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We've had an issue on and off for some time now...

We have an app which sync's to a server, we know the request is getting to the server as we have been running wireshark and can see the incoming request.

Now this is where I need some correcting if im wrong somewhere...

my understanding is that the traffic will go from the network card on the machine, to HTTP.sys, which forwards it to IIS6, which then sends it to my executable ISAPI, which in turn provides the response which goes back through IIS6, through the network card over the WWW back to the device.

Now these requests that are going missing, like I said we can see that the request has got to the network card thanks to wireshark, but we don't know what's happened to it from this point, there's no error in the HTTP.sys log, and nothing in the IIS log, same with the log for our ISAPI, nothing in here either.

The fact that the HTTP.sys log is empty indicates to me that the kernal thinks it has successfully passed it onto IIS6, but I dont know if IIS6 logs when it first receives the request, or once it has successfully responded to it, has anyone got any ideas on this one? its a very strange one.

Jeffrey
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  • Do you use "IP acceleration" a.k.a. IP checksum offloading, chimney, etc.? We have given up on using these with Windows because of unexplained packet loss. – Eugen Rieck Oct 06 '14 at 08:47
  • No we do not use this. The unexplained packet loss you had, was this when using Server 2003 / IIS6? – Jeffrey Oct 06 '14 at 10:24
  • Yes, this was 2K3 and IIS6. Ended up replacing it with a Linux box and never looked back. – Eugen Rieck Oct 06 '14 at 11:05
  • Ah so same as us. We also have 2008 servers running IIS7 but havn't seen this issue at all on these systems yet, its only on 2003 iis6 that we have identified so far. Do you know at which point IIS6 logs, if its when the traffics coming in or once its responding? – Jeffrey Oct 06 '14 at 11:28
  • I don't think it is an IIS issue, but a Windows issue: We were able to reproduce it with really high packet load on other services. It is just more visible with HTTP (no request retry after connection was established) – Eugen Rieck Oct 06 '14 at 12:43
  • Im trying to use logman to give me more information about the packet, when I run it on my windows 7 machine i can output a lovely xml file that shows me each movement of the packet, but I can seem to get the same report out of logman on a 2003 server, ever used logman? – Jeffrey Oct 06 '14 at 12:47

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