[Winpcap-users] Duplicate Outgoing Packets

[David Chang]

Duplicate Outgoing PacketsQuinton,

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 
  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 



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