Computer Network Assignment A134214 & A12453 & A134723

INTRODCUTION

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. While networking is creating a group of acquaintances and associates and keeping it active through regular communication for mutual benefits.

BACKGROUND
At the same time as the academic and research communities were creating a network for scientific purposes, a lot of parallel activity was going on elsewhere building computer networks as well.

A lot of the West Coast hackers belonged to the Homebrew Computer Club, founded by Lee Felsenstein. Lee had actually begun networking computers before the development of the PC, with his Community Memory project in the late 1970s. This system had dumb terminals (like computer screens with keyboards connected to one large computer that did the processing). These were placed in laundromats, the Whole Earth Access store, and community centres in San Francisco. This network used permanent links over a small geographical area rather than telephone lines and modems.

The first public bulletin board using personal computers and modems was written by Ward Christensen and Randy Seuss in Chicago in 1978 for the early amateur computers. It was about 1984 that the first bulletin boards using the IBM (Bill Gates/Microsoft) operating system and Apple operating systems began to be used. The most popular of these was FidoNet.

At that time the Internet technologies were only available on the UNIX computer operating system, which wasn't available on PCs. A piece of software called ufgate, developed by Tim Pozar, was one of the first bridges to connect the Fidonet world to the Internet world. An alternative approach undertaken by Scott Weikart and Steve Fram for the Association for Progressive Communications saw UNIX being made available on special low cost PCs in a distributed network.

In the community networking field early systems included PEN (Public Electronic Network) in Santa Monica, the WELL (Whole Earth 'Lectronic Link) in the Bay area of San Francisco, Big Sky Telegraph, and a host of small businesses with online universities, community bulletin boards, artists networks, seniors clubs, womens networks etc. ..

Gradually, as the 1980s came to a close, these networks also began joining the Internet for connectivity and adopted the TCP/IP standard. Now the PC networks and the academic networks were joined, and a platform was available for rapid global development.

By 1989 many of the new community networks had joined the Electronic Networkers Association, which preceded the Internet Society as the association for network builders. When they met in San Francisco in 1989, there was a lot of activity, plus some key words emerging - connectivity and interoperability. Not surprisingly in the California hippy culture f the time, the visions for these new networks included peace, love, joy, Marshall McLuhan's global village, the paperless office, electronic democracy, and probably Timothy Leary's Home Page. However, new large players such as America on Line (AOL) were also starting to make their presence felt, and a more commercial future was becoming obvious. Flower power gave way to communications protocols, and Silicon Valley just grew and grew.

PEN (The Public Electronic Network) in Santa Monica, may be able to claim the mantle of being the first local government based network of any size. Run by the local council, and conceived as a means for citizens to keep in touch with local government, its services included forms, access to the library catalogue, city and council information, and free email.

PEN started in February 1989, and by July 1991 had 3,500 users. One of the stories PEN told about the advantages of its system was the consultations they had with the homeless people of Santa Monica. The local council decided that it would be good to consult the homeless to find out what the city government could do for them. The homeless came back via email with simple needs - showers, washing facilities, and lockers. Santa Monica, a city of 96000 people at the time, was able to take this on board and provide some basic dignity for the homeless -and at a pretty low cost. This is probably the first example of electronic democracy in action.

Meanwhile, back in the academic and research world, there were many others who wanted to use the growing network but could not because of military control of Arpanet. Computer scientists at universities without defence contracts obtained funding from the National Science Foundation to form CSNet (Computer Science Network). Other academics who weren't computer scientists also began to show interest, so soon this started to become known as the "Computer and Science Network". In the early days, however, only a few academics used the Internet at most universities. It was not until the1990s that the penetration of Internet in academic circles became at all significant.

Because of fears of hackers, the Dept of Defence created a new separate network, MILNet, in 1982. By the mid-1980s, ARPANET was phased out. The role of connecting university and research networks was taken over by CSNet, later to become the NSF (or national science foundation) Network.

The NSFnet was to become the U.S. backbone for the global network known as the Internet, and a driving force in its early establishment. By 1989 ARPANet had disappeared, but the Information Superhighway was just around the corner.

==BENIFITS == 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.Upgrades are also easier because changes only have to be done once on the file server instead of on individual workstations. Security: 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.

== WHAT IS NETWORK CLASSIFICTION == Connection method The different types of network are Personal Area Network (PAN), Local Area Network (LAN), Campus Area Network (CAN), Metropolitan Area Network (MAN), Wide Area Network (WAN), and Global Area Network(GAN).

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.[citation needed]

Wireless technologies

Terrestrial microwave – Terrestrial microwaves use Earth-based transmitter and receiver. The equipment look 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.

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

Main article: Network topology

Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network. 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 TYPS OF NETWORKS BASED ON PHYSICAL SCOPE == Local Area Network '''A local area network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games or other applications. A LAN in turn often connects to other LANs, and to the Internet or other WAN.Most local area networks are built with relatively inexpensive hardware such as Ethernetcables, network adapters, and hubs. Wireless LAN and other more advanced LAN hardware options also exist.Specialized operating system software may be used to configure a local area network. For example, most flavors of Microsoft Windows provide a software package called Internet Connection Sharing (ICS) that supports controlled access to LAN resources.The term LAN party refers to a multiplayer gaming event where participants bring their own computers and build a temporary LAN.''' Examples: '''The most common type of local area network is an Ethernet LAN. The smallest home LAN can have exactly two computers; a large LAN can accommodate many thousands of computers. Many LANs are divided into logical groups called subnets. An Internet Protocol (IP) "Class A" LAN can in theory accommodate more than 16 million devices organized into subnets.''' ===Wide Area Network (WAN)

=The wide area network, often referred to as a WAN, is a communications network that makes use of existing technology to connect local computer networks into a larger working network that may cover both national and international locations. This is in contrast to both the local area network and the metropolitan area network, which provides communication within a restricted geographic area. Here is how the wide area networkfunctions, and why it is so important to communications today. The concept of linking one computer network with another is often desirable, especially for businesses that operate a number of facilities. Beginning with the local area network and going up to the wide area network, this is most easily accomplished by using existing telephony technology. Essentially, fiber optics are used to create the link between networks located in different facilities. Often, this means using standard phone lines, referred to as POTS, or employing PSTN (public switched telephone network) technology. During the 1990s, a third option, that of ISDN (integrated services digital network) solutions for creation a wide area network gained a great deal of popularity, mainly because the concept made it more cost effective to extend the networkbeyond national boundaries. With coverage in a broad area, a wide area network allows companies to make use of common resources in order to operate. For example, many retail drugstores make use of a wide area network as part of their support to customers who fill prescriptions with one of their stores. Once in the common customer database for the pharmacy, the client is free to fill a prescription at any of the company’s locations, even while vacationing in another state.

Companies also make good use of the wide area network as well. Internal functions such as sales, production and development, marketing and accounting can also be shared with authorized locations through this sort of broad area network application. The concept of a wide area network as a means of taking individual location based computer networks and using them to create a unified computer network for the entire corporation means that employees can work from just about anywhere. Should one facility be damaged or rendered inaccessible due to natural disaster, employees simply move to another location where they can access the unified network, and keep on working.

==BASIC HARDWARE COMPONENTS ==

1. Case with hardware inside:' 1. '''Power Supply - The power supply comes with the case, but this component is mentioned separately since there are various types of power supplies. The one you should get depends on the requirements of your system. This will be discussed in more detail later''' 2. '''Motherboard - This is where the core components of your computer reside which are listed below. Also the support cards for video, sound, networking and more are mounted into this board.'''


 * 1.Microprocessor - This is the brain of your computer. It performs commands and instructions and controls the operation of the computer.


 * 2.Memory - The RAM in your system is mounted on the motherboard. This is memory that must be powered on to retain its contents.


 * 3.Drive controllers - The drive controllers control the interface of your system to your hard drives. The controllers let your hard drives work by controlling their operation. On most systems, they are included on the motherboard, however you may add additional controllers for faster or other types of drives.

3. '''Hard disk drive(s) - This is where your files are permanently stored on your computer. Also, normally, your operating system is installed here.''' 4. '''CD-ROM drive(s) - This is normally a read only drive where files are permanently stored. There are now read/write CD-ROM drives that use special software to allow users to read from and write to these drives.'''

5. Floppy drive(s) - A floppy is a small disk storage device that today typically has about 1.4 Megabytes of memory capacity. 6. Other possible file storage devices include DVD devices, Tape backup devices, and some others. 2. Monitor - This device which operates like a TV set lets the user see how the computer is responding to their commands. 3. Keyboard - This is where the user enters text commands into the computer. 4. Mouse - A point and click interface for entering commands which works well in graphical environments.

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CONCLUSION

The Native Computer Communications Network Project was a good example of how a focus on creating a network of computers does not necessarily ensure the interpersonal networking of the potential users of that technology. If the people were not communicating with each other before, developing another method of communication doesn't mean they'll start.

REFERENCES

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

http://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htm

[http://wiki.answers.com/Q/What_are_the_classification_of_computer_network http://wiki.answers.com/Q/What_are_the_classification_of_computer_network'

]http://www.comptechdoc.org/hardware/pc/begin/hwcomputer.html