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My current development machine is Windows XP, and I use a modified tcpip.sys to allow me to exceed the 10 connection limit built in to IIS. I know that Vista's IIS has the same limit.

Can anyone confirm whether this connection limit is present in Windows 7 IIS as well?

RedFilter
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  • Are your eferring to the 10 authenticated connection limit in XP, or the 10 half-open connections limit? It seems that those answering your question are assuming the latter.. which doesn't make a lot of sense regarding IIS on desktop OS's. – Erik Funkenbusch Jun 06 '09 at 18:01
  • I am referring to the 10 half-open connection limit. – RedFilter Jun 06 '09 at 19:56
  • This question is badly-formed. The (outbound) half-open connection limit from Windows XP SP2 has nothing to do with the (inbound) IIS number-of-requests limit. The accepted answer covers both possibilities, but the question is like asking "what orange is the best pear?" – TristanK Mar 06 '12 at 22:47
  • @TristanK I framed the question as best as I could with my limited understanding. The issue I was trying to deal with was the IIS connection limit exceeded errors (actually EventID 4226) that you can get when hosting IIS on Windows XP. The reason I assumed half-open connections were the issue was that this is what was patched by the TCPIP.SYS patcher I used (http://www.lvllord.de/?lang=en&url=4226patch/faq), which resolved the issue. – RedFilter Mar 07 '12 at 15:30

5 Answers5

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From the base OS perspective, the limit has gone.

With Vista pre-sp2 it depended on the version. See https://stackoverflow.com/questions/413110/which-is-the-maximum-number-of-windows-concurrent-tcp-ip-connections/929973#929973

Since Vista SP2 the limitation have been removed from TCPIP.SYS, and has been configurable through a registry key. Windows7 should follow that same behavior (source and for 7, and here), but of course we will not know for 7 definitely until RTM since appart from technial there may be license restrictions.

However, IIS introduces its own limitations, depending on the version of the OS. For Windows 7 this limit is between 3 (Home Premium) and 10 (Business, Enterprise & Ultimate) simultaneous connections . Depending on your scenario, it might help to lower the connection timeout to free up slots sooner.

Community
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Peter Stuer
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The connection limit in IIS is NOT THE SAME as the 10 half-port open limit. This is a limit built into IIS and has nothing to do with TCP/IP. Pay for server or run Apache.

DrZaiusApeLord
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  • No need to pay for a server, as I was having no issue with connection limit - only half-open connection limit, which is a solved problem. – RedFilter Apr 21 '10 at 13:54
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There is a special version of TCP-Z, a tool for "patching" tcpip.sys, for Windows 7 - an indication that this setting still exists in Microsoft new operating system.

Disclaimer: it is not advised to change operating system drivers.

splattne
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  • You're confusing the "10 connection limit" of Desktop OS's with the "10 half-open connection limit" that was imposed as a security restriction. I'm not sure which the question asker was referring to. The "10 connection limit" is imposed on authenticated connections to prevent Desktop IIS from being used as a server. – Erik Funkenbusch Jun 06 '09 at 18:00
  • The question itself is a little confusing. The asked writes "IIS connection limit" (?) and "patching tcpip.sys", so I deduced he was referring to this limit. – splattne Jun 06 '09 at 18:59
  • I am referring to the 10 half-open connection limit. The same limit that was fixed by this Win XP patch: http://www.lvllord.de/?url=tools. – RedFilter Jun 06 '09 at 19:58
  • You deduced correctly. thanks for the link splattne, sounds like the limit is still there :( – RedFilter Jun 06 '09 at 20:02
  • I confirmed with this tool that on Windows 7 the limit is still 10. – RedFilter Jun 06 '09 at 20:11
  • Clarification - the tool shows what the limit WOULD be if it is turned on by the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Tcpip\Parameters\EnableConnectionRateLimiting=1 – RedFilter Jun 07 '09 at 02:49
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Edit: I stand corrected, there is a 10 concurrent connection HTTP limit, confirmed by testing.

JohnW
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  • What is the basis for your statement that there is no concurrent connection limit in Windows 7 IIS? Is it an assumption based on your knowledge of Vista, or have you confirmed it to be the case? – RedFilter Jun 06 '09 at 14:18
  • My original screenshot was against IIS7 server, not IIS 7.5 client due to a typo in hostname. Apologies. – JohnW Jun 06 '09 at 15:06
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Pleae see this link, and how to get more concurrent connections in IIS.

http://community.psion.com/knowledge/w/knowledgebase/1227.a-r-c-increase-iis-connection-limits.aspx

Regards

user167694
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    Welcome to Server Fault! Generally we like answers on the site to be able to stand on their own - Links are great, but if that link ever breaks the answer should have enough information to still be helpful. Please consider editing your answer to include more detail. See the [FAQ](http://www.serverfault.com/faq) for more info. – slm Apr 03 '13 at 20:15
  • -1: The information in the linked article is incorrect. – RedFilter Apr 03 '13 at 21:03