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Network Working Group                                       T. Dreibholz
Internet-Draft                              University of Duisburg-Essen
Intended status: Experimental                                    X. Zhou
Expires: June 16, 2009                                 Hainan University
                                                       December 13, 2008


      Takeover Suggestion Flag for the ENRP Handle Update Message
             draft-dreibholz-rserpool-enrp-takeover-00.txt

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Abstract

   This document describes the Takeover Suggestion Flag for the
   ENRP_HANDLE_UPDATE message of the ENRP protocol.












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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Takeover Suggestion Flag  . . . . . . . . . . . . . . . . . . . 3
     2.1.  Definition  . . . . . . . . . . . . . . . . . . . . . . . . 3
     2.2.  Reference Implementation  . . . . . . . . . . . . . . . . . 4
   3.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     3.1.  Normative References  . . . . . . . . . . . . . . . . . . . 4
     3.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 5
   Intellectual Property and Copyright Statements  . . . . . . . . . . 7






































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1.  Introduction

   Reliable Server Pooling as described in [RFC5351] defines protocols
   for providing highly available services.  The management component
   used for pool administration is denoted as ENRP Server or Pool
   Registrar (PR).  Since a single ENRP server constitutes a single
   point of failure, there must be multiple ENRP servers.  Servers,
   denoted as Pool Elements (PE), use an arbitrary ENRP server for
   registration into the pool.  The chosen ENRP server becomes the Home
   ENRP Server, also denoted as Home PR (PR-H), of the PE.  It is
   responsible for making the PE identity known to the other ENRP
   servers (by using ENRP_HANDLE_UPDATE messages) and also to monitor
   the PE health (by using keep-alive messages).

   As shown in [AINA2009], the following scenario leads to unbalanced
   ENRP server workload: consider a set of multiple ENRP servers with
   one subset being unreliable (for example, their network connection
   has problems) and some reliable ENRP servers.  After a while, the
   reliable ENRP server will get the home ENRP server role for almost
   all of the PEs, which results in high workload for this ENRP server.
   Since the home ENRP server role is more computation-intensive (as
   shown by [IJHIT2008]), this leads to highly unbalanced workload for
   large RSerPool setups.  This unbalanced workload remains, even when
   the unreliable ENRP servers become reliable again (for example, when
   the network problems have been solved).

1.1.  Scope

   The Takeover Suggestion Flag defined in this draft defines a flag for
   the ENRP_HANDLE_UPDATE message.  If the flag is set, the receiving
   ENRP server is suggested to take over the PE specified in the
   ENRP_HANDLE_UPDATE message.

1.2.  Terminology

   The terms are commonly identified in related work and can be found in
   the RSerPool Overview document RFC 5351 [RFC5351].


2.  Takeover Suggestion Flag

2.1.  Definition

   In this subsection, only the differences to the ENRP_HANDLE_UPDATE
   message defined in [RFC5353] are explained.  The following figure
   shows the ENRP_HANDLE_UPDATE message:





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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Type = 0x04 |0|0|0|0|0|0|0|T|        Message Length         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Sending Server's ID                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Receiving Server's ID                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Update Action          |        (reserved)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      :                     Pool Handle Parameter                     :
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      :                    Pool Element Parameter                     :
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   T flag: 1 bit (boolean)

   If set, the receiving ENRP server is suggested to take over the PE
   specified by the Pool Handle and Pool Element Parameters.  It is
   RECOMMENDED for the receiving ENRP server to perform this takeover if
   it has the resources to do so.

2.2.  Reference Implementation

   The reference implementation based on the RSerPool implementation
   RSPLIB can be found at [RSerPoolPage].


3.  References

3.1.  Normative References

   [RFC5351]  Lei, P., Ong, L., Tuexen, M., and T. Dreibholz, "An
              Overview of Reliable Server Pooling Protocols", RFC 5351,
              September 2008.

   [RFC5352]  Stewart, R., Xie, Q., Stillman, M., and M. Tuexen,
              "Aggregate Server Access Protocol (ASAP)", RFC 5352,
              September 2008.

   [RFC5353]  Xie, Q., Stewart, R., Stillman, M., Tuexen, M., and A.
              Silverton, "Endpoint Handlespace Redundancy Protocol
              (ENRP)", RFC 5353, September 2008.

   [RFC5354]  Stewart, R., Xie, Q., Stillman, M., and M. Tuexen,
              "Aggregate Server Access Protocol (ASAP) and Endpoint
              Handlespace Redundancy Protocol (ENRP) Parameters",



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              RFC 5354, September 2008.

   [RFC5355]  Stillman, M., Gopal, R., Guttman, E., Sengodan, S., and M.
              Holdrege, "Threats Introduced by Reliable Server Pooling
              (RSerPool) and Requirements for Security in Response to
              Threats", RFC 5355, September 2008.

   [RFC5356]  Dreibholz, T. and M. Tuexen, "Reliable Server Pooling
              Policies", RFC 5356, September 2008.

3.2.  Informative References

   [AINA2009]
              Dreibholz, T., Zhou, X., Du, W., and E. Rathgeb,
              "Evaluation and Optimization of the Registrar Redundancy
              Handling in Reliable Server Pooling Systems",
              Proceedings of the IEEE 23rd International Conference on
              Advanced Information Networking and Applications (AINA
              2009), May 2009.

   [RSerPoolPage]
              Dreibholz, T., "Thomas Dreibholz's RSerPool Page", URL:
               http://tdrwww.exp-math.uni-essen.de/dreibholz/rserpool/.

   [Dre2006]  Dreibholz, T., "Reliable Server Pooling -- Evaluation,
              Optimization and Extension of a Novel IETF Architecture",
              Ph.D. Thesis University of Duisburg-Essen, Faculty of
              Economics, Institute for Computer Science and Business
              Information Systems, URL: http://
              duepublico.uni-duisburg-essen.de/servlets/DerivateServlet/
              Derivate-16326/Dre2006-final.pdf, March 2007.

   [IJHIT2008]
              Dreibholz, T. and E. Rathgeb, "An Evalulation of the Pool
              Maintenance Overhead in Reliable Server Pooling Systems",
              International Journal of Hybrid Information Technology
              (IJHIT) Volume 1, Number 2, April 2008.














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Authors' Addresses

   Thomas Dreibholz
   University of Duisburg-Essen, Institute for Experimental Mathematics
   Ellernstrasse 29
   45326 Essen, Nordrhein-Westfalen
   Germany

   Phone: +49-201-1837637
   Fax:   +49-201-1837673
   Email: dreibh@iem.uni-due.de
   URI:   http://www.iem.uni-due.de/~dreibh/


   Xing Zhou
   Hainan University, College of Information Science and Technology
   Renmin Avenue 58
   570228 Haikou, Hainan
   China

   Phone: +86-898-66279141
   Email: zhouxing@hainu.edu.cn





























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