Re: limiting access

> The HTTP Last-Modified, Expires, Cache-Control/max-age and ETag 
> headers should help with clients that respect this protocol. I 
would 
> hazard a guess that not all do.
> 
> In principle it's a more effective way to preserve bandwidth, 
since 
> the client does not necessarily have to download the feed when the 
> initial expiry time passes. Clients can use an If-Modified-Since 
or 
> If-Match HEAD request to see if the feed really has changed before 
> downloading the content body.


Technically, I don't think you need the "If-Match HEAD", you can use 
a GET. But the idea is the same.

In the RSS aggregator check lists, the specific techniques of using 
the Last-Modified and the ETag headers I've seen referred to 
as "Conditional GET". I would expect that the combination of these 
headers with the Syndication module will get you the best control. 
Both of course require the cooperation of the aggregator.

The Expires and max-age would probably be considered hints to any 
Web cache mechanism between your server and the aggregator, but not 
to the aggregator itself.

At least that's how I view it in the aggregator I wrote.








 
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