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Re: Using of Connection header

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Tue, 25 Feb 97 10:28:47 PST
Message-Id: <9702251828.AA06176@acetes.pa.dec.com>
To: urbani@ares.mctel.fr
Cc: http-wg@cuckoo.hpl.hp.com
    if the request contains these headers:
    
    ---------------------------------------------------------------------
    Cache-Control: no-cache
    Connection: Cache-Control
    ---------------------------------------------------------------------
    
    could i use my cache or not ?  Because I must delete de
    Cache-Control header (because Connection) but I don't know if i
    must take or not care of it?
    
Although the HTTP/1.1 specification does not state this explicitly,
it is not legal to send

	Connection: Cache-Control

This is because the specification for Connection says

   The Connection general-header field allows the sender to specify
   options that are desired for that particular connection and MUST NOT
   be communicated by proxies over further connections.

while the specification for Cache-control says

   Cache directives must be passed through by a proxy or gateway
   application, regardless of their significance to that application,
   since the directives may be applicable to all recipients along the
   request/response chain.

which implicitly prohibits turning Cache-control into a hop-by-hop
header.

Because it would be against the rules to send this combination
of headers, the specification does not have to specify a particular
action to take if someone does it anyway.  (We cannot possibly
specify an action to take upon receipt of every possible contradictory
combination of headers.)

However, the robustness principle suggests that it's probably
safer to ignore the "Connection" header in this case than the
"Cache-control" header.

-Jeff
Received on Tuesday, 25 February 1997 10:39:58 EST

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