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What does sc-status = 200 and sc-win32-status = 64 mean, and why is time-taken large?

(Kristofer Gafvert, July 17, 2010)

Introduction

The combination of sc-status (also known as http status code) = 200 and sc-win-32-status = 64, together with a very large time-take, may happen in the following scenarios

Scenario 1

IIS first gets the request from the client. IIS execute the request without problems, and send back a response. This results in a sc-status code = 200 (but we still don't know if the client has received the response, hence at this moment sc-win32-status is unknown).

Next IIS tries to send the response to the client, but the connection is already lost (during the execution of the request), or gets lost during the transmission (this is a network issue). Now IIS logs sc-win32-status = 64 (which means "The specified network is no longer available"), and depending on how long it waits for the client, the time-taken log entry may be large.

Scenario 2

IIS first gets the request from the client. IIS execute the request without problems, and send back a response. This results in sc-status code = 200 (but we still don't know if the client has received the response, hence at this moment sc-win32-status is unknown).

Next IIS tries to send the response to the server, and waits for an ACK message from the client, but the client is unwilling of sending this (but do get a response, compare this to scenario 1 where the client did not get a response). Instead, the client resets the connection, to free up resources (instead of leaving the connection in a TIME_WAIT/CLOSE_WAIT state, which is more common). This behavior is very common by proxies, to not have too many socket connections. Since IIS did not get any ACK message, it logs a sc-win32-status code of 64. Depending on how long it waits for the client, the time-taken log entry may be large.

Conclusion

If you see sc-status = 200, sc-win32-status = 64 and a large time-taken value, it does not automatically mean you need to do anything. If you see it seldom, don't bother about it, because there is nothing you can do (the client is the problem). If you see it often, it may indicate an unreliable network near the web server. You may need to solve this yourself, or contact your ISP, depending on where the network issue is located.

Applies to [?]

IIS 6.0, IIS 7.0, IIS 7.5

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