Hey everyone, thanks for coming back to Wi Fi fundamentals with location and analytics. This course will help you to muster the a fire. This course main theme is to have a good understanding of the fundamentals and learn to analyze Wi Fi network including location and ranging. You just can't do it without the knowledge of frames. stations and access points are chatting all the time. They do it using frames, different types of frames.
Frames support the operation of your Wi Fi network, from setting it up, control its behavior in different states, sending the data frames and when needed. disconnect from one access point and roam to another frames are the building blocks your network is made of. If you understand frames, you understand why fi in its deepest form. You can troubleshoot your network and you can analyze the traffic that happens. analyze our stations conditions, who is behind the frames, and what can we tell from its exchange of frames. Let's see one of the fundamentals frames we have already mentioned the beacon frame.
To get a glimpse of a big country in all of its glory, we use Wireshark probably the best tool to sniff and capture Wi Fi frames that are in the air. We will have a dedicated Wireshark introduction in this course, for Wireshark to capture the frames. You will need a network card that is capable of Capturing wireless frames in promiscuous, or monitor mode. Fortunately, my MacBook already supports it. There is Wireshark main window. There are three main panes.
There is the list pane which displays a summary of each frame that is captured. By clicking on the frames. You can see what is in the other two panes. In the packet details pane, we can see way more information on the frame. And there is the packets bytes pain, which is not really of interest for us. We can see that we have many beacon frames coming out from different access points and routers around I can see the names of their SSI IDs and the information elements that uncovered just about anything on that frame.
Its type. Its sequence number, destination, access point capabilities, data rates and more. And this is just the beacon frame. Why frames are so important? Well, for many reasons, troubleshooting is one. But it can also help you to understand the behavior and situation, your station or the person behind if it's in a power management mode.
As you will see stations are asleep most of the time. Does it probe select? Does it send a lot of probe requests? If so, it is probably in an area where the signal strength is not good enough. You can have much more data on this And the RF environment of your network. So what are we up to today, we will look at the different types of frame used in Wi Fi.
There are actually three types and we will look at each. When do we use them, and we will look at the anatomy of a frame, how it is built. Frames main purpose is to control, manage and deliver data. We've already seen some frames in the air in our basic wind farm process. But these were just the beginning. There are actually three types of frames, management frames, control frames, and data frames.
Let's dive deeper every Wi Fi frame consists of three parts. The header, which we will look into very soon, the payload which is the data itself and the frame check sequence, why fi frames are very sensitive to interferences. And the FCS the frame check sequence is a mechanism that checks. Are there any errors in the frame. The header contains nine major fields. The frame control, which is one of the most important fields to understand and we have a dedicated chapter just to the frame control field.
It contains the protocol version, the type of frame, its subtype, power management and more. The duration field Do you remember that every station reads the duration value From the other transmitting station and sets its own Neff timer. What that is the duration value indicates the remaining duration needed to transmit the frame. address fields are used differently depending on the frame types and conditions. address one usually indicates the MAC address of our destination. address two is the MAC address of our transmitting access point or station.
Address tree is the MAC address of our source transmitter. Usually it is the same as our transmitter address. sequence number indicates the sequence number of each frame and helps us to map it. later on. You will see that we use sequence control field Which helps us to identify stations in different conditions. address for field is usually not used unless it is an ad hoc network or a wireless bridge mode access point.
Quality of Service control field indicates quality of service parameters if they do exist, the HD control field and also the VHD. The very high throughput control field indicates a high throughput frame starting from A to 11 and next up we will look at some of the fields in Wireshark. See you soon