HTTP Requirements for BITS Downloads

BITS supports HTTP and HTTPS downloads and uploads and requires that the server supports the HTTP/1.1 protocol. For downloads, the HTTP server's Head method must return the file size and its Get method must support the Content-Range and Content-Length headers. As a result, BITS only transfers static file content and generates an error if you try to transfer dynamic content, unless the ASP, ISAPI, or CGI script supports the Content-Range and Content-Length headers.

BITS can use an HTTP/1.0 server as long as it meets the Head and Get method requirements.

To support downloading ranges of a file, the server must support the following requirements:

• Allow MIME headers to include the standard Content-Range and Content-Type headers, plus a maximum of 180 bytes of other headers.
• Allow a maximum of two CR/LFs between the HTTP headers and the first boundary string.