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<DIV><FONT size=2>In the case of AirPcap packets are filtered in the AirPcap
driver.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>GV</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2></FONT> </DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=locationdev@gmail.com href="mailto:locationdev@gmail.com">John
Wang</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=winpcap-users@winpcap.org
href="mailto:winpcap-users@winpcap.org">winpcap-users@winpcap.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, May 09, 2009 9:33
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Winpcap-users] Where does
the Winpcaptimestampcomefrom?andothers</DIV>
<DIV><BR></DIV>Hi Gianluca,<BR><BR>Thanks for your information, That's great
helpful. I decide to use a hardware local timer to record the beacon frames
arrival time. After I looked close to the CACE AirPcap Classic wireless
adapter, I found there are a AIROHA transceiver and a ZYDAS USB driver chip.
Do you know where does the Winpcap implement the incoming packets
filtering?<BR><BR>Cheers<BR><BR>John<BR><BR>
<DIV class=gmail_quote>2009/5/7 Gianluca Varenni <SPAN dir=ltr><<A
href="mailto:gianluca.varenni@cacetech.com">gianluca.varenni@cacetech.com</A>></SPAN><BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0pt 0pt 0pt 0.8ex; BORDER-LEFT: rgb(204,204,204) 1px solid">
<DIV bgcolor="#ffffff">
<DIV><FONT size=2></FONT> </DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(0,0,0) 2px solid; MARGIN-RIGHT: 0px">
<DIV class=im>
<DIV
style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal">-----
Original Message ----- </DIV>
<DIV
style="BACKGROUND: rgb(228,228,228); FONT: 10pt arial; font-size-adjust: none; font-stretch: normal; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial"><B>From:</B>
<A title=locationdev@gmail.com href="mailto:locationdev@gmail.com"
target=_blank>John Wang</A> </DIV>
<DIV
style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>To:</B>
<A title=winpcap-users@winpcap.org href="mailto:winpcap-users@winpcap.org"
target=_blank>winpcap-users@winpcap.org</A> </DIV></DIV>
<DIV class=im>
<DIV
style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>Sent:</B>
Wednesday, May 06, 2009 6:36 AM</DIV>
<DIV
style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>Subject:</B>
Re: [Winpcap-users] Where does the Winpcap
timestampcomefrom?andothers</DIV>
<DIV><FONT size=2></FONT><BR></DIV></DIV>
<DIV>
<DIV></DIV>
<DIV class=h5>Hi,<BR><BR>I'm a little bit confused about where exactly the
arrival packets timestamps come from, in our first email, you
said:<BR><BR><SPAN style="COLOR: rgb(51,51,255)">"1. Where does the NPF
get the time information to timestamp these incoming packet? The time
information comes from a on board timer in the adapter or from a CPU or
similar computer clock?</SPAN>
<DIV style="COLOR: rgb(51,51,255)"><FONT color=#000000
size=2></FONT> </DIV>
<DIV style="COLOR: rgb(51,51,255)"><FONT size=2>--GV--</FONT></DIV>
<DIV><FONT style="COLOR: rgb(51,51,255)" size=2>From the computer clock
when the packet gets delivered to WinPcap.</FONT><SPAN
style="COLOR: rgb(51,51,255)">"</SPAN><BR><BR><FONT color=#000000>I think
that means the timestamps come from computer timer, like CPU timer. But in
you last email, you said:<BR><BR><SPAN
style="COLOR: rgb(51,51,255)">"</SPAN></FONT><FONT
style="COLOR: rgb(51,51,255)"><FONT size=2>The only way to obtain that is
to have some device that timestamps packets in hardware. And even in
that case, most of the times the timestamps have microsecond precision
(this is what we have with the AirPcap adapters in
hardware).</FONT></FONT><FONT color=#000000><SPAN
style="COLOR: rgb(51,51,255)">"<BR><BR><SPAN
style="COLOR: rgb(0,0,0)">That sounds like, the AirPcap adapter has a
timer build in it, and the arrival packets timestamps come from this build
in timer.<BR><BR>So I want to get the confirmation from you, whether the
arrival packets are timestamped by the computer timer or the AirPcap
adapter build in
timer.<BR></SPAN></SPAN></FONT></DIV></DIV></DIV></BLOCKQUOTE>
<DIV><FONT color=#000000><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)"><FONT size=2>In the case of the AirPcap adapters,
which are *custom* capture devices, we provide two timestamps: software
based ones and hardware based ones. The hardware based ones are generated by
the chipset itself and have microsecond precision.
</FONT></SPAN></SPAN></FONT></DIV>
<DIV><FONT color=#000000><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)"></SPAN></SPAN></FONT> </DIV>
<DIV><FONT color=#000000><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)"></SPAN></SPAN></FONT><FONT color=#000000><SPAN
style="COLOR: rgb(51,51,255)"><SPAN style="COLOR: rgb(0,0,0)"><FONT
size=2>If you use WinPcap on a standard network adapter (doesn't matter if
it's wireless or not), you just have software
timestamps.</FONT></SPAN></SPAN></FONT></DIV>
<DIV><FONT color=#000000><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)"></SPAN></SPAN></FONT> </DIV>
<DIV><FONT color=#000000><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)"></SPAN></SPAN></FONT><FONT color=#000000
size=2><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)">Let me know if this makes any sense to
you.</SPAN></SPAN></FONT></DIV>
<DIV><FONT color=#000000 size=2><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)"></SPAN></SPAN></FONT> </DIV>
<DIV><FONT color=#000000 size=2><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)"></SPAN></SPAN></FONT><FONT color=#000000
size=2><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)">Have a nice day</SPAN></SPAN></FONT></DIV>
<DIV class=im>
<DIV><FONT color=#000000 size=2><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)"></SPAN></SPAN></FONT><FONT color=#000000><SPAN
style="COLOR: rgb(51,51,255)"><SPAN style="COLOR: rgb(0,0,0)"><FONT
size=2>GV</FONT></SPAN></SPAN></FONT></DIV><FONT color=#000000><SPAN
style="COLOR: rgb(51,51,255)"><SPAN style="COLOR: rgb(0,0,0)"><FONT
size=2></FONT></SPAN></SPAN></FONT>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(0,0,0) 2px solid; MARGIN-RIGHT: 0px"><FONT
color=#000000><SPAN style="COLOR: rgb(51,51,255)"><SPAN
style="COLOR: rgb(0,0,0)">
<DIV><BR>Cheers<BR><BR>John<BR></DIV></SPAN></SPAN></FONT>
<P></P>
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