What does the Information Element with ElementID 221 represent in 802.11?

Hello

Please could some one shed light on what the Info Element with ID 221
represent? This element is found in beacons and probe responses. I
searched the net anf found out that this element is generally used for
WPA related stuff. But many places mention different uses for this
element like for WMM, QOS. Some say it is a generic info elem which can
be used for any stuff. If that is so then what is its format?

Nishchal

"NYA" <(E-Mail Removed)> hath wroth:

>Please could some one shed light on what the Info Element with ID 221
>represent? This element is found in beacons and probe responses. I
>searched the net anf found out that this element is generally used for
>WPA related stuff. But many places mention different uses for this
>element like for WMM, QOS. Some say it is a generic info elem which can
>be used for any stuff. If that is so then what is its format?

It appears (my guess) to be some type of catch all that's not owned by
Cisco, Symbol, Philips, or Agere. About all I can deduce from the
following is that the first 3 octets is an IEEE OUI (MAC address).
Apparently 221 is a catch all for smaller vendors propietary data.
There are notes in the IEEE-P80211-2003 minutes that underscore that
Element 221 is *NOT* reserved (which makes it a free for all).

http://grouper.ieee.org/groups/802/1...s_Jan-2003.pdf

> 4.7.1.1. Motion: Request the assignment of element IDs, preferably 0x85,
> 0x86,0x87, 0x88, 0x95, 0x96, 0x9b and 0x9c for use by Cisco, element
> IDs, preferably 173, 176, 178 and 179, for use by Symbol, an element
> ID, preferably 219, for use by Philips, element IDs, preferably 128 and
> 129, for use by Agere and request the assignment of an element ID,
> preferably 221, for the purposes of permitting a preferred format for all
> future vendor-specific elements in which the vendor is identified by an
> IEEE issued OUI in the first 3 octets of the element body. While P802.11
> is listing element IDs used for proprietary purposes in its registry of
> assigned numbers, it does not condone nor imply acceptance of such
> proprietary use. Further, P802.11 urges those using element IDs not
> assigned by P802.11 to abandon such usage and migrate to usage of
> element ID 221, as P802.11 reserves the right to assign all element IDs
> for its own standardization purposes.

Ethereal decodes it as:
DLC: Element ID = 221 (Unknown Information Field)
DLC: ...Length = 24 octet(s)
DLC: ...[24 byte(s) of Unknown Information Field]
which isn't terribly useful.

I tried to find a list of reserved element ID's in the various IEEE
specs, but failed. I know such a list exists because I can find
references to "table 20" in various IEEE proceedings. There's plenty
on "table 20" in various IEEE 802.11 specs, but nothing specific to
element id 221.



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Jeff Liebermann (E-Mail Removed)
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