I'm getting a 400 Error when attempting to import data into EPiServer

I'm trying to import two episerverdata files that are 2.6 GB & 6 GB onto a website that has no other content, and is just the source code of the website. I'm attempting to do this on a local development machine using IIS Express. However, whenever I attempt to upload either file, the file will hit 99%, and then show an HTTP Error 400 - Bad Request. The error says that ASP.NET detected invalid characters in the URL, but I don't see how considering it's just a file upload, and the name of the file is completely compliant, (Pages_ExportedFile).

I've attempted to increase IIS' file upload limit using the web.config of my project:

maxRequestLength="40960"
executionTimeout="7200"
maxAllowedContentLength="1073741824"

I've also attempted to upgrade the site slowly to ASP.NET Framework 4.6.1 from 4.5. I'm using EPiServer 10 right now, although I'm attempting to upgrade it to 11 to see if this resolves the issue.

Solution

maxRequestLength is set in kilobytes, if your file is 6.0 GB it should at least have the value 6291456,

executionTimeout is set in seconds, 7200 would mean two hours. This should be enough and I assume you set the element in the system.web section, ie.

<system.web>
    <httpRuntime executionTimeout="7200" />
</system.web>

maxAllowedContentLength is set in bytes, 6.0 GB = 6442450944 bytes

Since you are using IISExpress there are some limits

depending on your version there may be actual storage limits
you may need to tweak the applicationhost.config file in %userprofile%\Documents\IISExpress\config. Depending on the implementation the settings set above may also apply to the iis configuration and the timeouts may actually come from iisexpress and not iis.