless routers to allow for IEEE 802.11b/g wireless enabled devices to connect to the network without the need for a cabled connection. This article is about a computer networking device. ... The network layer is third layer out of seven in OSI model and it is the third layer out of five in TCP/IP model. ... The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design. ... Routing protocols allow different computer networks to communicate. ...


See also

Active networking is a communication paradigm that allows packets flowing through a communication network to dynamically modify the operation of the network. ... Bluetooth logo This article is about the electronic protocol named after Harald Bluetooth Gormson. ... This article or section is in need of attention from an expert on the subject. ... Computer networking devices are units that mediate data in a computer network. ... In combinatorics, an expander graph refers to a sparse graph which has high connectivity properties, quantified using vertex or edge expansion as described below. ... Prior to the widespread inter-networking that led to the Internet, most communication networks were limited by their nature to only allow communications between the stations on the network, and the prevalent computer networking method was based on the central mainframe method. ... A home network is a residential local area network, and is used to connect multiple devices within the homes. ... The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... “ISO” redirects here. ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... Network diagrams depict network elements and the connections between these elements. ... Network tomography is the study of a networks internal characteristics using information derived from end point data. ... For other uses of topology, see topology (disambiguation). ... Node(Latin nodus ‘knot’) is critical element of any computer network. ... For other senses of this word, see protocol. ... A scale-free network is a noteworthy kind of complex network because many real-world networks fall into this category. ... Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes is implemented without the use of wires, such as a computer network (a type of communications network). ...

References

  1. ^ R. Srikant, 2007. The Mathematics of Internet Congestion Control. Birkhäuser, 2004
  2. ^ S. P. Meyn, 2007. Control Techniques for Complex Networks, Cambridge University Press, 2007.
  3. ^ An example of a USB-based PAN is GeneLinkTM; USB Network (accessed 2008-02-11
  4. ^ Mobile Broadband Wireless Access (MBWA)
  5. ^ Pountain, Dick (2001), The New Penguin Dictionary of Computing, New York: Penguin Books, ISBN 0-14-051-4376 
  6. ^ Define switch.. www.webopedia.com. Retrieved on 2008-04-08.
  7. ^ Basic Components of a Local Area Network (LAN). NetworkBits.net. Retrieved on 2008-04-08.

This article contains material from the Federal Standard 1037C, which, as a work of the United States Government, is in the public domain. 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 42nd day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 98th day of the year (99th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 98th day of the year (99th in leap years) in the Gregorian calendar. ... Federal Standard 1037C, entitled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ... A work of the United States government, as defined by United States copyright law, is a work prepared by an officer or employee of the U.S. government as part of that persons official duties. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ...

An operating system (OS) is a software that manages computer resources and provides programmers with an interface used to access those resources. ... A kernel connects the application software to the hardware of a computer. ... Graphical overview of a microkernel A microkernel is a minimal computer operating system kernel providing only basic operating system services (system calls), while other services (commonly provided by kernels) are provided by user-space programs called servers. ... It has been suggested that Monolithic system be merged into this article or section. ... Graphical overview of a hybrid kernel Hybrid kernel is a kernel architecture based on combining aspects of microkernel and monolithic kernel architectures used in computer operating systems. ... In computer engineering the kernel is the core of an operating system. ... In computing, loadable kernel modules, or LKM, are object files that contain code to extend the running kernel, or so-called base kernel, of an operating system. ... In computer science, a nanokernel or picokernel is a very minimalist operating system kernel. ... A device driver, or software driver is a computer program allowing higher-level computer programs to interact with a computer hardware device. ... An operating system usually segregates the available system memory into kernel space and user space. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Process management is the ensemble of activities of planning and monitoring the performance of a process, especially in the sense of business process, often confused with reengineering. ... In computing, a process is an instance of a computer program that is being executed. ... In computing, multitasking is a method by which multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is... In computing, an interrupt is an asynchronous signal from hardware or software indicating the need for attention. ... Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later. ... In computer terms, supervisor mode is a hardware-mediated flag which can be changed by code running in system-level software. ... In computing, multitasking is a method by which multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is... For disk scheduling, see I/O scheduling. ... A context switch is the computing process of storing and restoring the state (context) of a CPU such that multiple processes can share a single CPU resource. ... In computing, cooperative multitasking (or non-preemptive multitasking) is a form of multitasking in which multiple tasks execute by voluntarily ceding control to other tasks at programmer-defined points within each task. ... Pre-emptive multitasking is a form of multitasking in which processes are not allowed to take an indefinitely long time to complete execution in the CPU. Each process, in turn, is granted a portion of CPU time (usually called a time slice, on the order of milliseconds). ... CPU modes (also called processor modes or privilege levels, and by other names) are operating modes for the central processing unit of some computers that place variable restrictions on the operations that can be performed by the CPU. Mode types At a minimum, any CPU with this type of architecture... Memory protection is a system that prevents one process from corrupting the memory of another process running on the same computer at the same time. ... Segmentation is one of the most common ways to achieve memory protection; another common one is paging. ... This article is about computer virtual memory. ... This 68451 MMU could be used with the Motorola 68010 MMU, short for memory management unit or sometimes called paged memory management unit as PMMU, is a class of computer hardware components responsible for handling memory accesses requested by the CPU. Among the functions of such devices are the translation... It has been suggested that Access violation be merged into this article or section. ... A General Protection Fault (GPF) in the Intel x86 and AMD x86-64 architectures is a fault (a type of an interrupt) which can encompass several cases, where protection mechanisms within the processor architecture are violated by any of the programs that is running, whether it be the kernel or... AmigaOS is the default native operating system of the Amiga personal computer. ... Windows redirects here. ... This article is about operating systems that use the Linux kernel. ... GNU (pronounced ) is a computer operating system composed entirely of free software. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®, sometimes also written as or ® with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... This article relates to both the original Classic Mac OS as well as Mac OS X, Apples more recent operating system. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... In computing, Bootstrapping refers to a process where a simple system activates another more complicated system that serves the same purpose. ... API redirects here. ... A virtual file system (VFS) or virtual filesystem switch is an abstraction layer on top of a more concrete file system. ... GUI redirects here. ... The history of computer operating systems recapitulates to a degree, the recent history of computing. ... A hardware abstraction layer (HAL) is an abstraction layer, implemented in software, between the physical hardware of a computer and the software that runs on that computer. ...


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Computer networking is the scientific and engineering discipline concerned with communication between computer systems.
Computer networking is sometimes considered a sub-discipline of telecommunications.
Computer networks may be implemented using a variety of protocol stack architectures, computer buses or combinations of media and protocol layers, incorporating one or more of:
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