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Windows 8 / IIS 8 Concurrent Requests Limit

IIS 8 on Windows Server 2012 doesn’t have any fixed concurrent request limit, apart from whatever limit would be reached when resources are maxed.

However, the client version of IIS 8, which is on Windows 8, does have a concurrent connection request limitation to limit high traffic production uses on a client edition of Windows.

Starting with IIS 7 (Windows Vista), the behavior changed from previous versions.  In previous client versions of IIS, excess requests would throw a 403.9 error message (Access Forbidden: Too many users are connected.).  Instead, Windows Vista, 7 and 8 queue excessive requests so that they will be handled gracefully, although there is a maximum number of requests that will be processed simultaneously.

Thomas Deml provided a concurrent request chart for Windows Vista many years ago, but I have been unable to find an equivalent chart for Windows 8 so I asked Wade Hilmo from the IIS team what the limits are.  Since this is controlled not by the IIS team itself but rather from the Windows licensing team, he asked around and found the authoritative answer, which I’ll provide below.

Windows 8 – IIS 8 Concurrent Requests Limit

Windows 8 (Basic edition) 3
Windows 8 Professional, Enterprise 10
Windows RT N/A since IIS does not run on Windows RT

Windows 7 – IIS 7.5 Concurrent Requests Limit

Windows 7 Home Starter 1
Windows 7 Basic 1
Windows 7 Premium 3
Windows 7 Ultimate, Professional, Enterprise 10

Windows Vista – IIS 7 Concurrent Requests Limit

Windows Vista Home Basic (IIS process activation and HTTP processing only) 3
Windows Vista Home Premium 3
Windows Vista Ultimate, Professional, Enterprise 10

Windows Server 2003, Windows Server 2008, Windows Server 2008 R2 and Windows Server 2012 allow an unlimited amount of simultaneously requests.

Posted: Nov 13 2012, 06:14 PM by OWScott | with 11 comment(s)
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Comments

javafun said:

Hi scott, does windows 8 mean enterprise edition? if that's the case, why professional has more concurrent request than enterprise?

# November 14, 2012 6:49 AM

Eric Lawrence said:

Are these IIS limits, or HTTP.SYS limits? Would they impact a .NET program using the HttpListener?

# November 14, 2012 12:02 PM

OWScott said:

@javafun, the naming in the editions for Windows 8 is confusing in that regard, but "Windows 8" edition is really the home edition. I just updated the post to mention that, and also to mention Enterprise edition.

# November 14, 2012 2:58 PM

OWScott said:

@Eric, I had to ask to get the answer on that. The limits are implemented in IIS specifically on the hand-off from http.sys. So, it would not affect other consumers of http.sys.

There may be other limits unrelated to this, but this particular limit wouldn't impact a http.sys based HttpListener.

# November 14, 2012 6:18 PM

javafun said:

Hi scott,thanks for your update, I wasn't realized there is a home edition at all :)

# November 14, 2012 7:25 PM

John said:

Thanks, but what about IIS ftp connections?

# November 15, 2012 5:36 AM

OWScott said:

Hi John,

Good question. Yet another question I had to look into to confirm for sure. There isn't any FTP throttling in place.

Scott

# November 20, 2012 6:14 PM

Curio said:

Is anyone aware of the of the concurrent request limit for Vista Enterprise 32bit?

Vista Ent is an OEM only / non retail version of Vista that shares some characteristics of Vista Ultimate such as BitLocker but not all of them such as the Vista Ultimate multimedia features.

Web research seems to explain these limits for every version EXCEPT the obscure Vista Ent.

Thanks in advance

# November 27, 2012 6:15 AM

OWScott said:

Hi Curio. You're right that Enterprise doesn't appear to be mentioned in the lists regarding this functionality. I updated my post to include it. It's in the same category as Ultimate and Professional with a limit of 10 concurrent requests.

# November 27, 2012 9:11 AM

Avram said:

I just got off the phone with a Microsoft sales rep, although they are researching it further and indicated that Windows 2012 Essentials only supports 25 con-current connections - which would obviously make this a non option for running it as a web hosting server using iis 8.0.  Can you confirm or deny if this is true as your beginning sentence suggests that all versions of windows 2012 server support unlimited number of con-current connections with regard to hosting utilizing iis 8.0.  Thank you.

# January 8, 2013 3:54 PM

OWScott said:

Hi Avram,

It may be possible that Windows 2012 Essentials follows yet another pattern. I'll try to find an authoritative answer for you.

# January 8, 2013 4:51 PM
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