the various protocols that are commonly used with computing devices for communi‐
cation. We’re going to skip Code Division Multiple Access (CDMA) and Global Sys‐
tem for Mobiles (GSM). While your smartphones and tablets use them to
communicate with carrier networks, they are really carrier protocols, and not proto‐
cols used for direct system-to-system communication.
802.11
The most common protocol you’ll run across is really a set of protocols. You probably
know it as
WiFi
or maybe even just
wireless
. In reality, it’s a set of protocols managed
by the Institute of Electrical and Electronics Engineers (IEEE, commonly called
I
Triple
E
). The IEEE manages standards, though they are not the only organization to
do so. It happens, however, that IEEE created and maintains the standards related to
wireless local area networks (WLANs). This standard is referred to collectively as
802.11
.
802.11 has specifications that cover different frequency spectra and, along with them,
different throughput capabilities. These are commonly named with letters after
802.11. One of the first was 802.11a, which was followed by 802.11b. Currently, the
release specification is 802.11ac, though specifications through 802.11ay are in devel‐
opment. Ultimately, the throughput is restricted by the frequency ranges in use,
though later versions of 802.11 have used multiple communications channels simul‐
taneously to increase throughput.
802.11 is commonly referred to as
WiFi
, though WiFi is a trade‐
mark of the WiFi Alliance, a group of companies involved in wire‐
less networking. WiFi is just another way of referring to the IEEE
wireless networking standards and is not separate from them.
802.11 is a set of specifications for the physical layer, to include MAC. We still need a
data link protocol. Ethernet, a common data link protocol that also specifies physical
and MAC elements, is layered over the top of 802.11 to provide system-to-system
communications over a local area network.
One of the early challenges with 802.11 is that wireless signals are not bounded physi‐
cally. Think about listening to radio stations, since that’s really what we are talking
about here—radio waves, just at a different set of frequencies. When you listen to
radio stations, it doesn’t matter whether you are inside or outside; the signal passes
through walls, ceilings, and floors so you can pick up the signal with your receiver.
We have the same challenge with the radio signals that are used for wireless LANs.
They will pass through walls, floors, windows, and ceilings. Since our LANs carry
sensitive information, this is a problem.
