Computer Network Assignment A131202 & A134647

INTRODUCTION


Computer networking, once strictly the domain of technologists and

characterized by experimentation with a diverse range of protocols and

network designs for machine-to-machine communication, has rapidly

standardized in recent years. This standardization is most easily apparent

in the ubiquitous Internet built predominantly on the now dominant

combination of Ethernet and TCP/IP protocols. Standardization and

the diffusion of the Internet has given rise to a lay experience of computer

networking and an accompanying lay vocabulary of computer networking

concepts. The lay experience of computer networking centers on human to-

human exchange via communication software systems such as e-mail,

Listserv, and UseNet News that support the sharing of meaningful symbolic

information encoded in human language, sounds, and visual images.

Two streams of discourse addressing computer networks exist simultaneously: (a) a formal, technical, scientific discourse shared

primarily among computer science professionals and (b) a generic discourse based on the common understanding of the lay

public, who nevertheless have extensive experience using computer systems that are attached to networks. In the past, when the

principal users of computer networks were professional

technologists and computer scientists, the technical language of computer science predominated. However, as computing has

radically diffused throughout society, the priority of these two distinctive systems of language and experience has, to an extent,

reversed.

A131202 10:46, September 26, 2010 (UTC)

BACKGROUND
The Internet of today is a complex and anarchic seeming worldwide network of computer networks. Applications such as

electronic mail and the World Wide Web seem on their way to becoming as ubiquitous as the telephone and television in earlier

generations. With hundreds of millions of users, the Internet of 2002 is larger than any corporation or government entity in history.

Indeed, the Net of the 2000s has more users than the United States or European Union has citizens. How the Internet became

what it is today is a story with long and tangled roots. Nobody planned the Internet as it exists today, and nobody controls it in

any usual sense of the word. Instead the Internet sprang from the visionary seeds planted by the forethought of men such as

Vannevar Bush and J. C. R. Licklider. The Net thrived quietly for three decades under the gentle guidance of Jon Postel and

others, and then sprang into worldwide prominence in the 1990s with the advent of the World Wide Web.

A131202 14:02, September 26, 2010 (UTC)

BENEFITS
Connectivity and Communication

Networks connect computers and the users of those computers. Individuals within a building or work group can be connected into

local area networks (LANs); LANs in distant locations can be interconnected into larger wide area networks (WANs). Once'''

connected, it is possible for network users to communicate with each other using technologies such as electronic mail. This

makes the transmission of business (or non-business) information easier, more efficient and less expensive than it would be

without the network.

Data Sharing

One of the most important uses of networking is to allow the sharing of data. Before networking was common, an accounting

employee who wanted to prepare a report for her manager would have to produce it on his PC, put it on a floppy disk, and then

walk it over to the manager, who would transfer the data to her PC's hard disk. (This sort of “shoe-based network” was sometimes

sarcastically called a “sneakernet”.)

True networking allows thousands of employees to share data much more easily and quickly than this. More so, it makes

possible applications that rely on the ability of many people to access and share the same data, such as databases, group

software development, and much more. Intranets and extranets can be used to distribute corporate information between sites and

to business partners.

Hardware Sharing

Networks facilitate the sharing of hardware devices. For example, instead of giving each of 10 employees in a department an

expensive color printer (or resorting to the “sneakernet” again), one printer can be placed on the network for everyone to share.

Internet Access

The Internet is itself an enormous network, so whenever you access the Internet, you are using a network. The significance of the

Internet on modern society is hard to exaggerate, especially for those of us in technical fields.

Internet Access Sharing

Small computer networks allow multiple users to share a single Internet connection. Special hardware devices allow the bandwidth

of the connection to be easily allocated to various individuals as they need it, and permit an organization to purchase one high-

speed connection instead of many slower ones.

Data Security and Management

In a business environment, a network allows the administrators to much better manage the company's critical data. Instead of

having this data spread over dozens or even hundreds of small computers in a haphazard fashion as their users create it, data can

be centralized on shared servers. This makes it easy for everyone to find the data, makes it possible for the administrators to

ensure that the data is regularly backed up, and also allows for the implementation of security measures to control who can read

or change various pieces of critical information.

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.

A131202 14:04, September 26, 2010 (UTC)

Local area network
A local area 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 LANs are most likely to be based on Ethernet technology, although new standards like ITU-T G.hn also provide a way to create a wired LAN using existing home wires (coaxial cables, phone lines and power lines).

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 characteristics of LANs, in contrast to WANs (Wide Area Networks), include their higher data transfer rates, smaller geographic range, and no need for leased telecommunication 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.

Personal area network

A personal area network (PAN) is a computer network used for communication among computer and different information technological devices close to one person. Some examples of devices that are used in a PAN are personal computers, printers, fax machines, telephones, PDAs, scanners, and even video game consoles. A PAN may include wired and wireless devices. The reach of a PAN typically extends to 10 meters A wired PAN is usually constructed with USB and Firewire connections while technologies such as Bluetooth and infrared communication typically form a wireless PAN.

Home area network A home area network (HAN) is a residential LAN which is used for communication between digital devices typically deployed in the home, usually a small number of personal computers and accessories, such as printers and mobile computing devices. An important function is the sharing of Internet access, often a broadband service through a CATV or Digital Subscriber Line (DSL) provider. It can also be referred as an office area network (OAN).

A131202 14:05, September 26, 2010 (UTC)

Wide area network
A wide area network (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental distances, using a communications channel that combines many types of media such as telephone lines, cables, and air waves. A WAN often uses transmission facilities provided by common carriers, such as telephone companies. 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.

Campus network

A campus network is a computer network made up of an interconnection of local area networks (LAN's) within a limited geographical area. The networking equipments (switches, routers) and transmission media (optical fiber, copper plant, Cat5 cabling etc.) are almost entirely owned (by the campus tenant / owner: an enterprise, university, government etc.). In the case of a university campus-based campus network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls.

Metropolitan area network A Metropolitan area network is a large computer network that usually spans a city or a large campus.

Enterprise private network An enterprise private network is a network build by an enterprise to interconnect various company sites, e.g., production sites, head offices, remote offices, shops, in order to share computer resources.

Virtual private network A virtual private network (VPN) is a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. The data link layer protocols of the virtual network are said to be tunneled through the larger network when this is the case. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.

A VPN may have best-effort performance, or may have a defined service level agreement (SLA) between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex than point-to-point.

Internetwork

An internetwork is the connection of two or more private computer networks via a common routing technology (OSI Layer 3) using routers. The Internet is an aggregation of many internetworks, hence its name was shortened to Internet.

A131202 14:05, September 26, 2010 (UTC)

Backbone network
Global Area Network A global area network (GAN) is a network used for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is handing off the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial wireless LANs.

Internet

The Internet is a global system of interconnected governmental, academic, corporate, public, and private computer networks. It is based on the networking technologies of the Internet Protocol Suite. It is the successor of the Advanced Research Projects Agency Network(ARPANET) developed by DARPA of the United States Department of Defense. The Internet is also the communications backbone underlying the World Wide Web (WWW).

Intranets and extranets

Intranet and extranets are parts of extensions of a computer network usually, a local area network.

An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.

An extranet is a network that is limited in scope to a single organization or entity and also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities—a company's customers may be given access to some part of its intranet—while at the same time the customers may not be considered trusted from a security standpoint. Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although an extranet cannot consist of a single LAN; it must have at least one connection with an external network.

A131202 14:06, September 26, 2010 (UTC)

Overlay Network
An overlay network is a virtual computer network that is built on top of another network. Nodes in the overlay are connected by

virtual or logical links, each of which corresponds to a path, perhaps through many physical links, in the underlying network.

For example, many peer-to-peer networks are overlay networks because they are organized as nodes of a virtual system of links run on top of the Internet. The Internet was initially built as an overlay on the telephone network. The Internet was initially built a Overlay networks have been around since the invention of networking when computer systems were connected over telephone lines using modem, before any data network existed.

A131202 14:06, September 26, 2010 (UTC)

local-area network
A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).

Most LANs connect workstations and personal computers. Each node(individual computer ) in a LAN has its own CPU with which it executesprograms, but it also is able to access data and devices anywhere on the LAN. This means that many users can share expensive devices, such aslaser printers, as well as data. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions.

There are many different types of LANs Ethernets being the most common forPCs. Most Apple Macintosh networks are based on Apple's AppleTalk network system, which is built into Macintosh computers.

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. LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.

PERSONAL AREA NETWORK
Definition: A personal area network - PAN - is a computer network organized around an individual person. Personal area networks typically involve a mobile computer, a cell phone and/or a handheld computing device such as a PDA. You can use these networks to transfer files including email and calendar appointments, digital photos and music. Personal area networks can be constructed with cables or wirelessly. USB and FireWiretechnologies often link together a wired PAN while wireless PANs typically use Bluetooth or sometimes infrared connections. Bluetooth PANs are also called piconets.

Personal area networks generally cover a range of less than 10 meters (about 30 feet).

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").

[edit]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.

[edit]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.

[edit]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.[7] It works on the Physical Layer of the OSI model..

[edit]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 whichMAC 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.

[edit]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.[8] 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).

[edit]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).

CONCLUSION
In conclusion,computer network is so important to us especially in today's generation.It had makes our life easier and lighten up our future.Computer networks are collections of computers which are connected together in order to communicate and transfer information.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.