Optimizing Active Channels over HTTP
This technology is obsolete as of Windows Internet Explorer 7 and should not be used. Web publishers are encouraged to follow the size guidelines discussed in the Designing Active Channel Sites article. In addition to considering bandwidth issues, Web publishers should support the following HTTP headers to ensure efficient use of their site by eliminating unnecessary data transfer.
- Send a "Last-Modified" response header upon HEAD and GET requests. This allows the Channel Definition Format (CDF) client to monitor changes to the channel without downloading any resources.
- Use the ITEM= attribute on ITEM elements. This optimization technique prevents Microsoft Internet Explorer 4.0 and later from hitting the server to retrieve the last modified date for each item referenced in the CDF file.
- Use the "Expires" response header to indicate the lifetime of the resource.
- Don't send the "Pragma: no-cache" response header unless absolutely necessary.
- Support the "If-Modified-Since" request header.