Computer networks in detail
In this article, I will explain computer networks in detail. In this I explained types of networks including Point-to-Point system, Client-server system, Types of networks / network classes and Network Topology in detail with the help of neat sketches.
The biological life as a whole is certainly the highest form of networking dar. which it will not go here. We use in daily life, many different technical networks. In a small selection of electrical and electronic networks are power supply networks, circuit-switched telephone networks, radio-television-radio networks, including broadband cable networks and in the last few decades to name the computer networks and wireless telephone networks.
In a network or network many participants are joined and / or connected to each other. By networking is possible to share information or to common facilities to access the resources that the individual can not usually afford. Here are some examples:
These few examples suggest a variety of network types including different rules of use, close the logs. The following statements deal primarily with computer networks. Point-to-Point system
The simplest cell in the network is a direct connection between two users or nodes. Both nodes are independent and have all the necessary hardware and software (English peer, the peer). This arrangement is a self-contained point-to-point connection. If additional computing nodes switched on, the result is an equal to the node network. Each node can claim and provide services. The peer-to-peer, P2P network is fully functional when all nodes are connected directly to each other. Switched off or the failure of a single node on the full functionality is limited.
In point-to-point networks structures can be formed, in which individual nodes together perform certain tasks. There will overlay networks that operate independently from the rest of P2P network. You can set the connected nodes special search functions and their evaluations. Gnutella and Freenet use as well as the bit torrent method structured overlay networks, and ultimately a direct connection between two peers is established for data exchange.Client-server system
In this computer network, many client computers are connected to a server computer. The system serves the task distribution and is found in many application areas. It is based on at least two separate software programs with different tasks.
The server, english for providers, service is installed on the central server computer running computer program, providing a particular service. The server is passive and waits for the client's request, english for customer. An installed on the user or client PC standalone client program calls the service running on the server to solve specific tasks. The server program responds to the client program and provides the service. The execution of a requested service, or data exchange takes place via a protocol created for this service. The following are some examples of known client-server systems and their protocols.
With simple terminal computers as client PCs that are connected to a central server, digitized inventory catalogs of large libraries to query. ATMs and printers work on the client-server system.Network types
With the types of course are not meant individuals who operate a network or hang around in it. A parent typing is performed by the spatial extent in which the network is operated. Network classes is a term used in this context accordingly. The following list describes the way rather bullet points known types in free order.LAN - Local Area Network
It is a localized computer network within a company headquarters, a company department, large offices, a work space with a few networked hardware components. The merger takes place mostly with Twisted-pair cables or split LANs through fiber optic cable. Twisted-pair cable allow for easy network expansion to 100 meters. The achievable data rates are between 10 ... 1000 Mbit / s A maximum data stream of 100 MB / s is realistic.WiFi - Wireless Local Area Network
A wireless, wireless connection built up on LAN. In the consumer area, there are limited in the range of variants of the IEEE 802.11 group. In some countries, Wi-Fi is synonymous with Wi-Fi. The computers within the wireless range are available on mobile phones. The data transfer rates are very low and depends on the location. A wireless network must necessarily be secured with special encryption techniques to prevent unauthorized use.MAN - Metropolitan Area Network
A normally connected by high-speed fiber optic cable network. It includes important business centers along major cities and economic centers of a region in a ring structure. The simple extension of a MAN can reach 100 km. Network operators and telecommunications companies are major providers of broadband cable television.WAN - Wide Area Network
This particular computer network is a wide area network that can extend across countries and continents. The number of computers connected in WAN is not fixed. A WAN connects several LANs, but can also have individual computers in the network. The computer can work only at the physical and data link layer and use a uniform addressing system. To the network operators include telecommunications (TC) companies and Internet service providers. In the conventional telecommunications networks with copper lines, the data transfer rate is 64 k bit / s per channel. The ISDN system with 32 channels per line can combine 30 data channels, which increases the data transfer rate to around 2 M bit / s. Other lines linked to process and especially the connection with fiber optic cables allow the WAN transmission rates up to 10 G bit / sGAN - Global Area Network
It combines some global wide area networks. GAN distributed by a company to an international company locations are connected worldwide. The remote connections use fiber optic technology and satellite radio. GAN can be sealed off to the outside scientific research networks. The Internet can be described as an open GAN. The transmission rate in the copper conductor is identical to the WAN.CAN - City Area Network
A lesser known telecommunications network with a simple radius to 5 km. It also includes public road networks and connects LANs urban branch operations. University and Institute of networks in the area of ??science and research can also be CNs are then more likely called Campus Area Network.PAN - Personal Area Network
In addition to the home LAN is the smallest network. The connection establishment and use of the network are only short term. The main network components, mobile phones, PDAs, MP3 players that are connected in the network in part by radio, wirelessly via Bluetooth and IrDA (Infrared Data Association) as well as via USB or Firewire cables.PLC - Power line Communication
The company Siemens and several others have developed for the low-voltage power grids, 230 V household networks, a data transmission system, the transmission rate can be achieved by 1 Mbit / s. The advantage is the multiple use of an existing pipeline network coverage. In addition to the disadvantage of low transmission rate is the increase of the EMS values ??of the electromagnetic radiation. For the higher frequency radiation health hazards are not explored. The long-range commercial use fails to date on various appeals and the lack of compatibility between the power supply vendors.Powerline - DLAN
It uses PLC as the existing low voltage power network. It is also under HomePlug, a well-known trademarks. The frequency range is mainly used between two ... 30 MHz. The achievable transmission rates depending on the system with 10 ... 200 Mbit / s, much higher than PLC. Since the cable acts as an antenna network, the data traffic should be encrypted. The DLAN adapter can interfere with the proven HF Amateur Radio, various safety radio equipment, air, sea and weather radio services. Outlets on different phases in the star-power network without existing phase couplers are not suitable for network construction with the DLAN.SAN - Storage Area Network
It is a storage area network, in parallel to an existing primary power, as will be operated, for example, LAN. All data storage are connected via a bus system installed with glass fiber. The potentially wide distributed data storage protocols are summarized by an overall unit and managed. The exchange of data within a SAN is perfect, redundantly and independently several times from the primary network, which network failures and congestion can be avoided.
All servers of the primary network have access to all data stored on the SAN and the free space available there. The separation of the two networks with different data protocols ensures high data security and data rates of 10 G bit / sEthernet - Fast Ethernet
Both types of networks are not independent, but partially to be counted. The Ethernet corresponds to a set standard for data networks. Traffic is controlled by specific protocols. The data is in the base band, ie unmodulated transmitted. The newer high-speed networks use a modulation method. The wired network based on coaxial cable and is today mainly done by twisted pair cables. The bit rate it reached 10 M bit / s The development of this concept is the Fast Ethernet. The data is transmitted through twisted-pair cables, but increasingly through fiber-optic lines with bit rates of 100 M bit / s and higher.Internet
Even the well-known Internet is not a separate type of network. It is a global network and connects many types of networks among themselves based on the TCP / IP protocols. The origins lie in 1972 in the Hawaiian island of radio ALOHA, in the Ethernet, English for ether .., radio network was renamed in 1976 and retained this name even in circuit switching.Network Topology
Topology is the study of the position and arrangement of geometric structures in space. Describes the network topology as the network elements or nodes are physically connected to the network structure. To the network nodes include active and passive components. When the computers are actually only the network cards. Nodes are also peripheral devices such as printers, scanners, and network components such as repeaters, hub, router, switch , required for the merger and expansion of networks. The physical connection can be wireless as well wired. The three basic topologies are ring, star and bus topology. They can be combined to more complex topologies such as tree and mesh structures.Bus structure
To a central line, bus, all nodes are connected. The bus is a RG-58 coaxial cable with 50 O impedance, which must be completed to avoid signal reflections at its open ends with 50 O resistors. The components are connected via coaxial BNC-T adapters. Between the nodes, there are no active components for signal conditioning and also the nodes behave passively in this regard.
The best known example of this is the Ethernet bus structure in the simplest form 10 Base-2 with a data rate of 10 M bit / s It is also thin-wire Ethernet called or ThinNet. A wire segment is limited to 185 m. Maximum of 30 nodes can be connected. The cable length between two nodes must be at least 0.5 m.
On the bus, only the signals of a node can be sent undisturbed for direct data exchange in the baseband process. A second node sends signals to the allocated bus is over-bearing which is referred to as collision. The data is no longer usable.
Particular advantages of bus topology are:
Important disadvantages of bus topology are:Star structure
All network nodes are connected directly to a central node. The central node may be active or passive network component. The terminal computer and the above-illustrated client-server system are connected in a star topology with the central computer as the active node. The peer-to-peer network with a central hub or passive active multi-port repeater is physically connected in a star structure. The traffic always goes through the central node.
The wiring is mostly over twisted pair cable with RJ45 connectors. The number of nodes is determined by the provided connectivity of the central node. The normal data rate reaches 10 Mbit / s The traffic through the central node corresponds to a point-to-point connection.
The main advantages of the star topology are:
Specific disadvantages of star topology are:Ring structure
All components in the ring are equal and directly connected to your network card, the actual node with its predecessor and successor. Data traffic passes through the entire ring in a predetermined direction. Since the network cards have repeater functions and regenerate the data signals to many nodes can join together to large ring structures. The failure of a component blocked the entire ring. With a double ring structure of the network receives a redundancy that can intercept this error and prevent the case. Fiber-optic cables can be data rates up to 100 Mbits / s and achieve distances up to 200 km. The traffic needs with the token passing protocol with a specific transport addressing. The ring structure is known the token ring.
Among the advantages of the ring structure include:
Important disadvantages of the ring structure are:
The left image shows the simple ring topology, the active network component is installed in the workstation's network card. The right image is an improved, secure against power station failures ring. The workstations, the hosts are connected radially with twisted-pair cables to the actual ring components. Several of these active loop distribution (RLV) or multistation access units (MAUs or MSAU) can be combined to form a large ring system. They automatically recognize the connected or disconnected hosts and grind the data signals through it. The ring with fiber optic connection allows data rates up to 100 M bit / s The method is specified to 1 G bit s /. Another chapter provides information about cable types and their properties .Tree
A network structure in tree topology is built up from combined star structures. In many mainframe systems, the central computer is the top node as the root. It is connected to a star coupler which is connected to another star distributors in communication in which the host is connected. The tree structure is hierarchical. The path to less important network components via multiple distribution uplinks to the central computer.
The advantages of the tree structure are:
The disadvantages of the tree are:Mesh structure
Each node is connected by point-to-point connections with various other nodes. All nodes are directly connected with each other, you get a fully meshed network. Almost all long-distance networks working in a mesh topology. Intelligent routing, data bottlenecks or failures can be circumvented.
The advantages of mesh topology are:
The disadvantages of mesh topology are:
By end-user computing we are interested in the capability provided by a user's computing environment and how these can be even more of use to the end user. End user computing empowers people by bringing computing power at their disposal. End users can be computer novices or experts. This means that computers can make the work of a variety of people easier especially with advent of miniature devices which can be used in different environments. End-user computing knit together the technology and the technology users.
Over the years computer technology and computer programs and packages have become increasingly complicated for the end-user to fully benefit from them. Programs are too lengthy to follow and devices too complex to operate as researchers try to reduce the learning curve of the end user. We need ways of rethinking our computing environment from the basics so as to make it more useful to the end-user.