A Wide Area Network (WAN) Tutorial:

A wide area network (WAN) is a large telecommunications network that consists of a collection of LANs and other networks. WANs generally span a wide geographical area, and can be used to connect cities, states, or even countries.

Although they appear like an up-scaled version of a LAN, WANs are actually structured and operated quite differently. This wide area network tutorial serves to explain how WANs are designed/constructed and why their use is beneficial.

Wide Area Network – Connection Options

“Many WANs are built for one particular organization and are private. Others, built by Internet service providers (ISPs), provide connections from an organization’s LAN to the Internet.” Several options are available for WAN connectivity: leased line, circuit switching, packet switching, and cell relay.

Leased Line:

WANs are often built using leased lines. These leased lines involve a direct point-to-point connection between two sites. Point-to-point WAN service may involve either analog dial-up lines or dedicated leased digital private lines.

Analog lines – a modem is used to connect the computer to the telephone line. Analog lines may be part of a public-switched telephone network and are suitable for batch data transmissions.

Dedicated lines – digital phone lines that permit uninterrupted, secure transmission at fixed costs.

At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other. Leased lines can get pretty expensive in the long run.

Circuit Switching:

Instead of using leased lines, WANs can be built using circuit switching. “In telecommunications, a circuit switching network is one that establishes a circuit (or channel) between nodes and terminals before the users may communicate, as if the nodes were physically connected with an electrical circuit.”

In other words, a dedicated circuit path is created between end points. The best example of this is a dialup connection. Circuit switching is more difficult to setup, but it does have the advantage of being less expensive.

Packet Switching:

Packet switching is a method that groups all transmitted data together into bits called packets. Devices transport packets via a shared single point-to-point/point-to-multipoint link across a carrier network. Sequences of packets are then delivered over a shared network.

Similar to circuit switching, packet switching is relatively inexpensive, but because packets are buffered and queued, packet switching is characterized by a fee per unit of information, whereas circuit switching is characterized by a fee per time unit of connection time (even when no data is transferred).

Cell Relay:

Cell relay is similar to packet switching but it uses fixed length cells instead of variable length packets. Data is divided into these cells and then transported across virtual circuits.

This method is best for simultaneous voice and data but can cause considerable overhead.

WANs vs LANs:

Depending on the service, WANs can be used for almost any data sharing purpose for which LANs can be used. The most basic uses of WANs are for email and file transfer, but WANs can also permit users to access data remotely.

New types of network-based software used for productivity, like work-flow automation software, can also be used over WANs. This allows workers to collaborate on projects easily, regardless of their location.

Unlike LANs, WANs typically do not link individual computers. WANs link LANs together. They provide communications links over great distances.

The Existence Of WANs:

WANs have existed for decades, but new technologies, services, and applications have developed over the years to dramatically increase their effect on business. WANs were originally developed for digital leased-line services carrying only voice (not data).

At first, they connected the private branch exchanges (PBXs) of remote offices of the same company. WANs are still used for voice services, but today they are used more frequently for data and image transmission (like videoconferencing). These added applications have spurred significant growth in WAN usage, primarily because of the surge in LAN connections to the wider networks.

A wide area network allows companies to make use of common resources in order to operate. Internal functions such as sales, production and development, marketing, and accounting can also be shared with authorized locations through this sort of network.

In the event of a problem – say a company facility is damaged from a natural disaster – employees can move to another location and access the network. Productivity is not lost.

Conclusion:

The wide area network has made it possible for companies to communicate internally in ways never before possible. Because of WANs, we (the consumers) can enjoy benefits from companies that we wouldn’t have been able to in the past.

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How you identify If Someone Is Using Your Wireless Network:

There are many reasons you should learn how to check if someone is on your wireless network. We all know there are security risks associated with it (someone can hack your computer or your internet use stealing important personal information). There can also be legal implications. For instance, your neighbor could be doing something illegal and the authorities may accidentally trace the activity back to your equipment.
Also, does your internet provider like the idea of the neighborhood using your internet service instead of paying for the service themselves? This could be construed as stealing from the service provider.

In any case, it is good to know how to check if someone is on your wireless network.

To find people on your wireless network, the process will be different depending on your router’s manufacturer but the basic idea is similar.

There are two main methods to tell if someone has been on your wireless network. You can check the logs to see if someone’s been on there recently or you can check out the DHCP Clients Table to see computers currently connected to your network.

First Things First, What’s Your IP Address?

The first step is to identify your own IP address.Finding out your own IP address (a.k.a. your LAN IP address) is quite simple.
* Click the start button
* Click run (in Vista, just type in the Start Search box)
* Type cmd then click OK.
* Type ipconfig when you are given the prompt. Your IP address will look something like this: “IPv4……………….: [THEN A STRING OF NUMBERS]” If you need to get a better visual, check out the screenshot below:

Go ahead and keep that window open because we’ll need more information from it soon.

Check The Log To See If Someone’s Been On:
The first way to see if someone’s been leeching off your wireless network is to check the logs for unknown IP addresses.

Log into your router by entering its IP address into your browser address bar. Not sure what the IP address is for the router? One way is to Google the manufacturer and find what the most likely default IP address is. Another way is to go back to the ipconfig screen and find it listed as “Default Gateway.”

If you haven’t really set anything up yet, you’ll probably be asked to log in with a username and password.

Routers are originally shipped with a default username and password. To find this out you’ll either have to find the documentation that came with the router or use Google to search for the manufacturer and the default login information.

Once in, different routers will have different looks and navigation.

Let’s check out the log by going to the “Administration” tab and then the “Log” sub-tab. Make sure logging is enabled. Once that is done, the router will log information.

The information we’re interested in for this article is IP addresses that should not be there. This obviously means that strangers are logging on to your network. To find this out, click the “Outgoing Log” button. The LAN IP column shows the IP address for the computers logging on. Incidentally you can see the site that was accessed in the “Destination URL/IP” column.

This should give you a good idea whether or not someone has been accessing the Internet via your wireless network.

Check The DHCP Clients Table To See If Someone’s Currently On:

First you must make sure this option is enabled on your router. Go to the setup tab and look for something similar to “DHCP Server” and make sure “enable” is marked.

Now you can go and check out who’s logged on by going to the “Status” tab and the “Local Network” sub-tab and clicking the “DHCP Clients Table” button.

he table that opens offers some useful information about the computers that are connected currently like the Client Host Name (the computers’ names), the IP addresses, and the MAC addresses.

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Simple Steps To Diagnose A Network Problem:

There are a couple of basic commands to diagnose a network problem.
You have an issue with a computer on your network. It cannot connect to the internet and doesn’t have any network resources. The first thing you need to do is check the condition of the physical connection i.e. the network cable. After that is secured, I jump to a command prompt and do a IPCONFIG /all like so:

I check that the IP address, default gateway and subnet mask are all correct. If they are not, I make my modifications and we are back online. Too bad the problems don’t usually go away that easily. Next up, I attempt to ping the servers by IP address using the ping command, like so:

Now I check for DNS issues by pinging the server’s name. If this fails, it is our internal DNS issue and I know where to move on to.

If I get a correct response, I try to ping a website like http://www.google.com. That tests external DNS resolution. If that works as well, the trouble runs deeper. I would then run a Netstat –a and see who is connected to my machine and determine if maybe a Trojan or virus has gained control of it.

Everything looks clean. Now I would try pathping or tracert between the machine and the internet to diagnose any remaining network problems.
During your tests you might conclude that another machine is using the same IP address or host name as your desktop and causing issues. For this, using Angry Ipscanner.exe (found here ) to query for that IP address or the entire network to find the host name…

If you cannot figure out what is going on and why you cannot get to the resource you are trying to, then the issue might be network-related and has nothing to do with your machine. First, check if you can get to the resource from a different machine.
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If i missed any commands means, share by comments!