Computer Network Assignment A134650 & A134689

Introduction
A computer network is a system in which computer are connected to share information and resources. The connection can be done as peer-to-peer or client/server. This web site reviews the techniques you can use to set up and possibly manage a network for home or a small business. It is also two or more computers connected so that they can communicate with each other and share information, software, peripheral devices, and/or processing power.

Background
In September 1940 George Stibitz used a teletype machine to send instructions for a problem set from his Model at Dartmouth Collegein New Hampshire to his Complex Number Calculator in New York and received results back by the same means. Advanced Researched Project Agency (ARPA) when, in 1962, J.C.R. Licklider was hired and developed a working group he called the "Intergalactic Network"Bold text, a precursor to the ARPANet.

In 1964, researchers at Dartmouth developed the Dartmouth Time Sharing System or distributed users of large computer systems.

Throughout the 1960s Leonard Kleinrock, Paul Baran and Donald Davies independently conceptualized and developed network systems which used datagrams or packets that could be used in a network between computer systems.

1965 Thomas Merrill and Lawrence G. Roberts created the first wide area network(WAN).

The first widely used PSTN switch that used true computer control was the Western Electric introduced in 1965.

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

Computer networks, and the technologies needed to connect and communicate through and between them, continue to drive computer hardware, software, and peripherals industries. This expansion is mirrored by growth in the numbers and types of users of networks from the researcher to the home user.

Today, computer networks are the core of modern communication. All modern aspects of the Public Switched Telephone Network (PSTN) are computer-controlled, and telephony increasingly runs over the Internet Protocol, although not necessarily the public Internet. The scope of communication has increased significantly in the past decade, and this boom in communications would not have been possible without the progressively advancing computer network.

Helps to enhance connectivity and communication capabalities
Networks connect and link unlimited number of computers. Individuals within a work group are connected through local area networks(LAN). Many LANs in far off locations are interconnected through larger wide area networks (WANs). Networks provide several different collaboration tools that can be used to communicate between network users. When connected to the internet, network users can communicate with people around the world via the network. Online collaboration tools include e-mail, forums and chats, voice and video, and instant messaging. With these tools, users can communicate with friends, family, and colleagues

Networking helps in sharing of hardware
All computers in the network can share resources such as printers, fax machines, modems, and scanners. For example, sharing of a single printer in an office of twenty people is done through networking of wires. This saves lot of cost that could otherwise have incurred if twenty different printers were provided for each computer in use. ==== Data Sharing

Data Sharing
Sharing of data through the use of networks helps save a lot of time and energy. It also facilitates the use of applications like databases that are based on ability of many individuals to access and to share exactly the same data. This 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.

Eases out management of data
Centralized administration reduces the number of people needed to manage the devices and data on the network, reducing time and cost to the company.The advantage of centralization of data from all the user systems to one system where it can be managed in an easy and better way.One administrator can control the data, devices, and permissions of users on the network. Backing up data is easier because the data is stored in a central location. Even the access of this data becomes easy for the users.

==What Is Network Classification ==

By 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 LAN, HomePNA, power line communication or G.hn.

By range
Networks are often classified depending on their scale, scope and purpose. For example:


 * personal area network (PAN)
 * wireless PAN
 * local area network (LAN)
 * wireless LAN
 * metropolitan area network (MAN)
 * wide area network (WAN)

By functional relationship
Computer networks may be classified according to the functional relationships which exist among the elements of the network, examples are


 * client-server
 * multitier architecture
 * Peer-to-peer

By 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, tree and hypertree networks

By specialized function

 * Storage area networks
 * Server farms
 * Process control networks
 * Value added network
 * SOHO network
 * Wireless community network

Two Types Of Network Based On Physical Scope
Wide Area Network (WAN)

A network of computer in a large geographic area for sharing resources or exchanging data.The internet connects multiple WANs; as its name suggests, it is a network of networks. In a WAN, one network may be anywhere from several hundred miles away, to across the globe in a different country. The first known of wide area network is in 1982. A wide area network that consists of the client and server computers that are distributed throughout the WAN, the functionalities of the network are distributed throughout the WAN. The internet is an example of the wide area network and is the most popular wide area network in this wolrd. The wide area network has made it possible for companies to communicate internally in ways never before possible. As a bonus, consumers can enjoy a number of benefits that vendors were not able to extend in the past.

WAN technologies and protocols are mostly data link layer (layer 2) protocols which are defined by many organizations over time. The key organizations in this space are IETF for PPP, ITU-T for ATM, Frame Relay, ISO for X.25 and SONET etc.

WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.

The main purpose of the WAN is to establish a secure, fast and reliable communicate channel among the people who are widely away from each other. Wide area networks are often privately owned networks. A wide area network uses many types of network devices such as WAN switches, access servers, CSU/DSU, modems, ISDN terminal adapters, routers, multiplexers, ATM switches and other networking devices. An example of the WAN is SURFnet, which is a research network and that connects the universities and research centers of the Netherlands with each other.

Local Area Network (LAN)

A local area network, also referred to as a LAN, is the local connection of computers to a network that share resources. Most LANs are confined to a single building or group of buildings. Typically, connected devices share the resources of a single processor or server within a small geographic area (for example, within an office building). Usually, the server has applications and data storage that are shared in common by multiple computer users. A local area network may serve as few as two or three users (for example, in a home network) or as many as thousands of users (for example, in an FDDI network).

The following characteristics differentiate one LAN from another:

 topology  : The geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a straight line.

 protocols  : The rules and encoding specifications for sending data. The protocols also determine whether the network uses a peer-to-peer or client-server architecture.

 media  : Devices can be connected by twisted-pair wire, coaxial cables, or fiber optic cables. Some networks do without connecting media altogether, communicating instead via radio waves.

Because the technologies used to build LANs are extremely diverse, it is impossible to describe them except in the most general way. Universal components consist of the physical media that connect devices, interfaces on the individual devices that connect to the media, protocols that transmit data across the network, and software that negotiates, interprets, and administers the network and its services. Many LANs also include signal repeaters and bridges or routers, especially if they are large or connect to other networks.

Basic Hardware Components of Network
A network operation needs devices that are designed to handle certain network functions. The devices are often called networking devices or equipment and specifically referred to as network components.

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. Network adapter converts a computer message into electrical or optical signals for transmission across the network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of Mac addresses. It allows users to connect to each other either by using cables or wirelessly.You may need Ethernet, WiFi , HomePNA, or HomePlug network adapter depending on the type of network your computer is connecting to.

Repeaters
A repeater is an electronic device that receives a signal 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.Repeater receives signal from a transmitter, amplifies it, and retransmits it to a receiver. A repeater is put in a network to extend the network to a longer distance or a greater area. There can be more than one repeater between a transmitter and a receiver, however the number of repeaters is not unlimited, because additional repeaters may introduce more interference or noise.

Hubs
Hub is the central connection point in a network.A hub contains multiple ports. A sending computer transmits its signal to a hub, the hub then retransmits the signal to all other computers.When a packet arrives at one port, it is copied to all the ports of the hub for transmission. A passive hub functions as a relay station that receives and retransmits signal. When the packets are copied, the destination address in the frame does not change to a broadcast address. It does this in a rudimentary way: It simply copies the data to all of the Nodes connected to the hub. An active hub functions as a repeater that regenerates signal before retransmitting.

Bridges
A bridge function can be handled by a software application. In Windows XP, when you install two or more network adapters, a Network Bridge is automatically created for you. A Network Bridge icon will appear in the Network Connections folder. However in Windows XP Service Pack 2 (SP2), a Network Bridge will be created only after user confirmation. This behavior is in line with SP2 main goal, that's to improve computer and network security.

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

Switches
A switch is a device that performs switching. Specifically, it forwards and filters OSI layer 2 datagrams (chunk of data communication) between ports (connected cables) based on the MAC addresses in the packets. Using a switch, the whole bandwidth can be used by each connected computer. That's why most big networks in which a large amount of data must be transferred at any given time, use a switch instead of hub. Switch is not always a separate device, it is very often integrated with router. Switch is a marketing term that encompasses routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier). Switches may operate at one or more OSI model layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch.

Routers
Router functions to forward packets across different networks using headers and forwarding tables to determine the best path to forward the packets.Routers work at the network layer of the TCP/IP model or layer 3 of the OSI modelRouter maintains a routing table. The routing table contains IP addresses of other networks routers. In a static router the routing table is configured manually, while a dynamic router can communicate with other routers and configure the routing table according to information it receives from other routers.A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Some DSL and cable modems, for home (and even office) use, have been integrated with routers to allow multiple home/office computers to access the Internet through the same connection. Many of these new devices also consist of wireless access points (waps) or wireless routers to allow for IEEE 802.11g/b wireless enabled devices to connect to the network without the need for cabled connections.

Conclusion
Computer networking is one of the most exciting and important technological fields. It have changed the way humans work, play, and communicate. It allows sharing of resources and information among interconnected devices. Computer networks will make our life become better and more comfortable.