Network Working Group                                       T. Dreibholz
Internet-Draft                              University of Duisburg-Essen
Expires: August 6, 2006                                         L. Coene
                                                               P. Conrad
                                                  University of Delaware
                                                       February 02, 2006

 Reliable Server Pooling Applicability for IP Flow Information Exchange

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   Copyright (C) The Internet Society (2006).


   This document describes the applicability of the Relialeble Server
   Pooling architecture to the IP Flow Information Exchange using the
   Aggregate Server Access Protocol (ASAP) functionality of RSerPool
   only.  Data exchange in IPFIX between the router and the data
   collector can be provided by a limited retransmission protocol.

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1.  Introduction

   Reliable Server Pooling provides 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 transfered
   to the other server taking over.

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

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

   The application wishing to make use of RSerPool protocols may use
   different transport layers (such as UDP, TCP and SCTP).  However,
   some transport layers may have restrictions build in in the way they
   might be operating in the RSerPool architecture and its protocols.

1.1  Scope

   The scope of this document is to explain the way that a minimal
   version of Reliable Server Pooling protocols have to be used in order
   to provide a higly available service towards IP Flow Information
   Exchange (IPFIX) protocols.

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 [7]

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2.  IPFIX using RSerPool

2.1  Architecture

   IP flow information is exchanged between observation points and
   collector points.  The observation points may try to find out via the
   Aggregate Server Access Protocol (ASAP, see ietf-rserpool-asap [5])
   which collector point(s) are active.  Both the observation and the
   collector point may have limitations for exchanging the information
   (observation point may have limited buffer space and collectors
   points may be overburdened with receiving lots of flow information
   from different observation points).

   The observation point will query the ENRP server for resolution of a
   particular collector pool name and the ENRP server will return a list
   of one or more collector points to the observation point.

   The observation point will use its own transport protocols (TCP, UDP,
   SCTP, SCTP with PR-SCTP extension) for exchanging the IPFIX data
   between the observation point and the collector point.  If a
   collector point would fail, then the observation point will send its
   data towards a different collector point, belonging to the same
   collector pool.

   Collector points will announce themselves to the ENRP server and will
   be monitored for their avialebility.  The observation point will only
   query the ENRP server for server pool name resolution.

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3.  Transport protocols suitable for IPFIX

   The exchange of IP flow information data between an observation point
   and a collection point consists of massive ammounts of data.

   One collection point can service many observation points, therefore
   transport protocols must do congestion control (example: modifying
   the receive buffer space, thus reducing the incoming flow of data),
   so that the collection point is not overburdened by its observation
   points.  Some data must arrive at the collector while other data
   migth arrive (if it gets lost: no problem).  The choice of reliable
   or partial reliable delivery has to be made by the observation point
   These requirements demand a protocol which provides variable
   transport reliability of its data: it should be able to chose the
   reliability by the IPFIX protocols on a a per-message base.

   SCTP with PR-SCTP extension is the only know protocol which allows
   the choice of full, partial or unrelialeble delivery of the message
   to its peer node.  TCP will only allow fully relialable delivery,
   while UDP only provides unrelialeble delivery and NO congestion

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4.  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 RFC2057 [10] for guidance on
   this issue.

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5.  Acknowledgments

   The authors wish to thank M. Stillman and many others for their
   invaluable comments.

6.  Normative References

   [1]   Dreibholz, T., "Thomas Dreibholz's RSerPool Page",

   [2]   Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L., Loughney,
         J., and M. Stillman, "Requirements for Reliable Server
         Pooling", RFC 3237, January 2002.

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

   [4]   Tuexen, M., Xie, Q., Stewart, R., Shore, M., Loughney, J., and
         A. Silverton, "Architecture for Reliable Server Pooling",
         draft-ietf-rserpool-arch-09 (work in progress), February 2005.

   [5]   Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, "Aggregate
         Server Access Protocol (ASAP)", draft-ietf-rserpool-asap-11
         (work in progress), February 2005.

   [6]   Xie, Q., Stewart, R., Stillman, M., and M. Tuexen, "Enpoint
         Handlespace Redundancy Protocol (ENRP)",
         draft-ietf-rserpool-enrp-11 (work in progress), February 2005.

   [7]   Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, "Aggregate
         Server Access Protocol (ASAP) and Endpoint Name Resolution
         (ENRP) Parameters", draft-ietf-rserpool-common-param-08 (work
         in progress), February 2005.

   [8]   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.

   [9]   Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. Conrad,
         "Stream Control Transmission Protocol (SCTP) Partial
         Reliability Extension", RFC 3758, May 2004.

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

   [11]  Conrad, P. and P. Lei, "Services Provided By Reliable Server
         Pooling", draft-ietf-rserpool-service-01 (work in progress),

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         June 2004.

Authors' Addresses

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

   Phone: +49-201-1837637
   Fax:   +49-201-1837673

   Lode Coene
   Atealaan 32
   Herentals  2200

   Phone: +32-14-252081

   Phillip Conrad
   University of Delaware
   103 Smith Hall
   Newark  DE 19716

   Phone: +1 302 831 8622

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