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Re: Comments on Byte range draft

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Tue, 14 Nov 95 11:13:49 PST
Message-Id: <9511141913.AA04414@acetes.pa.dec.com>
To: Laurent Demailly <dl@hplyot.obspm.fr>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
    I agree that there should be some *opaque* string used to select if the
    object is the same or not (string which could be for instance a last
    modified date, an MD5 digest,... whatever the server wants)
    And the client could for instance blindy use what the server sent as
    Content-Digest: (for instance, but we could use a different name if that
    one is 'burned' ;-) )
I would recommend against using the Content-Digest as the
cache-authenticator.  This means that if a server wants to control
caching, it is forced to generate a Content-Digest that is also
semantically correct for whatever other uses a Content-Digest
is useful for.

In short, Content-Digest is NOT opaque to the client.

It also means that the server must either re-digestify the object
to do a validity check, or keep a database of Digest values.

If the server wants to use a simpler scheme (such as file modification
time) to generate a validator, it should be able to do so.

Received on Tuesday, 14 November 1995 12:07:31 UTC

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