rfc2756.txt

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   TST responses have the following OP-DATA, if RESPONSE is one (1):

                 +0 (MSB)                            +1 (LSB)
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |                                                               |
      /                           CACHE-HDRS                          /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   6.3. MON (OPCODE 2):

   Monitor activity in a proxy cache's local object store (adds, deletes,
   replacements, etc).  Since interleaving of HTCP transactions over a
   single pair of UDP endpoints is not supported, it is recommended that a
   unique UDP endpoint be allocated by the requestor for each concurrent
   MON request.  MON requests with RD=0 are equivalent to those with RD=1
   and TIME=0; that is, they will cancel any outstanding MON transaction.

   MON requests have the following OP-DATA structure:

                  +0 (MSB)
      +---+---+---+---+---+---+---+---+
   0: |             TIME              |
      +---+---+---+---+---+---+---+---+

   TIME  is the number of seconds of monitoring output desired by the
         initiator.  Subsequent MON requests from the same initiator
         with the same TRANS-ID should update the time on a ongoing MON
         transaction.  This is called "overlapping renew."

   RESPONSE codes for MON are as follows:

   0   accepted, OP-DATA is present and valid
   1   refused (quota error -- too many MON's are active)

   MON responses have the following OP-DATA structure, if RESPONSE is
   zero (0):

                 +0 (MSB)                            +1 (LSB)
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |             TIME              |     ACTION    |     REASON    |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   2: |                                                               |
      /                            IDENTITY                           /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+





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   TIME      is the number of seconds remaining for this MON
             transaction.

   ACTION    is a numeric code indicating a cache population action.
             Codes are:

             0   an entity has been added to the cache
             1   an entity in the cache has been refreshed
             2   an entity in the cache has been replaced
             3   an entity in the cache has been deleted

   REASON    is a numeric code indicating the reason for an ACTION.
             Codes are:

             0   some reason not covered by the other REASON codes
             1   a proxy client fetched this entity
             2   a proxy client fetched with caching disallowed
             3   the proxy server prefetched this entity
             4   the entity expired, per its headers
             5   the entity was purged due to caching storage limits

   6.4. SET (OPCODE 3):

   Inform a cache of the identity of an object.  This is a "push"
   transaction, whereby cooperating caches can share information such as
   updated Age/Date/Expires headers (which might result from an origin
   "304 Not modified" HTTP response) or updated cache headers (which
   might result from the discovery of non-authoritative "vary"
   conditions or from learning of second or third party cache locations
   for this entity.  RD is honoured.

   SET requests have the following OP-DATA structure:

      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |                                                               |
      /                            IDENTITY                           /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   RESPONSE  codes are as follows:

             0   identity accepted, thank you
             1   identity ignored, no reason given, thank you

   SET responses have no OP-DATA.






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


   6.5. CLR (OPCODE 4):

   Tell a cache to completely forget about an entity.  RD is honoured.

   CLR requests have the following OP-DATA structure:

      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |                   RESERVED                    |     REASON    |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   2: |                                                               |
      /                           SPECIFIER                           /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   REASON    is a numeric code indicating the reason why the requestor
             is asking that this entity be removed.  The codes are as
             follows:

             0   some reason not better specified by another code
             1   the origin server told me that this entity does not
                 exist

   RESPONSE  codes are as follows:

             0   i had it, it's gone now
             1   i had it, i'm keeping it, no reason given.
             2   i didn't have it

   CLR responses have no OP-DATA.

   Clearing a URI without specifying response, entity, or cache headers
   means to clear all entities using that URI.

7.  Security Considerations

   If the optional AUTH element is not used, it is possible for
   unauthorized third parties to both view and modify a cache using the
   HTCP protocol.

8.  Acknowledgements

   Mattias Wingstedt of Idonex brought key insights to the development
   of this protocol.  David Hankins helped clarify this document.








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9.  References

   [RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
             Resource Identifiers (URI): Generic Syntax", RFC 2396,
             August 1998.

   [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter,
             L., Leach, P. and T. Berners-Lee, "Hypertext Transfer
             Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-
             Hashing for Message Authentication", RFC 2104, February,
             1997.

   [RFC2186] Wessels, D. and K. Claffy, "Internet Cache Protocol (ICP),
             version 2", RFC 2186, September 1997.

10.  Authors' Addresses

   Paul Vixie
   Internet Software Consortium
   950 Charter Street
   Redwood City, CA 94063

   Phone: [phone]
   EMail: [e-mail]


   Duane Wessels
   National Lab for Applied Network Research
   USCD, 9500 Gilman Drive
   La Jolla, CA 92093

   Phone: [phone]
   EMail: [e-mail]
















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


11.  Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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