[Winpcap-users] Duplicate Outgoing Packets

[Quinton Tormanen]

>From your comments, I took a look and found that I had a "Virtual PC
Emulator Ethernet Switch" installed for my NIC.  This was installed by
some of Visual Studio's embedded tools, which after uninstalling, the
problem went away.  Thanks for pointing me in the right direction!
 
--Quinton

________________________________

From: winpcap-users-bounces at winpcap.org
[mailto:winpcap-users-bounces at winpcap.org] On Behalf Of David Chang
Sent: Friday, June 03, 2005 1:28 PM
To: winpcap-users at winpcap.org
Subject: Re: [Winpcap-users] Duplicate Outgoing Packets


Quinton,
 
This can happen when running a software VPN product like Checkpoint's
Secure Remote.  In fact newer versions of Secure Remote eliminate
packets rather than duplicate them (that's really bad!).  If you're
running any kind of network filter or driver that operates at a low
level, it may be affecting Winpcap's packet capturing mechanism.
 
DC

	----- Original Message ----- 
	From: Quinton Tormanen <mailto:quintont at deltacompsys.com>  
	To: winpcap-users at winpcap.org 
	Sent: Friday, June 03, 2005 11:19 AM
	Subject: [Winpcap-users] Duplicate Outgoing Packets
	
	

	This is related to my last question, which was answered VERY
well, thank you all! 

	I am consistently seeing duplicate packets several microseconds
apart.  These are always packets being sent by my PC (the one running
winPcap).  So, I have traffic between the PC and our own device in
development.  It is a client/server protocol.  The PC sends a request,
and our device sends a response.  However, what I'm seeing is that the
PC sends two packets, which is 100% identical (including the IP
identification field, and TCP sequence numbers).  I highly doubt that
both are really making it onto the wire, in the same way that the bogus
TCP checksums apparently never made it on the wire.

	Has anyone seen this?  Does anyone have a theory for why it
happens? 

	I'm using Windows 2000 with a 3Com on-board NIC. 

	Quinton Tormanen 
	Software Engineer 
	Delta Computer Systems, Inc. 
	http://www.deltacompsys.com <http://www.deltacompsys.com>  

	

	
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