Administering an ISP Installation

With a Custom HTTP Header

This sample code shows the same request sent with an HTTP header that causes content to expire in 30 minutes:

CLIENT REQUEST
GET /samplecorp/images/undercon.gif HTTP/1.1
Accept: */*
Referer: http://bicent/samplecorp/
Accept-Language: en-us
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 5.0; Windows 2000)
Host: bicent
Connection: Keep-Alive
Cookie: ASPSESSIONIDGQQGQGBE=PGIFFNMBCAOPEHGGKOGJODID

SERVER RESPONSE
HTTP/1.1 200 OK
Server: Microsoft-IIS/5.0
Cache-Control: max-age= 1800
Expires: Tue, 14 Oct 1999 18:24:21 GMT
Date: Tue, 14 Oct 1999 17:54:21 GMT
Content-Type: image/gif
Accept-Ranges: bytes
Last-Modified: Tue, 14 Oct 1999 15:53:27 GMT
ETag: "0d1974fb9d8bc1:ecb"
Content-Length: 293

Notice the two lines enabling content expiration. While Cache-Control affects the proxy cache, Expires affects the browser cache.

You can set custom HTTP headers and content expiration globally or apply them to a specific directory.

To set HTTP headers for content expiration

In the IIS snap-in under Internet Information Services, right-click the Web site or virtual directory on which you want to set custom HTTP headers.
Click Properties.
Select Enable Content Expiration.
On the HTTP Headers property sheet, add a custom header in the Custom HTTP Headers box.
For help in creating a custom header, click the Help button on the property sheet.
Click OK.

For more information, see the IIS 5.0 online product documentation.