Re: HTTP Compression issues with IIS 5

From: WenJun Zhang[msft] (v-wzhang_at_online.microsoft.com)
Date: 09/23/04 

Date: Thu, 23 Sep 2004 11:02:33 GMT

Hi Tony,

"Won't this expire all content on the client immediately including
images, javascript files, etc? This could defeat the purpose of
having compressed content if we have to resend everything every time."

Sorry I forgot this question. You needn't worry about this. I did
test and see IIS still would send 304(not modified) response to
clients when using HTTP compression. 304 response doesn't have any
actual data, it simply tells client the local cache still can be used
and hasn't been expired. IIS will reply 304 if client attach a last
modified time of its local cache in http request and the time isn't
earlier than the file's on server.

Formerly IIS5 did have a bug on this behavior but it has been fixed
in service pack 3: 307633 IIS Does Not Return an HTTP 304 Not
Modified Message for Compressed
http://support.microsoft.com/?id=307633

I previously suggest you select 'expire immediately' to see if this
can help resolve the ASP caching problem. Since the problem is worked
out by max-age=0, now you can rollback it or use the content
expiration options(in HTTP Headers tab) to control the web client
cache behavior, the setting can be set at each individual file level.

Furthermore, actually css and js are not compressed file types by
default. The default ones are only: html/htm and txt. You can
manually add them to HcFileExtensions by using MetaEdit:

HOW TO: Specify Additional Document Types for HTTP Compression
http://support.microsoft.com/default.aspx?scid=kb;en-us;234497

Best regards,

WenJun Zhang
Microsoft Online Support
This posting is provided "AS IS" with no warranties, and confers no
rights.
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