On Feb 5, 2010, at 6:41 PM, Liu Feng wrote:
> when I use tcpdump to capture wifi signals, this is the result I get:
>
> 15:47:31.547609 285163963350us tsft 1.0 Mb/s 2437 MHz (0x00a0) -98dB signal
> -102dB noise antenna 1 [0x0000000e] BSSID:00:23:69:29:10:5b
> DA:ff:ff:ff:ff:ff:ff SA:00:23:69:29:10:5b Beacon (EKAHAU) ESS, PRIVACY
>
> can you tell me the meanings of the highlighted information?
Highlighted? Nothing highlighted above. :-)
(Yeah, some of us send plain-text mail by default.)
In any case:
285163963350us tsft:
the Time Synchronization Function Timer value for the frame:
http://www.radiotap.org/defined-fields/TSFT
1.0 Mb/s:
the data rate at which the frame was received:
http://www.radiotap.org/defined-fields/Rate
(0x00a0):
I'm not sure - I don't see anything in top-of-tree tcpdump that would
print that in a radiotap header; what version of tcpdump are you using? (What
does "tcpdump -h" print, and what version of what OS is this on? If it's a
Linux distribution, give the name of the distribution, and the release of the
distribution, rather than the version of the kernel.)
[0x0000000e]:
In theory, that would be an indication that there's a radiotap
"presence bit" that tcpdump doesn't know about, except that 0x0000000e has 3
bits set.
DA:ff:ff:ff:ff:ff:ff:
that's the Destination Address of the frame; see IEEE 802.11-2007 -
IEEE 802.11 has more MAC addresses than does, for example, Ethernet
SA:00:23:69:29:10:5b
that's the Source Address of the frame; see IEEE 802.11-2007-
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