Networks
Networking Basics
Sharing Data Anywhere, Anytime
When PCs first appeared in business, software program was designed for a single user. There were few obvious advantages to connecting PCs, and the technology was not adequate for doing so. As computers spread throughout business, developers began offering complex software designed for multiple users. Many organizations the electronic transfer of information between computers became a major focus of the computer industry. Dur computers became a major focus of the computer industry. During the past decade, networking technology has become the most explosive area of growth in the entire computer industry. The demand for larger and faster high-capacity networks has increased as businesses have realized the value of networking their computer systems. Networks come in many varieties. When most people think of a network, they imagine several computers in a single location sharing documents and devices such as printers. But a network can include all the computers and devices in a department, a building, or multiple building spread over a wide geographic area, such as a city or even a country. By interconnecting many individual networks into a massive single network, people around the world can share information they were across the hall from one another. The information they share can be much more than text documents. Many networks carry voice, audio, and video traffic, enabling videoconferencing and types of collaboration that were not possible just a few years ago. The Internet is an example of one such network and is possibly the single largest networks in existence today.
The Uses of a Network
A network is a set of technologies including hardware, software, and media that can be used to connect computers together, enabling them to communicate, exchange information, exchange information, and share resources in real time. You should think of a network as a group of technologies. Nearly all networks require hardware, software, and media such as wires to connect computer system together. Networks allow many users to access shared data and programs almost instantly. When data and programs are stored on a network and are shared, individual users can substantially reduce the need for programs on their own computers. Networks open up new ways to communicate, such as e-mail and instant messaging. By allowing users to share expensive hardware resources such as printers, networks reduce the cost of running an organization.
Simultaneous Access
There are moments in any business when several workers may need to use the same data at the same time. A good example is a company’s quarterly sales report, which needs to be viewed and updated by several managers. Without a network that allows workers to share files, workers must keep separate copies of data stored on different disks by each worker who accesses the data. When the data is modified on one computer, data on the other computers becomes outdated. It becomes difficult to determine which copy of the data is the most current. Companies can solve this problem by storing commonly used data at a central location, usually on a network server (also called a server). A network server is a central computer with a large storage device and other resources that all the users can share. You learned about the kinds of computers that can function as network servers.
If the server stores data files for users to access, it is commonly called a file server. The business can store a signle copy of a data file on the server that employee can access whenever thay want. Then, if one user makes a change to the file, other users will see the change when they use the file, and no one needs to figure out who has the latest copy of the data. Advanced software is needed to allow simultaneous access to the same file.
In addition to using many of the same data files, most office workers also use the same program. In an environment where PCs are not networked, a separate copy of each program must be installed on every computer. This setup can be costly for two reasons. First, software can be expensive, especially when you must buy many dozens or hundreds of copies. Second, installing and configuring a program on many different computers can take a lot time and labor, and maintaining many separate installations of a program is an ongoing expense. There are two basic solutions to this problem.
Site Licenses.
One solution to this problem is to purchase a site licenses for an application. Under a site license, a business buys a single copy (or a few copies) of an application and then pays the developer for a license to copy the application onto a specified number of computers. Under a site license, each user has a complete, individual copy of the program running on his or her PC, but the business generally pays less money than it would by purchasing a complete copy of the software for each user.
Network Versions.
Another solution is to connect users’ computers to a central network server and enable users to share a network version of a program. In a network version, only one copy of the application is stored on the server, with a minimum number of supporting files copied to each user’s PC. When workers need to use a program, they simply load it from the server into the RAM of their own desktop computers.
There are trade-offs with placing application on a centrally located server. In some networks, and with certain types of programs, the user’s computer handles all the processing tasks required by the application, even through the application’s core files are stored on the network. In other cases, the network server also handles some or all of the processing tasks.
Shared Peripheral Devices
The ability to share peripheral devices (especially expensive ones such as high-volume laser printers, which can cost thousands of dollars) is one of the best reasons for small business to set up a network. Although printers are more affordable than they were a few years ago, it is still too expensive to provide every worker with a personal printer. Aside from the cost of buying multiple printers, maintenance contracts and supplies increase the total cost of ownership. When several people can share a printer on a network, printing becomes less expensive and easier to manage.
There are two common ways to share a printer. A printer can connect directly to the network or it can be attached to a print server, which is a computer that manages one or more printers. Either way, users on desktop PCs will be able to submit documents across a network to a printer. ## Personal Communications
One of the most far-reaching applications of data communication is electronic mail (e-mail), a server for exchanging written messages (and, increasingly, voice and video messages) through a network.
- The sender composes an e-mail message and sends it.
- **The messages are stored on the server. **
- The server alerts the recipient that there is a message.
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When the recipient is ready to read the message, the recipient’s computer retrieves it from the server.
In addition to e-mail, the spread of networking technology is adding to the popularity of teleconferencing. A teleconference is any kind of multiway communication carried out in real time using telecommunications or computer networks and equipment. In a teleconference, audio and video signals travel across a local area network through the use of cables and switches or across the network’s Internet connections to remote sites located throughout the world. Subcategories of teleconferencing include. Videoconferencing.
Videoconferencing.
enables real-time communication over a distance by the allowing people at two or more sites to communicate with each other by seeing a video picture of the people at the other sites. Each site has one or more cameras, microphones, loudspeakers, and monitors, as well as a CODEC (compressor/decompressive), which process the audio and video. It aims to create a sense of a person at a distant site appearing to be there in the same room, an effect that has been called virtual presence.
Audio conferencing.
Audio-conferencing provides an audio link similar to that of a conventional telephone, expect that it offers much higher-quality audio and enables more than two sites to be linked together. Using hands-free audio units with sensitive microphones and sophisticated echo cancellation software, audio-conferencing enables communication between groups of participants.
Data-conferencing.
Data-conferencing enables participants at two or more sites to have a shared workspace on their computer desktops. They might be a shared “whiteboard” where they can draw, write, or import and manipulate images collaboratively in real time. Or it might be “application sharing,” where a piece of software can be run and controlled by both users. Data-conferencing is often used in conjunction with video-or audio-conferencing and can be useful when users at different sites want to work together on documents.
Easier Data Backup
In business, data is extremely valuable, so it is important that employees back up their data. One way to assure that data is backed up is to keep it on a shared storage device that employee can access through a network. Often the network manager makes regular backups of the data on the shared storage devices. Managers also can use special software to back up files stored on employee’ hard drives from a central location. With this method, files do not have to be copied to the server before they can be backup up.
Types of Networks
If you want to understand the different types of networks and how they operate, you need to know how networks are structured. There are two main types of networks:
Local area network.
A local area network (LAN) is a data communication system consisting of several devices such as computers and printers. This type of network contains computers that are relatively near each other and are physically connected using cables, infrared links, or wireless media. A LAN can consist of just two or three PCs connected together to share resources, or it can include hundreds of computers of different kinds. Any network that exists within a single building, or even a group of adjacent buildings, is considered a LAN. A LAN is not a system that connects to the public environment (such as the Internet) using phone or data lines. It is often helpful to connect separate LANs together so they can communicate and exchange data. In a large company, for example, two departments located on the same floor of a building may have their own separate LANs, but if the department need to share data, then they can create a link between the two LANs.
Wide Area Network
Typically, a wide area network (WAN) is two or more LANs connected together generally across a wide geographical area. For example, a company may have its corporate headquarters and manufacturing plant in one city and its marketing office in another. Each site needs resources, data, and programs locally, but it also needs to share data with the other sites. To accomplish this feat of data communication, the company can attach devices that connect over public utilities to create WAN: (Note, however, that a WAN does not have to include any LAN systems. For example, two distant mainframe computers can communicate through a WAN, even though neither is part of a local area network.) These remote LANs are connected through a telecommunication network (a phone company) or via the internet through an internet through an internet service provider (ISP) that contracts with the telecommunication networks to gain access to the internet’s backbone.
Hybrid Networks
Between the LAN and WAN structure, you will find hybrid network such as campus area networks (CANs) and metropolitan area networks (MANs). In addition, a new form of network type is emerging called home area networks (HANs). The need to access corporate web sites has created two classifications known as intranets and extranets. The following section introduce these networks.
Campus Area Network
A campus area network (CAN) follows the same principles as a local area network, only on a larger and more diversified scale. With a CAN, different campus offices and organizations can be linked together. ### For example,
in a typical university, settings, bursar’s office might be linked to a register’s office. In this manner, once a student has paid his or her tuitions fees to the bursar, this information is transmitted to the register’s system so the student can enroll for classes. Some university department or organization might be linked to the CAN even through they already have own separate LANs.
Metropolitan Area Network
The metropolitan area network (MAN) is a large-scale network that connects multiple corporate LANs together. MANs usually are not owned by a single organization; their communication devices and equipment are usually maintained by a group or single network provider that sells its networking services to corporate customers. MANs also can provide a shared connection to other networks using a WAN link. The relationship between LANs, MANs, and WANs. ## Home Area Network.
A Home area network (HAN) is a network contained within a user’s home that connects a person’s digital devices, from multiple computers and their peripheral devices, such as a printer, to telephones, VCRs, DVDs, television, video games, home security system, “smart” appliances, fax machines, and other digital devices that are wired into the network.
Intranets and Extranets
Much of the technology available on the internet is also available for private network use. The company’s internal version of the internet is called an intranet. As you learned an intranet uses the same web server software that gives the public access to web sites over the internet. The major difference is that an intranet usually limits access to employee and selected contractors having ongoing business with the company. Web pages have become very popular and, using integrated software, many operating systems offer complete web server software or at least a personal web server. This gives users the ability to create web pages on their local computers that can be viewed by another member of the same network. Just like on the internet, users can allow others (again, usually employee) to browse their web site and to upload or download files, video clips, audio clips, and other such site and to upload or download files, video clips, audio clips, and other such media. Users also can set controls and limit who may access the web site. Extranets are becoming a popular method for employees to exchange information using the company’s web site or e-mail while traveling or working from home. An extranet is a partially accessible internet company web site for authorized users physically located outside the organization. Whereas an intranet resides completely within the company’s internet network and accessible only to people that are member of the same company or organization, an extranet provides various levels of accessibility to outsiders. You can access an extranet only if you have a valid username and password, and your identity determines which parts of the extranet you can view.
How Networks Are Structured
Networks can be categorized by the roles the servers and PCs play in terms of hierarchical and security interaction. Some networks use servers (server-based networks) and some do not (peer-to-peer networks). These terms are defined in detail in the following sections.
Server-Based Network
To understand a server-based network, it is important to know the meaning of the term node in a network. A node is a processing location that can be a PC or some other device such as a networked printer. Usually, server-based networks include many nodes and one or more servers, which control user access to the network’s resources.
Client Server Network
One popular type of server-based network is the client/server network, where individual computers share the processing and storage workload with a central server. This arrangement requires special software for the nodes and the server. It does not, however, require any specific type of network. Client/server software can be used on LANs or WANs, and a signal client/server program can be used on a LAN where all the other software is based on a simple file server system.
Peer to Peer Network
In a peer-to-peer network (abbreviated as “P2PN” and sometimes called a work-group), all nodes on the network have equal relationships to all others, and all have similar types of software that support the sharing of resources. In the resources on all other nodes. If they are set up correctly, many multi-user operating system give users access to files on hard disks and to printers attached to other computers in the network.