In earlier posts we have learnt about P2P Group formation method using Negotiation Method. Now we will learn about the P2P Group Formation using Autonomous GO Method, and also understand the differences between these two methods.
In the AUTO GO method, one device will declare itself as a Group Owner. So we don’t see the Negotiation Phase (Frame Exchange between two devices to negotiate which device will become the Group Owner). In AUTO GO method we don’t see this negotiation phase because one device has already declared as a group owner.
Check out the below links that I have written to know more about the Group Formation using Negotiation Method, so that it will be clear.
Below figure shows the frame exchange for P2P Group formation using Negotiation Method, and then we will move to AUTO GO method.
Observe the above figure and I have marked the GO Negotiation , In this process there will be frame exchange to decide which device will become the Group Owner. In Autonomous GO (AUTO GO) method we don’t see this step because one device is already declared itself as a Group Owner.
P2P Autonomous Group Formation
In P2P Auto GO method device declares itself as a GO, and immediately becomes the P2P GO, by sitting on a channel and starting a beacon . Now observe the below frame exchanges to know about the P2P Autonomous Group Formation.
See the below picture for P2P Auto GO method.
Discovery Phase
In the discovery phase , Discovery happens based on the Beacon sent by the GO or active discovery procedure. In Autonomous Group Formation Group Owner will send a beacon as well so that discovery may happen using passive scan as well.
Checkout the below link to know about the detailed discovery procedure using active scanning method.
P2P Device Discovery Procedure
We do have optional service discovery as well, you can checkout the below link for service discovery procedure procedure.
P2P Service Discovery Procedure
Now , I have added the autonomous group in one P2P Device and observe that the supplicant logs and observe the beacon that the device is sending as soon as the group is started.
Supplicant Log
IFNAME=p2p-wlan-0 <3>CTRL-EVENT-STATE-CHANGE id=0 state=9 BSSID=xx:xx:xx:74:40:a0 SSID=DIRECT-pF
<3>P2P-GROUP-STARTED p2p-wlan0-0 GO ssid=”DIRECT-Ww” freq=2437 passphrase=”6NmClTZ8″ go_dev_addr=xx:xx:xx:74:c0:a0
Observe the Beacon and Probe request and probe response frame exchange as per the diagram show in the Figure 3 for the Device discovery. Observe the below sniffer capture. And we have a optional service discovery procedure( P2P Service Discovery Procedure).
P2P Provision Discovery
We do see the P2P Provisional Discovery Request and Response when any P2P device trying to connect to the existing P2P Group. The Provision Discovery Request frame shall have a single method set in the Config Methods attribute to indicate which of the receiving P2P Device’s methods the sending P2P Device intends to use. A P2P Device shall respond to a received Provision Discovery Request frame with a Provision Discovery Response frame. The Config Methods attribute in the Provision Discovery Response frame may have the same single method set as in the received Provision Discovery Request frame to indicate success or shall be null to indicate failure.
Observe the below frame capture to see the Provision Discovery Request Frame. And the config method is set to “Push Button” , because we are connecting using Push button method.
Observe the below frame capture to see the Provision Discovery ResponseFrame. And the config method is set to “Push Button“.
Phase 1 and Phase 2 of the Group Formation
After this we will have Phase 1 and Phase 2 of the Group Formation Procedure. See the below capture to see the Phase 1 and Phase 2 of the Group Formation. I have filtered only the required frames.
Observe the below image to know about the Phase 1 and Phase 2 of the Group Formation.
This Phase 1 and Phase 2 of the Group Formation procedures are similar to the one we see in the Group formation Method using Negotiation Method.
Checkout the below link to know about the Phase 1 of the Group Formation Procedure.
Phase-1 Phase-2 of the Group Formation Procedure.
Once the Group Formation is success, we see the below event in the supplicant logs of the GO.
Supplicant Log
IFNAME=p2p-wlan0-0 <3>AP-STA-CONNECTED xx:xx:xx:74:43:dc p2p_dev_addr=xx:xx:xx:7
4:c3:dc
<3>AP-STA-CONNECTED xx:xx:xx:74:43:dc p2p_dev_addr=xx:xx:xx:74:c3:dc
After the successful Phase-1 and Phase-2 , DHCP procedure happens and Data transfer between GO and GC happens using AES encryption.
In the Next Post we will learn about the Persistent Group Formation Method.
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