In June 1997 the first wireless protocol was released, this is what we now know as "legacy". At the time more and more people were beginning to use laptops as they become more and more portable, gone were the laptops that required you to haul around a box bigger than a suitcase, and in came computer the size of brief cases, and with more portable devices, a more portable connection to the internet was wanted. A connection that didn't require you having to plug your device into a switch or hub. Thus someone came up with the idea of wireless local area communications. The first implementation would transfer data at 2MB/s and used FHSS and DSSS modulation. With a range of 100m it allowed for a certain amount of cable-free portability.
Then in September 1999 two new wireless protocols were released, aimed to expand their its predecessor. One protocol was called 802.11a, its purpose was to increase the speed mainly and range of the network, and it did, using a different type of modulation (OFDM) it reached 54MB/s and a range of 120m. The other was 802.11b, its purpose was to increase range primarily, stretching to 140m, but sacrifices speed in comparison to 802.11a, having only 11MB/s maximum transfer rates.
As with all invention, progress was desired, and in June 2003, a standard was released which unified the best parts of 802.11a and 802.11b, this protocol was called 802.11g. This protocol had the range (140m) from 802.11b and the speed (54MB/s) from 802.11a. This protocol used both ODFM and DSSS to achieve this.
Next, something new was needed, and 802.11n was the answer. It had almost double the range of 802.11g (250m) and triple the maximum speed (150MB/s). The speed of this however is often quoted as being 300MB/s or 600MB/s. This is because it has the ability to use multiple streams at once, but dispute this the maximum throughput to a single device is 150MB/s.
Finally, we come to 802.11ac, this protocol was released December 2012, and allowed for speeds of nearly 900MB/s, with up to 8 streams, giving it a maximum throughput of 6.8GB/s (but no one device will see those speeds).
802.11ac also gives a new safety measure, which will be covered when we talk about specific attacks, called beam-forming. This means that the router knows approximately where the client is and the client knows approximately where the router is. Due to this, the devices can send traffic in the direction of each other, so MITM (man in the middle) becomes much harder, you will now need to be close to the targets to capture traffic from the air, but all this will be covered later.
Channels
With most wireless devices being on the 2.4GHz wave band, there is a lot of interference, so to tackle this, channels are used. So far I have been careful to call them wavebands, because 2.4GHz is not a select frequency, it is split into multiple wavebands.The wavebands in 2.4GHz band are commonly 22MHz, meaning that a band contains 22 different frequencies. The following image is lifted from taurus2.co.uk and demonstrates perfectly.
As we can see, there are 14 channels, channel 14 is Japan only, and 12/13 are banned in the USA. Each channel uses a specific band, spanning 22MHz, allowing for multiple channels on the 2.4GHz band, that do not overlap and thus have very little interference. The most commonly used are 1,6 and 11, as these channels cannot interfere with each other.
And now for the end to todays session, next week ill start on WEP, how it was implemented and why, so we can start looking at breaking things :) - Spectr3
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