Differences between LAN and WAN

The differences between LAN and WAN is as follows:

LAN (Local Area Network)
1.	LAN is used to connect computers at one place, in one room or a building.
2.	LAN covers small and limited area.
3.	Data transfer speed is very fast in LAN because of small distance.
4.	Local Area network speed is normally form 1 to l00 Mbps.
5.	LAN is less costly.
6.	LAN is usually connected through wires.
7.	Normally, the   connection    in    a    LAN    is permanent using wires.
8.	LAN is used for sharing data, information, files and hardware like printers, hard disk, modem etc.
9.	LAN has   less   possibility   of data transmission error.
10.	LAN is used to transfer data over small distances.
11	LAN is easy to install and configure.
12	LAN is easy to troubleshoot.
WAN (Wide Area Network)
1	WAN is used to connect computers anywhere in the world.
2	WAN can cover larger area. It can cover cities, countries and even continents.
3	Data transfer speed is slower in WAN.
4	Transmission     speeds     are     normally 56 kbps to 45 Mbps.
5	The hardware needed for a WAN is more expensive.
6	WAN is usually connected through telephone lines, fiber optic cable or through wireless media.
7	The    connection    in    WAN    may not be permanent.
8	WAN is used to share only data and information like Email and file transfer
9	WAN has more possibility of data transmission error because of long distance.
10	WAN is used to transfer data over long distances.
11	WAN is difficult to install and configure due to connecting computers at multiple and distant sites.
12	WANs are difficult to troubleshoot.

Types Of Computer Networks

Explain different types of computer networks:(LAN,WAN,MAN)

Main types of computer networks are:

1.    LAN - Local-Area Network

2.    WAN - Wide-Area Network

3.    MAN - Metropolitan-Area Network

1)LAN (Local Area Network)

LAN stands for Local Area Network. It covers a small area. Most LANs are used to connect computers in a single building or group of near buildings. Hundreds or thousands of computers may be connected through LAN. LANs are used in office buildings, college or university campus etc. Local Area Networks can transfer data at a very high speed. Data transmission speeds of LAN are 1 to 100 megabits per second.

Examples:

Following are two examples of LAN:

• LAN is used in a computer lab to connect computers. The students can share software, files and data in the lab.
• In Internet cafe, many computers can be connected through LAN. These computers can share single connection of Internet.
• Local Area Network can be used in an office to share common data and a network printer and any other software or hardware.
• A local area network in a digital library can provide access to centralized collection of digital books for many readers using different computers in library building.

2)WAN (Wide Area Network)

WAN stands for wide area network. It covers a large area. WAN connects computers in different cities, countries and continents. So, Wide Area Networks are used to transfer data over very long distances across cities, countries or even in whole world. WANs are used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations.

Computers in WAN are often connected through leased lines telephone lines. They can also be connected through satellites. Transmission rate of WAN is 56 kbps to 45 Mbps. WAN is expensive than LAN. WAN is not as fast as LAN. There is a possibility of error in data transmission due to very long distance they cover. The largest WAN  is the Internet. With the help of internet, we can send our data in any part of the world.

Examples of WAN

• In air line ticketing system, many offices of an air line company can be joined together using WAN. A person can get a ticket from any office in the country.
• A bank with many branches in different cities can connect its branches through WAN. The customer can use his account from any branch.

3)MAN (Metropolitan-Area Network)

A metropolitan area network (MAN) is a network that covers an area of the size of a city. So, a MAN is larger than a local area network but it is smaller than a WAN. A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities. MANs can use communications channels of moderate-to-high data transfer rates. It may use fiber Optic cable for fast speeds.

A MAN typically includes one or more LANs but cover a small area than WAN. A MAN often acts as a high-speed network.

Example:

• Mobile phones systems often use MAN.
• Many local ISPs manage MAN with the help of cable modems within a city.
• Local cable TV networks also uses MAN technologies.

How To Protect Your Computer From Spyware And Viruses

How to protect your computer from spyware and viruses? If your computer is still experiencing slow performance problems after cleaning your hard drive, you may need to do a scan with anti virus or anti-spyware. Negative computer viruses can slow down your computer by changing the user's data or information without permission or without the knowledge of real users.

Spyware collects personal information without telling you and without asking for permission. From the web site you visit where you enter your username and passwords, spyware can steal your confidential information. In addition to privacy concerns, spyware can hamper your computer's performance. To remove spyware, scan your PC security of Windows Live OneCare. Scanning This is a free service and will help to check and remove viruses. Apart from the above that can throw garbage on your computer, it should also prevent viruses and spyware from your computer, here are some tips & tricks to prevent viruses and spyware:

1. Always activate the anti-virus and anti-spyware, and keep updated on a regular basis. So, your computer will be protected. You will get a warning when the program detects something wrong. You can schedule regular updates to ensure the program is updated regularly to prevent the new virus.

2. Do not open e-mails that are not known to the sender, and always scan email attachments before downloading, even if you know the sender of the message, because sometimes the email accounts of your friends have been hacked to deliver viruses.

3. Do not install anything suspicious. Sometimes you'll see a popup window that appears from your browsing. Do not download anything before you scan with antivirus them thoroughly.

4. Minimize use via USB drive or external hardware. Viruses can be carried from one computer to another computer with a USB stick.

5. Always backup your important data so that data if you have a virus, there is still a backup.

Similarly, Ways to Protect Your Computer From Spyware and Viruses may be useful.

Computer Network Security

Computer Network Security, especially if we connect a computer as a computer lab in the office or home computer network. Network security involves access authorization data in the network, which is controlled by the network administrator. Users select or have an ID and password or other authentication information that allows them access to information and programs within their authority. Network security includes a variety of computer networks, both public and private, which are used in daily work and communication transactions between businesses, government agencies and individuals.

If observed on the security of computer network security can be reviewed in terms of its form is as follows:

- Hardware Security
Security-related hardware hardware used in computer networks. Security hardware is often overlooked but is key to maintaining the network to remain stable. In the security hardware, servers and data storage should be a major concern. Physical access to servers and critical data should be limited as much as possible.

It would be easier for thieves to take the hard drive or tape backup of servers and data storage instead of having to press the software from the network. Garbage should also be considered because many hackers who come to the garbage company to find information on its computer network. One way to secure the hardware is placed in a room that has good security. Airways hole needs to be given attention because people just get into the server room through the channel. Cable networks should be protected so as not easy for hackers to bypass the cable and then connect to the computer.

Access to computers can also be restricted by security settings on the BIOS level that would prevent access to a computer, format the hard drive, and change the contents of the Main Boot Record (where the partition information) hard drive. The use of smart cards and hardware autentifikasiseperti fingerprint detector is also worth considering to improve security.

- Security Software
As the name suggests, it must be guaranteed is the software. The software we mean here can include operating systems, application systems, data and information stored in computer networks especially on the server. For example, if the server is only responsible to the router, do not need web server software and an FTP server installed. Limit the installed software will reduce the conflict between the software and limit access, for example if the router is also equipped with an FTP server, then people from outside with anonymous logins may be able to access the router.

Software to be installed must also have good security arrangements. The ability of encryption (data scrambling) is a specification that must be owned by the software to be used, mainly because the encryption 128 bit encryption with 56-bit systems should be solved with ease today. Some software has a security hole is the sendmail mail server and telnet applications. Sendmail has a weakness that can ditelnet without logging in port (25) and accessor can create an email with a fake address. Telnet application has deficiencies transmit data without encryption (data scrambling) so that when it can be tapped will be very easy to get the data.

The second thing to note is the password. Should set the minimum password length fatherly complicate memcahkan password hacker. The password will also be better if it does not consist only letters or angak, small or capital letters, but must be combined. Encryption can improve network security by randomizing passwords and usernames, either in the notes to the host as well as password and username that is passed the current network to log into another computer.

Routing can not be separated from security breaches. Disorder that often arises is the provision of false information about the routing path (routing in the IP header). Giving false information is usually meant to be a datagram-datagram can be tapped. To prevent such a thing, the router must be set to not allow source routing and routing protocols are included in or some sort of password authentication for routing information is obtained only from trusted routers.

Similarly introductory Computer Network Security, may be useful.

Explain Advantages Of Networks

Define Network with examples. Give importance of Computer Network.

COMPUTER NETWORK

We can define a Computer Network as a set of two or more connected computers to share information and other resources (data, files, printers, hard disk, modem, CD-Rom Drive, CD-Writer, DVD-Rom Drive, DVD-Writer etc.). The computers in a network can share:
Data, Information, Files
Software
Hardware (printers, disk, modems)etc.

EXAMPLES OF COMPUTER NETWORK

• Computer network can be used in an office. Different people in the office can share common information and printer.

• Net Cafes use Computer Network for internet sharing. Net Cafe Owners can save money by sharing one DSL Routers / Modem and a single Internet Connection.

• Computer Network is used in Computer Laboratories of Schools, Colleges and other educational institutes.

• Internet, is also an example of a computer network. Internet is a network of millions of computers connected through phone lines. People can share information, files and talk with one another through internet.

ADVANTAGES OF COMPUTER NETWORKS

Following are some important advantages of computer networks:

1. Data and Information Sharing

Different employees of an organization can share common information with the help of computer network.

2. Software Sharing

Different software can be shared with the help of computer networks.

3. Hardware Sharing

Different hardware can be shared with the help of computer networks. For example, if there are five computer users in an office, we can save cost by using only one printer with the help of computer networking. In a computer network, only one computer will manage all printing needs of the computer users in a small office. In addition, we can share other hard ware devices like hard disks, CD-Rom Drives / Writers, modems, routers and scanners etc.

4. Money Saving

We can save a lot of money by using computer networking, because of sharing the same software and hardware in a network.

5. Internet Sharing

We can buy only one DSL internet connection and share it with in whole organization with the help of computer networking.

6. Easy Communication Within Organization

We can send and receive messages and files through network. In this way, a file can be moved to one place to another within an organization without the need of a physical worker to take and carry the files to a destination. With the help of a command in a computer we can transfer file within seconds from one room to another.

7. Easy Communication Outside Organization

We can send and receive emails and share files with other people outside organization using internet.

Computer Security Software

For security software can be done with actions/specific settings. But the question that arises is: Where is the setting you need and which ones are not? If you use certain programs where the program? The problem, is a more secure system should have a comfort level decreases. Why is that?

If you want to improve computer security by installing a firewall, of course, the system is more secure thanks to a wall of fire. But of course, comfort is reduced because of warnings that often arise, the system is also getting heavier because of too many doing the screening process. That's why people think 1024 times before installing a firewall. But, that does not mean security is not important. Security remains important. It's just a different level for each use of the computer.

The question now, the level of security you need? If the computer is used is limited only by your own home of course you do not have to bother switching to another operating system just to get security. Quite simply optimize the security settings in your PC and adjust to the conditions you face.

The following are various options to secure and optimize the Windows operating system. The setting overall there is no necessity for you to do because the setting will have its own consequences, although the possibility was very small. Our advice before trying something

1. Make your first system restore order if something goes wrong the system can go back to the starting position.

2. Also did backup for a registry editor for guard duty

3. Read carefully about the purpose and how to do every settings you will do

Are the first three points above, and other security types I describe in the next article.

Types Of Scanners Input Device

Scanner / Optical Scanner

A scanner is an input device for computer. It can scan any printed document with text as well as images. It will :

• Read any printed paper or picture,
• Convert text or images into digital form
• Saves this converted digital file into computer storage for later use

Uses Of Optical Scanners

You can scan your documents or pictures to:

1. Store into computer memory.
2. To save lot of effort and time because if you type the whole text on printed page, it will take effort as well as time).
3. Show image or text on computer screen or on a multimedia projector's screen.
4. In addition, you can send this scanned document or image to your friends all over the world with the help of Internet & Email.
5. You can publish the scanned documents or images on your website or blog.
6. You can apply online and send the scanned images of your academic documents in any part of the world within minutes.
7. If your scanner supports OCR - Optical Character Recognition, you can scan a page with printed text and save it in an editable computer file. You can change or add more contents in this scanned file.

Types Of Optical Scanners

There are different types of scanners:

1. Flat Bed Scanner

A flatbed scanner is the most common type of optical scanners used to scan printed text and images and save into computer storage as a digital file. It works on the principle of a photo copier machine. We pickup the cover of the scanner and place the printed page on the glass surface of the scanner. Now we will instruct scanner through computer software to start scanning. The scanner will scan with the help of light and save the digital file into computer storage. If you have an OCR scanner, you can save your text into editable form. This will save a lot of hard work and time to enter text by keyboard too. It is widely used in offices, schools, colleges, universities and homes for common scanning needs. If a book is very rare or difficult to find, we can scan its all pages one by one. Later on we can take prints of these scanned pages through a color printer.

2. Sheet Fed Scanner

A sheet fed scanner works like a fax machine mechanism. In a sheet fed scanner, pages are entered into scanner like a fax machine.

Advantages of Sheet Fed Scanner

1. A feet shed scanner is relatively smaller in size.
2. It is more portable.
3. It takes less space.

Disadvantages Of Sheet Fed Scanner

1. It requires separate pages to scan. But, it cannot scan a book because of its binding. 
2. It can scan normal papers with normal thickness only. 

3. Hand Held Scanner

Hand Held scanner is a small, light weight scanner and portable scanner. It is used to scan small amount of data like short articles from news papers. It is held in hand and is moved over the text page or image slowly and smoothly from start to end. Its scan quality may be lower than flat bed or sheet fed scanner but it can used to capture small amounts of text or small images, quickly.

SkyPix Hand held Scanner

This is a portable, cordless hand held scanner that is used to scan and save important documents, letters, or pictures. It records scanned documents in its memory card. you can transfer these scanned documents on yor computer for later use. You can scan and save important news from the news papers or interesting articles from magazines.

4. Drum Scanners

Drum scanners are used by the Publishers to scan images with details. Drum scanners use photomultiplier tube technology. In drum scanners, the document to be scanned is mounted on a glass cylinder. At the center of the cylinder is a sensor that splits light bounced from the document into three beams. Each beam is sent through a color filter into a photomultiplier tube where the light is changed into an electrical signal. And in this way a complete image with immense details can be obtained. Drum scanners are widely used in publishing industry.