<p dir="auto">In BinaryFilesResponse.php's "prepare" method, the partial response is created only if no "If-Range" request header found, or if it matches the response's ETag.<br>
Default behavior of this response is to not send ETag header, but Last-Modified, so we have no browser cache.<br>
As per the spec, "If-Range" request header value may also be compared with the response's Last-Modified time.<br>
And that would be usefull :-)</p>
<p dir="auto">According to w3c specification <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html" rel="nofollow">http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html</a>,<br>
in the request, If-range header can contains last modified date of file, but in BinaryFileResponse(symfony v2.6.8) only  etag accepted.<br>
As in current realization etag generating by  sha1_file function in takes much time with big files.</p>