[Winpcap-users] Out-going TCP/IP checksums

[Gianluca Varenni]

Out-going TCP/IP checksumsHi Quinton.

Some boards do TCP offloading, i.e. they compute the checksum on the board. So you were right. 

This ethereal FAQ provides some more details about it

http://www.ethereal.com/faq.html#q5.14

Have a nice day
GV
  ----- Original Message ----- 
  From: Quinton Tormanen 
  To: winpcap-users at winpcap.org 
  Sent: Friday, June 03, 2005 7:54 AM
  Subject: [Winpcap-users] Out-going TCP/IP checksums


  I am using the direct Packet interface (e.g. PacketReceivePacket), and I have found that the vast majority of TCP/IP packets being sent out by the PC running packet show up with invalid TCP header checksums.  I am running on Windows 2K, SP4 and the interface I am monitoring is a 3COM Ethernet card.

  I am assuming that the invalid checksums are not actually getting out onto the wire, but instead has something to do with when the checksums are computed.  Can anyone confirm that this is the case?

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



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