Monday, February 28, 2011

If you have lost the Administrator password, you must have the following to recover:
  1. A regular user account that can logon locally to your Windows NT Workstation, Server, or PDC whichever you are recovering. If you already have an alternate install of NT, skip to The Process, Set 02.
  2. The Windows NT CD-ROM and setup diskettes (winnt /ox to make them from the CD-ROM).
  3. Enough room to install a temporary copy of NT (Workstation will suffice, even to recover on a PDC).
  4. Your latest Service Pack.
  5. The Process:
  6. Install a copy of Windows NT as TEMPNT, on any drive. Install your latest Service Pack.
  7. Boot the alternate install.
  8. At a command prompt, type AT HH:MM /INTERACTIVE CMD /K where HH:MM is 10 minutes from now (or however much time you need to complete the remaining steps and logon to your primary installation).
  9. Use Regedt32 to edit:
  10. Double click Schedule and click the one sub-key.
  11. Double click the Schedule value name in the right hand pane and copy the REG_BINARY string to the clipboard.
  12. Select HKEY_LOCAL_MACHINE and Load Hive from the Registry menu.
  13. Navigate to your original installation\System32\Config folder and double-click System.
  14. At the Key Name prompt, type ORIGSYS.
  15. Navigate to ORIGSYS\Select and remember the value of Current; i.e. n.
  16. Browse to ORIGSYS\ControlSet00n\Services\Schedule and if Start is not 0x2, set it to 0x2.
  17. With Schedule selected, Add Key from the Edit menu.
  18. Type 001 in Key Name and click OK.
  19. Select 001 and Add Value name Command as type REG_SZ and set the string to CMD /K.
  20. Select 001 and Add Value name Schedule as type REG_BINARY and paste the string from step 06.
  21. Select ORIGSYS and Unload Hive from the Registry Menu.
  22. Use Conrol Panel / System / Startup... to make your original install the default.
  23. At a CMD prompt:
    attrib -r -s -h c:\boot.ini edit c:\boot.ini and either change the id of the TEMPNT lines to Maint 4.0 on both entries if you intend to keep this maintenance install or delete them. attrib +r +s +h c:\boot.ini
  24. Shutdown and restart your original install.
  25. Logon as your user account and wait for HH:MM from step 03.
  26. When the CMD prompt opens, it will be under the context of the Schedule user, either the System account or an administrative account. If this machine is the NOT the PDC, type MUSRMGR.EXE, if it is the PDC, type USRMGR.EXE. If you get an error, click YES and type your domain name.
  27. Set the Administrator password and logoff.
  28. Logon as Administrator.
  29. If you are deleted the TEMPNT entries in step 18, delete \TEMPNT
  30. Promise To: Never forget the Administrator password again implement physical security.
Note: If the Schedule service runs under the context of a Domain Administrator on any member workstation, all you need to recover the PDC Administrator is a network login.
A hacker is a computer user who, for either negative or positive motivations, will manipulate and break into computer systems. You will see the "hacker" term spelled creatively in different ways, such as "haxor", "Hax0r", and "H4X0R", all of which mean the same thing.

Originally, a hacker of the 1980's was strictly evil and dishonest: a criminal who would illegally and unethically take control of computers and networks. And indeed, that criminal definition still applies today in the 21st century. However, the term hacker has also broadened to include non-criminal computer users. Today, "hacker" encompasses "black hat", "white hat", and "grey hat" computer users:

There are 3 modern types of hackers:
  1. Black Hats: Criminal Hackers. Common job: Penetration Tester.
  2. White Hats: Ethical Hackers. Common job: Network Security Specialist.
  3. Grey Hats: Deals in both of the above (jack of all trades, master of none).

1) Classic "Black Hat" Hackers = Criminals/Lawbreakers
This is the classic definition of a hacker: a computer user who willfully seeks to vandalize or commit theft on other people's networks. This classic hacker is also known as a "black hat hacker" because of his malicious motivations. Black hats are gifted but unethical computer users who are motivated by feelings of power and petty revenge. They are electronic thugs, in every sense of the word, and share the same personality traits as punk teens who smash bus stop windows for personal satisfaction.

Black hat hackers are renowned for the following common cybercrimes:
  • DOS/DDOS attacks that overload Internet servers.
  • Defacing websites by hijacking control and replacing the main page photos with rude slogans.
  • Performing identity theft by stealing private information of individuals.
  • Botnetting: taking remote control of dozens of personal computers, and programming them to "zombie" as spam broadcasters.

2) White Hat "Ethical Hackers" = Network Security Specialists
Different from the classic black hat hackers, white hat hackers have honorable, or at least benign, motivations. A white hat "ethical hacker" is a talented computer security user employed to help protect computer networks. These white hats are not unlike former convicts who take on work as store security guards. While they themselves may not be completely ethical, their vocation is considered white hat. Ethical hackers are usually motivated by a steady paycheck. It is not surprising to see ethical hackers spending those paychecks on very expensive personal computers in their personal lives, so they can play online games after work. As long as they have a good-paying job to support their personal habits, an ethical hacker is usually not motivated to destroy nor steal from their employer.

Related: White Hat "Academic Hackers" = Creative Computer Artists
Another kind of white hat is the "academic hacker": a computer artisan who is not interested in protecting systems, but rather in creating clever programs and beautiful interfaces. If you are an academic hacker, for example, you will take existing programmatic code, and improve upon it through clever alterations and additions. "Academic hacking" is about obsessively innovating computer code so that it becomes more beautiful or more efficient as a program. Academic hackers, in general, are harmless and do not seek to hurt other people's networks. Academic white hats are often graduate students in computer programming.

3) Grey Hat Hackers = Uncertain which side of the law to stand for.
Grey hats are often "hobby hackers": users with basic or intermediate tech skills who like to disassemble and modify their own computers for hobby pleasure, and who also dabble in minor white collar crimes, like file-sharing movies or cracking software. Yes, millions of p2p downloaders are hobby hackers. And indeed, if you have ever modified your router and firewall to allow faster p2p downloads, you could describe yourself as a "grey hat" hobby hacker. Gratefully, only a small percentage of hobby hackers ever escalate into becoming serious black hat hackers.

While phishing is starting to show up in many different forms, basically it's the practice of tricking someone on the Web in order to retrieve their sensitive personal information: passwords, banking information, etc. Most often, phishing takes the form of fraudulent emails that ask you to "confirm your password", or "verify your account", or "confirm your identity." You might've gotten an email (we all have!) that had this wording in it; I just pulled this out of my email spam filter:

"We suspect an unauthorized transaction on your account. To ensure that your account is not compromised, please click the link below and confirm your identity."

"During our regular verification of accounts, we couldn’t verify your information. Please click here to update and verify your information."

How do I know it's a phishing scam?

There's a couple of different ways that you'll be able to spot a phishing scam right off the bat.
  • A phishing scam will ask you for personal information. Any email that you get from a reputable institution - eBay, banks, Amazon, etc. - will NEVER, ever, ever, EVER ask you for your password or your personal security information. Period. Email is not an absolutely secure medium for transporting that kind of information (yet) and there's no good reason that any company would be asking you for that info. In fact, most reputable companies will have this tagline: "(insert company name here) will never ask you to give us your personal or billing information."
  • A phishing email, if clicked, will open up to an insecure site. Every site that uses security encryption will have the HTTPS protocol at the beginning of the URL. Did I lose you? No problem - What is HTTPS?. The HTTPS is a great way to instantly identify a phishing scam - no matter how legit the website may look, if it doesn't have the HTTPS at the beginning of the URL, it's not for real.
  • Misspelled words in the site's URL address. A quick tip off that a phishing scam is underway is if the name of the site is misspelled in the site address; for example,
  • Personal information asked for via the phone. A very slick phishing scam I've seen: you'll get an email from your banking institution, asking you to call a "secure" number in order to confirm your account number, billing address, or other personal information. This is NOT a legitimate request.
  • Generic greeting in the phishing email. One subtle way to detect a phishing attempt is to check if you're personally identified in the email content. For instance, if eBay ever contacts me, they're going to identify me by my eBay user ID, not "Dear eBay Customer."

How do I avoid phishing attempts?

Be Critical:For starters, you'll want to get very skeptical of any emails sent to you that ask for your personal information. If a bank or other company really needs to get a hold of you to verify something, they'll most likely send it in writing or via a secure email. Make sure you familiarize yourself with the above phishing ID tips so you won't get caught.
Be Protected: While researching this email, I opened up a phishing email in my spam filter and clicked on the "secure" site. Instantly, my Google toolbar went crazy on me, and threw a security warning, a big red emergency button in my URL address bar, and grayed out my browser window! That's the kind of protection you need to have,

In addition, Firefox has some stellar security features. I highly recommend using Firefox as your Web browser if you'd like to stay safe on the Web.

Don't get caught in a phishing scam

The bottom line: phishing scams are just going to get more and more sneaky. In order to avoid being caught, you're going to have to be very wary of any attempt to retrieve your personal information, and take proper security procedures everytime you're on the Web.
Sometimes we just want to be left alone. It's just plain creepy to think that somewhere in a bunch of digital data warehouses there are files containing our search habits, buying preferences, socio-economic status, etc. It's gotten to the point where Amazon knows what I want to buy before I even start searching for it.
How do we get our anonymity-sexy back? I'm going to give you a few tips that you can use to keep a low profile while on the net. Please note that even after using all these methods you can still be found by digital forensic CSI-type folks, so don't do anything illegal because, as the internet sensation Antoine Dodson once said, "We gon' find you". These are merely tips to protect your privacy and anonymity and not a handbook for becoming the next Jason Bourne.

1. Use a Web Browsing Proxy Service
Using an anonymous browser proxy service is one of the easiest ways to prevent the websites you visit from determining your actual IP address. Your true IP address aids advertisers in targeting you, hackers in attacking you, and stalkers in finding you. Your IP can also provide your actual location (at least down to the city and local zip code if you're using a local internet service provider).
An anonymous web proxy service acts as an intermediary between you and the website you are trying to visit. When you try to visit a website using a proxy, your request goes through the web proxy service and then onto the website. The proxy relays the web page you requested back to you, however, since the proxy is the middle man, the website only sees their IP address information and not yours.
There are literally hundreds of both commercial and free anonymous web proxy services available, but you need to be careful before you just randomly pick one, as you're essentially relying on them to protect your data and ensure privacy. The web browsing proxy service is privy to the entire conversation so eavesdropping is still possible. A couple of the more well known commercially available proxies include and GhostSurf.
Whatever proxy service you choose, be sure to check their privacy policy to see how your identity and other information is protected.

2. Opt-out of Everything Whenever Possible
Google and other search engines feature the ability for you to remove your personal information such as your phone numbers and physical address. They even let you control whether or not the Google Street View of your house is fully available to the public. If you've never used Google Street View, I urge that you try it. Google Street View can be used by criminals to virtually "case" your home or business. They can virtually pull up right in front of your door to see what the best method of entering your home or business is. While you can't have your house completely removed you can have it blurred. Visit the Google Maps Privacy page for details.
Additionally, you can opt-out of targeted advertising and cookie tracking on some of the larger search engines and at many internet-based retailers.
Other Opt-out Resources:
Google Phone Book Name Removal
Yahoo Phone Number Removal Tool

3. Setup a Throwaway E-mail Account for Site Registrations and Online Purchases
One thing most people hate is giving their e-mail address to everybody and his brother when they have to register for something online. Every time you give someone your e-mail address you risk having it sold to spammers or used for excessive marketing e-mails.
Many people would love to just put a fake e-mail address instead of the real thing but we all know that a confirmation e-mail has to be verified before we can register or purchase something.
Consider opening a throw-away e-mail account devoted to just your site registrations and online purchases. Chances are your ISP allows more than one e-mail account per subscriber or you can use Gmail, Microsoft, or any other free e-mail services available

4. Check and Update Your Facebook Privacy Settings
Most people set their Facebook privacy settings when they first sign up, but rarely check back to see what additional privacy options are available now. Facebook is constantly evolving and changing their privacy options. It's best to check them frequently to ensure that you haven't granted more information to the public than you intended to.
The best rule of thumb is to set most items viewable to "Friends Only". Be sure to check your application settings as well to see which Facebook Apps you have installed vs. what you think you have installed. Remove any that look sketchy or that you don't frequently use. The more Facebook apps you have installed, the more chances there are that one of them will be a scam or spam app that is stealing your personal information or using it for unlawful purposes.
If you want the Facebook equivalent of turning off your porch light (like when you want the trick-or-treaters to go away), Click the chat button, and then choose "Go Offline". Now you can be invisible so people will quit "poking" you.

5. Turn on Your Router's Stealth Mode
Many home wired and wireless network routers have a feature called "Stealth Mode". Stealth mode allows you to make the computers on the inside of your home network virtually invisible to hackers.
Stealth mode prevents your router from responding to "pings" from hacker's port scanning tools. Hackers use these scanning tools to find unsecured ports and services on your computer. They could use this knowledge to mount a port or service specific attack. By not responding to these requests your router makes it look like there is nothing running inside your network.
Check your router's setup guide for instructions on how to enable this feature if it is available.
I will cover 4 methods over here:

1. Facebook Phishing
2. Keylogging
3. Social engineering
4. Primary email address hack

Facebook phishing:

I have taken this method first because i think this is the most popular method/way of hacking facebook. I studied various facebook surveys taken on web about hacking facebook. The results of these surveys show "Phishing" as the most used method to hack facebook and to note…"Phishing is favorite method of facebook hackers". So, friends.. beware of facebook Phishing. Facebook staff is working hard to avoid these Facebook phishers. Phishing not only allows you to hack Facebook but also almost any email account. You have to only get the trick used to make a phisher, which i think is very easy. I learnt it without any difficulty. But, remember, this is only for educational purpose. I will not extend this topic over here as i have added more on Phishing in my article How to hack facebook password


This is my second favorite, as only thing you have to do is remotely install a keylogger application (if you don't have any physical access to victim computer). Keylogging becomes more easy if you have physical access to victim computer as only thing you have to do is install a keylogger and direct it to your destination so that it will send all recorded keystrokes to pointed destination. What a keylogger does is it records the keystrokes into a log file and then you can use these logs to get required Facebook password and thus can hack facebook password. I have posted detailed information of top keyloggers in the trade for more information see my password hacking softwares section

3. Social engineering:

This sounds to be pretty not working at beginning. Even I was neglecting this way. But, once, I thought of using it against my friend on orkut and i got his Facebook password very easily by this method. I think many of you might be knowing how what this social engg is. For newbies, social engineering is method of retrieving password or answer of security question simply be quering with the victim. You have to be very careful while using this as victim must not be aware of your intention. Just ask him cautiously using your logic.

4.Primary email address hack

If Facebook hacker, by some means, hacks your gmail or yahoo account which you are using as primary email address, then this Facebook hacker can easily hack your Facebook password using "Forgot password" trick. He will simply ask Facebook to send password reset email to your primary email address- which is already hacked. Thus, your Facebook account password will be reset and orkut account hacked !!!

So, always remember to protect your Facebook primary email address and try to keep unknown or useless mail id as your primary email address
So far, i found these Facebook hacking methods as best and working ways to hack facebook account passwords. I never encourage hacking Facebook or any email account,,I just wanna make you aware about Facebook dangers online. I will appreciate your effort if you mention any other Facebook hacking method.
 Posted by Kriishley Hyb
Facebook has become the Google of social networks. If you're not updating your status right now, chances are that you are uploading photos or taking some sort of odd quiz. We post tons of intimate details about our lives that we normally wouldn't share with anyone. We think that as long as we make sure our privacy settings are set correctly that we are safe and snug within our circle of friends.

The problem is that we never know who's really looking at our information. Our friend's account could have been hacked when they installed some rogue application, or their creepy uncle might be using their account because they forgot to log out. For the sake of the safety of you and your family, there is some information that you should never post on Facebook. Here are 5 things you should consider removing or not posting to Facebook and/or other social networks.

1. You or Your Family's Full Birth Dates

We all love getting “happy birthdays” from our friends on our Facebook wall. It makes us feel all warm inside knowing that people remembered and cared enough to write us a short note on our special day. The problem is when you list your birthday you are providing identity thieves with one of the 3 or 4 pieces of personal information that is needed to steal your identity. It’s best to not list the date at all, but if you must, at least leave out the year. Your real friends should know this info anyway.

2. Your Relationship Status

Whether you are in a relationship or not, it may be best not to make it public knowledge. Stalkers would love to know that you just became newly single. If you change your status to "single" it gives them the green light they were looking for to resume stalking now that you're back on the market. It also lets them know that you might be home alone since your significant other is no longer around. Your best bet is to just leave this blank on your profile.

3. Your Current Location

There are a lot of people who love the location tagging feature on Facebook that allows them to let people know where they are 24/7. The problem is that you have just told everyone that you're on vacation (and not at your house). If you add how long your trip is then thieves know exactly how much time they have to rob you. My advice is not to provide your location at all. You can always upload your vacation pictures when you get home or text your friends to let them know how jealous they should be that you're sipping an umbrella drink while they toil away at work.

4. The Fact That You Are Home Alone

It is extremely important that parents make sure their children never put the fact that they are home alone in their status. Again, you wouldn’t walk into a room of strangers and tell them you are going to be all alone at your house so don’t do it on Facebook either.

We may think that only our friends have access to our status, but we really have no idea who is reading it. Your friend may have had their account hacked or someone could be reading over their shoulder at the library. The best rule of thumb is not to put anything in your profile or status that you wouldn’t want a stranger to know. You may have the most stringent privacy settings possible, but if your friend’s account gets compromised than those settings go out the window.

5. Pictures of Your Kids Tagged With Their Names

We love our kids. We would do anything to keep them safe, but most people post hundreds of tagged pictures and videos of their kids to Facebook without even giving it a second thought. We even go so far as to replace our profile pictures with that of our children.

Probably 9 out of 10 parents posted their child’s full name, and exact date and time of birth while they were still in the hospital after delivery. We post pictures of our kids and tag them and their friends, siblings, and other relatives. This kind of information could be used by predators to lure your child. They could use your child’s name and the names of their relatives and friends to build trust and convince them that they are not really a stranger because they know detailed information that allows them to build a rapport with your child.

If you must post pictures of your children then you should at least remove personally identifying information such as their full names and birth dates. Untag them in pictures. Your real friends know their names anyway.

I would be a hypocrite if I said that I have completely removed all tagged pictures of my kids on facebook. It is a daunting task given the amount of pictures that we take as proud parents, but I have started on it and I'll do a little bit each day until it's finished.

Lastly, think twice before you tag pictures of the children of friends and relatives. They might not want you tagging their kids for the reasons mentioned above. You can send them a link to the pictures and they can tag themselves in place of their children if they want to.


PING is used to check for a response from another computer on the network. It can tell you a great deal of information about the status of the network and the computers you are communicating with.

Ping returns different responses depending on the computer in question. The responses are similar depending on the options used.

Ping uses IP to request a response from the host. It does not use TCP

.It takes its name from a submarine sonar search - you send a short sound burst and listen for an echo - a ping - coming back.

In an IP network, `ping' sends a short data burst - a single packet - and listens for a single packet in reply. Since this tests the most basic function of an IP network (delivery of single packet), it's easy to see how you can learn a lot from some `pings'.

To stop ping, type control-c. This terminates the program and prints out a nice summary of the number of packets transmitted, the number received, and the percentage of packets lost, plus the minimum, average, and maximum round-trip times of the packets.

Sample ping session

PING localhost ( 56 data bytes
64 bytes from icmp_seq=0 ttl=255 time=2 ms
64 bytes from icmp_seq=1 ttl=255 time=2 ms
64 bytes from icmp_seq=2 ttl=255 time=2 ms
64 bytes from icmp_seq=3 ttl=255 time=2 ms
64 bytes from icmp_seq=4 ttl=255 time=2 ms
64 bytes from icmp_seq=5 ttl=255 time=2 ms
64 bytes from icmp_seq=6 ttl=255 time=2 ms
64 bytes from icmp_seq=7 ttl=255 time=2 ms
64 bytes from icmp_seq=8 ttl=255 time=2 ms
64 bytes from icmp_seq=9 ttl=255 time=2 ms

localhost ping statistics

10 packets transmitted, 10 packets received, 0% packet loss
round-trip min/avg/max = 2/2/2 ms

The Time To Live (TTL) field can be interesting. The main purpose of this is so that a packet doesn't live forever on the network and will eventually die when it is deemed "lost." But for us, it provides additional information. We can use the TTL to determine approximately how many router hops the packet has gone through. In this case it's 255 minus N hops, where N is the TTL of the returning Echo Replies. If the TTL field varies in successive pings, it could indicate that the successive reply packets are going via different routes, which isn't a great thing.

The time field is an indication of the round-trip time to get a packet to the remote host. The reply is measured in milliseconds. In general, it's best if round-trip times are under 200 milliseconds. The time it takes a packet to reach its destination is called latency. If you see a large variance in the round-trip times (which is called "jitter"), you are going to see poor performance talking to the host


NSLOOKUP is an application that facilitates looking up hostnames on the network. It can reveal the IP address of a host or, using the IP address, return the host name.

It is very important when troubleshooting problems on a network that you can verify the components of the networking process. Nslookup allows this by revealing details within the infrastructure.


NETSTAT is used to look up the various active connections within a computer. It is helpful to understand what computers or networks you are connected to. This allows you to further investigate problems. One host may be responding well but another may be less responsive.


This is a Microsoft windows NT, 2000 command. It is very useful in determining what could be wrong with a network.

This command when used with the /all switch, reveal enormous amounts of troubleshooting information within the system.

Windows 2000 IP Configuration

Host Name . . . . . . . . . . . . : cowder
Primary DNS Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Broadcast
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . :
WAN (PPP/SLIP) Interface
Physical Address. . . . . . . . . : 00-53-45-00-00-00
DHCP Enabled. . . . . . . . . . . : No
IP Address. . . . . . . . . . . . :
Subnet Mask . . . . . . . . . . . :
Default Gateway . . . . . . . . . :
DNS Servers . . . . . . . . . . . :


Traceroute on Unix and Linux (or tracert in the Microsoft world) attempts to trace the current network path to a destination. Here is an example of a traceroute run to

$ traceroute

traceroute to amber.Berkeley.EDU (, 30 hops max, 40 byte packets

1 ( 3.135 ms 3.021 ms 3.616 ms

2 ( 1.829 ms 3.886 ms 2.772 ms

3 ( 5.327 ms 4.597 ms 5.729 ms

4 ( 4.842 ms 4.615 ms 3.425 ms

5 ( 7.488 ms 38.804 ms 7.708 ms

6 ( 6.560 ms 6.631 ms 6.565 ms

7 ( 7.638 ms 7.948 ms 8.129 ms

8 ( 9.504 ms 12.684 ms 16.648 ms

9 ( 9.762 ms 10.611 ms 10.403 ms

10 f0-0.inr-107-eva.Berkeley.EDU ( 11.478 ms 10.868 ms 9.367 ms

11 f8-0.inr-100-eva.Berkeley.EDU ( 10.738 ms 11.693 ms 12.520 ms

An IP (Internet Protocol) address is a unique identifier for a node or host connection on an IP network. An IP address is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 (known as octets) separated by decimal points. This is known as "dotted decimal" notation.


It is sometimes useful to view the values in their binary form.

140 .179 .220 .200


Every IP address consists of two parts, one identifying the network and one identifying the node. The Class of the address and the subnet mask determine which part belongs to the network address and which part belongs to the node address.

Address Classes:

There are 5 different address classes. You can determine which class any IP address is in by examining the first 4 bits of the IP address.

Class A addresses begin with 0xxx, or 1 to 126 decimal.

Class B addresses begin with 10xx, or 128 to 191 decimal.

Class C addresses begin with 110x, or 192 to 223 decimal.

Class D addresses begin with 1110, or 224 to 239 decimal.

Class E addresses begin with 1111, or 240 to 254 decimal.

Addresses beginning with 01111111, or 127 decimal, are reserved for loopback and for internal testing on a local machine. [You can test this: you should always be able to ping, which points to yourself] Class D addresses are reserved for multicasting. Class E addresses are reserved for future use. They should not be used for host addresses.

Now we can see how the Class determines, by default, which part of the IP address belongs to the network (N) and which part belongs to the node (n).

Class A -- NNNNNNNN.nnnnnnnn.nnnnnnn.nnnnnnn

Class B -- NNNNNNNN.NNNNNNNN.nnnnnnnn.nnnnnnnn


In the example, is a Class B address so by default the Network part of the address (also known as the Network Address) is defined by the first two octets (140.179.x.x) and the node part is defined by the last 2 octets (x.x.220.200).

In order to specify the network address for a given IP address, the node section is set to all "0"s. In our example, specifies the network address for When the node section is set to all "1"s, it specifies a broadcast that is sent to all hosts on the network. specifies the example broadcast address. Note that this is true regardless of the length of the node section.

Private Subnets:

There are three IP network addresses reserved for private networks. The addresses are,, and They can be used by anyone setting up internal IP networks, such as a lab or home LAN behind a NAT or proxy server or a router. It is always safe to use these because routers on the Internet will never forward packets coming from these addresses

Subnetting an IP Network can be done for a variety of reasons, including organization, use of different physical media (such as Ethernet, FDDI, WAN, etc.), preservation of address space, and security. The most common reason is to control network traffic. In an Ethernet network, all nodes on a segment see all the packets transmitted by all the other nodes on that segment. Performance can be adversely affected under heavy traffic loads, due to collisions and the resulting retransmissions. A router is used to connect IP networks to minimize the amount of traffic each segment must receive.

Subnet Masking

Applying a subnet mask to an IP address allows you to identify the network and node parts of the address. The network bits are represented by the 1s in the mask, and the node bits are represented by the 0s. Performing a bitwise logical AND operation between the IP address and the subnet mask results in the Network Address or Number.

For example, using our test IP address and the default Class B subnet mask, we get:

10001100.10110011.11110000.11001000 Class B IP Address

11111111.11111111.00000000.00000000 Default Class B Subnet Mask

10001100.10110011.00000000.00000000 Network Address

Default subnet masks:

Class A - - 11111111.00000000.00000000.00000000

Class B - - 11111111.11111111.00000000.00000000

Class C - - 11111111.11111111.11111111.00000000

CIDR -- Classless InterDomain Routing.

CIDR was invented several years ago to keep the internet from running out of IP addresses. The "classful" system of allocating IP addresses can be very wasteful; anyone who could reasonably show a need for more that 254 host addresses was given a Class B address block of 65533 host addresses. Even more wasteful were companies and organizations that were allocated Class A address blocks, which contain over 16 Million host addresses! Only a tiny percentage of the allocated Class A and Class B address space has ever been actually assigned to a host computer on the Internet.

People realized that addresses could be conserved if the class system was eliminated. By accurately allocating only the amount of address space that was actually needed, the address space crisis could be avoided for many years. This was first proposed in 1992 as a scheme called Supernetting.

The use of a CIDR notated address is the same as for a Classful address. Classful addresses can easily be written in CIDR notation (Class A = /8, Class B = /16, and Class C = /24)

It is currently almost impossible for an individual or company to be allocated their own IP address blocks. You will simply be told to get them from your ISP. The reason for this is the ever-growing size of the internet routing table. Just 5 years ago, there were less than 5000 network routes in the entire Internet. Today, there are over 90,000. Using CIDR, the biggest ISPs are allocated large chunks of address space (usually with a subnet mask of /19 or even smaller); the ISP's customers (often other, smaller ISPs) are then allocated networks from the big ISP's pool. That way, all the big ISP's customers (and their customers, and so on) are accessible via 1 network route on the Internet.

It is expected that CIDR will keep the Internet happily in IP addresses for the next few years at least. After that, IPv6, with 128 bit addresses, will be needed. Under IPv6, even sloppy address allocation would comfortably allow a billion unique IP addresses for every person on earth

Device Servers

A device server is defined as a specialized, network-based hardware device designed to perform a single or specialized set of server functions. It is characterized by a minimal operating architecture that requires no per seat network operating system license, and client access that is independent of any operating system or proprietary protocol. In addition the device server is a "closed box," delivering extreme ease of installation, minimal maintenance, and can be managed by the client remotely via a Web browser.

Print servers, terminal servers, remote access servers and network time servers are examples of device servers which are specialized for particular functions. Each of these types of servers has unique configuration attributes in hardware or software that help them to perform best in their particular arena.

Print Servers

Print servers allow printers to be shared by other users on the network. Supporting either parallel and/or serial interfaces, a print server accepts print jobs from any person on the network using supported protocols and manages those jobs on each appropriate printer.

Print servers generally do not contain a large amount of memory; printers simply store information in a queue. When the desired printer becomes available, they allow the host to transmit the data to the appropriate printer port on the server. The print server can then simply queue and print each job in the order in which print requests are received, regardless of protocol used or the size of the job.

Multiport Device Servers

Devices that are attached to a network through a multiport device server can be shared between terminals and hosts at both the local site and throughout the network. A single terminal may be connected to several hosts at the same time (in multiple concurrent sessions), and can switch between them. Multiport device servers are also used to network devices that have only serial outputs. A connection between serial ports on different servers is opened, allowing data to move between the two devices.

Given its natural translation ability, a multi-protocol multiport device server can perform conversions between the protocols it knows, like LAT and TCP/IP. While server bandwidth is not adequate for large file transfers, it can easily handle host-to-host inquiry/response applications, electronic mailbox checking, etc. And it is far more economical than the alternatives of acquiring expensive host software and special-purpose converters. Multiport device and print servers give their users greater flexibility in configuring and managing their networks.

Whether it is moving printers and other peripherals from one network to another, expanding the dimensions of interoperability or preparing for growth, multiport device servers can fulfill your needs, all without major rewiring.

Access Servers

While Ethernet is limited to a geographic area, remote users such as traveling sales people need access to network-based resources. Remote LAN access, or remote access, is a popular way to provide this connectivity. Access servers use telephone services to link a user or office with an office network. Dial-up remote access solutions such as ISDN or asynchronous dial introduce more flexibility. Dial-up remote access offers both the remote office and the remote user the economy and flexibility of "pay as you go" telephone services. ISDN is a special telephone service that offers three channels, two 64 Kbps "B" channels for user data and a "D" channel for setting up the connection. With ISDN, the B channels can be combined for double bandwidth or separated for different applications or users. With asynchronous remote access, regular telephone lines are combined with modems and remote access servers to allow users and networks to dial anywhere in the world and have data access. Remote access servers provide connection points for both dial-in and dial-out applications on the network to which they are attached. These hybrid devices route and filter protocols and offer other services such as modem pooling and terminal/printer services. For the remote PC user, one can connect from any available telephone jack (RJ45), including those in a hotel rooms or on most airplanes.

Network Time Servers

A network time server is a server specialized in the handling of timing information from sources such as satellites or radio broadcasts and is capable of providing this timing data to its attached network. Specialized protocols such as NTP or udp/time allow a time server to communicate to other network nodes ensuring that activities that must be coordinated according to their time of execution are synchronized correctly. GPS satellites are one source of information that can allow global installations to achieve constant timing.

A firewall is a system or group of systems that enforces an access control policy between two networks. The actual means by which this is accomplished varies widely, but in principle, the firewall can be thought of as a pair of mechanisms: one which exists to block traffic, and the other which exists to permit traffic. Some firewalls place a greater emphasis on blocking traffic, while others emphasize permitting traffic. Probably the most important thing to recognize about a firewall is that it implements an access control policy. If you don't have a good idea of what kind of access you want to allow or to deny, a firewall really won't help you. It's also important to recognize that the firewall's configuration, because it is a mechanism for enforcing policy, imposes its policy on everything behind it. Administrators for firewalls managing the connectivity for a large number of hosts therefore have a heavy responsibility.

Network Design Criteria:

Ethernets and Fast Ethernets have design rules that must be followed in order to function correctly. Maximum number of nodes, number of repeaters and maximum segment distances are defined by the electrical and mechanical design properties of each type of Ethernet and Fast Ethernet media.

A network using repeaters, for instance, functions with the timing constraints of Ethernet. Although electrical signals on the Ethernet media travel near the speed of light, it still takes a finite time for the signal to travel from one end of a large Ethernet to another. The Ethernet standard assumes it will take roughly 50 microseconds for a signal to reach its destination.

Ethernet is subject to the "5-4-3" rule of repeater placement: the network can only have five segments connected; it can only use four repeaters; and of the five segments, only three can have users attached to them; the other two must be inter-repeater links.

If the design of the network violates these repeater and placement rules, then timing guidelines will not be met and the sending station will resend that packet. This can lead to lost packets and excessive resent packets, which can slow network performance and create trouble for applications. Fast Ethernet has modified repeater rules, since the minimum packet size takes less time to transmit than regular Ethernet. The length of the network links allows for a fewer number of repeaters. In Fast Ethernet networks, there are two classes of repeaters. Class I repeaters have a latency of 0.7 microseconds or less and are limited to one repeater per network. Class II repeaters have a latency of 0.46 microseconds or less and are limited to two repeaters per network. The following are the distance (diameter) characteristics for these types of Fast Ethernet repeater combinations:
Fast Ethernet Copper Fiber
No Repeaters
One Class I Repeater
One Class II Repeater
Two Class II Repeaters
* Full Duplex Mode 2 km

When conditions require greater distances or an increase in the number of nodes/repeaters, then a bridge, router or switch can be used to connect multiple networks together. These devices join two or more separate networks, allowing network design criteria to be restored. Switches allow network designers to build large networks that function well. The reduction in costs of bridges and switches reduces the impact of repeater rules on network design.

Each network connected via one of these devices is referred to as a separate collision domain in the overall network.

Ethernet Switches:

Ethernet switches are an expansion of the concept in Ethernet bridging. LAN switches can link four, six, ten or more networks together, and have two basic architectures: cut-through and store-and-forward. In the past, cut-through switches were faster because they examined the packet destination address only before forwarding it on to its destination segment. A store-and-forward switch, on the other hand, accepts and analyzes the entire packet before forwarding it to its destination.

It takes more time to examine the entire packet, but it allows the switch to catch certain packet errors and keep them from propagating through the network. Both cut-through and store-and-forward switches separate a network into collision domains, allowing network design rules to be extended. Each of the segments attached to an Ethernet switch has a full 10 Mbps of bandwidth shared by fewer users, which results in better performance (as opposed to hubs that only allow bandwidth sharing from a single Ethernet). Newer switches today offer high-speed links, FDDI, Fast Ethernet or ATM. These are used to link switches together or give added bandwidth to high-traffic servers. A network composed of a number of switches linked together via uplinks is termed a "collapsed backbone" network.


Routers filter out network traffic by specific protocol rather than by packet address. Routers also divide networks logically instead of physically. An IP router can divide a network into various subnets so that only traffic destined for particular IP addresses can pass between segments. Network speed often decreases due to this type of intelligent forwarding. Such filtering takes more time than that exercised in a switch or bridge, which only looks at the Ethernet address. However, in more complex networks, overall efficiency is improved by using routers.

The standards and technology that have just been discussed help define the specific products that network managers use to build Ethernet networks. The following text discusses the key products needed to build an Ethernet LAN.


Transceivers are used to connect nodes to the various Ethernet media. Most computers and network interface cards contain a built-in 10BASE-T or 10BASE2 transceiver, allowing them to be connected directly to Ethernet without requiring an external transceiver. Many Ethernet devices provide an AUI connector to allow the user to connect to any media type via an external transceiver. The AUI connector consists of a 15-pin D-shell type connector, female on the computer side, male on the transceiver side. Thickwire (10BASE5) cables also use transceivers to allow connections.

For Fast Ethernet networks, a new interface called the MII (Media Independent Interface) was developed to offer a flexible way to support 100 Mbps connections. The MII is a popular way to connect 100BASE-FX links to copper-based Fast Ethernet devices.

Network Interface CardsNetwork Interface Cards:

Network interface cards, commonly referred to as NICs, and are used to connect a PC to a network. The NIC provides a physical connection between the networking cable and the computer's internal bus. Different computers have different bus architectures; PCI bus master slots are most commonly found on 486/Pentium PCs and ISA expansion slots are commonly found on 386 and older PCs. NICs come in three basic varieties: 8-bit, 16-bit, and 32-bit. The larger the number of bits that can be transferred to the NIC, the faster the NIC can transfer data to the network cable.

Many NIC adapters comply with Plug-n-Play specifications. On these systems, NICs are automatically configured without user intervention, while on non-Plug-n-Play systems, configuration is done manually through a setup program and/or DIP switches.

Cards are available to support almost all networking standards, including the latest Fast Ethernet environment. Fast Ethernet NICs are often 10/100 capable, and will automatically set to the appropriate speed. Full duplex networking is another option, where a dedicated connection to a switch allows a NIC to operate at twice the speed.


Hubs/repeaters are used to connect together two or more Ethernet segments of any media type. In larger designs, signal quality begins to deteriorate as segments exceed their maximum length. Hubs provide the signal amplification required to allow a segment to be extended a greater distance. A hub takes any incoming signal and repeats it out all ports.

Ethernet hubs are necessary in star topologies such as 10BASE-T. A multi-port twisted pair hub allows several point-to-point segments to be joined into one network. One end of the point-to-point link is attached to the hub and the other is attached to the computer. If the hub is attached to a backbone, then all computers at the end of the twisted pair segments can communicate with all the hosts on the backbone. The number and type of hubs in any one-collision domain is limited by the Ethernet rules. These repeater rules are discussed in more detail later.
Network Type Max Nodes
Per Segment
Max Distance
Per Segment

Adding Speed:

While repeaters allow LANs to extend beyond normal distance limitations, they still limit the number of nodes that can be supported. Bridges and switches, however, allow LANs to grow significantly larger by virtue of their ability to support full Ethernet segments on each port. Additionally, bridges and switches selectively filter network traffic to only those packets needed on each segment - this significantly increases throughput on each segment and on the overall network. By providing better performance and more flexibility for network topologies, bridges and switches will continue to gain popularity among network managers.


The function of a bridge is to connect separate networks together. Bridges connect different networks types (such as Ethernet and Fast Ethernet) or networks of the same type. Bridges map the Ethernet addresses of the nodes residing on each network segment and allow only necessary traffic to pass through the bridge. When a packet is received by the bridge, the bridge determines the destination and source segments. If the segments are the same, the packet is dropped ("filtered"); if the segments are different, then the packet is "forwarded" to the correct segment. Additionally, bridges do not forward bad or misaligned packets.

Bridges are also called "store-and-forward" devices because they look at the whole Ethernet packet before making filtering or forwarding decisions. Filtering packets, and regenerating forwarded packets enable bridging technology to split a network into separate collision domains. This allows for greater distances and more repeaters to be used in the total network design.

Ethernet is a shared media, so there are rules for sending packets of data to avoid conflicts and protect data integrity. Nodes determine when the network is available for sending packets. It is possible that two nodes at different locations attempt to send data at the same time. When both PCs are transferring a packet to the network at the same time, a collision will result.

Minimizing collisions is a crucial element in the design and operation of networks. Increased collisions are often the result of too many users on the network, which results in a lot of contention for network bandwidth. This can slow the performance of the network from the user's point of view. Segmenting the network, where a network is divided into different pieces joined together logically with a bridge or switch, is one way of reducing an overcrowded network.

What is a Network topology?

A network topology is the geometric arrangement of nodes and cable links in a LAN,

There are three topology's to think about when you get into networks. These are the star, rind, and the bus.

Star, in a star topology each node has a dedicated set of wires connecting it to a central network hub. Since all traffic passes through the hub, the hub becomes a central point for isolating network problems and gathering network statistics.

Ring, a ring topology features a logically closed loop. Data packets travel in a single direction around the ring from one network device to the next. Each network device acts as a repeater, meaning it regenerates the signal

Bus, the bus topology, each node (computer, server, peripheral etc.) attaches directly to a common cable. This topology most often serves as the backbone for a network. In some instances, such as in classrooms or labs, a bus will connect small workgroups

In the network you will commonly find three types of cables used these are the, coaxial cable, fiber optic and twisted pair.

Thick Coaxial Cable

This type cable is usually yellow in color and used in what is called thicknets, and has two conductors. This coax can be used in 500-meter lengths. The cable itself is made up of a solid center wire with a braided metal shield and plastic sheathing protecting the rest of the wire.

Thin Coaxial Cable

As with the thick coaxial cable is used in thicknets the thin version is used in thinnets. This type cable is also used called or referred to as RG-58. The cable is really just a cheaper version of the thick cable.

Fiber Optic Cable

As we all know fiber optics are pretty darn cool and not cheap. This cable is smaller and can carry a vast amount of information fast and over long distances.

Twisted Pair Cables

These come in two flavors of unshielded and shielded.

Unshielded Twisted Pair and Shielded Twisted Pair

Shielded Twisted Pair (STP)

Is more common in high-speed networks. The biggest difference you will see in the UTP and STP is that the STP use's metallic shield wrapping to protect the wire from interference.

-Something else to note about these cables is that they are defined in numbers also. The bigger the number the better the protection from interference. Most networks should go with no less than a CAT 3 and CAT 5 is most recommended.

-Now you know about cables we need to know about connectors. This is pretty important and you will most likely need the RJ-45 connector. This is the cousin of the phone jack connector and looks real similar with the exception that the RJ-45 is bigger. Most commonly your connector are in two flavors and this is BNC (Bayonet Naur Connector) used in thicknets and the RJ-45 used in smaller networks using UTP/STP.

Unshielded Twisted Pair (UTP)

This is the most popular form of cables in the network and the cheapest form that you can go with. The UTP has four pairs of wires and all inside plastic sheathing. The biggest reason that we call it Twisted Pair is to protect the wires from interference from themselves. Each wire is only protected with a thin plastic sheath.

Ethernet Cabling

Now to familiarize you with more on the Ethernet and it's cabling we need to look at the 10's. 10Base2, is considered the thin Ethernet, thinnet, and thinwire which uses light coaxial cable to create a 10 Mbps network. The cable segments in this network can't be over 185 meters in length. These cables connect with the BNC connector. Also as a note these unused connection must have a terminator, which will be a 50-ohm terminator.

10Base5, this is considered a thicknet and is used with coaxial cable arrangement such as the BNC connector. The good side to the coaxial cable is the high-speed transfer and cable segments can be up to 500 meters between nodes/workstations. You will typically see the same speed as the 10Base2 but larger cable lengths for more versatility.

10BaseT, the “T” stands for twisted as in UTP (Unshielded Twisted Pair) and uses this for 10Mbps of transfer. The down side to this is you can only have cable lengths of 100 meters between nodes/workstations. The good side to this network is they are easy to set up and cheap! This is why they are so common an ideal for small offices or homes.

100BaseT, is considered Fast Ethernet uses STP (Shielded Twisted Pair) reaching data transfer of 100Mbps. This system is a little more expensive but still remains popular as the 10BaseT and cheaper than most other type networks. This on of course would be the cheap fast version.

10BaseF, this little guy has the advantage of fiber optics and the F stands for just that. This arrangement is a little more complicated and uses special connectors and NIC's along with hubs to create its network. Pretty darn neat and not to cheap on the wallet.

An important part of designing and installing an Ethernet is selecting the appropriate Ethernet medium. There are four major types of media in use today: Thickwire for 10BASE5 networks, thin coax for 10BASE2 networks, unshielded twisted pair (UTP) for 10BASE-T networks and fiber optic for 10BASE-FL or Fiber-Optic Inter-Repeater Link (FOIRL) networks. This wide variety of media reflects the evolution of Ethernet and also points to the technology's flexibility. Thickwire was one of the first cabling systems used in Ethernet but was expensive and difficult to use. This evolved to thin coax, which is easier to work with and less expensive.

Introduction to TCP/IP Networks:

TCP/IP-based networks play an increasingly important role in computer networks. Perhaps one reason for their appeal is that they are based on an open specification that is not controlled by any vendor.

What Is TCP/IP?

TCP stands for Transmission Control Protocol and IP stands for Internet Protocol. The term TCP/IP is not limited just to these two protocols, however. Frequently, the term TCP/IP is used to refer to a group of protocols related to the TCP and IP protocols such as the User Datagram Protocol (UDP), File Transfer Protocol (FTP), Terminal Emulation Protocol (TELNET), and so on.

The Origins of TCP/IP

In the late 1960s, DARPA (the Defense Advanced Research Project Agency), in the United States, noticed that there was a rapid proliferation of computers in military communications. Computers, because they can be easily programmed, provide flexibility in achieving network functions that is not available with other types of communications equipment. The computers then used in military communications were manufactured by different vendors and were designed to interoperate with computers from that vendor only. Vendors used proprietary protocols in their communications equipment. The military had a multi vendor network but no common protocol to support the heterogeneous equipment from different vendors

Ethernet Network ArchitectureEthernet

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.

Fast Ethernet

For Ethernet networks that need higher transmission speeds, the Fast Ethernet standard (IEEE 802.3u) has been established. This standard raises the Ethernet speed limit from 10 Megabits per second (Mbps) to 100 Mbps with only minimal changes to the existing cable structure. There are three types of Fast Ethernet: 100BASE-TX for use with level 5 UTP cable, 100BASE-FX for use with fiber-optic cable, and 100BASE-T4 which utilizes an extra two wires for use with level 3 UTP cable. The 100BASE-TX standard has become the most popular due to its close compatibility with the 10BASE-T Ethernet standard. For the network manager, the incorporation of Fast Ethernet into an existing configuration presents a host of decisions. Managers must determine the number of users in each site on the network that need the higher throughput, decide which segments of the backbone need to be reconfigured specifically for 100BASE-T and then choose the necessary hardware to connect the 100BASE-T segments with existing 10BASE-T segments. Gigabit Ethernet is a future technology that promises a migration path beyond Fast Ethernet so the next generation of networks will support even higher data transfer speeds.

Token Ring ArchitectureToken Ring

Token Ring is another form of network configuration which differs from Ethernet in that all messages are transferred in a unidirectional manner along the ring at all times. Data is transmitted in tokens, which are passed along the ring and viewed by each device. When a device sees a message addressed to it, that device copies the message and then marks that message as being read. As the message makes its way along the ring, it eventually gets back to the sender who now notes that the message was received by the intended device. The sender can then remove the message and free that token for use by others.

Various PC vendors have been proponents of Token Ring networks at different times and thus these types of networks have been implemented in many organizations.

FDDI architectureFDDI

FDDI (Fiber-Distributed Data Interface) is a standard for data transmission on fiber optic lines in a local area network that can extend in range up to 200 km (124 miles). The FDDI protocol is based on the token ring protocol. In addition to being large geographically, an FDDI local area network can support thousands of users.


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,"

Some Important Protocols and their job:
Protocol Acronym Its Job
Point-To-Point TCP/IP The backbone protocol of the internet. Popular also for intranets using the internet
Transmission Control Protocol/internet Protocol TCP/IP The backbone protocol of the internet. Popular also for intranets using the internet
Internetwork Package Exchange/Sequenced Packet Exchange IPX/SPX This is a standard protocol for Novell Network Operating System
NetBIOS Extended User Interface NetBEUI This is a Microsoft protocol that doesn't support routing to other networks
File Transfer Protocol FTP Used to send and receive files from a remote host
Hyper Text Transfer Protocol HTTP Used for the web to send documents that are encoded in HTML.
Network File Services NFS Allows network nodes or workstations to access files and drives as if they were their own.
Simple Mail Transfer Protocol SMTP Used to send Email over a network
Telnet   Used to connect to a host and emulate a terminal that the remote server can recognize

Peer to Peer and Server/Client NetworkNetwork can be divided in to two main categories:

  • Peer-to-peer.
  • Server – based.
In peer-to-peer networking there are no dedicated servers or hierarchy among the computers. All of the computers are equal and therefore known as peers. Normally each computer serves as Client/Server and there is no one assigned to be an administrator responsible for the entire network.

Peer-to-peer networks are good choices for needs of small organizations where the users are allocated in the same general area, security is not an issue and the organization and the network will have limited growth within the foreseeable future.

The term Client/server refers to the concept of sharing the work involved in processing data between the client computer and the most powerful server computer.

The client/server network is the most efficient way to provide:

  • Databases and management of applications such as Spreadsheets, Accounting, Communications and Document management.
  • Network management.
  • Centralized file storage.
The client/server model is basically an implementation of distributed or cooperative processing. At the heart of the model is the concept of splitting application functions between a client and a server processor. The division of labor between the different processors enables the application designer to place an application function on the processor that is most appropriate for that function. This lets the software designer optimize the use of processors--providing the greatest possible return on investment for the hardware.

Client/server application design also lets the application provider mask the actual location of application function. The user often does not know where a specific operation is executing. The entire function may execute in either the PC or server, or the function may be split between them. This masking of application function locations enables system implementers to upgrade portions of a system over time with a minimum disruption of application operations, while protecting the investment in existing hardware and software.

OSI ModelThe OSI Model:

Open System Interconnection (OSI) reference model has become an International standard and serves as a guide for networking. This model is the best known and most widely used guide to describe networking environments. Vendors design network products based on the specifications of the OSI model. It provides a description of how network hardware and software work together in a layered fashion to make communications possible. It also helps with trouble shooting by providing a frame of reference that describes how components are supposed to function.

There are seven to get familiar with and these are the physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and the application layer.
  • Physical Layer, is just that the physical parts of the network such as wires, cables, and there media along with the length. Also this layer takes note of the electrical signals that transmit data throughout system.
  • Data Link Layer, this layer is where we actually assign meaning to the electrical signals in the network. The layer also determines the size and format of data sent to printers, and other devices. Also I don't want to forget that these are also called nodes in the network. Another thing to consider in this layer is will also allow and define the error detection and correction schemes that insure data was sent and received.
  • Network Layer, this layer provides the definition for the connection of two dissimilar networks.
  • Transport Layer, this layer allows data to be broken into smaller packages for data to be distributed and addressed to other nodes (workstations).
  • Session Layer, this layer helps out with the task to carry information from one node (workstation) to another node (workstation). A session has to be made before we can transport information to another computer.
  • Presentation Layer, this layer is responsible to code and decode data sent to the node.
  • Application Layer, this layer allows you to use an application that will communicate with say the operation system of a server. A good example would be using your web browser to interact with the operating system on a server such as Windows NT, which in turn gets the data you requested.

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)

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.


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.


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.

MANs (Metropolitan area Networks)

The refers to a network of computers with in a City.

VPN (Virtual Private Network)

VPN uses a technique known as tunneling to transfer data securely on the Internet to a remote access server on your workplace network. Using a VPN helps you save money by using the public Internet instead of making long–distance phone calls to connect securely with your private network. There are two ways to create a VPN connection, by dialing an Internet service provider (ISP), or connecting directly to Internet.

A network is any collection of independent computers that communicate with one another over a shared network medium.A computer network is a collection of two or more connected computers. When these computers are joined in a network, people can share files and peripherals such as modems, printers, tape backup drives, or CD-ROM drives. When networks at multiple locations are connected using services available from phone companies, people can send e-mail, share links to the global Internet, or conduct video conferences in real time with other remote users. As companies rely on applications like electronic mail and database management for core business operations, computer networking becomes increasingly more important.
Every network includes:
  • At least two computers Server or Client workstation.
  • Networking Interface Card's (NIC)
  • A connection medium, usually a wire or cable, although wireless communication between networked computers and peripherals is also possible.
  • Network Operating system software, such as Microsoft Windows NT or 2000, Novell NetWare, Unix and Linux.