asp.net - Resuming HTTP download in IE9

Question

i'm really stuck with resuming download process in IE 9. Everything works great in other browsers and download managers. I know about required headers to resume download, but IE does not send them after i try to resume download. HTTP header log: Requesting file:

======================= Request ===========================
Connection=Keep-Alive
Accept=*/*
Accept-Encoding=gzip, deflate
Host=localhost
User-Agent=Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
======================= Response ===========================
Status code 200
Server=Microsoft-IIS/7.5
X-AspNetMvc-Version=3.0
Last-Modified=Thu, 07 Jun 2012 14:31:35 GMT
ETag="BCZFgJdhKko3IfS9D4nojw=="
Accept-Ranges=bytes
Expires=Sat, 10 Oct 2020 07:10:10 GMT
Content-Length=4048784811
Content-Disposition=attachment; filename=DEM_AK_Bristol Bay.zip
Cache-Control=private
X-AspNet-Version=4.0.30319
Content-Type=application/zip

And here is log for resuming:

======================= Request ===========================
Connection=Keep-Alive
Accept=*/*
Accept-Encoding=gzip, deflate
Host=localhost
User-Agent=Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
======================= Response ===========================
Status code 200
Server=Microsoft-IIS/7.5
X-AspNetMvc-Version=3.0
Last-Modified=Thu, 07 Jun 2012 14:31:35 GMT
ETag="BCZFgJdhKko3IfS9D4nojw=="
Accept-Ranges=bytes
Expires=Sat, 10 Oct 2020 07:10:10 GMT
Content-Length=4048784811
Content-Disposition=attachment; filename=DEM_AK_Bristol Bay.zip
Cache-Control=private
X-AspNet-Version=4.0.30319
Content-Type=application/zip

As you can see they are absolutely the same. And here is log for firefox: First request:

======================= Request ===========================
Connection=keep-alive
Accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding=gzip, deflate
Accept-Language=ru-RU,ru;q=0.8,en-US;q=0.5,en;q=0.3
ASP.NET_SessionId=zv0ro2lhiumuijipzuamuemg
Host=localhost
User-Agent=Mozilla/5.0 (Windows NT 6.1; WOW64; rv:18.0) Gecko/20100101 Firefox/18.0
======================= Response ===========================
Status code 200
Server=Microsoft-IIS/7.5
X-AspNetMvc-Version=3.0
Last-Modified=Thu, 07 Jun 2012 14:31:35 GMT
ETag="BCZFgJdhKko3IfS9D4nojw=="
Accept-Ranges=bytes
Expires=Sat, 10 Oct 2020 07:10:10 GMT
Content-Length=4048784811
Content-Disposition=attachment; filename=DEM_AK_Bristol Bay.zip
Cache-Control=private
X-AspNet-Version=4.0.30319
Content-Type=application/zip

And resuming download

======================= Request ===========================
Connection=keep-alive
Accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding=gzip, deflate
Accept-Language=ru-RU,ru;q=0.8,en-US;q=0.5,en;q=0.3
ASP.NET_SessionId=zv0ro2lhiumuijipzuamuemg
Host=localhost
<b>If-Match="BCZFgJdhKko3IfS9D4nojw=="
If-Unmodified-Since=Thu, 07 Jun 2012 14:31:35 GMT
Range=bytes=526057028-</b>
User-Agent=Mozilla/5.0 (Windows NT 6.1; WOW64; rv:18.0) Gecko/20100101 Firefox/18.0
======================= Response ===========================
Status code 206
Server=Microsoft-IIS/7.5
X-AspNetMvc-Version=3.0
Last-Modified=Thu, 07 Jun 2012 14:31:35 GMT
ETag="BCZFgJdhKko3IfS9D4nojw=="
Accept-Ranges=bytes
Expires=-1
Content-Length=3522727783
Content-Range=bytes 526057028-4048784810/4048784811
Cache-Control=no-cache
X-AspNet-Version=4.0.30319
Content-Type=application/zip
Pragma=no-cache

Does anybody know what can cause this problem? Thanks.

Answer 1

I found the solution and its very easy. Caching settings is my application made "the best browser in the world" think that file has been modified and redownload from the very beginning. It's very strange behaviour because other browsers and download managers are fine.