```json
{
    "title": "Microsoft Gets Web Site Security — and breaks performance",
    "url": "https://performancezen.com/2005/01/11/microsoft-gets-web-site-security-and-breaks-performance/",
    "datePublished": "2005-01-11",
    "dateModified": "2005-01-11",
    "language": "en-US",
    "description": "Sigh. The team at Port80 Software discovered this little nugget around Microsoft's ISA Server. I quote it here in its entirety because the permalink is returning a 404. UPDATE (January…",
    "author": "spierzchala",
    "publisher": "Performance Zen"
}
```

# Microsoft Gets Web Site Security — and breaks performance

> **
>  Does Microsoft ISA Server 2004 support compression?**
>
>
> One of the most popular questions of 2004 was, without a doubt, "Why does Microsoft ISA Server 2004 break HTTP compression?"
>
> Many users of our httpZip and ZipEnable compression products have
> been scratching their heads over why implementing ISA Server suddenly
> makes their compression products stop working. Actually, what is
> happening is that ISA Server by default removes the Accept-encoding
> header from all inbound requests. This is *the* header that the
> Web server uses to determine whether it is OK to return compressed
> content to the browser making the request. Without this header,
> compression products are just doing what they are supposed to do:
> responding with uncompressed content.
>
> Although they have not done a good job of getting the word out,
> Microsoft has published this informative article that explains how Web
> publishing rules can be written for ISA Server 2004 to ensure that the
> Accept-encoding request headers get passed to the web server. If you're
> new to ISA, or just confused about why compression worked perfectly on
> your test server but is mysteriously MIA in your production server
> environment, check it out:
>
> [http://support.microsoft.com/default.aspx?scid=kb;en-us;838365](http://support.microsoft.com/default.aspx?scid=kb;en-us;838365)