Re: Dates vs. Deltas [was: An alternative to explicit revocation? ]

On Wed, 3 Jan 1996, Daniel W. Connolly wrote:

> 
> What exactly is the test for freshness using deltas, and what are the
> input parameters? Does the number of parameters increase with the

First I must assume reasonable local integrity of the server's clock.

Then, when a delta expiration arrives, an actual expiration is computed
(and probably stored as an epoc time suitable to the server).

This expiration now is tested just as a parsed and stored absolute
time.

When a cached entity is served, a new delta expiration is computed 
and provided in the response header.


> themselves). The second caching proxy requests this resource at
> 1:15. Does the first proxy re-write the Cache: header? Yuk.  What
> about latency?

I don't believe re-writing the header is a big deal. Caching related
header data is going to be processed and manipulated in any event.

Latency is a much smaller issue than out of sync clocks. Latency will
generally be in the rage of seconds (assume first byte in is approx
sent time + minimum latency) while system clocks are easily minutes
off.  I assert that any document which won't still be servable  
over an interval >> latency shouldn't be marked cachable in the
first place.  Again, this problem is samller than clock differences
and hence the result will more closely reflect what is desired by
the information providers.

Dave Morris

Received on Wednesday, 3 January 1996 22:13:56 UTC