Computer Network Assignment A134429 & A134469

INTRODUCTION
A network or communication network is a system of interconnected communication devices that can communicate with one another and share infoormation.Therefore computer network can be defined as:

A system in which more than one computers or large number of computers are interconnected together,communicate freely with one another and share information is called computer network.

A network can be internal to an organization or span the world by connecting itself to the internet.In computer network,network operating systeem is used that controls and co-ordinated the activities of computer that are connected to the network.The example of these operating system are:windows NT,UNIX,and Novell etc.

BACKGROUND
Before the advent of computer networks that were based upon some type of telecommunications system,communication between calculation machines and early computers was perfomed by human users by carrying instructions between them.Many of the social behaviors seen in today's Internet were demonstrably present in the nineteenth century and arguably in even earlier network using visual signals.

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 system like teletypes to computers was an interest at the Advanced Research Projects Agency (ARPA) when ,in 1962,J.C.R. Licklider was hired and developed a working group he called the 'Integrated Network' Bold text, a precursor to the ARPANet.

In 1964,researchers at Dartmouth the Dartmouth Time Sharing System for distributed users of large computer systems.The same year,at MIT,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 independent 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).

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

BENEFITS
Some benefits of computer networks are given below. (1) Computers which are connected through a network can share resources as hard drives, printers, scanners etc with each other. (2) They can send files from one computer to another quite easily. (3) You can connect all the computers which are connected through a network to the internet by using a single line. So it means that you can save the connection cost for each computer but you internet connection must be fast. (4) IF you want to access data from the other computer which is the part of network then you can access data from that computer. (5) Users can run those programs which are not installed on their computers but are installed on any other user's computer.

NETWORK CLASSIFICATION
The following list presents categories used for classifying networks.

1)Connection methodsasacacasca

2)Wired technologies acas

3)WIreless technologies a as

4)Scalesasasa

5)Functional relationship(network architecture)

6)Network topology asac a

TYPES OF NETWORK
Network are of 2 types.These are:


 * Local Area Network (LAN)
 * Wide Area Network (WAN)

LOCAL AREA NETWORK
A local area network network (LAN) is a network that connects computers and devices in a limited geographical area such as home,school,,computer laboratory,office building,or closely positioned group of buildings.Each computer or device on the network is a node.Current wired LAN using existing home wires (coaxial cables,phone lines nad power lines) Typical library network, in a branching tree topology and controlled access to resources All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers.

The defining characteristic of LANs,in contrast to WANs (Wide Area Networks),include their higher data transfer rates,smaller geographic range,and no need for leased telecommuncation lines.Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s.This is the data transfer rate.IEEE has projects investigating the standardization of 40 and 100 Gbit/s.

WIDE AREA NETWORK
Wide area network is a computer network that covers a large geographic area such as city or country using a communications channel that combines many types of media such as telephone lines and cables. WAN often uses transmission facilities provided by common carriers such as telephone companies

BASIC HARDWARE COMPONENT
All network are made of basic hardware building blocks to interconnect networks nodes, such as Network Interface Cards(NICs), Bridges, Hubs, Switches and routers

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 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 segment 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 associations of ports and address 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 which the frame arrived

Bridge come in 3 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.

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.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 of packet (Internet protocol information from Layer 3 of the OSI Model). In many situations, this information is processed in conjuction with the routing table(also know as forwarding table). Routers use routing table to determine what interface to forward packets(this can include the "null" also know as the "black hole" interface because data can go into it, however no futher processing is done for said data).

CONCLUSION
Computer network can be used all over the world as it can be interconnected with over billions of people in the world. The variety of facilitaties that provides in computer network make all the users life just awesome. It make people move faster and more easier. This situation has make internet grow faster than human being