Archives for February 2005

How to Make Sense of Your website’s statistics? 

In the early days of the Internet it was common to visit a web site and see a counter informing you that “you are the 118,456th visitor to this site”, and various webmasters would proudly talk of how many “hits” their sites were getting. Now, things have changed and you will mostly find counters on amateur sites, and wiser webmasters now know that the term “hits” doesn’t really mean much.

The term hit refers to a request for a file on your web site. When someone visits your web page, they request your URL, but in order to see the page, they also have to get all the graphic files that are located on your page. So, one visitor to your page may be requesting 25 different files, and thus you have 25 hits.

The counters of the Internets early days only measured whether someone requested a particular page where the counter was located. They did not give any indication of what the visitor activity was like on the other pages of the site. Those counters often did not differentiate between a “unique visitor” and total visitors. The number of unique visitors is the number of different people (as measured by their computer’s distinct IP number) as opposed to total visitors, which could even be only one person visiting the page many times. (I used to visit my first site a few times a day to see how I was doing!)

So what then is the professional and up-to-date way of gathering statistics and what are the statistics that really count?

Web servers keep logs of all visitor activity. When someone visits your site, he or she requests the various files on the site. The log records all of these requests and records other vital information as well including: the referrer page (or the last page where the surfer was prior to entering your site), what operating system the surfer is using, what screen resolution he or she is using, what search terms he or she made to request your site and a lot of other vital data that could be crucial to your ability to have Internet success or failure.

If you would look a the raw logs of your site you will see a long text file with the date of each entry and would see a few interesting items but you would not be able to put them together very well due to the volume of information. (a line of text for each file requested). There are log analysis programs that do this work for you. One way of using them is to download the log file from your server. Your host should be able to tell you where the file is located, and you can retrieve it using an FTP program. The log file is then fed into the analysis program and the results are generated. There are many programs that do this work. I got started with a simple program (open web scope-and there is free version available). Alternatively, your host may have an analysis program preinstalled on the server, and the results may be able to be seen online (some hosts have the Webalizer program installed for their client’s use)

So what are the things to look for when analyzing the logs?

You should look for the number of unique visitors per day. This will give you an idea of how many people are viewing your site and will give you a broad overview of how you are doing.

Another indication of overall activity on the site is the number of “page views” per day.. Unlike hits, page-views refers to distinct html files or pages that were requested. Suppose you get 200 unique visitors per day, and there are about 2000 page views per day, then you can infer that your average visitor is viewing 10 pages of your site.

Another indication of overall activity is the amount of bandwidth used, or to put it another way, the total of the amount of data that has been transferred per day. This will vary according to how many visitors you have, how many files they view, and of course the type of site you have. If your site is heavy with graphics, or if there are e-books and mp3s to download then the data transfer on your site will be higher than on a site with plain text. This is an important statistic to look at if you have bandwidth restrictions. If you are not worried about this, it is also a good figure to look at just to see the overall activity of the site.

After you have seen the overall activity, it is good to look at the specifics and find more about how your visitors are using your site and how they got to your site.

One of the things I am most interested to see is what are the most accessed pages, and least accessed pages on the site. There are many ways to use this particular piece of information. For example, hopefully your order page will show up in the top ten. If no one is making it to your order page then maybe that is the reason why you are not making any money from the site. Or by looking at this list you may find some pages that are unexpectedly popular, and then you can add more content of the same type.

Related to the popularity of pages is the “click path” through the site. You can see the order in which people visit the various pages of the site and this information may help you to set up your site in a better way. Related to this are the “entry” and “exit” pages. Where do people enter your website? You will be surprised to learn that many people do not enter through your main page. Your inner pages may be attracting much of your traffic, and by learning which pages are popular entry points, you can set up other pages, optimize them and use them to attract more visitors. People have to leave your site sometimes, but it is important to know where the exit points are, and the “exit pages” stat will show you where these pages are.

How did the visitors get to your site in the first place? The referrers list will tell you this information. A referrer is a web site where a visitor was just prior to reaching your site. You can see, first of all, that if you have 100 unique visitors in a day, and if 50 of them were referred, this means that 50 of them probably typed in your URL directly or clicked on an e-mail link or used a bookmark, while 50 of them came from search engines or links on other web sites. Here you will find out which search engines are sending you traffic. You will find out which of your links on other sites are performing well. By carefully looking at your referrers you can go to work on improving your overall promotion strategy.

Another interesting piece of information related to the referrers are the search terms that were used in the various searches. This statistic gives you an idea of what people are looking for when they visit your site. This information can give you an idea of whether you are getting the right kind of audience for your particular product or service.

Finally there is also technical information about your visitors. What type of browser are they using, what operating system (Windows, Mac, Linux) are they using? What screen resolution do they use? You have to make sure that your site can display well to fit the needs of the majority of your visitors.

This information can be obtained using many of the log analysis programs, and also some of the trackers which you can put on your site (for example www.extremetracker.com ) give some of this information. But remember that trackers often only give you the information about one page (where the tracker has been pasted in) If you want to get the total picture, the best way is to analyze the logs. By gathering and understanding this information and making changes to your site based on it, you may be able to increase the profitability and success of your web site. 

About the author

Donald Nelson is a web developer, editor and social worker. He has been promoting web sites since 1995 and now runs A1-Optimization (http://www.a1-optimization.com)  a company that provides low-cost search engine optimization and submission services. He can be reached at support@a1-optimization.com

Automating Tasks in Linux using Cron

Linux has a powerful task scheduler called Cron. Cron will
allow you to run commands automatically at times specified
by you. Cron is similar to the task scheduler you find in
Windows. To keep track of the schedules and tasks it has
to run, Cron requires a file called Crontab (CRON TABle).
All the Cron schedules and tasks should be stored in this
table. The Crontab files cannot be directly edited. You can
add or delete entries in the crontab file using the crontab
command.

What’s Cron and Crontab ?

You must be wondering what the difference between cron and
crontab or wether they are the same. Cron is a process or
program which wakes up every minute and looks for jobs it
has to execute at that moment. Crontab is the list of jobs
and times at which they have to execute.

Crontab Format:

Each entry in Crontab has at least 6 fields separated by a
single space.

Field 1 Minute Range of Values : 0-59
Field 2 Hour Range of Values : 0-23
Field 3 Day Range of Values : 1-31
Field 4 Month Range of Values : 1-12
Field 5 Day of week Range of Values : 0-6 (Sunday being 0)
Field 6 Command to Execute

Now let’s see how to make a crontab entry. Let’s say you
want to run a script backup.sh every day at 6:00pm.The
entry would look like this:

0 18 * * * /home/user/backup.sh

The asterisk (*) is used to indicate that every instance of
the particular time period will be used (i.e. every hour,
every weekday, etc.). I’ve used to full path to the script
/home/user/backup.sh instead of just using backup.sh. This
is because cron runs as root, you should fully qualify your
path names to any scripts that will be run. Let’s see some
more examples :

* Let’s run the script printinvoices.sh every sunday
at 12:45pm.

45 12 * * 0 /home/account/printinvoices.sh

* How about clearaccount.sh every month beginning
at 1:32am ?

21 1 1 * * /home/accont/clearaccount.sh

* Let’s see how to schedule a task to run only on
weekdays(monday to friday)

0 10 * * 1-5 /home/account/cleartemp.sh

Adding and Editing Entries in Crontab
and
Now that you know how crontab entries are formated, it’s time
to put some of your entries into the crontab list. To do this,
you can use the crontab command. By specifying the -e option,
you’ll be taken to the default text editor to add and edit
your crontab list. [crontab -e]

Another method of manipulating your crontab entries is to create
and save a text file with your crontab entries. You can load
your list into crontab by using the following command:
[crontab mycrontablist]
where mycrontablist is the file containing your entries.

Viewing Crontab: [crontab -l]

You can view your current crontab list by specifying the -l
option. Issuing this command will print out a list of all your
current jobs in the crontab list

Removing Crontab: [crontab -r]

The -r option removes your current crontab file. Issuing this
command will empty the contents of the current user’s crontab
file

Output from cron

Usually the output of cron gets mailed to the owner of the
process or the person or email id specified in the MAILTO
variable. To set the MAILTO variable, you’ll have to add the
following command to the top of your crontab :
MAILTO=”your_email_address@domain.com”

If you have a command that is run frequently, and you don’t
want the output to be emailed each time, you can redirect the
output to a log file cmd >> log.file, so your job would be
something like this.

0 18 * * * /home/user/backup.sh>>log.file

If you don’t want any output at all, you can redirect the
output to a null file : cmd>>/dev/null

0 18 * * * /home/user/backup.sh>>/dev/null

About the Author

Vinu Thomas is a consultant on Web design and Internet Technologies.
His website is http://www.vinuthomas.com. You can read more articles
on Linux @ http://www.vinuthomas.com/sections-listarticles-6.html

The Hard Disk Guide

From throwing our unnecessary files, to defragmenting, from partitions to formats-learn how to keep your hard disk in top shape

The hard disk is the place where all your programs and data are stored. If the hard disk Stops working you could end up losing all your data. What we’ll do here is take you on. A quick tour of the different things you need to know about it, so you can keep it working smoothly.

What is the hard disk?
The hard disk is a magnetic mass storage device installed in special bays within the system unit. The hard disk could do compared to a large cupboard having several shelves
With different items being neatly arranged and stored on each self. The hard disk stored all the data you need to store on your PC-the operating system (for example, Windows),
Software program (for example an office suit), business or household applications and data, games, e-mail message, address books and so on.

A hard disk off the assembly line is just a mass of magnetic media. The magnetic surface of the hard disk has to be structured into specific areas where data can be stored properly, a process known as formatting. When you buy a new computer, the system comes with a formatted hard disk.

A hard disk needs to be divided into partitions before it can be used. The hard disk on a newly purchased computer comes configured with a single large partitions, the primary partition (C: in My Computer) and an extended partition, which may be further subdivided into logical partitions (D: E: and so on in My Computer) if required. Partitioning makes the storage of data more efficient and reduces the access time to retrieve data.

The storage capacity of hard disk has increased by leaps and bounds since IBM XT’s first 10 MB hard disk. Nowadays, 10GB is the entry level and 17 GB is common. The hard disk communicates with a PC’s motherboard through an expansion card or a disk interface card.

How does it wok?

The dusk is formatted to divide its magnetic surface into concentric circular paths called tracks (these are like the grooves on a phonograph record) and wedge-shaped slices called sectors. Data is stored in the form of a file or groups of disk sector called clusters. A disk drive locates data by moving its magnetic read-write head to specific track within a specific sector.

When a new file is created in a freshly formatted hard disk, it is assigned cluster numbers in a sequential order. If the file is expanded, then the first available clusters are assigned. When file is deleted, their cluster numbers are simply marked as available. Over course of time, when files grow in size to require additional cluster or are deleted, the perfectly ordered sequence of clusters gets disturbed, a process known as fragmentation.

Partitioning the hard disk
Partitioning divides a large hard disk into smaller virtual-not physical-hard disk or partitions, leading to an efficient utilization of space and boosting your PC’s performance. Partitioning could be very useful in following circumstances:

1-One PC, several users-If several persons have to work on the same PC, partitions could be assigned for each of them so that each person has his or her own “working space.” This could be useful in home setting too, where you could have separate partitions for your spouse, children’s games, business applications and data and so on.

2-Work on multiple operating systems-You may want to work on more than one operating system on your PC, for example Win98, Linux and Windows95. (Maybe you have applications that work perfectly in Win95 but suddenly crashed in Win98). You can keep these various operating systems safely on the same hard disk by installing them in separate partitions.

Partitioning Tools There’re several partitioning tools available for your hard drive. Two of the most popular ones are:

1-PartitionMagic Version 4.o for Windows95 and 98-Partition Magic, from Power Quest is a useful and powerful partitioning program. It effortlessly creates, moves, converts and resizes partitions on your hard disk without the necessity of reformatting the disk of erasing valuable data.

2-FDISK- is a freely available partitioning utility that runs in the DOS environment. Its greatest UPS is that it is available for free. It is cumbersome to use and also requires formatting of the hard disk (perhaps its biggest drawback).

Formatting a hard disk

As with most mechanical devices, prolonged use of the hard disk results in inevitable wear and tear and malfunction. Repeated adding and deleting of files takes its toll on the hard disk and you may get disk error, including the notorious “fatal error” of Windows. This is an indication that you may need to re-format your hard disk to have it working properly again.
However, before deciding to re-format the disk it may be worthwhile to try out other alternative-
1-Run Disk Defragmenter
2-Use a cleanup shareware programs such asregclean.exe, available for download.

However, if after trying out these alternatives, you continue to get fatal error message, then you probably need to format your hard disk.

The procedure of formatting is simple enough but has to be done carefully. When you format the hard disk, all the data on the disk is lost-Windows operating system, software programs, business applications data, games, e-mails messages. In short everything.

How to do the formatting

Windows 95
1- Double-click on My Computer icon. Then click the icon for the drive you want to format. (e. g. C:)

2- On the File menu, click Format and follow the instructions.

Remember that you can not format a disk if there are files open on that disk. If the disk has been compressed, use Drivespace or other compression to format the disk.

Windows 98

1- Click Start, click Shutdown, click Restart, and then click on OK.
2- Press and hold the CTRL key until the Microsoft Windows 98 Startup Menu appears.

3- Select Command prompt only and press Enter.
4- At the C:prompt, type format C: and press ENTER.
5- Follow the instruction on the screen.

After formatting you’re left with a blank hard disk with more space then before. The next step is to restore the programs you need on your disk.

1- First reinstall Windows and then application programs you use.
2- Restore your backups into appropriate files. If you use a Zip drive or a CD-writer, these need to be installed first.
3- Reinstall all drivers for the printer, modem or other peripherals.

Do the defrag

A file on your disk may not be stored all in one place or cluster. For example, if you create a Word document and make changes to it at a later date, the change may get saved in a different cluster from the original file. The more often you make changes to a file, the more disorganized the cluster becomes, and the disk becomes fragmented. This makes the magnetic head that reads and writes data to and from the disk, works harder to retrieve the entire file. Fragmentation of hard drive reduces the storage efficiency and then access time for retrieving information.

The process of defragging helps to rearrange the files and unused space on your hard disk so that programs run faster.

Before Defragging, it may be a good idea to check how much of your hard drive is fragmented. You can do this by running ScanDisk. Empty the temp folders and Recycle Bin before defragging.

Windows 95 and Windows 98-: Open the Start Menu, choose Programs, choose Accessories, and choose System Tools and click on Disk Defragmenter.
You defragging schedule will depend on how much you use the PC. A good rule of the thumb is to defrag every two weeks.
Make sure all your files are closed and then you have turned of the screensaver also.

Spring Cleaning
No more hard disk space left? Getting disk error or illegal operations? It may be time to clean up your hard disk. A few spring cleaning pointers to help you out.

1- Toss out unwanted applications-: check out all the software applications you have loaded on the PC. Delete the old applications if you have installed newer versions. Go to the Control Panel’s Add/Remove program option and uninstall those applications you don’t need.

2- Run ScanDisk-: the ScanDisk option in Windows is very useful application which fixes problem like lost clusters, invalid directory entries and physical disk errors. Run ScanDisk once a month.

Go to start, choose Programs, choose Accessories, and choose System Tools and click on ScanDisk. Click the drive that contains the folders and files you want to check.

3- Defrag often, once in two weeks.

4- Empty Recycle Bin-: Right-click on Recycle Bin icon on the Desktop and choose Empty Recycle Bin from the dropdown menu.
5- Clean out your folders-: do you really need all those download you had undertaken for a past research project or those games you seldom plays? Delete those folders that are not required.

6- Delete .tmp files and create more space on hard disk.

Close all programs. Go to Windows Explorer. Press the key to open find dialog box. Enter *.tmp in the box. Make sure that C: Drive is listed in the Look-in box. Include subfolders by checking them. When .tmp files appear, delete them.

7- Delete temporary Net files to create more space.

Go to the temp Internet Files folder in Windows Explorer. Delete all present files.

8- There are several Windows components on your hard disk that you could do without. You could remove these individual components from the Add/Remove Windows setup option and create more space on your disk

Some windows components that are not necessary are accessories such as Desktop Wallpapers (a saving of 700kB) and games (a saving of 600kB

Before you format…..
1- Enter the hard drive’s technical specifications (number of cylinders, tracks, sectors etc.) into the PC’s BIOS setup table so that it is available for the machine’s Startup program.

2- Backup all your important data onto another hard disk, recordable CDs, Zip Drive, magnetic tapes or floppies. If you have a sort of backup space or are in hurry, copy only important folders. Backup your e-mail and address books too. After taking the backups, check them out to make sure that they are okay.

3- Backup any folders that you share with others over a network.

4- Keep handy the installation disks or CDs of the application software you use, such as Windows or an office suite. These will have to be re-installed after formatting.

5- Keep handy the driver disks for your printer, sound card, CD ROM driver, modem or other devices. These will have to be re-installed after formatting.

FAT Facts

When a hard disk is formatted, a File Allocation Table (FAT) is created on the disk. FAT keeps a record of the locations of all the files on the disk FAT 16 is the file allocation system used in DOS and Windows 95. FAT 32 file system is used in Windows 98 or Win 95 OSR 2. FAT 32 is considered to be more efficient as it saves more space on the disk.

The performance of hard disk largely affects the overall performance of a PC. Hard disk performance factors include storage capacity, data access time (the time it takes for the read write heads to find a required position on the magnetic surface), data transfer time (measure how many million bit per second can be transferred from disk to RAM) and reliability.

TIP
Keep your hard disk in tip-top condition and optimize its performance.
1- Create separate folders for each business application, data or for each family member. This will keep your disk clean and organized.

2- Avoid the compression
Though file compression increases the amount of storage space, it also considerably slowdown system performance.
3- Keep 10% free. Always keep at least 10% of your hard disk free-filling it beyond 90% of its capacity will lead to system slowdown and potential loss of information.

4- Run the Maintenance Wizard utility of Windows 95 and 98. This utility make your programs run faster, checks your hard disk for problems and free hard disk space. You can schedule it to0 run on a regular basis at a specific time, for example once a week or other interval of your choice.

Start maintenance Wizard by clicking on Start, choose Programs, choose Accessories, choose system tools and click on Maintenance Wizard.

5- Use software package that help to optimize your hard disk’s performance, e.g. Symantec’s Norton Utilities.

About the author

Pawan Bangar,
Technical Director,
Birbals,
(Hbirbals,Seobirbals,Ebirbals,Ibirbals)
Cell:91-175-3150734
Cell:+91-98153-52253
email:
pawan@ebirbals.com
pawan@birbals.com
pawan@hbirbals.com
Yahoo Messenger:pawanishappy@yahoo.com
MSN messenger:ebirbals@hotmail.com

Linux Runlevels 

Linux systems today generally use eight runlevels. Runlevels
define what services or processes should be running on the
system. The init process can run the system in one of eight
runlevels. The system runs only one of the eight runlevels
at a time. The main runlevels are from 0 – 6. Here’s what
each runlevel is for

Runlevel 0: Halt System – To shutdown the system
Runlevel 1: Single user mode
Runlevel 2: Basic multi user mode without NFS
Runlevel 3: Full multi user mode (text based)
Runlevel 4: unused
Runlevel 5: Multi user mode with Graphical User Interface
Runlevel 6: Reboot System

Runlevels 1 and 2 are generally used for debugging purposed
only, and are not used during normal operations. Most desktop
linux distributions boot into runlevel 5, which starts up the
Graphical Login Prompt. This allows the user to use the system
with X-Windows server enabled. Most servers boot into runlevel
3, which starts the text based login prompt.

Linux runlevels can be changed on the fly using the init tool.
If you want to switch from text based operations to the
Graphical Interface, you just have to type in ‘telinit 5’ in the
root prompt. This will bring up the Graphical Interface in your
system.

Each runlevel can be configured by the system administrator. The
“/etc/inittab” file has information on which runlevel to start
the system at and lists the processes to be run at each runlevel.

Each runlevel has its own directory structure where you can
define the order in which the services start. These directories
are located in the /etc/rc.d/ directory, under which you have
rc1.d, rc2.d, rc3.d…. rc6.d directories where the number from
0 through 6 that corresponds to the runlevel. Inside each directory
are symbolic links that point to master initscripts found in
/etc/init.d or /etc/rc.d/init.d.

You can also change the runlevel at boot time. If your system uses
LILO as the boot manager, you can append the runlevel to the boot
command :
LILO: linux 3 or
LILO: linux 5

If your system uses GRUB, you can change the boot runlevel by
pressing the `e’ key to edit the boot configuration. append the
runlevel to the end of the boot command as shown:
kernel /vmlinuz ro root=/dev/hda1 5 

About the author

Vinu Thomas is a consultant on Web design and Internet Technologies.
His website is http://www.vinuthomas.com. You can read more articles
on Linux @
http://www.vinuthomas.com/sections-listarticles-6.html  

What Is Data Recovery?
 by: Jakob Jelling

Data recovery is the retrieval of inaccessible or contaminated data from media that has been damaged in some way. Data recovery is being increasingly used and is an important process nowadays.

There has been a lot of progress in increasing the memory capacity of data storage devices. Therefore data loss from any one incident also tends to be very high. The relevance of lost data can vary greatly. Maybe you have had the experience of storing a homework assignment on a floppy disk only to have it missing on the day the assignment in due.

Consider the fact that a large amount of businesses nowadays have vital organizational related data stored on machines. Also hospitals store data on patients on computers. Large amounts of websites nowadays use databases technology to enhance their websites and make them more dynamic. Php and MySql use has been on the rise on the Internet. Database failure is not uncommon and so it is not a fail proof method of storing information.

Companies have high reliance on computer technology to write and store data relevant to their business operations. Thus the data being stored can have a great deal of impact on personal lives and operations of companies.

There can be several causes of data loss.

Data loss can occur from unexpected incidences including national tragedies such as floods and earthquakes.

Often power failure can cause loss of data from hard drives. Sudden power surges can also cause a lot of damage to a computer’s hard drive.

Accidentally deleting a file or formatting a hard drive or floppy disk is a common reason for data loss.

If you have accidentally lost any important documents there are several steps you can take. Remember that if you have accidentally erased a file, it may not have vanished from your computer. It may have left an imprint in a different format on the computer’s hard drive or other storage devices. Recovering the data involves locating it and transforming it into human readable form.

Not all data may be recoverable.

You can either hire professional service to help you solve your problem or attempt a recovery on your own.

You can carry out data recovery operations on your own computer if you know what you are doing. There is data recovery software widely available that can assist you in the process.

Data recovery can become complicated if you overwrite on the storage device that has the lost data. Therefore if you do not know what you are doing, it is advisable to contact a professional service firm.

Data recovery professionals are experts in recovering data from all sorts of media and from a variety of damages done. There are many specialists out there who have years of experience in the IT field. The kind of data recovery operation to use will depend a great deal on the storage device and other variables such as the amount of damage done or the operation system used such as Macintosh, Windows or Linux.

There are some cases where it may be impossible to recover any data. However do not fret as the odds lie in your favor since a high percentage of data recovery operations are successful.

Preventing data loss

Of course the best way is to prevent data loss in the first place.

Data backup allows for restoring data if data loss occurs. Even ordinary pc users can set up their computer to carry out regularly scheduled backup operations. In the event of a hard drive crash or an unwise change in settings by an uninformed user, the restore tool can be used to retrieve deleted data or to restore the computer’s settings from an earlier time.

For the back up process to be useful it should involve several reliable backup systems and performing drills to make sure the data is being stored correctly. Additional protection methods from data loss include making sure that the hard drive is protected from damages from the external environment. This includes protection from sunlight and temperature extremes.

Also plugging in your pc into a surge protector rather than an ordinary outlet can give your computer a protection layer from electricity fluctuations. Keep your virus protection up to date. Also remember to keep your backup data separate from your computer.

Nevertheless a lot of companies will go through a disaster and experience data loss. The best thing to do is not to panic and also not to ignore the situation. The quicker you rectify the situation the better. Counting on data loss will help you be prepared for any such event. 

About The Author

Jakob Jelling is the founder of http://www.sitetube.com. Visit his website for the latest on planning, building, promoting and maintaining websites.

Networking Basics
 by: Kashif Raza

A network is a group of computers, printers, and other devices that are connected together with cables. The sharing of data and resources. Information travels over the cables, allowing network users to exchange documents & data with each other, print to the same printers, and generally share any hardware or software that is connected to the network. Each computer, printer, or other peripheral device that is connected to the network is called a node. Networks can have tens, thousands, or even millions of nodes.

Cabling:

The two most popular types of network cabling are twisted-pair (also known as 10BaseT) and thin coax (also known as 10Base2). 10BaseT cabling looks like ordinary telephone wire, except that it has 8 wires inside instead of 4. Thin coax looks like the copper coaxial cabling that’s often used to connect a VCR to a TV set.

Network Adapter:

A network computer is connected to the network cabling with a network interface card, (also called a “NIC”, “nick”, or network adapter). Some NICs are installed inside of a computer: the PC is opened up and a network card is plugged directly into one of the computer’s internal expansion slots. 286, 386, and many 486 computers have 16-bit slots, so a 16-bit NIC is needed. Faster computers, like high-speed 486s and Pentiums, , often have 32-bit, or PCI slots. These PCs require 32-bit NICs to achieve the fastest networking speeds possible for speed-critical applications like desktop video, multimedia, publishing, and databases. And if a computer is going to be used with a Fast Ethernet network, it will need a network adapter that supports 100Mbps data speeds as well.

Hubs

The last piece of the networking puzzle is called a hub. A hub is a box that is used to gather groups of PCs together at a central location with 10BaseT cabling. If you’re networking a small group of computers together, you may be able to get by with a hub, some 10BaseT cables, and a handful of network adapters. Larger networks often use a thin coax “backbone” that connects a row of 10BaseT hubs together. Each hub, in turn, may connect a handful of computer together using 10BaseT cabling, which allows you to build networks of tens, hundreds, or thousands of nodes. Like network cards, hubs are available in both standard (10Mbps) and Fast Ethernet (100Mbps) versions.

LANs (Local Area Networks)

A network is any collection of independent computers that communicate with one another over a shared network medium. LANs are networks usually confined to a geographic area, such as a single building or a college campus. LANs can be small, linking as few as three computers, but often link hundreds of computers used by thousands of people. The development of standard networking protocols and media has resulted in worldwide proliferation of LANs throughout business and educational organizations.

WANs (Wide Area Networks)

Often a network is located in multiple physical places. Wide area networking combines multiple LANs that are geographically separate. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone lines (both synchronous and asynchronous), satellite links, and data packet carrier services. Wide area networking can be as simple as a modem and remote access server for employees to dial into, or it can be as complex as hundreds of branch offices globally linked using special routing protocols and filters to minimize the expense of sending data sent over vast distances.

Internet

The Internet is a system of linked networks that are worldwide in scope and facilitate data communication services such as remote login, file transfer, electronic mail, the World Wide Web and newsgroups. With the meteoric rise in demand for connectivity, the Internet has become a communications highway for millions of users. The Internet was initially restricted to military and academic institutions, but now it is a full-fledged conduit for any and all forms of information and commerce. Internet websites now provide personal, educational, political and economic resources to every corner of the planet.

Intranet

With the advancements made in browser-based software for the Internet, many private organizations are implementing intranets. An intranet is a private network utilizing Internet-type tools, but available only within that organization. For large organizations, an intranet provides an easy access mode to corporate information for employees.

Ethernet

Ethernet is the most popular physical layer LAN technology in use today. Other LAN types include Token Ring, Fast Ethernet, Fiber Distributed Data Interface (FDDI), Asynchronous Transfer Mode (ATM) and LocalTalk. Ethernet is popular because it strikes a good balance between speed, cost and ease of installation. These benefits, combined with wide acceptance in the computer marketplace and the ability to support virtually all popular network protocols, make Ethernet an ideal networking technology for most computer users today. The Institute for Electrical and Electronic Engineers (IEEE) defines the Ethernet standard as IEEE Standard 802.3. This standard defines rules for configuring an Ethernet network as well as specifying how elements in an Ethernet network interact with one another. By adhering to the IEEE standard, network equipment and network protocols can communicate efficiently.

Protocols

Network protocols are standards that allow computers to communicate. A protocol defines how computers identify one another on a network, the form that the data should take in transit, and how this information is processed once it reaches its final destination. Protocols also define procedures for handling lost or damaged transmissions or “packets.” TCP/IP (for UNIX, Windows NT, Windows 95 and other platforms), IPX (for Novell NetWare), DECnet (for networking Digital Equipment Corp. computers), AppleTalk (for Macintosh computers), and NetBIOS/NetBEUI (for LAN Manager and Windows NT networks) are the main types of network protocols in use today. Although each network protocol is different, they all share the same physical cabling. This common method of accessing the physical network allows multiple protocols to peacefully coexist over the network media, and allows the builder of a network to use common hardware for a variety of protocols. This concept is known as “protocol independence,” which means that devices that are compatible at the physical and data link layers allow the user to run many different protocols over the same medium.

Topologies

A network topology is the geometric arrangement of nodes and cable links in a LAN, and is used in two general configurations: bus and star. These two topologies define how nodes are connected to one another. A node is an active device connected to the network, such as a computer or a printer. A node can also be a piece of networking equipment such as a hub, switch or a router. A bus topology consists of nodes linked together in a series with each node connected to a long cable or bus. Many nodes can tap into the bus and begin communication with all other nodes on that cable segment. A break anywhere in the cable will usually cause the entire segment to be inoperable until the break is repaired. Examples of bus topology include 10BASE2 and 10BASE5. 10BASE-T Ethernet and Fast Ethernet use a star topology, in which access is controlled by a central computer. Generally a computer is located at one end of the segment, and the other end is terminated in central location with a hub. Because UTP is often run in conjunction with telephone cabling, this central location can be a telephone closet or other area where it is convenient to connect the UTP segment to a backbone. The primary advantage of this type of network is reliability, for if one of these ‘point-to-point’ segments has a break, it will only affect the two nodes on that link. Other computer users on the network continue to operate as if that segment were nonexistent.

Peer-to-Peer Networks

A peer-to-peer network allows two or more PCs to pool their resources together. Individual resources like disk drives, CD-ROM drives, and even printers are transformed into shared, collective resources that are accessible from every PC.

Unlike client-server networks, where network information is stored on a centralized file server PC and made available to tens, hundreds, or thousands client PCs, the information stored across peer-to-peer networks is uniquely decentralized. Because peer-to-peer PCs have their own hard disk drives that are accessible by all computers, each PC acts as both a client (information requestor) and a server (information provider). A peer-to-peer network can be built with either 10BaseT cabling and a hub or with a thin coax backbone. 10BaseT is best for small workgroups of 16 or fewer users that don’t span long distances, or for workgroups that have one or more portable computers that may be disconnected from the network from time to time.

After the networking hardware has been installed, a peer-to-peer network software package must be installed onto all of the PCs. Such a package allows information to be transferred back and forth between the PCs, hard disks, and other devices when users request it. Popular peer-to-peer NOS software includes Most NOSs allow each peer-to-peer user to determine which resources will be available for use by other users. Specific hard & floppy disk drives, directories or files, printers, and other resources can be attached or detached from the network via software. When one user’s disk has been configured so that it is “sharable”, it will usually appear as a new drive to the other users. In other words, if user A has an A and C drive on his computer, and user B configures his entire C drive as sharable, user A will suddenly have an A, C, and D drive (user A’s D drive is actually user B’s C drive). Directories work in a similar fashion. If user A has an A & C drive, and user B configures his “C:WINDOWS” and “C:DOS” directories as sharable, user A may suddenly have an A, C, D, and E drive (user A’s D is user B’s C:WINDOWS, and E is user B’s C:DOS). Did you get all of that?

Because drives can be easily shared between peer-to-peer PCs, applications only need to be installed on one computer–not two or three. If users have one copy of Microsoft Word, for example, it can be installed on user A’s computer–and still used by user B.

The advantages of peer-to-peer over client-server NOSs include: � No need for a network administrator � Network is fast/inexpensive to setup & maintain � Each PC can make backup copies of its data to other PCs for security. By far the easiest type of network to build, peer-to-peer is perfect for both home and office use.

Client-Server Networks

In a client-server environment like Windows NT or Novell NetWare, files are stored on a centralized, high speed file server PC that is made available to client PCs. Network access speeds are usually faster than those found on peer-to-peer networks, which is reasonable given the vast numbers of clients that this architecture can support. Nearly all network services like printing and electronic mail are routed through the file server, which allows networking tasks to be tracked. Inefficient network segments can be reworked to make them faster, and users’ activities can be closely monitored. Public data and applications are stored on the file server, where they are run from client PCs’ locations, which makes upgrading software a simple task–network administrators can simply upgrade the applications stored on the file server, rather than having to physically upgrade each client PC.

In the client-server diagram below, the client PCs are shown to be separate and subordinate to the file server. The clients’ primary applications and files are stored in a common location. File servers are often set up so that each user on the network has access to his or her “own” directory, along with a range of “public” directories where applications are stored. If the two clients below want to communicate with each other, they must go through the file server to do it. A message from one client to another is first sent to the file server, where it is then routed to its destination. With tens or hundreds of client PCs, a file server is the only way to manage the often complex and simultaneous operations that large networks require.

Computer Networking is the very important and the crucial part of the Information Technology. Millions of the computers are networked together to form the Internet. Networking plays a important role in every kind of organization from small to medium sized, in Banks, Multinataional Companies, Stock Exchanges, Air Ports, Hospitals, Police Stations, Post Offices, Colleges, Universities, and even in home, in short networking plays an important role everywhere where computers are used. This article will be interesting for the students, network professionals and for the people who are interested in the computer networking 

About The Author

This article is created and submitted by Kashif Raza http://www.cisconotes.net

kashif414@yahoo.com