SharePoint 2010 / IIS 7.5 Byte-Range Request Responds With Entire File

I'm having problems getting SharePoint 2010/IIS 7.5 to respect byte-range requests. I'm developing a SharePoint 2010 Web Part using Si开发者_开发知识库lverlight, and am trying to retrieve part of a document stored inside SharePoint.

When I request a byte range of a file in SharePoint, the server responds with the entire file. However, if I request the same byte range from a file sitting on an Apache server, everything works as expected. Below are the http headers observed with Fiddler.

Any help would be really appreciated! Thanks.

Sent:

GET http://example.com/file.abc HTTP/1.1
Accept: */*
Accept-Language: en-US
Referer: http://example.com/index.html
Accept-Encoding: identity
Range: bytes=1061285-1064594
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/533.4 (KHTML, like Gecko) Chrome/5.0.375.127 Safari/533.4
Host: example.com
Connection: Keep-Alive

SharePoint also takes login credentials:

Authorization: Negotiate TlRMTVNTUAABAAAAl4II4gAAAAAAAAAAAAAAAAAAAAAGAbAdAAAADw==

Received from Apache:

HTTP/1.1 206 Partial Content
Date: Wed, 25 Aug 2010 22:40:34 GMT
Server: Apache/2.0.54
Last-Modified: Fri, 20 Aug 2010 23:27:18 GMT
ETag: "b68e346-103ea9-a3c20180"
Accept-Ranges: bytes
Content-Length: 3310
Vary: User-Agent
Content-Range: bytes 1061285-1064594/1064617
Keep-Alive: timeout=5, max=99
Connection: Keep-Alive
Content-Type: application/x-zip

Received from SharePoint 2010 / IIS 7.5

HTTP/1.1 200 OK
Cache-Control: private,max-age=0
Content-Length: 1064617
Content-Type: application/octet-stream
Expires: Tue, 10 Aug 2010 22:40:56 GMT
Last-Modified: Wed, 25 Aug 2010 19:28:39 GMT
ETag: "{5A1DF927-D8CD-4BC0-9590-8188CF777A3D},1"
Server: Microsoft-IIS/7.5
SPRequestGuid: 99799011-5bdc-489f-99fd-d060a56d3ae4
Set-Cookie: WSS_KeepSessionAuthenticated={7703be10-bb56-4fa1-ba8b-cd05f482859f}; path=/
X-SharePointHealthScore: 5
ResourceTag: rt:5A1DF927-D8CD-4BC0-9590-8188CF777A3D@00000000001
X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename=file.abc
X-Download-Options: noopen
Public-Extension: http://schemas.microsoft.com/repl-2
Set-Cookie: WSS_KeepSessionAuthenticated={7703be10-bb56-4fa1-ba8b-cd05f482859f}; path=/
Persistent-Auth: true
X-Powered-By: ASP.NET
MicrosoftSharePointTeamServices: 14.0.0.4762
Date: Wed, 25 Aug 2010 22:40:56 GMT

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The problem is that SharePoint caching is off be default, and needs to be turned on to enable byte-range requests. See Disk-Based Caching for Binary Large Objects.

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Note http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35.2:

"A server MAY ignore the Range header."

Thus whenever you are using a Range header you must be able to handle a 200 response. The fact that your server doesn't appear to support range serving is unfortunate, but conformant.