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WLAN Authentication Frame

This page describes WLAN authentication frame and deauthentication frame as per IEEE 802.11 WLAN standard. It mentions WLAN status codes and reason codes.

Authentication in WLAN network refers to establishing the station's identity prior to complete the association. Deauthentication refers to terminating the same.

Different algorithms are developed for this purpose. Authentication Algorithm Number decides which algorithm will be selected. As there are many steps involved in the process, sequence number is used for all the frames during exchange authentication frames.

WLAN authentication frame

The 'Status Code' and 'Challenge Text' fields are used in various ways by different authentication algorithms

The challenge text is transmitted using the 'Challenge Text information element'. This shared key authentication system requires that mobile station need to successfully decrypt the encrypted challenge text.

Challenge Text Information Element:-
Element ID - 1 byte
Length- 1 byte
Challenge text- 1 to 253 bytes

WLAN Status Codes

Status code field is of 16 bits in size. It indicates success or failure of an operation. O indicates success and non-zero value indicates failure.

WLAN Status Code Description
Code-0 Operation completed successfully
Code-1 Unspecified failure
Code-2-9 Unused
Code-10 requested capability is too broad and hence can not be supported
Code-11 reassociation denied, prior association can not be identified and transferred
Code-12 association denied for a reason not specified in WLAN 802.11 standard
Code-13 requested authentication algorithm not supported
Code-14 unexpected authentication sequence number
Code-15 authentication rejected,, the response to the challenge failed
Code-16 authentication rejected,, the next frame in the sequence did not arrive in the expected window
Code-17 Association denied; the access point is resource constrained
Code-18 Association denied;; the mobile station does not support all the data rates required by the BSS
Code-19 Association denied; the mobile station does not support the short preamble option
Code-20 Association denied; the mobile station does not support PBCC modulation
Code-21 Association denied,, mobile station does notsupport channel agility option
Code-22-65535 reserved

WLAN Deauthentication Frame

WLAN deauthentication frame

As the name suggests, it is used to end an authentication relation between AP and STA. Reason code field of size 16 bits is used here. It mentions the reason of why sender has not joined the network.

WLAN reason codes

WLAN Status Code Description
Code-0 reserved
Code-1 Unspecified
Code-2 prior authentication is not valid
Code-3 station has left the basic service area or extended service area and is de-authenticated
Code-4 Inactivity timer expired and station was disassociated
Code-5 Disassociated due to insufficient resources at the access point
Code-6 Incorrect frame type or subtype received from unauthenticated station
Code-7 Incorrect frame type or subtype received from unassociated station
Code-8 Station has left the basic service area or extended service area and is disassociated
Code-9 Association or reassociation requested before authentication is complete
Code-10 to 65535 reserved

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WLAN MAC frames Links

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WLAN authentication Request and deauthentication frame
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