Computer Network Assignment A134396 & A133765

Computer Network

  Introduction  

Computer network technology continues to advance, and this is resulting in the availability of new and improved hardware and services along with greater ease of use and lower cost. Among the many areas of development are ad hoc networks, which can be created instantly as needed and can then dismantled just as quickly, and networks of things, which can include virtually any item in a network through the use of technologies such as RFID (radio frequency identification) tags and IPv6 (Internet protocol version 6) addressing. However, it is important to keep in mind that along with all of these advances come new dangers, as is typically the case with technological advance.



A computer network, also referred to as just a network, consists of two or more computers, and typically other devices as well (such as printers, external hard drives, modems and routers), that are linked together so that they can communicate with each other and thereby exchange commands and share data, hardware and other resources.

The devices on a network are referred to as nodes. They are analogous to the knots in nets that have traditionally been used by fishermen and others. Nodes can be connected using any of various types of media, including twisted pair copper wire cable, optical fiber cable, coaxial cable and radio waves. And they can be arranged according to several basic topologies (i.e., layouts), including bus (in which all nodes are connected along a single cable), star (all nodes are connected to a central node), tree (nodes successively branch off from other nodes) and ring.

The smallest and simplest networks are local area networks (LANs), which extend over only a small area, typically within a single building or a part thereof. A home network is a type of LAN that is contained within a user's residence. Wide area networks (WANs) can extend over a large geographic area and are connected via the telephone network or radio waves. A metropolitan area network (MAN) is designed to serve a town or city, and a campus area network is designed to serve a university or other educational institution.

An intranet is a private network within an organization that uses the same communications protocols as the Internet. When part of an intranet is made accessible to suppliers, customers or others outside the organization, that part becomes an extranet.

An internet (spelled with a lower case i) is a network that is composed of a number of smaller computer networks. The Internet (spelled with an upper case I) is the world-wide network of interconnected internets that operates using a standardized set of communications protocols called TCP/IP (transmission control protocol/Internet protocol), or the Internet protocol suite. This ultimate internet is vastly larger than any other internet and connects thousands of networks and hundreds of millions of computers throughout the world.

A protocol defines a common set of rules and signals that computers on the network use to communicate. TCP/IP is not only the protocol of the Internet, but it has also become the dominant protocol for computer networks of virtually all types. Originally developed for use in UNIX, TCP/IP is now built into virtually all major computers. Reasons for its success, and thus for the astonishing success of computer networks in general, include the facts that it is intelligent, robust, compatible with nearly all types of hardware and operating systems, relatively simple and free software (which means that it free with regard to both cost and use).

An important feature of modern computer networks, at least when Linux and other Unix-like operating systems are used, is network transparency. This means that a users can access resources (e.g., application programs or data) without needing to know, and usually not being aware of, whether the resources are located on the local (i.e., the computer which the user is currently using) or on a remote machine (i.e., a computer elsewhere on the network). Network transparency can be a major convenience to users, as it relieves them from having to be concerned about the details of the structure of the network and of having to take special steps to access remote data. It can also help simplify the tasks of program developers and system administrators.

  Background  

The field of computer networking and today's Internet trace their beginnings back to the early 1960s, a time at which the telephone network was the world's dominant communication network. The global Internet's origin was the Advanced Research Projects Agency Network (ARPANET) of the U.S. Department of Defense in 1969. Here are some of the highlights of the progression of computer networking within the last 35 years.

1974 - Ethernet is demonstrated by networking Xerox PARC’s new Alto computers.

1978 - The appearance of the first very small computers and their potential for communication via modem to dial up services.

1981 - Bill Joy incorporates the new TCP/IP suite into the next release of the UNIX operating system. The first “portable” computer is launched in the form of the Osborne, a 24 pound suitcase sized device.

1981 - The IBM PC is launched

1982 - TCP/IP (Transmission Control Protocol and Internet Protocol) is established as the standard for ARPANET.

1983 - ARPANET standardizes on the TCP/IP protocols adopted by the Department of Defense.

1986 - TCP/IP is available on workstations and PCs such as the newly introduced Compaq portable computer.

1987 - The number of network hosts breaks 10,000.

1989 - The number of hosts breaks 100,000.

1990 - ARPANET formally shuts down. Several search tools, such as ARCHIE, Gopher, and WAIS start to appear.

1991 - The NSFNET backbone upgrades to T3 (44 Mbps). A wide-area network developed under the auspices of the National Science Foundation. NSFnet replaced ARPANET as the main government network linking universities and research facilities.

1991- Tim Berners-Lee develops the World Wide Web. Lee is the director of the World Wide Web Consortium, which oversees its continued development. CERN also releases the first Web server.

1992 - The WWW bursts into the world and the growth of the Internet explodes.

Computers were originally stand-alone systems that consisted of a mainframe that was connected to a number of input and output devices (mainly keyboards, punched card reading/punching machines and printers). The ability for multiple computers to be connected over long distances began in 1969 at the University of California at Los Angeles (UCLA) with the development of ARPANET, which was established by the U.S. Defense Advanced Research Project Agency. This ability has made computers vastly more powerful and useful, because it has, in effect, made the network into a computer1.

Networks have existed as long as there have been communications. Indeed, networking is an inherent part in any natural system, whether it be a single organism (in which the cells and other body parts communicate via electrical and chemical signals), an ecosystem (in which the various organisms communicate through sensing organs, chemicals and other means) or even a planetary system (in which the various bodies are connected through gravity, solar radiation, etc.)

The first long distance human communication networks were formed using runners2, smoke signals, drum beats and semaphores. The first type of electrical network was the telegraph, which began operation around 1833 in the UK. Telephone networks began replacing the already extensive telegraph networks soon after Alexander Graham Bell received his patents for the telephone in 1876. Computer networks started out by operating over telephone networks that were designed primarily to carry voice traffic. But now computer networks are rapidly moving to replace telephone networks as the dominant type of network, and voice traffic, in the form of VoIP (voice over Internet protocol), is just one of many types of traffic carried by such networks.

  Benefits  

A network isn't just a bunch of computers with wires running between them. Properly implemented, a network is a system that provides its users with unique capabilities, above and beyond what the individual machines and their software applications can provide.

Most of the benefits of networking can be divided into two generic categories: connectivity and sharing. Networks allow computers, and hence their users, to be connected together. They also allow for the easy sharing of information and resources, and cooperation between the devices in other ways. Since modern business depends so much on the intelligent flow and management of information, this tells you a lot about why networking is so valuable.

File Sharing: Networks offer a quick and easy way to share files directly. Instead of using a disk or USB key to carry files from one computer or office to another, you can share files directly using a network.

Software Cost and Management: Many popular software products are available for networks at a substantial savings in comparison to buying individually licensed copied for all of your computers. You can also load software on only the file server which saves time compared to installing and tracking files on independent computers, it also make upgrades are also easier because changes only have to be done once on the file server instead of on individual workstations.

Data Security and Management: Specific directories can be password protected to limit access to authorized users. Also, files and programs on a network can be designated as "copy inhibit" so you don’t have to worry about the illegal copying of programs.

Resource Sharing: All computers in the network can share resources such as printers, fax machines, modems, and scanners.

Communication: Even outside of the internet, those on the network can communicate with each other via electronic mail over the network system. When connected to the internet, network users can communicate with people around the world via the network.

Flexible Access: Networks allow their users to access files from computers throughout the network. This means that a user can begin work on a project on one computer and finish up on another. Multiple users can also collaborate on the same project through the network.

Workgroup Computing: Workgroup software like Microsoft BackOffice enables many users to contribute to a document concurrently. This allows for interactive teamwork.

Performance Enhancement and Balancing: Under some circumstances, a network can be used to enhance the overall performance of some applications by distributing the computation tasks to various computers on the network.

Entertainment: Networks facilitate many types of games and entertainment. The Internet itself offers many sources of entertainment, of course. In addition, many multi-player games exist that operate over a local area network. Many home networks are set up for this reason, and gaming across wide area networks (including the Internet) has also become quite popular. Of course, if you are running a business and have easily-amused employees, you might insist that this is really a disadvantage of networking and not an advantage!

  Network classification   

The following list presents categories used for classifying networks.

===Connection method === Computer networks can be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as optical fiber', Ethernet, wireless, HomePNA, 'power line communication' or 'G.hn.

Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches, bridges, or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium. ITU-T' 'G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network. ===

=== ===Wired technologies === § Twisted pair wire is the most widely used medium for telecommunication. Twisted-pair wires are ordinary telephone wires which consist of two insulated copper wires twisted into pairs and are used 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 2 million bits per second to 100 million bits per second.'''

§ Coaxial cable is widely used for cable television systems, office buildings, and other worksites for local area networks. The cables consist of copper or aluminum wire wrapped with insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer. The layers of insulation help minimize interference and distortion. Transmission speed range from 200 million to more than 500 million bits per second.

§ Optical fiber cable consists of one or more filaments of glass fiber wrapped in protective layers. It transmits light which can travel over extended distances. Fiber-optic cables are not affected by electromagnetic radiation. Transmission speed may reach trillions of bits per second. The transmission speed of fiber optics is hundreds of times faster than for coaxial cables and thousands of times faster than a twisted-pair wire.'''

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=== ===Wireless technologies === § Terrestrial microwave – Terrestrial microwaves use Earth-based transmitter and receiver. The equipment looks similar to satellite dishes. Terrestrial microwaves use low-gigahertz range, which limits all communications to line-of-sight. Path between relay stations spaced approx, 30 miles apart. Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks.

§ Communications satellites – The satellites use microwave radio as their telecommunications medium which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically 22,000 miles (for geosynchronous satellites) above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.

§ Cellular and PCS systems – Use several radio communications technologies. The systems are divided to different geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area.

§ Wireless LANs – Wireless local area network 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. An example of open-standards wireless radio-wave technology is IEEE.

§ Infrared communication, which can transmit signals between devices within small distances not more than 10 meters peer to peer or (face to face ) without any body in the line of transmitting.

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=== ===Scale === Networks are often classified as local area network' (LAN), 'wide area network (WAN), metropolitan area network (MAN), personal area network (PAN), virtual private network (VPN),campus area network (CAN), storage area network (SAN), and others, depending on their scale, scope and purpose, e.g., controller area network (CAN) usage, trust level, and access right often differ between these types of networks. LANs tend to be designed for internal use by an organization's internal systems and employees in individual physical locations, such as a building, while WANs may connect physically separate parts of an organization and may include connections to third parties. ===Functional relationship (network architecture) === Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., active networking, client–server and peer-to-peer (workgroup) architecture. ===

=== ===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. Network topology is the coordination by which devices in the network are arranged in their logical relations to one another, independent of physical arrangement. Even if networked computers are physically placed in a linear arrangement and are connected to 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. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks.

Two Types of networks based on physical scope:
  LOCAL AREA NETWORK (LAN ''' ) '''

Local Area Network (LAN) is the smallest network compared to the other two networks.The simplest form of LAN is to connect two computers together.LAN is operated within a limited physical area, such as at home, school, a single building or several buildings.A network which consists of less than 500 interconnected devices across several buildings, is still recognised as a LAN. Inexpensive hardware used in LAN previously include twisted pair, coaxial cables and the higher end is fiber optic or wireless. However, coaxial cables are now being replaced by a higher speed cabling system such as CAT5 using RJ45 connectors.

 METROPOLITAN AREA NETWORK (MAN) 

MAN can be defined as a group of computers and network devices connected together within a large physical area. First, you have to understand the word metropolitan. Metropolitan describes important cities such as Kuala Lumpur, Manila, Singapore, Tokyo, London and New York. MAN is a network of computers located at different sites within a large physical area, such as a city. Companies that have several branches within the Kuala Lumpur city such as banks, might find a MAN useful to them. In this case, setting up a MAN across long distances can be best connected using fiber optics. Sometimes, a MAN can be a collection of several LANs within the same city. MAN often acts as a high speed network (although not as fast as a LAN) to allow sharing of regional resources.

==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 802.12) or optical cable ("optical fiber"). ===Network interface cards === 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.

===Repeaters === A repeater is an electronic device that receives a signal, cleans it of unnecessary noise, regenerates it, and retransmits it 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. Repeaters work on the Physical Layer of the OSI model. ===Hubs === A network hub contains multiple ports. When a packet arrives at one port, it is copied unmodified to all ports of the hub for transmission. The destination address in the frame is not changed to a broadcast address. It works on the Physical Layer of the OSI model.. ===Bridges === A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges broadcast to all ports except the port on which the broadcast was received. However, bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address to that port only.

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: ===Switches === A network switch is a device that forwards and filters OSI layer 2 datagrams (chunk of data communication) between ports (connected cables) based on the MAC addresses in the packets. A switch is distinct from a hub in that it only forwards the frames to the ports involved in the communication rather than all ports connected. A switch breaks the collision domain but represents itself as a broadcast domain. Switches make forwarding decisions of frames on the basis of MAC addresses. A switch normally has numerous ports, facilitating a star topology for devices, and cascading additional switches.[9] Some switches are capable of routing based on Layer 3 addressing or additional logical levels; these are called multi-layer switches. The term switch is used loosely in marketing to encompass devices including routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier). ===Routers === A router is an internetworking device that forwards packets between networks by processing information found in the datagram or packet (Internet protocol information from Layer 3 of the OSI Model). In many situations, this information is processed in conjunction with the routing table (also known as forwarding table). Routers use routing tables to determine what interface to forward packets (this can include the "null" also known as the "black hole" interface because data can go into it, however, no further processing is done for said data).
 * Local bridges: Directly connect local area networks (LANs)
 * 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 with routers.
 * Wireless bridges: Can be used to join LANs or connect remote stations to LANs.

  Conclusion:  

As the nowadays technology improvement network will be a part from today's relatively ones that simply carry packets from one end to the other. With the explosion of Peer-To-Peer high definition video streaming and ubiquitous computing projects like Internet are looking at a scenario where even light bulbs and toasters will have an Internet Protocol (IP) address in affect making household compliances capable of accessing as well as being controlled by the internet. This said networks of the future will look different and will most probably work on different protocols. Such networks will not need full time chaperoning which is the job of many a systems administrator. Thus, user must use wisely the network in their daily life because many advantages can obtained from here.

  References:  

i. 'http://en.wikipedia.org/wiki/Computer_network

'''ii. http://www.linfo.org/network.html''

'''iii. http://www.onlinecomputertips.com/networking/networking_history.html'''

'''iv. http://www.linfo.org/network.html''

v. 'http://www.tcpipguide.com/free/t_TheAdvantagesBenefitsofNetworking.htm

'''vi. http://www.spamlaws.com/network-advantage.html'''

'''vii. http://wapedia.mobi/en/Computer_network''

'''viii. http://compnetworking.about.com/od/basicnetworkingconcepts/a/network_types.htm''