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Re: Entity Tags

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Tue, 13 Aug 96 13:59:47 MDT
Message-Id: <9608132059.AA06107@acetes.pa.dec.com>
To: Gavin Button <gavinb@imaging.co.uk>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
    I am in the process of designing an HTTP 1.1 server which  provides
     JPEG Images when a GET method with a certain URL is received, but am
     unsure about the use of entity tags.  Should an entity of this type
    respond with an ETag field ?
    
Generally, an HTTP/1.1 server would return Etag fields whenever
there is a straightforward way of generating them.  It has nothing
to do with the precise data type; that is, it doesn't matter if the
images are JPEG, GIF, MPEG, or drawings made up of ASCII characters.

If your server does not have a way to generate an ETag field that
meets the specification, then don't send one.

    In turn, should I support If-Match/If-None-Match?
    
It's almost entirely pointless to send an ETag response header unless
you also support the request headers that use entity tags (i.e.,
If-Match, If-None-Match, and If-Range if you support subranges).

    If so ,How?

We tried to describe this in the specification.  If there is some
part of the specification (draft-ietf-http-v11-spec-07.txt) that
is unclear to you, please describe the specific problem.  The
purpose of this mailing list is to produce a good specification,
and we need to know if people are confused after they have read 
it carefully.
    
-Jeff
Received on Tuesday, 13 August 1996 14:24:23 EDT

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