Wireshark-dev: Re: [Wireshark-dev] AVS-WLAN header changes to support 802.11n

From: Solomon Peachy <solomon@xxxxxxxxxxxxxx>
Date: Sat, 2 Sep 2006 20:47:26 -0400

On Fri, Sep 01, 2006 at 01:08:53PM -0400, Jose Graziani wrote:
> The current AVS-WLAN header/spec doesn't provide for support for 802.11n
> radio cards.

802.11n doesn't exist yet, and won't for some time.  While the first
draft is out, I expect many more revisions before it settles down. If
past 802.11 specs are any indication, a lot can change, even at the PHY
layer.

> *	Per antenna RSSI (up to 4 antennas) - packet is split between them
> *	Aggregation bit

The only pre-802.11n chipset I've seen [specs on] so far don't provide 
this information to the driver, nor anything else of use.

> Are there any plans to add this support?  Who maintains this header?

I maintain this header, as the source code to the dissector (and the 
header specification document linked therein) states.

New stuff will be added as needed, of course.  At the very least, the 
enumerations will need to include 802.11n PHYs and modulations.

The AVS WLAN header was built as a replacement for the old
prism2-specific capture header that was sort of an accident.  This newer
capture header is an amalgation of real hardware capabilities and AVS's
internal needs, wrapped into a self-contained per-packet capture 
header. 

> Also why was the MAC time changed from nanoseconds to microseconds?

As Guy Harris has already stated, this is because the IEEE 802.11-1999
spec specifies that timekeeping happens in microseconds (for the TSF 
timer), and no hardware I've seen uses anything more accurate.

If you need something *now* that does what you want, I suggest the 
wiretap header that allows variable header bits.

 - Solomon
-- 
Solomon Peachy                        solomon@xxxxxxxxxxxxxx
AbsoluteValue Systems                 http://www.linux-wlan.com
721-D North Drive                     +1 (321) 259-0737  (office)
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