These guys apparently did work on the IIS engine, but also have an enhanced product for sale:
They offer a free test to determine if your (public) site has compressed output or not.
Update:
Even better:
wfetch is offered for free from Microsoft. it\'s a program that will allow you to determine if HTTP compression is working on your local (i.e. not accessible to pipeboost.com(!) intranet servers).
284285 HOW TO: Use Wfetch.exe to Troubleshoot HTTP Connections
With wfetch, if IIS Compression is working:
Send a RAW request like this (replace URL):
GET /ourIntranet/login.asp HTTP/1.1\\r\\n
Accept: */*\\r\\n
Accept-Language: en-us\\r\\n
Connection: Keep-Alive\\r\\n
Referer: http://localhost/links.asp\\r\\n
Host: www.domain.com\\r\\n
User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0)\\r\\n
Accept-Encoding: gzip, deflate\\r\\n
\\r\\n
(Source Deja.com: From: Dave - Subject: gZip / Deflate - How to verify from client side - Newsgroups: comp.infosystems.www.servers.ms-windows -Date: 2003-01-02 10:07:30 PST )
Output should look like this, note \"deflate\" (from a separate GoogleGroups post):
--log start-----------------------------------
HTTP/1.1 200 OK\\r\\n
Cache-Control: private\\r\\n
Date: Mon, 08 Sep 2003 00:45:07 GMT\\r\\n
Transfer-Encoding: chunked\\r\\n
Content-Type: text/html\\r\\n
Content-Encoding: deflate\\r\\n
Vary: Accept-Encoding\\r\\n
Server: Microsoft-IIS/6.0\\r\\n
X-Powered-By: ASP.NET\\r\\n
..
--log end-----------------------------------