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Re: If-Modified-Since and forged dated

From: Brian Behlendorf <brian@organic.com>
Date: Wed, 16 Aug 1995 22:20:42 -0700 (PDT)
To: Shel Kaphan <sjk@amazon.com>
Cc: masinter@parc.xerox.com, sjk@amazon.com, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <Pine.SOL.3.91.950816221254.604J-100000@eat.organic.com>
On Wed, 16 Aug 1995, Shel Kaphan wrote:
> What about servers that are constantly creating dynamic documents?
> If they're 1 minute ahead, none of their documents will be cacheable.

RealTime	ServerTime	Action

12:00		12:01		C: GET /this-dynamic-object
				S: 200 Ok
				   Last-Modified: some-old-time

				   (some-old-time calculated by determining age
				   of the data it assembles to produce the page)

12:05		12:06		C: GET /this-dynamic-object
				   If-modified-since: some-old-time
				S: 304 Not Modified

				   (the calculation to check last_modified of
				   the data is much faster than assembling the
				   whole page)

12:07		12:08		(some data changes on the server which 
				affects this-dynamic-object)

12:08		12:09		C: GET /this-dynamic-object
				   IMS: some-old-time
				S: 200 Ok
				   Last-Modified: 12:08

Only objects which truly change with every minute (i.e., the data used to
determine what the page looks like) need be uncacheable.

	Brian


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Received on Wednesday, 16 August 1995 22:20:35 EDT

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