Why doesn't IIS support chunked transfer encoding?
Take a look at your client.
Both IIS & Apache support POST requests using chunked transfer-encoding. You can verify this using the curl utility:
curl <upload-url> --form "upfile=@<local_file>" --header "Transfer-Encoding: chunked"Verify the transfer is chunked using Wireshark
My understanding is that chunked encoding can only be used in a HTTP response. A chunked request body would have the property of being incompatible with a 1.0 server, and in any case, there would be no way of a user-agent knowing that the server was a 1.0 server until it had already sent the request.
But I agree it's unclear from the documentation.
It goes both ways. try uploading a image 2MB++ to photobucket and record it. their uploader uploads chunked to their apache servers.