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Connection tokens

From: J.P. Martin-Flatin <martin-flatin@epfl.ch>
Date: Sun, 14 Jun 1998 19:17:27 +0200
Message-Id: <199806141717.TAA19206@tcomhp31.epfl.ch>
To: http-wg@cuckoo.hpl.hp.com
Cc: martin-flatin@epfl.ch
There is no clear definition of the connection tokens supported by the 
Connection general-header field. Section 14.10 remains vague:

    connection-token = token

and gives "close" as an example of token, a few lines further.

RFC 2068 refers to the following connection tokens:

  close: pp. 44, 45, 109 and 161
  Keep-Alive: p. 161
  Persist: p. 161

"Keep-Alive" and "Persist" are described in RFC 2068 section 19.7.1 as the "HTTP/1.0 form of persistent connections". But they are specified in neither RFC 1945 nor RFC 2068. In Rev-03, references to" Keep-Alive" and "Persist" have been deleted from section 19.6.2.

I interpret this as meaning that the sole connection-token supported in HTTP/1.1 is "close", and that the experimental tokens "Keep-Alive" and "Persist" have been deprecated. This should be stated clearly in the spec. I suggest 2 ways of doing this:


1) Rephrase section 14.10 as follows:

  14.10 Connection

  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.

  The Connection header has the following grammar:

         Connection = "Connection" ":" 1#(connection-token)
         connection-token  = token

  HTTP/1.1 proxies MUST parse the Connection header field before a message
  is forwarded and, for each connection-token in this field, remove any
  header field(s) from the message with the same name as the connection-
  token. Connection options are signaled by the presence of a connection-
  token in the Connection header field, not by any corresponding
  additional header field(s), since the additional header field may not be
  sent if there are no parameters associated with that connection option.

  Message headers listed in the Connection header MUST NOT include end-to-
  end headers, such as Cache-Control.

  The only connection-token defined by HTTP/1.1 is "close". Tokens
  "Keep-Alive" and "Persist", which were used in some HTTP/1.0
  experimental implementations of persistent connections, have been
  deprecated. The "close" token allows the sender to signal that the
  connection will be closed after completion of the response. For example,

         Connection: close

  in either the request or the response header fields indicates that the
  connection should not be considered `persistent' (section 8.1) after the
  current request/response is complete.

  HTTP/1.1 applications that do not support persistent connections MUST
  include the "close" connection option in every message.

  A system receiving an HTTP/1.0 (or lower-version) message that includes
  a Connection header MUST, for each connection-token in this field,
  remove and ignore any header field(s) from the message with the same
  name as the connection-token. This protects against mistaken forwarding
  of such header fields by pre-HTTP/1.1 proxies.


2) Add a new section between sections 3.8 and 3.9:

    Connection Tokens

    Connection tokens are used to control the persistence of connections.
    The only connection-token defined by HTTP/1.1 is "close" (sections
    8.1 and 14.10).
    
    connection-token = "close"

    Tokens "Keep-Alive" and "Persist", which were used in some HTTP/1.0
    experimental implementations of persistent connections, have been
    deprecated.


Jean-Philippe Martin-Flatin
Received on Sunday, 14 June 1998 10:20:33 EDT

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