Preauthentication allows a station to perform RSN authentication with an Access Point it is currently not associated to while associated to a different Access Point. This allows the station to move to a different Access point faster when the station has to roam and prevents the Data port being blocked on account of authentication during […]
Wireless Capture Example – EAP Handshake – Part 3
The reader can understand the association mechanism between a WLAN station and Access point for 802.1X authentication here — <Wireless Capture Example – EAP Handshake – Part 1> and the EAP exchange mechanism in 802.1X here — <Wireless Capture Example – EAP Handshake – Part 2>. The final phase of the 802.1X authentication mechanism is […]
Management Frame Protection – IGTK
The interested reader can look at an overview of Management Frame Protection in the following article<Management Frame Protection> The 802.11w amendment provided a new key termed IGTK – Integrity Group Temporal Key. The IGTK would be used for integrity check of broadcast/multicast management frames and is used to compute the MIC for Broadcast/multicast frames. The […]
WEP Encryption – Key Size and Initialization Vector
WEP KEY sizes WEP provided two Key Lengths for encryption – 40 bit WEP Key – 104 bit WEP Key An Initialization vector (IV) of length 24 bits was added to these key lengths to make the WEP keys as 64 bit/ 128 bit keys. Initialization vector (IV): As is seen from the above, the […]
WLAN Open System Authentication
The WLAN Open System authentication as the name suggests does not perform any authentication of the WLAN station desirous of joining the network. The WLAN client device will send an 802.11 authentication request frame and the Access point will respond with an 802.11 authentication response frame with a success code (0x0). The below packet captures […]
Beacon Transmission in IBSS Mode
Beacon transmission in an IBSS network is slightly different. In an IBSS network – each station connected to the IBSS network competes to transmit the beacon at beacon interval time. At the start of each beacon period – there is a beacon generation window consisting of a number of slots. If the window is 0 […]
Access Point Contending for Beacon Transmission
A Master device (Access point /P2P GO device) also needs to contend for the medium as any regular 802.11 station connected to the BSS. There are instances when the Beacon transmission might be delayed due to a delay in obtaining channel access. The connected stations need to wait till a beacon is received by them […]
Beacons Explained
Before we discuss how a WLAN station associates to a network, it is important to understand how a beacon is transmitted and the important parameters that are a part of a beacon frame. This article provides an overview of the beacon mechanism in the 802.11 WLAN standard. 802.11 Beacons are broadcast transmissions. In WLAN Beacons […]
Associating to an Access point – Part 1
Association is the process by which a WLAN station device connects to an Access Point. The Association frame exchange for AP-Station connection which does not have any security enabled is the simplest association process and follows the below steps The WLAN station device sends out a probe-request to the Access Point On receipt of the […]
Some WLAN Network Topologies – BSS, IBSS, Mesh BSS and P2P
WLAN standard supports different Network Topologies. Infrastructure Network Topology Ad-hoc Network Topology Wireless Mesh Topology P2P Network Topology In addition to the above, WLAN is also employed in automotive communication and the Automotive Dedicated Short Range Communication topology will be discussed separately later Infrastructure Topology An Infrastructure topology is shown below. The area marked by […]