Computer Network Assignment A134464 & A131115

Introduction
Computer network is a system in which computer are connected to share information and resources and is the engineering discipline concerned with the communication between computer systems or devices. The connection can be done as peer-to-peer or client/server. It can be connected by two or more computers or devices with the ability to exchange data. Computer networking sometime considered a sub-discipline of telecommunications, computer science, information technology and computer engineering since it relies heavily upon theoretical and practical application of these scientific and engineering disciplines. The three types of networks are the Internet, the intranet and the extranet.

Examples of different network methods are:

All networks are interconnected to allow communication with a variety of different kinds of media, including twisted-pair copper wire cable, coaxial cable, optical fibre, power lines and various wireless technologies. The devices can be separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances (e.g. via the interconnections of the Internet). Networking, routers, routing protocols, and networking over the public Internet have their specifications defined in documents called RFCs.
 * Local-area network (LAN), which is usually a small network constrained to a small geographic area. An example of a LAN would be a computer network within a building.
 * Metropolitan-area network(MAN), which is used for medium size area. examples for a city or a state.
 * Wide-area network (WAN) that is usually a larger network that covers a large geographic area.
 * Wireless LANs and WANs (WLAN & WWAN) are the wireless equivalent of the LAN and WAN.

Background
In September 1940,George Stibitz used a teletype machine to send instructions for a problem set from his Model at Dartmouth College in New Hampshire to his Complex Number Calculator in New York and received results back by the same means. Linking output systems liketeletypes to computers was an interest at the Advanced Search Project Agency(ARPA) when, in 1962, J.C.R Licklider was hired and develop a workinggroup he called the " Intergalactic Network:Bold text, a precursor to the ARPAN.

In 1964, researchers at Dartmouth developed the Dartmouth Time Sharing System for distributed users of large computer systems. The sameyear, a tMIT, a research group supported by General Electric and Bell Labs used a computer DEC's to route and manage telephone connections.Throughout the 1960s Leonard Kleinrock, Paul Baran and Donald Davies independently conceptualized and developed network systems which useddatagrams 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.In 1969 the University of California at Los Angeles,SRI(in Stanford) University of California at Santa Barbara and the University of Utah were connected as the beginning of the ARPANET network using 50 kbit/s circuits. Commercial services using X.25 were deployed in 1972, and later used as an underlying infrastructure for expanding TCP/I networks.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.

Benefit
Technically speaking networking can be defined as a bunch of computers that have with wires running in between them. If proper implementation of a network is done it acts as a system that provides unique capabilities, to its users. These are much beyond the abilities of individual machines and software applications associated with them. The benefits networking offers to its users can be separated into two main groups i.e. sharing and connectivity. Networks make computers and their users capable of being connected together. This facilitates sharing of resources and information between the users. The modern businesses are expanded all over the world. So, uses and significance of networking has gained momentum during the last years. The many benefits that networking offers to us are:

1.Helps to enhance connectivity Networks connect and link unlimited number of computers. This in turn connects the people using those computers. Individuals within a work group are connected through local area networks. Many LANs in far off locations are interconnected through larger wide area networks (WANs). These connections ease out communication between people using technologies like e-mail. Today e-mail has become the easiest, and cheapest mode of transformation of information between the users.

2.Networking helps in sharing of hardware: Networks help in sharing of different kinds of hardware devices. 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.

3.Eases out management of data. Networking provides 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. Administrators can thus manage all this data efficiently and in the best interest of the company. Even the access of this data becomes easy for the users.

4.Internet The most beautiful gift of networking is internet that is massively used by people all over the world. Whenever you are accessing Internet, you are making use of a network. The benefits of internet need no mentioning. Thanks to the wonderful world of networking.

5.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.

6.Networking has promoted gaming. Many internet games like WOW accounts are being played by players all over the world using common servers. These give fun and enjoyment to people and also improve their skills.

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 fibre, Ethernet, wireless LAN,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 wves or infrared signals as a transmission medium. ITU-TG.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 fibre 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.

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 communications, 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

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)
 * Metropolitan-area network (MAN)

about Local-area network(LAN):

Local-area network(LAN) describes a network that spans a limited area that belong to the network are physically close to one another. However, LANs can vary drastically in the numbers of users and computers. For instance, LAN could consist of two PCs sitting a few feet apart in home or office or even in some cases multiple office buildings in close proximity. Large LANs can be divide into workgroups for easier management. In this context, a workgroup consists of users share the same resources such as files,printers and applications. LANs is a basis of larger network.

about Metropolitan-area network(MAN):

A Metropolitan-area network(MAN) consists of two or more LANs networked together within the confines of a space roughly corresponding to a metropolitan area. The typical area MAN is a high performance, public network. The maximum distance defining a MAN is approximately 50 miles or 80 kilometers.

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 Cateogory 5 Cable). Less common are microwave links or optical cable ("optical fibre").

1. Network interface card
A network cards, 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.

2.Repeaters
A repeaters is an electronic device that receives a signals, 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.

3.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.

4.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:
 * 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
A computer network can be used over the world as it has wide of field that can be interconnected to people over the world. The variety of facilitaties that provided in computer network make their users life easier and faster. Thus,network within internet growth faster than human themselves even computer wass created by human being.