The Meter general-header field is used to:

      - Negotiate the use of hit-metering and usage-limiting among
        origin servers and proxy caches.

      - Report use counts and reuse counts.

   Implementation of the Meter header is optional for both proxies and
   origin servers.  However, any proxy that transmits the Meter header
   in a request MUST implement every requirement of this specification,
   without exception or amendment.

   The Meter header MUST always be protected by a Connection header.  A
   proxy that does not implement the Meter header MUST NOT pass it
   through to another system (see section 5.5 for how a non-caching
   proxy may comply with this specification).  If a Meter header is





 
RFC 2227            Hit-Metering and Usage-Limiting         October 1997


   received in a message whose version is less than HTTP/1.1, it MUST be
   ignored (because it has clearly flowed through a proxy that does not
   implement Meter).

   A proxy that has received a response with a version less than
   HTTP/1.1, and therefore from a server (or another proxy) that does
   not implement the Meter header, SHOULD NOT send Meter request
   directives to that server, because these would simply waste
   bandwidth.  This recommendation does not apply if the proxy is
   currently hit-metering or usage-limiting any responses from that
   server.  If the proxy receives a HTTP/1.1 or higher response from
   such a server, it should cease its suppression of the Meter
   directives.

   All proxies sending the Meter header MUST adhere to the "metering
   subtree" design described in section 3.

       Meter = "Meter" ":" 0#meter-directive

       meter-directive = meter-request-directive
                       | meter-response-directive
                       | meter-report-directive

       meter-request-directive =
                         "will-report-and-limit"
                       | "wont-report"
                       | "wont-limit"

       meter-report-directive =
                       | "count" "=" 1*DIGIT "/" 1*DIGIT

       meter-response-directive =
                         "max-uses" "=" 1*DIGIT
                       | "max-reuses" "=" 1*DIGIT
                       | "do-report"
                       | "dont-report"
                       | "timeout" "=" 1*DIGIT
                       | "wont-ask"

   A meter-request-directive or meter-report-directive may only appear
   in an HTTP request message.  A meter-response-directive may only
   appear in an HTTP response directive.

   An empty Meter header in a request means "Meter: will-report-and-
   limit".  An empty Meter header in a response, or any other response
   including one or more Meter headers without the "dont-report" or
   "wont-ask" directive, implies "Meter:  do-report".





 
RFC 2227            Hit-Metering and Usage-Limiting         October 1997


   The meaning of the meter-request-directives are as follows:

   will-report-and-limit
                   indicates that the proxy is willing and able to
                   return usage reports and will obey any usage-limits.

   wont-report     indicates that the proxy will obey usage-limits but
                   will not send usage reports.

   wont-limit      indicates that the proxy will not obey usage-limits
                   but will send usage reports.

   A proxy willing neither to obey usage-limits nor to send usage
   reports MUST NOT transmit a Meter header in the request.

   The meaning of the meter-report-directives are as follows:

   count "=" 1*DIGIT "/" 1*DIGIT