Management Frames Flashcards
Authentication frame
Device will send a authentication frame (authentication request) at a time when it wishes to connect to a network. The AP will either send an acceptance or rejection authentication frame (authentication response).
With shared key authentication, NIC sends frame then the AP sends challenge text. NIC returns encrypted version of challenge text (using WEP key). AP checks once encrypted text is decrypted that it’s the same as original. AP sends frame to accept or reject.
Deauthentication Frame
Station send this to another station if it wishes to terminate secure connections.
Association Request Frame
802.11 association enables the AP to allocate resources and synchronise with a NIC.
NIC initiates by sending association request to AP. Frame carries info about the NIC (supported data rates & the SSID of the network it wants to associate with).
If AP accepts will reserve memory space and establishes association ID for the NIC.
Reassociation Request Frame
If NIC roams away from currently associated AP and finds another AP with a stronger beacon signal, the NIC will send this frame to the new AP.
New AP then coordinates the forwarding of data frames that may still be in the buffer of the old AP waiting for transmission to the NIC.
Reassociation Response Frame
AP sends this to the NIC containing an acceptance or rejection notice.
Similar to association process, frame includes info regarding the association (ID & supported data rates).
Disassociation Frame
Station send this to another station if it wishes to terminate the association.
If a NIC is shut down gracefully, will send this frame to alert the AP that the NIC is powering off. AP can then relinquish memory allocations and remove the NIC from the association table.
Beacon Frame
AP broadcasts a beacon frame every 0.1024sec to announce its presence and relay info like: timestamp, SSID, current channel, BSSID, source MAC, other parameters regarding the AP.
Broadcast MAC is FF:FF:FF:FF:FF:FF.
NICs continually scan all 802.11 radio channels and listen to beacons for choosing which AP is the best to associate with.
Probe Request Frame
A NIC would send this to determine which APs are within range as well as to identify and connect to previously associated APs.
Probe request uses the broadcast destination and receiver address FF:FF:FF:FF:FF:FF
Probe Response Frame
AP will respond to a probe request, containing capability information / supported data rates / etc.
It is a unicast frame addressed to the STA that sent the probe request.
Management Frames
Are sent at the basic transmission rate or the lowest common rate supported.
Most common: beacon frames, probe requests and responses.
Association Response Frame
AP sends this containing an acceptance or rejection notice to the NIC that is requesting association.
If accepted frame includes: association ID, supported data rates.
If association is successful the NIC can utilize the AP to communicate with other NICs on the network and systems on the distribution side of the AP (such as ethernet).
