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Today as we continue on our WPA cracking adventure we'll learn some more fundamentals of these ubiquitous wireless protocols including some 802.11 history, the WiFi Alliance and the lettered protocols B, A and G.
WiFi as we know it is standard for wireless communications. The actual term WiFi is a trademark of the Wi-Fi Alliance -- a trade association that promotes wireless LAN technologies and certifies products.
The actual term Wi-Fi was adopted in 1999 as a branding term as it's a bit catchier than "IEEE 802.11". It's considered an acronym for Wireless Fidelity. The alliance actually used the phrase as an advertising slogan "back in the day" but quit using it early on.
If you've seen the WiFi Certified logo on a device that means it has completed the WiFi Alliance interoperability certification.
Of course WiFi is synonymous with IEEE 802.11, which comes in many flavors, but first let's take a moment to understand how they came to be.
The story of WiFi or IEEE 802.11 actually began, well, based on our viewer survey, before half of you were born :)
Back in 1985 the FCC released what is known as the ISM band for unlicensed use. This means anyone could use these frequencies. The ISM stands for Industrial, Scientific and Medical and is a radio band reserved all over the world for those purposes.
A microwave for instance creates a lot of electromagnetic interference so they're reserved to these specific frequencies. This is also why microwaves interfere with WiFi.
Now the two ranges that interest us are 902 to 928 MHz and 2.4 to 2.5 GHz. The former is only unlicensed in what the ITU, or International Telecommunication Union designates as Region 2 -- basically North America, South America, Greenland and the eastern Pacific Islands.
So with this spectrum available our favorite corporation, AT&T, began working on a wireless technology in 1991. WaveLAN -- now known as WaveLAN Classic -- operated in the 900 MHz spectrum. It was developed in the Netherlands initially as a technology for cashier systems and supported 1 and 2 Mbps data rates.
It wasn't until 1997 that the first actual 802.11 protocol made its debut. Appropriately named 802.11-1997 or sometimes referred to as 802.11 legacy, it too only supported 1 and 2 Mbps data rates and is in effect obsoltete.
Of course this brings us to the lettered protocols we know and love today.
In 1999 two protocols, 802.11A and 802.11B hit the scene.
Both A and B offered much higher data rates than their predecessor the former clocking in at 54 Mbps while the later a mere 11. Another major differentiator are the frequencies used by the technologies. B takes advantage of the commonly used 2.4 GHz spectrum while A avoids congestion at 5 GHz.
802.11a aka 802.11a-1999
802.11 A is a pretty beefy protocol. It's more resiliant to poor channel conditions as it uses the Orthogonal Frequency-Division Multiplexing method. This is the very same method used today in ADSL lines, power-line communication, WiMAX, digital cable TV and a bunch of other technologies we take for granted today.
Now due to complexities in manufacturing processes, 802.11A products were considered late to market. And while the technology offers higher datarates than 802.11 B, the signal rage was at first much shorter due to the smaller wavelengths of the 5 GHz band. 802.11 A was mostly adopted in enterprises who needed the higher data rates, though today it is quite common to see dual-band or dual-mode access points supporting the A protocol as well as B and G.
802.11b aka 802.11b-1999
802.11b was widely adopted all over the world in mid 1999 and is considered the first mainstream wireless networking protocol.
Unlike 802.11a however, 802.11b uses the same media access method as 802.11-legacy which is known as CSMA/CA.
So while 802.11b has a maximum data rate of 11 Mbps the added protocol overhead means that best one can achieve with normal TCP streams are just under 6 Mbps, or just over 7 Mbps for UDP.
What's CSMA/CA? It stands for Carrier Sense Multiple Access with Collision Avoidance, and basically it's a means for multiple stations to communicate with an access point without talking all over each other.
Carrier Sense Multiple Access is a Media Access Control protocol that uses probabilities to make a best guess at when a radio should talk.
Carrier Sensing means the radio listens for signals from other stations transmitting and waits for them to finish before it begins. Multiple Access is just that, it's a protocol for more than two parties. And Collision Avoidance is a modification that uses less of the channel if it notices a lot of traffic. How sweet?
802.11g aka 802.11g-2003
In 2003 802.11g was ratified, bringing best of both worlds between 802.11a and b. This new standard takes advantage of the 2.4GHz band while using the more robust Orthogonal Frequency-Division Multiplexing transmission scheme. With a maximum data rate of 54Mbps and backwards compatability with 802.11b the G protocol was adopted in droves by consumers at the start of 2003 before ratification was even complete.
802.11g isn't without its issues. As part of backwards compatability, transmissions from an 802.11b station will reduce the network as a whole down to the older 11Mbps speeds. The 2.4GHz band is still susceptible to interference from microwaves, bluetooth devices, baby monitors and other junk in the spectrum. And the protocols high popularity is also a bit of a problem in densely populated areas as only three of the channels -- in the US that is -- don't overlap. But we'll get into channels later.
Next week we'll wrap up the protocols with our new favorite, 802.11n, as well as going over channels and finally dig into the actual frames with a lesson on BSSIDs, ESSIDs and a practical example with a fun tool in BackTrack Linux.
I hope you enjoyed learning a little of the backstory here. I find that while I could spend 5 minutes telling you what to type to crack a key it's so much more important to understand why those commands do what they do.
Now before I get going it's time for the giveaway. Last week I asked for the manufacturer of my favorite USB WiFi device based on the OUI and youtube commenter JokingTiger was the first to answer with Realtek Semiconductor Corp, so we'll get your information and have one of these puppies sent out right away.
This week I'd like to know what 802.11b channel is only allowed in Japan? Be the first to answer in the comments and the radio I use on HakTip is yours.
And as always we value your feedback and suggestions. If you have a tip to share with me, email email@example.com. And be sure to check out our sister show Hak5 for more great stuff, just like this. I'll be there reminding you to trust your technolust.
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