Networking software | Wikipedia audio article
A computer. Network, is a digital. Telecommunications. Network, which allows modes to share resources, in. Computer. Networks, computing. Devices exchange. Data with each other using, connections data links, between nodes. These. Data links, are established, over cable, media such as wires, or optic, cables, or wireless, media, such as Wi-Fi. Network. Computer, devices, that originate, route and terminate, the data are called Network nodes. Nodes. Are identified. By network addresses, and can include hosts, such as personal, computers phones. And servers, as well as networking, hardware, such as routers and switches to. Such. Devices, can be said to be networked, together when, one device is able to exchange information, with the other device, whether, or not they have a direct, connection to each other in most. Cases, application. Specific, communications. Protocols. Are layered ie carried, as payload, over other more general, communications. Protocols. This. Formidable, collection. Of information, technology. Requires, skilled, network management. To keep it all running reliably. Computer. Networks, support, an enormous, number of applications. And services, such as access. To the world wide web digital. Video digital, audio. Shared, use of application and, storage, servers, printers, and fax machines and, use of email and instant messaging, applications. As well as many others. Computer. Networks, differ in the transmission. Medium used to carry their signals, communications. Protocols. To organize network, traffic the network size, topology. Traffic, control, mechanism, and organizational. Intent, the. Best-known, computer. Network, is the Internet. You. Topic. History. The, chronology of significant. Computer, network development, includes. In the late 1950s. Early, networks. Of computers included, the US military. Radar, system, semi-automatic. Ground environment sage. In. 1959. Anatoly. Ivanishin. Proposed. To the Central, Committee of the Communist. Party of the Soviet Union. A detailed, plan for the reorganization. Of the control, of the Soviet, armed forces, and of the Soviet, economy on, the basis, of a network of computing, centers, the Ogas, in. 1960. The commercial, airline, reservation. System, semi-automatic. Business, research environment. Sabre went online with two connected, mainframes, in. 1963. JCR. Licklider sent. A memorandum to office, colleagues, discussing. The concept, of the intergalactic. Computer. Network, a computer. Network, intended, to allow general, communications. Among computer, users, in. 1964. Researchers. At Dartmouth College 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. Paul Baran and Donald, Davies independently. Developed, the concept, of packet, switching to transfer, information between, computers. Over a network. Davies. Pioneered, the implementation. Of the concept, with the NPL, Network a local, area network at, the National, Physical Laboratory. United. Kingdom using a line speed of, 768. Kilobits, per second, in. 1965. Western, Electric introduced. The first widely used telephone. Switch that implemented, true computer control, in. 1966. Thomas Merrill and Lawrence G Roberts, published a paper on an experimental, wide, area, network, one for computer, time sharing, in.
1969. The first four nodes of the ARPANET, were connected, using 50, kilobits, per second, circuits between the University. Of California. At Los Angeles the. Stanford, Research Institute the. University of, California. At Santa Barbara and the University. Of Utah. Leonard. Kleinrock carried. Out theoretical. Work to model the performance, of packet, switched networks, which underpinned, the development. Of the ARPANET, his. Theoretical. Work on hierarchical. Routing in the late, 1970s. With student, Farouk commune remains, critical to the operation of, the Internet today in. 1972. Commercial. Services, using, by 0.25. Were, deployed, and later used as an underlying infrastructure. For expanding. Tcp/ip. Networks. In. 1973. The French Cyclades, Network was the first to make the hosts responsible. For the reliable, delivery, of data rather, than this being a centralized, service, of the network itself in. 1973. Robert Metcalfe, wrote a formal, memo at Xerox, PARC describing. Ethernet, a networking, system, that was based on the Aloha network developed, in the 1960s. By, Norman Abramson, and colleagues, at the University, of Hawaii in, July. 1976. Robert, Metcalfe and David Boggs published, their paper, Ethernet. Distributed. Packet, switching, for local computer, networks, and. Collaborated. On several patents. Received, in. 1977. And 1978. In. 1979. Robert Metcalfe, pursued, making, Ethernet, an open standard in. 1976. John Murphy of data point corporation. Created arc, net a token, passing Network first used to share storage, devices. In, 1995. The transmission. Speed capacity for. Ethernet, increased, from 10 megabits, per second, to 100, megabits per second, by. 1998. Ethernet. Supported, transmission. Speeds of a gigabit. Subsequently. Higher speeds, of up to 400. Gigabits, per second, were added as of 2018. The. Ability, of Ethernet, to scale easily such as quickly adapting, to support, new fiber optic, cable speeds is a contributing. Factor to, its continued, use. You. Topic. Properties. Computer. Networking, may be considered. A branch of Electrical, Engineering electronics. Engineering. Telecommunications. Computer. Science, information. Technology. Or computer engineering. Since, it relies upon the theoretical. And practical, application. Of the related disciplines. A. Computer. Network, facilitates. Interpersonal. Communications. Allowing users, to communicate, efficiently. And easily via, various means, email, instant.
Messaging, Online chat. Telephone. Video telephone. Calls and video conferencing. A network. Allows sharing, of network and computing, resources. Users. May access and. Use resources, provided. By devices. On the network such, as printing, a document on, a shared network printer. Or use of a shared storage, device, a, network. Allows, sharing, of files data, and other types of information giving. Authorized, users, the ability to access information, stored. On other computers, on the network. Distributed. Computing, uses, computing, resources, across, a network to accomplish, tasks, a. Computer. Network, may be used by security, hackers, to deploy computer, viruses, or computer, worms on devices, connected, to the network or to prevent these devices. From accessing, the network via, a denial, of service attack. You. Topic. Network, packet. Computer. Communication. Links, that do not support packets. Such as traditional point-to-point. Telecommunications. Links. Simply, transmit, data as a bit stream. However. The overwhelming, majority of, computer, networks, carry, their data in packets, a network. Packet as a formatted. Unit of data a list of bits or bytes usually. A few tens of bytes to a few kilobytes long, carried, by a packet, switched network. Packets. Are sent through the network to their destination. Once, the packets, arrived they are reassembled, into their original message. Packets. Consist of two kinds of data control. Information, and user data payload. The. Control, information, provides, data the network, needs to deliver the user data for example source. And destination network. Addresses. Error detection, codes, and sequencing. Information. Typically. Control. Information is, found in packet, headers and trailers with. Payload, data in between. With. Packets, the bandwidth, of the transmission medium. Can be better shared among users than if the network were circuit-switched. When. One user is not sending, packets, the link can be filled with packets, from other users and so the cost can be shared with relatively, little interference, provided. The link isn't overused. Often. The route a packet needs, to take through a network is not immediately, available in, that. Case the packet, is queued and waits until a link is free. You. Topic. Network. Topology. The, physical, layout of a network, is usually, less important, than the topology, that connects, network nodes. Most. Diagrams. That describe, a physical, network are therefore, topological. Rather than Geographic. The symbols. On these diagrams, usually. Denote network links, and network nodes. You. Topic. Network, links. The, transmission. Media often, referred to in the literature as, the physical, media used to link devices, to form a computer, network, include, electrical, cable optical fiber, and radio, waves in the. OSI, model these, are defined at layers 1 & 2 the. Physical, layer and the data link layer a. Widely. Adopted family. Of transmission. Media used, in local area network, LAN technology. Is collectively, known as Ethernet, the. Media and protocol. Standards. That enable, communication. Between network, devices, over Ethernet, are defined, by I Triple. E, 802.3. Ethernet. Transmits, data over, both copper, and fiber cables. Wireless. LAN standards. Use radio, waves others. Use infrared signals, as a transmission. Medium, power. Line communication, uses. A building's, power cabling. To transmit, data. You. Topic. Wired. Technologies. The, following, classes, of wired technologies. Are used in computer, networking. Coaxial. Cable, is widely used for, cable, television systems. Office, buildings, and other work sites for local area networks. Transmission. Speed ranges, from 200, million bits, per second, to more than 500. Million bits per second. Itu-t. Ghn. Technology. Uses, existing, home wiring coaxial. Cable, phone lines and power lines to create a high-speed, local area network. Twisted. Pair cabling, is used for wired Ethernet, and other standards, it, typically, consists, of four pairs of copper, cabling, that can be utilized for both voice and data transmission. The. Use of two wires twisted together, helps, to reduce crosstalk. And electromagnetic. Induction. The.
Transmission. Speed ranges. From two megabits, per second, to 10 gigabits, per second. Twisted. Pair cabling, comes in two forms unshielded, twisted. Pair UTP, and. Shielded, twisted, pair STP. Each. Form, comes in several category. Ratings, designed, for use in various scenarios, an. Optical. Fiber as a glass fiber it, carries, pulses, of light that represent, data some. Advantages. Of optical, fibers, over metal wires are very low, transmission. Loss and immunity, to electrical, interference. Optical. Fibers, can simultaneously, carry. Multiple, streams of data on, different wavelengths, of light which, greatly increases, the rate that data can be sent to up to trillions, of bits per second. Optic. Fibers, can be used for long runs of cable, carrying, very high data rates and are used for undersea, cables, to interconnect, continents. There. Are two basic, types of fiber optics. Single mode optical fiber, SMF. And multimode. Optical fiber. MMF. Single, mode fiber has the advantage, of being able to sustain a coherent. Signal for dozens, or even a hundred kilometers. Multimode. Fiber is cheaper, to terminate, but is limited, to a few hundred or, even only, a few dozens, of meters depending on the data rate and cable, grade price, is a main factor distinguishing. Wired and wireless technology. Options in a business. Wireless. Options, command a price premium that can make purchasing. Wired computers. Printers and other devices of financial, benefit, before. Making the decision to purchase hardwired. Technology. Products, a review, of the restrictions. And limitations of. The selections, is necessary. Business. And employee, needs may override any cost, considerations. You. Topic. Wireless. Technologies. Terrestrial. Microwave. Terrestrial. Microwave, communication. Uses earth-based, transmitters. And receivers resembling. Satellite, dishes. Terrestrial. Microwaves. Are in the low gigahertz range, which limits all communications. To line-of-sight. Relay. Stations, are spaced approximately, 48. Kilometers. 30 miles apart. Communication. Satellites, satellites. Communicate. Via microwave, radio, waves which, are not deflected, by the Earth's atmosphere. The. Satellites, are stationed, in space typically. In geosynchronous, orbit. 35,000. 400, kilometres. 22,000. Miles above the equator, these. Earth orbiting, systems, are capable, of receiving, and relaying voice data, and TV, signals. Cellular. And PC systems. Use several radio, communications. Technologies. The. Systems, divide, the region covered, into multiple, geographic areas. Each. Area has a low-power transmitter or, radio relay antenna, device, to relay calls from one area to the next area. Radio. And spread spectrum technologies. Wireless. Local area networks. Use a high frequency, radio technology. Similar to digital, cellular and, a low frequency radio, technology. Wireless. LANs use spread spectrum technology. To, enable communication, between multiple, devices in a limited area I. Triple. E. 802.11. Defines. A common, flavor of open standards wireless. Radio wave technology, known, as Wi-Fi. Free. Space optical. Communication. Uses, visible, or invisible light. For communications. In most.
Cases, Line-of-sight. Propagation is. Used which limits, the physical, positioning, of communicating. Devices. You. Topic. Exotic. Technologies. There, have been various, attempts, at transporting. Data over, exotic, media. IP. Over, avian, carriers, was a humorous, April, Fool's request, for comments issued, as RFC. 11:49. It. Was implemented, in real life in 2001. Extending. The Internet, to interplanetary. Dimensions. Via radio waves the interplanetary, internet. Both cases have a large round-trip. Delay time which gives slow two-way, communication. But doesn't prevent sending, large amounts, of information. You. Topic. Network. Nodes. Apart. From any physical transmission. Media, there may be networks. Comprise additional. Basic, system, building blocks such, as network, interface, controllers. Knicks repeaters. Hubs, bridges. Switches. Routers modems. And firewalls. Any. Particular. Piece of equipment will, frequently, contain, multiple, building, blocks and perform, multiple, functions. You. Topic. Network. Interfaces. A network. Interface, controller, Nick is computer. Hardware that provides, a computer, with the ability, to access the transmission. Media and has the ability to process low-level. Network information. For. Example the, Nick may have the connector, for accepting, a cable, or an aerial for wireless transmission. And reception and, the associated, circuitry. The. Nick responds. To traffic, addressed, to a network, address for either the Nick or the computer, as a whole in. Ethernet. Networks, each network, interface controller, has a unique, media access control MAC. Address. Usually. Stored in the controller's, permanent, memory, to. Avoid address, conflicts. Between networked devices, the, Institute, of Electrical and. Electronics. Engineers, I Triple, E maintains. And administers, MAC address, uniqueness. The. Size of an Ethernet MAC address, as six octets, the. Three most significant. Octets are reserved to identify. Nick manufacturers. These. Manufacturers. Using, only their assigned prefixes. Uniquely, assign the three least significant. Octets of every Ethernet, interface, they produce. You. Topic. Repeaters. And hubs. A repeater. Is an electronic. Device that receives, a network signal, cleans it of unnecessary. Noise and regenerates, it, the. Signal, is retransmitted. At a higher power level, or to 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 that runs longer, than 100, meters with. Fiber optics, repeaters, can be tens or even hundreds.
Of Kilometers, apart a. Repeater. With multiple, ports, is known as an Ethernet, hub repeaters. Work on the physical layer of the OSI model. Repeaters. Require, a small, amount of time to regenerate the signal this, can cause a propagation. Delay that, affects network, performance and, may affect proper. Function, as a. Result, many network, architectures. Limit the number of repeaters, that can be used in a row eg. The ethernet, five-four-three. Rule. Hubs. And repeaters, in lands, have been mostly obsoleted. By modern, switches. You. Topic. Bridges. A network. Bridge connects. And filters, traffic, between two network segments, at the data link layer layer, 2 of the OSI model, to form a single network this. Breaks the network's collision, domain but maintains, a unified, broadcast. Domain. Network. Segmentation. Breaks, down a large, congested. Network into an aggregation, of smaller more efficient, networks. Bridges. Come in three basic types. Local. Bridges directly. Connect lands. Remote. Bridges, can be used to create a wide area network. One link between lands. Remote. Bridges, where the connecting, link is slower than the end networks, largely, have been replaced, with routers. Wireless. Bridges, can be used to join lands, or connect remote devices, to lands. You. Topic. Switches. A network. Switch is a device, that forwards, and filters, OSI, layer 2 datagrams. Frames, between, ports, based on the destination MAC address, in each frame a, switch. Is distinct, from a hub in that it only forwards, the frames to the physical, ports involved, in the communication, rather, than all ports connected, it. Can be thought of as a multi, port bridge it, learns to associate, physical. Ports to MAC addresses, by examining, the source addresses, of received frames, if an. Unknown destination is. Targeted, the switch broadcasts. To all ports, but the source. Switches. Normally, have numerous ports, facilitating. A star topology for. Devices, and cascading, additional, switches.
You. Topic. Routers. A router. Is an internet working device that forwards, packets, between networks, by processing. The routing information, included, in the packet, or Datagram, Internet, Protocol, information. From layer 3, the. Routing, information is, often processed in, conjunction, with the routing table, or forwarding. Table, a router. Uses, its routing, table to determine where to forward packets a. Destination. In a routing table can include a null. Interface. Also known as the black. Hole, interface. Because, data can go into it however no, further processing. Is done for said data ie the, packets, are dropped. You. Topic. Modems. Modems, modulator. Demodulator are. Used to connect network, nodes via wire not originally. Designed for digital network, traffic or for wireless, to. Do this one or more carrier, signals, are modulated, by the digital, signal, to produce an analog signal that can be tailored to give the required properties. For transmission. Modems. Are commonly, used for telephone lines, using, a digital subscriber. Line technology. You. Topic. Firewalls. A firewall. Is a network device for, controlling network, security. And access rules. Firewalls. Are typically, configured to reject, access, requests. From unrecognized. Sources. While allowing actions, from recognized, ones, the. Vital, role firewalls. Play in network security grows. In parallel, with the constant, increase in cyberattacks. You. Topic. Network, structure. Network. Topology. As the layout or organizational. Hierarchy. Of interconnected. Nodes of a computer, network. Different. Network topologies. Can affect throughput, but reliability. Is often, more critical, with. Many technologies. Such, as bus networks, a single, failure can cause the network to fail entirely, in. General. The more interconnections. There are the more robust, the network is but the more expensive, it is to install. You. Topic. Common. Layouts. Common. Layouts, are. A bus, Network all nodes are connected to a common medium, along this medium, this. Was the layout used, in the original Ethernet. Called 1o base-5. And 1o base-2. This. Is still a common topology. On the data link layer although modern physical. Layer variants. Use point-to-point, links, instead a. Star. Network, all nodes, are connected to a special, central, node this. Is the typical, layout found, in a wireless LAN where each wireless, client connects, to the central wireless, access point, a, ring. Network, each node, is connected to its left and right neighbor node such that all nodes are connected and that each node can reach each other node by traversing, nodes left or right words, the. Fiber distributed, data interface. FDDI. Made, use of such a topology. A mesh. Network each, node is connected to an arbitrary, number of neighbors, in such a way that there is at least one traversal, from any node to any other a. Fully. Connected Network each node, is connected to every other node in the network a. Tree. Network nodes, are arranged, hierarchically note. That the physical, layout of the nodes in a network may, not necessarily reflect. The network topology, as an. Example, with FDDI, the, network topology, as a rain actually two, counter-rotating, rings. But, the physical, topology is, often a star because, all neighboring connections. Can be routed via a central physical. Location. You. Topic. Overlay. Network. An overlay. Network is, a virtual, computer network. That is built on top of another network, nodes.
In The overlay, network are connected by virtual, or logical, links, each. Link corresponds. To a path perhaps, through many physical, links in the underlying network, the. Topology, of the overlay, network may and often does differ from that of the underlying, one, for. Example, many peer-to-peer, networks. Are overlay, networks, they. Are organized, as nodes of a virtual, system of links that run on top of the Internet overlay, networks, have been around since the invention of networking, when computer, systems, were connected, over telephone, lines using. Modems before, any data network, existed. The. Most striking, example, of an overlay, network is the internet itself, the. Internet itself was initially built, as an overlay on the telephone, network. Even. Today each internet, node can communicate, with virtually, any other through an underlying, mesh of sub networks, of wildly, different, topologies, and technologies. Address. Resolution, and routing, are the means that allow mapping, of a fully connected, IP overlay. Network, to its underlying network. Another. Example, of an overlay, network is a distributed. Hash table, which Maps keys to nodes in the network in this. Case the underlying network. Is an IP network and, the overlay, network, is a table, actually a map indexed, by keys. Overlay. Networks, have also been proposed, as a way to improve, Internet routing such, as through quality, of service, guarantees, to achieve higher quality, streaming media. Previous. Proposals. Such as intserv, diffserv, and IP multicast, have, not seen wide acceptance, largely. Because, they require, modification. Of all routers in the network on the other, hand, an overlay, network can be incrementally. Deployed on end hosts, running the overlay, protocol, software. Without cooperation from. Internet, service providers, the. Overlay, network, has no control over how packets, are routed in the under, network, between two overlay, nodes but it can control for example the, sequence of overlay, nodes that a message, traverses. Before, it reaches its destination. For. Example, Akamai, Technologies, manages. An overlay, network that, provides reliable. Efficient. Content, delivery, a kind of multicast. Academic. Research includes, end system, multicast, resilient. Routing and quality, of service, studies among others. You. Topic. Communication. Protocols. A, communication. Protocol. Is a set of rules for exchanging. Information, over a network in a. Protocol, stack also, see the OSI, model each protocol. Leverages. The services, of the protocol, layer below it until, the lowest layer controls, the hardware, which sends, information across the media the. Use of protocol, layering is today ubiquitous. Across the field of computer networking. An, important. Example, of a protocol, stack is, HTTP. The world wide web protocol. Running over TCP. / IP the. Internet protocols. Override. Triple, E. 802.11. The Wi-Fi, protocol. This. Stack is used between the wireless, router and the home users personal, computer, when the user is surfing, the web. Communication. Protocols. Have various, characteristics. They. May be connection. Oriented or, connectionless, they may use circuit, mode or packet, switching, and they may use hierarchical. Addressing or, flat addressing. There. Are many communication. Protocols, a few, of which are described, below. You. Topic. I Triple. E 802. I Triple. E 802. As a family, of I Triple, E standards, dealing, with local area, networks, and metropolitan area. Networks. The. Complete, I Triple, E 802. Protocol. Sweep provides, a diverse, set of networking. Capabilities. The. Protocols. Have a flat addressing, scheme they, operate, mostly, at levels one and two of the OSI model. For. Example Mac, bridging, I Triple. E. 802.1. D deals with the routing of Ethernet, packets, using a spanning, tree protocol. I. Triple. E. 802.1. Q describes. VLAN. S and I Triple, E. 802.1. X defines, a port based network, access control, protocol, which forms the basis, for the authentication.
Mechanisms. Used in VLAN. S but it is also found in WLAN. S it is what the home user sees when the user has to enter a wireless. Access key. Topic. Ethernet. Ethernet. Sometimes. Simply, called LAN, is a family, of protocols used. In wired lands, described, by a set of standards, together called, I Triple, E, 802.3. Published. By the Institute of Electrical and. Electronics. Engineers. You. Topic. Wireless. LAN. Wireless, LAN, also, widely known as WLAN. Or Wi-Fi, is probably. The most well known member, of the I Triple, E 802. Protocol. Family, for home users today, it. Is standardized. By I Triple. E. 802.11. And, shares many properties. With wired Ethernet. You. Topic, Internet. Protocol, suite. The, Internet, Protocol, suite also called, tcp/ip. Is. The foundation. Of all modern networking. It. Offers, connection-less, as well as connection oriented services. Over an inherently, unreliable network. Traversed, by Datagram. Transmission. At the Internet, Protocol, IP level. At its. Core, the protocol, suite defines, the addressing. Identification. And routing. Specifications. For Internet, Protocol, version 4 ipv4. And. For ipv6, the, next generation. Of the protocol, with a much enlarged, addressing, capability. You. Topic. Sown, at SDH. Synchronous. Optical networking. So, net and synchronous, digital hierarchy. SDH. Are standardized. Multiplexing. Protocols, that transfer, multiple digital. Bit streams over optical, fiber using lasers. They. Were originally. Designed to transport, circuit, mode communications. From a variety of different sources, primarily. To support real-time uncompressed. Circuit, switched voice encoded. In PCM, pulse code modulation. Format. However. Due, to its protocol. Neutrality. And transport, oriented, features SONET. SDH also. Was the obvious choice for transporting. Asynchronous. Transfer mode ATM. Frames. You. Topic. Asynchronous. Transfer mode. Asynchronous. Transfer. Mode ATM. Is a switching, technique, for telecommunication. Networks, it. Uses asynchronous. Time division, multiplexing. And encodes, data into, small fixed, sized cells. This. Differs, from other protocols. Such as the Internet, Protocol, suite or, Ethernet, that use variable. Sized packets, or frames. ATM. Has similarity. With both circuit, and packet, switched networking. This. Makes it a good choice for a network that must handle both traditional. High throughput data, traffic, and real-time low, latency, content, such as voice and video. ATM. Uses, a connection-oriented, model, in which a virtual, circuit, must be established between, two endpoints before.
The Actual data exchange, begins. While. The role of ATM. Is diminishing, in favor of next generation, networks, it still plays a role in the last mile which is the connection, between an Internet service provider, and the home user. You. Topic. Cellular. Standards. There, are a number of different, digital cellular standards, including. Global, system, for mobile communications. Gsm. General. Packet radio service. GPRS. CDMA. One, CDMA. 2000. Evolution. Data optimized. Ev-do, enhanced. Data rates for, GSM, evolution edge. Universal. Mobile telecommunications. System. UMTS. Digital. Enhanced, cordless telecommunications. DECT. Digital, amps, is, 136. TDMA. An integrated. Digital enhanced. Network, iDEN. You. Topic. Geographic. Scale. A network. Can be characterized. By its physical capacity. Or its organizational. Purpose. Use. Of the network including. User authorization. And access, rights differ accordingly. Nano-scale. Network, on nanoscale, communication. Network has key components. Implemented, at the nano scale including. Message, carriers, and leverages, physical, principles, that differ from macroscale. Communication. Mechanisms. Nano. Scale communication. Extends, communication. To very small sensors and actuators, such as those found in biological systems. And also tends to operate in, environments, that would be too harsh for classical. Communication. Personal. Area network, of personal area, network, pan is a computer. Network, used for communication. Among computer, and different information. Technological. Devices close, to one person, some. Examples. Of devices that are used in a pan are personal, computers, printers, fax, machines, telephones. PDAs. Scanners. And even videogame, consoles, a pen. May include wired, and wireless devices, the. Reach of a pen, typically, extends, to 10 meters a wired. Pen is usually, constructed, with USB and firewire connections. While technologies. Such as Bluetooth, and infrared, communication, typically. Form a wireless, pan. Local. Area network, a local, area network LAN. Is a network, that connects computers. And devices in, a limited geographical. Area such as a home school, office, building, or closely, positioned. Group of buildings, each. Computer. Or device on, the network is, a node wired. Lands, are most likely based on Ethernet, technology, newer. Standards. Such as itu-t. G, H, n also provide, a way to create a wired LAN using existing, wiring, such, as coaxial. Cables, telephone. Lines and power lines the defining, characteristics. Of a LAN in contrast. To a wide area network. One include. Higher data transfer. Rate limited. Geographic, range and lack of reliance, on leased lines to provide connectivity. Current. Ethernet, or other I Triple. E, 802.3. Land, technologies. Operate. At data transfer. Rates up to 100. Gigabits, per second, standardized. By I Triple. E in 2010. Currently. 400. Gigabits, per second, Ethernet is, being developed a, land. Can be connected to a one using, a router. Home. Area, network a home area network han is a residential. Land used for communication. Between digital, devices, typically. Deployed, in the home usually a small, number of personal, computers, and accessories. Such, as printers, and mobile computing devices an. Important. Function as the sharing, of Internet access often, a broadband, service, through a cable, TV, or digital, subscriber, line DSL. Provider. Storage. Area, network, a storage, area network, San is a dedicated. Network that provides access to, consolidated. Block level data storage. Sans. Are primarily, used to make storage, devices, such, as disk, erase tape, libraries. And optical, jukeboxes. Accessible. To servers, so that the devices appear like locally, attached devices, to the operating, system. Ascend, typically, has its own network of storage, devices that, are generally, not accessible. Through the local area, network by, other devices. The. Cost and complexity, of sans dropped, in the early 2000s. To levels, allowing wider, adoption across, both enterprise. And small to medium sized business, environments. Campus. Area network, a campus, area network, can is made up of an interconnection. Of lands within a limited, geographical. Area, the. Networking, equipment, switches. Routers and, transmission. Media optical. Fibre copper, plant cat5, cable, line etc, are almost entirely, owned, by the campus, tenant owner an enterprise.
University, Government. Etc. For example, a university. Campus network. Is likely to link a variety, of campus, buildings to connect academic, colleges, or departments. The library, and student, residence, halls. Backbone. Network a backbone, network, is part of a computer, network infrastructure. That provides a path for the exchange, of information between. Different lands. Or sub networks, a, backbone. Can tie together diverse, networks. Within the same building, across different, buildings, or over a wide area. For. Example a large company, might implement, a backbone, network, to connect departments. That are located, around the world the. Equipment, that ties together the departmental. Networks, constitutes. The network backbone. When. Designing, a network backbone network. Performance, and network congestion are. Critical, factors, to take into account. Normally. The backbone, networks, capacity. Is greater than that of the individual, networks, connected, to it. Another. Example, of a backbone, network, is the internet backbone, which is the set of wide area networks, Wan's and core routers, that tie together all networks, connected, to the Internet. Metropolitan. Area network, a metropolitan. Area network, man is a large, computer, network, that usually, spans a city or a large campus. Wide. Area, network, a wide area network, one is a computer. Network, that covers, a large geographic. Area such as a city country. Or spans, even intercontinental. Distances, a one. Uses, a communications. Channel, that combines, many types of media such as telephone, lines cables. And airwaves, a one. Often makes use of transmission. Facilities. Provided, by common, carriers, such, as telephone, companies. One. Technologies. Generally function. At the lower three layers of the OSI reference, model, the, physical, layer the data link layer and, the network layer. Enterprise. Private, network and enterprise, private network, is a network that, a single, organization, builds. To interconnect, its office locations. Eg, production. Sites head offices, remote, offices, shops, so they can share computer, resources. Virtual. Private network, of virtual, private network, VPN is. An overlay, network in which some of the links between nodes are, carried by open, connections, or virtual, circuits, in some larger, network eg, the internet instead, of by physical, wires, the. Data link layer protocols. Of the virtual, network are, said to be tunneled through the larger, network when this is the case one. Common, application, as secure, communications. Through the public Internet, but a VPN, need not have explicit, security. Features, such as authentication, or, content, encryption. VPNs. For example, can be used to separate, the traffic, of different, user communities. Over, an underlying, network, with strong security features. VPN. May have best effort performance, or may have a defined, service, level agreement, SLA, between, the VPN, customer. And the VPN, service, provider. Generally. A VPN. Has a topology. More complex, than point-to-point. Global. Area network, a global, area network, gone is a network, used for supporting, mobile across an arbitrary, number of wireless, LANs satellite.
Coverage, Areas, etc, the. Key challenge, in mobile communications. Is handing off user communications. From one local coverage area to the next an I. Triple, E project, 802. This involves, a succession, of terrestrial wireless, LANs. You. Topic. Organizational. Scope. Networks. Are typically, managed, by the organizations. That own them private. Enterprise, networks, may use a combination of, Internet's, and extra nets they, may also provide, network, access to the Internet which has no single owner and permits, virtually, unlimited global. Connectivity. You. Topic. Intranet. An intranet. As a set of networks, that are under the control of a single administrative. Entity, the. Intranet uses, the IP protocol. And IP based, tools such as web browsers and file transfer, applications. The. Administrative. Entity, limits, use of the Internet to its authorized, users. Most. Commonly, an intranet, as the internal, land of an organization. A large. Intranet, typically, has at least one web server to provide users, with organizational. Information, an, intranet. Is also, anything, behind the router on a local, area network. You. Topic. Extranet. An extranet. As a network, that is also under the administrative. Control of a single organization, but supports, a limited, connection, to a specific, external, network, for. Example an, organization may. Provide access to some aspects, of its intranet, to share data with its business partners, or customers, these. Other entities, are not necessarily. Trusted. From a security, standpoint. Network. Connection, to an extranet, as often but not always implemented. Via one technology. You. Topic. Internetwork. An internetwork. As the connection, of multiple, computer, networks, via a common, routing technology. Using routers. You. Topic. Internet. The, Internet, is the largest example. Of an Internet work it is, a global, system, of interconnected, governmental. Academic. Corporate public. And private, computer, networks, it. Is based on the networking, technologies.
Of The Internet, Protocol, suite it is. The successor, of the Advanced, Research Projects. Agency Network, ARPANET, developed, by DARPA of the United, States Department of Defense the, Internet. Is also the communications. Backbone, underlying, the worldwide, web ww. Artists. Apin sin the internet use a diverse array of methods, of several, hundred, documented. And often standardized. Protocols. Compatible. With the Internet, Protocol, suite and, an addressing, system, IP addresses. Administered. By the internet, assigned numbers authority, and address, registries. Service. Providers, and large enterprises. Exchange. Information. About the reach ability, of their address, spaces, through the border gateway protocol. BGP. Forming, a redundant, worldwide, mesh of transmission. Paths. You. Topic. Darknet. A darknet. As an overlay Network typically. Running on the internet that is only accessible through, specialized. Software a. Darknet, as an anonymizing, network. Where connections, are made only between trusted, peers sometimes. Called. Friends. F2f. Using. Non-standard, protocols. And ports. Darknets. Are distinct, from other distributed. Peer-to-peer networks. As sharing, is anonymous, that as IP addresses. Are not publicly, shared and therefore, users, can communicate with, little fear of governmental, or corporate, interference. You. Topic. Routing. Routing. Is, the process, of selecting, network paths to carry network, traffic. Routing. Is performed, for many kinds of networks, including. Circuit, switching, networks, and packet, switched networks, in. Packet. Switched networks, routing, directs, packet, forwarding the, transit, of logically, addressed, network, packets, from their source toward their ultimate destination, through. Intermediate, nodes. Intermediate. Nodes are typically, network hardware, devices, such as routers bridges. Gateways. Firewalls. Or switches. General-purpose. Computers. Can also forward, packets and perform, routing, though they are not specialized. Hardware, and may suffer from limited, performance, the. Routing, process usually, directs. Forwarding, on the basis, of routing tables, which maintain, a record of the routes to various, network destinations. Thus. Constructing. Routing, tables, which are held in the routers memory, is very, important, for efficient, routing. There. Are usually multiple, routes, that can be taken and to choose between them, different, elements, can be considered, to decide which routes get installed, into the routing, table, such as sorted, by priority. Prefix. Length where longer subnet, masks, are preferred independent. If it is within a routing protocol, or over different routing protocol.
Metric, Where a lower metric, cost is preferred, only valid, within one and the same routing protocol. Administrative. Distance, where a lower distance, is preferred, only, valid, between different, routing protocols, most, routing, algorithms. Use only one network path at a time. Multipath. Routing techniques, enable. The use of multiple, alternative. Paths. Routing. In a more narrow sense, of the term is often contrasted, with bridging, in its assumption, that network, addresses, are structured, and that similar, addresses, imply proximity. Within the network. Structured. Addresses. Allow a single routing, table entry to, represent, the route to a group of devices in, large. Networks, structured. Addressing, routing, in the narrow sense outperforms. Unstructured, addressing. Bridging. Routing. Has become the dominant form of addressing, on the Internet bridging. Is still widely used within, localized, environments. You. Topic. Network, service. Network. Services, are applications. Hosted by servers, on a computer, network to provide some functionality. For members or users of the network or to help the network itself, to operate. The. Worldwide, web email printing. And network file sharing are examples, of well-known network, services. Network. Services. Such as DNS. Domain name, system, give names for IP and, MAC addresses. People, remember, names like n m dot land better than numbers, like to 100 dot 1 to. 1.67. Dot 18, and DHCP. To ensure that the equipment on the network has a valid, IP address. Services. Are usually, based on a service, protocol, that defines, the format and sequencing, of messages, between clients. And servers of, that network, service. You. Topic. Network. Performance. You. Topic. Quality-of-service. Depending. On the installation, requirements, Network, performance, is usually measured, by the quality of service, of a telecommunications. Product, the. Parameters. That affect, this typically, can include throughput, jitter bit error rate and latency. The. Following, list gives examples, of network, performance measures. For a circuit, switched network, and one type of packet, switched network, this. ATM. Circuit. Switched networks in circuit, switched networks network. Performance is, synonymous with the grade of service, the. Number of rejected, calls as a measure of how well the network is performing under heavy traffic, loads, other. Types, of performance, measures, can include the level of noise and echo. ATM. In an asynchronous, transfer, mode ATM. Network, performance, can be measured by line rate quality, of service QoS data. Throughput, connect, time stability. Technology. Modulation. Technique, and modem enhancements. There are many ways to measure the performance of a network as each network is different, in nature and design. Performance. Can also be modelled instead. Of measured, for, example, state, transition. Diagrams, are often used to model queueing performance, in a circuit, switch network, the. Network planner, uses, these diagrams. To analyze, how the network performs. In each state ensuring. That the network is optimally, designed. You. Topic. Network. Congestion. Network. Congestion occurs, when, a link or node is carrying, so much data that its quality, of service, deteriorates. Typical. Effects, include, queuing, delay packet, loss or the blocking of new connections a. Consequence. Of these latter two is, that incremental, increases, in offered load lead either only to small increase, in network throughput or to an actual, reduction in, network throughput. Network.
Protocols. That use aggressive, retransmissions. To compensate, for packet loss tend, to keep systems, in a state of network, congestion. Even. After the initial, load is reduced to a level that would not normally induce, network, congestion. Thus. Networks. Using these protocols. Can exhibit two stable, States under the same level of load the. Stable, state with low throughput, is known as congestive, collapse. Modern. Networks, use congestion. Control congestion, avoidance, and, traffic, control techniques, to try to avoid congestion collapse. These. Include, exponential. Back-off in protocols. Such, as 802. 11. Csma/ca. In the original, Ethernet window, reduction, in TCP. And fair queuing, in devices, such as routers. Another. Method, to avoid the negative effects, of network congestion as, implementing. Priority, schemes so that some packets, are transmitted, with higher priority. Than others. Priority. Schemes do not solve network, congestion by, themselves. But they help to alleviate the effects of congestion, for some services, an, example. Of this is. 802.1. P a third. Method to avoid network, congestion as. The explicit, allocation. Of network resources, to specific, flows, one. Example, of this is the use of contention. Free transmission. Opportunities. Cf, t XO p s in the itu-t. Ghn, standard, which provides, high speed up, to 1 gigabit per. Second, local area networking, over existing, home wires power lines phone lines and coaxial, cables. For, the Internet, RFC. 2914. Addresses. The subject, of congestion, control in detail. You. Topic. Network, resilience. Network, resilience. Has the ability to provide, and maintain an acceptable level, of service, in the face of faults, and challenges, to normal, operation. You. Topic. Security. You. Topic. Network. Security. Network. Security consists. Of provisions, and policies, adopted by the network, administrator to. Prevent, and monitor unauthorized. Access misuse. Modification. Or denial, of the computer, network, and its network accessible, resources. Network. Security, is the authorization. Of access, to data in a network, which is controlled, by the network, administrator. Users. Are assigned an ID and password that, allows them access to information and. Programs, within their authority. Network. Security is used on a variety of computer, networks, both public, and private to, secure, daily transactions. And communications. Among businesses. Government, agencies and. Individuals. Topic. Network surveillance, network, surveillance, as the monitoring, of data being, transferred, over computer, networks, such as the internet the. Monitoring, is often, done surreptitiously. And may be done by or at the behest of governments. By corporations, criminal.
Organizations. Or individuals. It. May or may not be legal in may or may not require, authorization, from. A court or other independent. Agency. Computer. And network surveillance, programs. Are widespread today. And almost, all Internet, traffic is, or could potentially be, monitored, for clues to illegal, activity. Surveillance. Is very useful, to governments. And law enforcement to. Maintain social, control, recognize. And monitor threats, and prevent, investigate. Criminal activity. With. The advent of programs, such as the Total Information Awareness, program. Technologies. Such as high-speed surveillance. Computers, and biometric software. And laws such as the communications. Assistance, for Law Enforcement Act. Government's. Now possess, an unprecedented. Ability, to monitor, the activities, of citizens, however many, civil, rights and privacy, groups such. As reporters. Without borders. The Electronic. Frontier Foundation and. The American Civil Liberties Union, have, expressed, concern, that increasing, surveillance, of citizens may, lead to a mass surveillance society. With limited, political and, personal freedoms. Fears. Such as this have led to numerous lawsuits, such, as hep ting V. AT&T. The. Hacktivist, group Anonymous has. Hacked into government, websites, in protest, of what it considers, draconian, surveillance. You. Topic. End to, end encryption. End-to-end. Encryption. E to EE is, a digital, communications. Paradigm, of uninterrupted, protection. Of data travelling between two, communicating. Parties, it. Involves, the originating, party, encrypting, data so, only the intended recipient. Can decrypt it with no dependency. On third parties. End-to-end. Encryption. Prevents. Intermediaries. Such as internet, providers, or application. Service, providers, from discovering, or tampering, with communications. End-to-end. Encryption, generally. Protects, both, confidentiality. And integrity. Examples. Of end-to-end encryption. Include. HTTPS. For web traffic, PGP. For email OTR. For instant, messaging, ZRTP. For, telephony and Tetra, for radio. Typical. Server based, communication. Systems, do not include, end-to-end, encryption. These. Systems, can only guarantee protection. Of communications. Between clients. And servers not between the communicating. Parties themselves. Examples. Of non e to EE systems. Are Google Talk Yahoo Messenger, Facebook. And Dropbox. Some. Such systems, for example lavabit. And secreting, have even described, themselves as, offering, end-to-end. Encryption. When they do not some. Systems, that normally, offer end-to-end, encryption. Have turned out to contain a backdoor, that subverts, negotiation. Of the encryption, key between the communicating. Parties for, example Skype. Or hush mail. The. End-to-end, encryption, paradigm. Does not directly, address risks. At the communications. Endpoints. Themselves, such as the technical, exploitation. Of clients, poor quality random, number generators. Or key, escrow e, to. EE also, does not address traffic, analysis. Which relates, to things such as the identities, of the endpoints and the times and quantities, of messages, that are sent. You. Topic. Ssl/tls. The, introduction. And rapid, growth of e-commerce on, the worldwide web in, the mid-1990s, made. It obvious that some form of authentication, and, encryption was, needed. Netscape. Took the first shot at a new standard, at the, time the dominant web, browser was, Netscape, Navigator. Netscape. Created, a standard called, secure, socket, layer SSL. SSL. Requires, a server, with a certificate, when. A client, requests, access to an SSL, secured, server the server sends a copy of the certificate to, the client, the. SSL. Client checks, this certificate all web browsers come. With an exhaustive. List of CA root, certificates. Pre-loaded, and if the certificate checks, out the server is authenticated.
And The client negotiates. A symmetric, key cipher. For use in the session, the. Session is now in a very secure, encrypted, tunnel between the SSL, server and the SSL, client. You. Topic. Views, of networks. Users. And network administrator's. Typically. Have different, views of their networks, users. Can share printers, and some servers, from a workgroup which, usually means, they are in the same geographic. Location. And are on the same land whereas a network, administrator is. Responsible, to keep that network, up and running a, community. Of interest has less of a connection of being in a local, area and should be thought of as a set of arbitrarily. Located. Users, who share a set of servers and possibly. Also communicate. Via peer-to-peer, technologies. Network. Administrators. Can see met works from both physical and logical perspectives. The, physical, perspective involves. Geographic. Locations. Physical, cabling, and the network elements, eg routers. Bridges, and application. Layer gateways, that interconnect. Via the transmission. Media. Logical. Networks, called, in the tcp/ip. Architecture. Subnets. Map onto one or more transmission. Media, for. Example a, common practice in a campus, of buildings, as to make a set of LAN cables, in each building appear to be a common, subnet, using, virtual, land VLA and technology. Both. Users, and administrators are. Aware to varying extents of the trust, and scope characteristics. Of a network. Again. Using, tcp/ip. Architectural. Terminology. An intranet as a community, of interest under private, administration. Usually, by an enterprise, and is only accessible, by authorized. Users, eg, employees. Internet's. Do not have to be connected, to the internet but generally, have a limited, connection an, extranet. As an extension, of an internet, that allows secure. Communications. To users outside of the intranet eg, business partners. Customers and officially. The Internet as the set of users, enterprises. And content. Providers that, are interconnected, by Internet, service providers, ISP. From. An engineering, viewpoint, the internet is the set of subnets, and aggregates, of subnets, which share the registered. IP address, space and exchange, information about, the reach ability, of those IP addresses. Using the border gateway protocol. Typically. The human readable names of servers, are translated. To IP addresses. Transparently. To users, via the directory, function, of the domain name System, DNS. Over. The Internet, there can be business-to-business. B2b. Business. To consumer, b2c. And consumer. To consumer, c2c. Communications. When. Money or sensitive, information is, exchanged. The communications. Are apt to be protected, by some form of communication, security. Mechanism. Intranets. And extra, nets can be securely, superimposed. Onto the internet without any access, by general, Internet users, and administrators, using. Secure, Virtual Private Network VPN technology. You. Topic. Journals. And newsletters. Open. Computer, science, open access journal. Topic. C also. Comparison. Of network diagram, software. Cyberspace. History. Of the internet. Network. Simulation. Network. Planning and design. Network. Traffic, control. Minimum. Pairs protocol.
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