IIS/ASP.NET: Issue with sending (POST) 1M bytes length requests - asp.net

Question

I encountered a weird case during debugging a WebAPI controller for saving files.
My controller has a method for posting data
[HttpPost]
[HttpPut]
public async Task<HttpResponseMessage> Upload()
{
if (!request.Content.IsMimeMultipartContent())
{
throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
}
var provider = await request.Content.ReadAsMultipartAsync();
MultipartFileData file = provider.FileData.FirstOrDefault();
// this is the uploaded file: file.LocalFileName
}
Controller's logic doesn't matter much here. The key point here is that the controller expects multipart-content.
Now from the client where I'm using jquery.fileupload library I send files via POST method.
I set a breakpoint on the first line of the controller's Upload method and send a file from the client. The breakpoint goes off. It goes off before all file were uploaded to the server. It's expected behavior and everything is good.
Now the problem. I send a large file and the breakpoint doesn't go off. The file is being uploaded (POSTed) and the controller isn't being called!
Event worse that after the file is finally uploaded I get 404 Not Found on the client.
My site is on localhost under IIS with ASP.NET Web API 5.1.2 (.NET 4.5).
I start changing file size to choose the size when the things works. It turns out that is't 1000000000 (one million bytes). If a request's length (data and headers) is 1M bytes that everything works: breakpoint goes off and the file is uploaded. If a request's length 1 byte more that nothing works: breakpoint doesn't go off, the file seems to being uploaded (i.e. tha data is sending) but it's unclear where it's uploaded as the controller isn't called.
As my site on localhost I can't believe it's caused by proxy server.
So my question is what is going on? What can be wrong with posting 1M bytes requests?
p.s. I'm aware of IIS and ASP.NET hard limits for request lengths (4Gb and 2Gb) - they are not exceeded.

Answer 1

In IIS Manager click on your site and go Configuration Editor - you will need to alter maxRequestLength to a value that will work with your requirements.
Edit:
The second place request limits are set are here:
<system.webServer>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="1000000000" /> <!-- change this -->
</requestFiltering>
</security>
</system.webServer>

Answer 2

So I completely forgot about settings in web.config. It turns out that 1M was the limit set there :(
<system.web>
<httpRuntime maxRequestLength="1000000000" />
</system.web>
<system.webServer>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="1000000000" />
</requestFiltering>
</security>
</system.webServer>