Hey everyone, thanks for coming back to Wi Fi fundamentals with location and analytics. This course will help you to muster the air and what to look for in your Wi Fi connection. We have looked at the Mac header where the different fields and subfields tells us a lot of our connection and the far devices. Let's see each frame types main role. Management frames are the negotiators. They are used mainly to establish and maintain the connection in our Wi Fi network.
In other words, they are used by our wireless stations to join and leave the BSS there 12 management frames subtypes. When dealing with positioning and analytics management frames are the ones you want to know more about. We're already familiar with several frames. The probe request is used to scan in an active way. And we have the authentication request and the association request which is almost the final step before our station is in the authenticated and associated state, where it can send data frame and then there's the D associate and D authenticate frames. Once the station leaves the access point for several reasons, as when your smartphone just get away from its coverage area, home or office, your smartphone sense at the authenticate frame to the access point telling it I am leaving On the other side, your access point can send a dissociation frame for a station that sends him invalid parameters, such as a wrong password.
And then there's the specific action frame, which we will look at one type as we get into the round trip time of flight, ranging and location part. Let's see again how the probe request looks in Wireshark. Alright, let's take a look at probe request. In Wireshark, we can see that it comes from this source to that destination. We can see in the frame control field that it is a management frame, it's bit value is zero. It's subtype value equals four.
So it's a probe request. We can see also that it's retransmitted So this frame was retransmitted. And our station sold our access point that it goes to sleep it's in power management. We can also see from the two DS and from the s, that the bit value is 01. So our friend actually goes from the station to the access point and from the access point to the distribution system, which is probably your home gateway. Frames are sent in different data rates.
Usually the first management frames, the probe request, the authentication requests are at the lowest freight, every one even our legacy devices that supports old standards can hear them once associated declared starts to send at a higher rate. We are moving to control frames and their main purpose is to assist us with the delivery of data and management frames. There are eight control frame subtypes, they do not have a frame body. They must be heard by all wireless stations this they are sent it once the basic rate and the acknowledgment and RTS CTS are among the most used control frames. We will look at RTS CTS in a coming video. But for now let's look at the acknowledgment frame.
Every time a data frame is being sent either way from the access point to the station or the other way. There has to be an acknowledgement acknowledgement happens only in the unicast frames. In multicast or broadcast frame there are no acknowledged. Let's take a look at the block acknowledgement in Wireshark acknowledgement frame is being sent every time a data frame reaches your station. It checks for the frame check sequence if there everything if everything is okay it sends an acknowledgment. If there are error, it doesn't send anything and the other station knows that it has to retransmit the frame again.
In the latest standards, we use a block acknowledgment a bluffing lodgement is actually one acknowledgment for multiple frames. That makes things much more faster. So we finally have an established connection. Our station is connected to the access point and data frames comes after The connection and carries a payload. The payload usually is from higher levels of the OSI layers such as layer seven, an HTTP request, or the content itself that comes from the access point towards our station. But that's not always the case stations use different data frames.
They often use the now data frame with no payload, where they want the access point know that they go to sleep to power management mode. Let's see a data frame in Wireshark. Here in Wireshark, I've captured several now data frames. This one is coming from my PC which I have a USB dongle attached to it a typical dangle and this destination is actually my gateway And as you can see, it is a data frame and in the frame control the bit value for the map power management is one the station will go to sleep. That's my PCs way to tell the access point that it goes to sleep. Coming up is RTS and CTS to control frames that are worth mentioning.
After that, we will start with arranging location and analytics part. See you soon