RFC 2756 (rfc2756) - Page 3 of 15

Hyper Text Caching Protocol (HTCP/0

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RFC 2756         Hyper Text Caching Protocol (HTCP/0.0)     January 2000


   2.5. An HTCP Message has the following general format:

   +---------------------+
   |        HEADER       | tells message length and protocol versions
   +---------------------+
   |         DATA        | HTCP message (varies per major version number)
   +---------------------+
   |         AUTH        | optional authentication for transaction
   +---------------------+

   2.6. An HTCP/*.* HEADER has the following format:

                 +0 (MSB)                            +1 (LSB)
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |                             LENGTH                            |
      +   +   +   +   +   +   +   +   +   +   +   +   +   +   +   +   +
   2: |                             LENGTH                            |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   2: |             MAJOR             |             MINOR             |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   LENGTH  is the message length, inclusive of all header and data
           octets, including the LENGTH field itself.  This field will
           be equal to the datagram payload size ("record length") if a
           datagram protocol is in use, and can include padding, i.e.,
           not all octets of the message need be used in the DATA and
           AUTH sections.

   MAJOR   is the major version number (0 for this specification).  The
           DATA section of an HTCP message need not be upward or
           downward compatible between different major version numbers.

   MINOR   is the minor version number (0 for this specification).
           Feature levels and interpretation rules can vary depending on
           this field, in particular RESERVED fields can take on new
           (though optional) meaning in successive minor version numbers
           within the same major version number.

   2.6.1.  It is expected that an HTCP initiator will know the version
   number of a prospective HTCP responder, or that the initiator will
   probe using declining values for MINOR and MAJOR (beginning with the
   highest locally supported value) and locally cache the probed version
   number of the responder.

   2.6.2.  Higher MAJOR numbers are to be preferred, as are higher MINOR
   numbers within a particular MAJOR number.





Vixie & Wessels               Experimental
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