Wi-Fi.... Complete Interoduction...

What is WiFi?

Wi-Fi allows you to use your computer or other device to connect to the internet from anywhere there is a Wi-Fi access point (often known as a hot Spot)

Short for "wireless fidelity", Wi-Fi is one of the most popular wireless communications standards on the market.

Wireless Standards

The official name for the specification is IEEE 802.11, and it is comprised of more than 20 different standards, each of which is denoted by a letter appended to the end of the name. The most familiar standards are 802.11b and 802.11g (Wireless B and G) which are used in the majority of commercial Wi-Fi devices. Both of these standards operate in the 2.4 GHz band, and the only major difference between the two is the transfer rate.
Some consumer electronics, however, use a different standard—Wireless A. These devices operate within the 5 GHz range and have transfer rates equivalent to 802.11g. However, since they operate on different frequencies, devices using the 802.11a standard cannot communicate with B and G-enabled devices. For this reason, it is important to check the compatibility of components with your wireless network prior to purchasing them.
The 802.11 standard reserves the low levels of the OSI model for a wireless connection that uses electromagnetic waves, i.e.:
* The physical layer (sometimes shortened to the "PHY" layer), which offers three types of information encoding.
* The data link layer, comprised of two sub-layers: Logical Link Control (or LLC) and Media Access Control (or MAC).
The physical layer defines the radio wave modulation and signalling characteristics for data transmission, while the data link layer defines the interface between the machine's bus and the physical layer, in particular an access method close to the one used in the Ethernet standard and rules for communication between the stations of the network. The 802.11 standard actually has three physical layers, which define alternative modes of transmission:
Wireless Networking, WiFi, is not a new technology, but it is only recently that it has become mainstream. What are the benefits of wireless networks and should you be considering using it?

Benefits:

The advent of portable computing devices is one of the main drivers for the adoption of wireless networking. Today, around 50% of new laptops come wireless enabled out of the box. All of Apple’s latest line of laptops come with both wireless & bluetooth built in. Many Microsoft Windows laptops are similarly wireless enabled.

A powerful alliance of vendors joined together in 1999 to form the WiFi Alliance. You can be assured that any device approved by the WiFi Alliance will interoperate happily with any other approved device. The term WiFi has become corrupted in common usage to mean wireless networks in general, not just devices approved by the WiFi alliance.

Why adopt WiFi?

Today’s workforce, equipped with PDAs, laptops and other mobile devices, demand access to your network from wherever they are, without the hassle of a fixed network. WiFi allows your business to deploy a network more quickly, at lower cost, and with greater flexibility than a wired system.
Productivity increases too, since workers can stay connected longer, and are able to collaborate with their co-workers as and where needed.
WiFi networks are more fluid than wired networks. A network is no longer a fixed thing, networks can be created and ripped down in an afternoon instead of the days or weeks required to create a structured cable network.

Architecture:

Wireless cards can operate in two modes, Infrastructure and Ad-hoc.
Most business systems use wireless in Infrastructure mode. This means that devices communicate with an access point. Typically the access point also has a connection to the company wired network, allowing users access to servers and files as if they were physically attached to the LAN.
Ad-hoc connections are direct connections between wireless cards. This type of connection is more common amongst home users, but if used by business users could have serious management and security implications.
Management
You can easily connect to a WiFi network anywhere within range of an access point. This is a boon for your workers, but unfortunately, it also brings with it a few headaches for the IT department.

Security:

Security is the bane of everybody who puts together a wireless network. access points, using factory default settings, are not secure at all.
So, if security is such a concern does that mean I shouldn’t deploy WiFi? No, it doesn’t. But it is something that you should bear in mind when in the planning stage.
When talking about security there is no such thing as having a completely secure system. Everything is insecure to some degree or other. The degree of security you require is dictated by the sensitivity of the information you possess.
If you require very high levels of security then you cannot rely on the built in security measures of a WiFi network alone.
On the other hand, most small to medium sized companies do not require very high levels of security. In which case you may use the standard WiFi security measures.
If you already have a wireless network you may be concerned about whether it is secure. There are four things you can do to ensure that you are secure.
1. Make sure that your access point(s) are not broadcasting the SSID (basically an identifier for your network)
2. Make sure that your access point(s) are encrypting the wireless traffic using Wireless Equivalent Privacy (WEP)
3. Buy a wireless intrusion detection system. A number of products are available designed to help you monitor the security of your WiFi network as well as who is using it.
4. If you have a high security requirement, then you should either ensure your network people are appropriately trained or hire a wireless consultant. You may also need to buy proprietary, non-standard access points from the likes of Cisco (although even some proprietary standards from the likes of Cisco have their problems). Unfortunately, this will substantially increase the cost of your wireless network.