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Re: HTTP HEAD requests for Last-Modified info

From: Larry Masinter <masinter@parc.xerox.com>
Date: Thu, 20 Jun 1996 11:38:04 PDT
To: marc@ckm.ucsf.edu
Cc: www-talk@w3.org
Message-Id: <96Jun20.113804pdt."2763"@golden.parc.xerox.com>
> Caching can't function to its potential if servers don't advertise L-M whenever
> possible.  Caching is essential to HTTP scalability in the near-term.  Server
> authors: N.B. above.

Actually, caching can work without Last-Modified, as long as the
origin server sends Expires and an ETag.

Expires is actually what lets a cache do its work: give the cache
permission to hold on to something. And the ETag lets the cache use
If-None-Match instead of If-Modified-Since with date stamps, since
dates are unreliable in some systems which might otherwise be able to
use cache validators.

Received on Thursday, 20 June 1996 15:27:59 UTC

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