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Network Working Group                                       T. Dreibholz
Internet-Draft                              University of Duisburg-Essen
Intended status: Standards Track                           July 11, 2008
Expires: January 12, 2009


   Applicability of Reliable Server Pooling for Real-Time Distributed
                               Computing
            draft-dreibholz-rserpool-applic-distcomp-05.txt

Status of this Memo

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Abstract

   This document describes the applicability of the Reliable Server
   Pooling architecture to manage real-time distributed computing pools
   and access the resources of such pools.











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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Distributed Computing using RSerPool  . . . . . . . . . . . . . 3
     2.1.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . 3
       2.1.1.  Architecture  . . . . . . . . . . . . . . . . . . . . . 4
       2.1.2.  Limitations . . . . . . . . . . . . . . . . . . . . . . 5
       2.1.3.  Implementation  . . . . . . . . . . . . . . . . . . . . 5
   3.  Security considerations . . . . . . . . . . . . . . . . . . . . 5
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     4.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     4.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9



































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1.  Introduction

   Reliable Server Pooling defines protocols for providing highly
   available services.  The services are located in a pool of redundant
   servers and if a server fails, another server will take over.  The
   only requirement put on these servers belonging to the pool is that
   if state is maintained by the server, this state must be transferred
   to the other server taking over.

   The goal is to provide server-based redundancy.  Transport and
   network level redundancy are handled by the transport and network
   layer protocols.

   The application may choose to distribute its traffic over the servers
   of the pool conforming to a certain policy.

1.1.  Scope

   The scope of this document is to explain the way of using Reliable
   Server Pooling mechanisms to manage and access pools of Distributed
   Computing resources.

1.2.  Terminology

   The terms are commonly identified in related work and can be found in
   the Aggregate Server Access Protocol and Endpoint Handlespace
   Redundancy Protocol Common Parameters document ietf-rserpool-common-
   param [I-D.ietf-rserpool-common-param]


2.  Distributed Computing using RSerPool

2.1.  Requirements

   The application scenario for Distributed Computing is defined as
   follows:

   o  Clients generate large computation jobs.  Jobs have to be
      processed by servers as soon as possible (real-time), i.e. unlike
      concepts like SETI@home [SETIatHome], it is not possible to let
      clients fetch a job, process it later and may be some day upload
      the result.

   o  Jobs may be partitionable, i.e. they can be split up to smaller
      pieces which can be processed independently and the processing
      results can be concatenated to the processing result of the
      complete job.  Jobs have to be processed by servers.




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   o  Servers may be unreliable; i.e. user computers may be temporarily
      added to the pool of computing resources and may be revoked when
      they are used again by their owners.  Furthermore, they may simply
      disappear because of broken network connections (modems, etc.) or
      power turned off.

   o  The processing power of servers in a pool of computing resources
      may be very heterogeneous, i.e. a few supercomputers and many low-
      end user PCs.

   o  It must be possible to manage large server pools, e.g. up to some
      hundreds or even thousands of servers.

   o  Due to heterogeneous processing resources within a pool, it must
      be possible to use appropriate server selection procedures to
      meaningfully utilize the available resources.

   o  It must be possible to dynamically add and remove servers.

   o  Servers may be unreliable, especially when the servers are
      represented by user PCs.  Failover mechanisms are required to
      continue an interrupted computation session.

2.1.1.  Architecture

   o  An efficient implementation of the handlespace management
      structures allows pools to contain thousands of elements.
      Handlespace management structures have been proposed, implemented
      and analyzed in [Contel2005], [Dre2006].

   o  RSerPool allows to specify server selection rules by pool member
      selection policies [I-D.ietf-rserpool-policies].  A set of
      adaptive and non-adaptive policies is already defined.  To fulfill
      the requirements of new applications, it is also possible to
      define new policies.  Research has already been made on the
      subject of load distribution efficiency of pool policies in
      Distributed Computing scenarios: see [LCN2005], [Dre2006],
      [Tencon2005], [Euromicro2007], [ICN2005] for details.

   o  Dynamic addition and removal of PEs is a feature of RSerPool
      [I-D.ietf-rserpool-asap].

   o  The control/data channel concept [I-D.ietf-rserpool-service] of
      RSerPool realizes a session layer.  That is, RSerPool already
      handles the main task of maintaining and monitoring connections
      between PUs and PEs; the only task of the application layer to
      provide full failover functionality is to realize an application-
      dependent failover procedure.  By the usage of client-based state



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      synchronization [LCN2002], [Euromicro2005] in the form of ASAP
      Cookies, a failover may be fully transparent to the PU while only
      a state restoration is necessary on the PE side.  A demo
      application [RSerPoolPage] using the RSerPool session layer in a
      Distributed Computing application is described in [Infocom2005].

2.1.2.  Limitations

   Applying RSerPool for distributed computing applications, the duties
   of the RSerPool architecture are still limited to the management of
   pools and independent sessions only.  It is in particular a non-goal
   to provide functionalities like data synchronization among sessions,
   user authentication, accounting or the support for more than one
   administrative domain.  Such functionalities are considered to be
   application-specific and are therefore out of the scope of RSerPool.

2.1.3.  Implementation

   A proof of concept implementation of a Distributed Computing
   application based on the RSerPool prototype rsplib can be found at
   [RSerPoolPage].  This system provides a fractal graphics computation
   service; the failover procedure is handled by ASAP cookies.


3.  Security considerations

   The protocols used in the Reliable Server Pooling architecture only
   try to increase the availability of the servers in the network.
   RSerPool protocols do not contain any protocol mechanisms which are
   directly related to user message authentication, integrity and
   confidentiality functions.  For such features, it depends on the
   IPSEC protocols or on Transport Layer Security (TLS) protocols for
   its own security and on the architecture and/or security features of
   its user protocols.

   The RSerPool architecture allows the use of different transport
   protocols for its application and control data exchange.  These
   transport protocols may have mechanisms for reducing the risk of
   blind denial-of-service attacks and/or masquerade attacks.  If such
   measures are required by the applications, then it is advised to
   check the SCTP applicability statement RFC3257 [RFC3257] for guidance
   on this issue.


4.  References






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4.1.  Normative References

   [RFC2960]  Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
              Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
              Zhang, L., and V. Paxson, "Stream Control Transmission
              Protocol", RFC 2960, October 2000.

   [RFC3257]  Coene, L., "Stream Control Transmission Protocol
              Applicability Statement", RFC 3257, April 2002.

   [I-D.ietf-rserpool-arch]
              Tuexen, M., "Architecture for Reliable Server Pooling",
              draft-ietf-rserpool-arch-12 (work in progress),
              November 2006.

   [I-D.ietf-rserpool-asap]
              Stewart, R., Xie, Q., Stillman, M., and M. Tuexen,
              "Aggregate Server Access Protocol (ASAP)",
              draft-ietf-rserpool-asap-20 (work in progress), May 2008.

   [I-D.ietf-rserpool-enrp]
              Xie, Q., Stewart, R., Stillman, M., Tuexen, M., and A.
              Silverton, "Endpoint Handlespace Redundancy Protocol
              (ENRP)", draft-ietf-rserpool-enrp-20 (work in progress),
              May 2008.

   [I-D.ietf-rserpool-common-param]
              Stewart, R., Xie, Q., Stillman, M., and M. Tuexen,
              "Aggregate Server Access Protocol (ASAP) and Endpoint
              Handlespace Redundancy  Protocol (ENRP) Parameters",
              draft-ietf-rserpool-common-param-17 (work in progress),
              May 2008.

   [I-D.ietf-rserpool-policies]
              Tuexen, M. and T. Dreibholz, "Reliable Server Pooling
              Policies", draft-ietf-rserpool-policies-09 (work in
              progress), May 2008.

   [I-D.ietf-rserpool-service]
              Conrad, P. and P. Lei, "Services Provided By Reliable
              Server Pooling", draft-ietf-rserpool-service-02 (work in
              progress), October 2005.

   [RFC3668]  Bradner, S., "Intellectual Property Rights in IETF
              Technology", RFC 3668, February 2004.






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4.2.  Informative References

   [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.

   [LCN2005]  Dreibholz, T. and E. Rathgeb, "On the Performance of
              Reliable Server Pooling Systems", Proceedings of the 30th
              IEEE Local Computer Networks Conference, November 2005.

   [Tencon2005]
              Dreibholz, T. and E. Rathgeb, "The Performance of Reliable
              Server Pooling Systems in Different Server Capacity
              Scenarios", Proceedings of the IEEE TENCON, November 2005.

   [LCN2002]  Dreibholz, T., "An efficient approach for state sharing in
              server pools", Proceedings of the 27th IEEE Local Computer
              Networks Conference, October 2002.

   [Euromicro2005]
              Dreibholz, T. and E. Rathgeb, "RSerPool -- Providing
              Highly Available Services using Unreliable Servers",
              Proceedings Proceedings of the 31st IEEE EuroMirco
              Conference on Software Engineering and Advanced
              Applications, August 2005.

   [Euromicro2007]
              Dreibholz, T., Zhou, X., and E. Rathgeb, "A Performance
              Evaluation of RSerPool Server Selection Policies in
              Varying Heterogeneous Capacity Scenarios", Proceedings of
              the 33rd IEEE EuroMirco Conference on Software Engineering
              and Advanced Applications, August 2007.

   [ICN2005]  Dreibholz, T., Rathgeb, E., and M. Tuexen, "Load
              Distribution Performance of the Reliable Server Pooling
              Framework", Proceedings of the 4th IEEE International
              Conference on Networking, April 2005.

   [Infocom2005]
              Dreibholz, T. and E. Rathgeb, "An Application



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              Demonstration of the Reliable Server Pooling Framework",
              Proceedings of the 24th IEEE Infocom, March 2005.

   [Contel2005]
              Dreibholz, T. and E. Rathgeb, "Implementing the Reliable
              Server Pooling Framework", Proceedings of the 8th IEEE
              International Conference on Telecommunications, June 2005.

   [SETIatHome]
              "SETI@home: Search for Extraterrestrial Intelligence at
              home", URL: http://setiathome.ssl.berkeley.edu.


Author's Address

   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/


























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