Saturday, November 24, 2012

Wireless Networking: Beacon Frames

Beacon Frames are the management packets broadcasted from Access Points(AP) to announce its presence. Beacon Frames contain critical information which is used by Clients to establish connections.


If Type is Zero and Subtype is 8 of a wireless packet then it is a Beacon Frame.

Critical information sent from AP areTimestamp for syncing between AP and Client.
Beacon Interval tells Client at what intervals AP sends Beacon Frames.
BSS ID or MAC Address of Access Point.
Service Set IDentifier(SSID) of AP, NETGEAR here.
Channel (11) being used which tells the frequency in which signals are transferred.
Rate at which AP can transmit data.

The receiver radio(Client) Interfaces/NIC's frequently scan all 802.11 radio channels and listen to beacons and interpret the to associates with AP with given credentials.
There are three main types of wireless packets
        Management (Type 0)
        Control (Type 1) and
        Data (Type 2)
Beacon Frames are sub classified under management packets, under these types of wireless packets there are many subtypes of packets.

Other posts which might be of interest to you.
http://darshanams.blogspot.in/2012/04/certifications-for-ids-ips-fw-webemail.html
http://darshanams.blogspot.in/2012/05/cain-and-abel-password-cracking.html