Re: proposal: rename DLT_PRISM_HEADER

[Solomon Peachy <solomon () linux-wlan com>]

On Mon, Dec 16, 2002 at 06:56:24PM -0600, David Young wrote:
> Sounds like hosttime is redundant.

Quite possibly, but it seemed like a good idea at the time.

> Hmm. Seems like mactime should be some suitably high-resolution unit
> for 802.11, such as 10ns or 1ns, or else a second header in the radio
> header should tell the units. The point of DLT_IEEE802_11_RADIO is to
> smooth over hardware differences.

it would be at least microsecond-accurate, but beyond that.
 
> (For some applications, it may be handy to know which frame feature
> the mactime indicates. E.g., whether it is the start of the PLCP or MAC
> header, or the end of frame.)

Hmm.  I don't recall seeing this in any of the hardware docs I'm privvy
to, but it's certianly an interesting thought.

> BTW, I keep thinking of reasons to adopt length-type-value tuples for
> the radio header. There are three, so far.  First, records such as RSSI
> are meaningless for transmitted frames, so they may as well be omitted.
> Second, certain records are not supported by certain hardware.  Third,
> the radio header is likely to change fast: one may desire to adopt a
> new device driver without breaking compatibility with your tcpdump.
> With LTVs, your tcpdump may skip records whose type it does not know.

No, the old DLT_IEEE80211_PRISM type did that; whet you end up with is
a header twice as long that can't be parsed or constructed as easily and
quickly.  

 - Solomon
-- 
Solomon Peachy                        solomon () linux-wlan com
AbsoluteValue Systems                 http://www.linux-wlan.com
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