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


    Applicability of Reliable Server Pooling for SCTP-Based Endpoint
                                Mobility
            draft-dreibholz-rserpool-applic-mobility-04.txt

Status of this Memo

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Abstract

   This document describes a novel mobility concept based on a
   combination of SCTP with Dynamic Address Reconfiguration extension
   and Reliable Server Pooling (RSerPool).











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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Existing Mobility Solutions . . . . . . . . . . . . . . . . . . 3
     2.1.  Mobile IP and Mobile IPv6 . . . . . . . . . . . . . . . . . 3
     2.2.  SCTP with Dynamic Address Reconfiguration . . . . . . . . . 3
   3.  Solutions for Simultaneous Handovers  . . . . . . . . . . . . . 4
     3.1.  SCTP with Add-IP and Mobile-IP  . . . . . . . . . . . . . . 4
     3.2.  SCTP with Add-IP and RSerPool . . . . . . . . . . . . . . . 4
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     4.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     4.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9





































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1.  Introduction

   An increasing amount of Internet devices is getting mobile.
   Therefore, there is a growing demand for software solutions allowing
   for a seamless handover of communication sessions between multiple
   networks, e.g. to allow for a laptop or PDA to use a fast Ethernet
   connection when available, hand over to a WLAN when moving and hand
   over again to UMTS when the WLAN becomes unreachable - without
   interrupting the running communication sessions.

   Mobility handling is a deficiency of the common IP-based networks.
   Most of the available solutions are based on the network layer.  The
   disadvantage of such solutions is that fundamental changes in the
   network infrastructure are needed.  Therefore, we propose a new
   solution based on the upper layers to overcome these disadvantages.
   In this document, we present our mobility solution based on the SCTP
   protocol with Dynamic Address Reconfiguration extension and Reliable
   Server Pooling (RSerPool).


2.  Existing Mobility Solutions

2.1.  Mobile IP and Mobile IPv6

   In the concept of Mobile IP [RFC3344] every node must register to a
   Home-Agent (HA) in its own home network.  Then, the nodes are
   reachable under their home addresses managed by the HA.  When a node
   leaves its home network, it must also register at a Foreign Agent
   (FA) in the new network.  After that, a tunnel is established between
   the HA and the FA.  Any traffic to the mobile node is then tunnelled
   by its HA to the FA and forwarded by the FA to the node itself.
   Clearly, the detour of all traffic via HA and FA is inefficient and
   results in an increased transmission delay.

   Mobile IPv6 [RFC3775] is an extension of Mobile IP.  In Mobile IPv6,
   the FA is not needed.  The packets will be tunnelled from the HA to
   the Gateway Router in the foreign network, which forwards the packets
   to the endpoint.  The inefficiency due to the detour of traffic as
   described for Mobile IP remains.

2.2.  SCTP with Dynamic Address Reconfiguration

   Using the SCTP protocol (see [RFC2960], [RFC3309]) together with its
   Dynamic Address Reconfiguration extension (Add-IP, see
   [I-D.ietf-tsvwg-addip-sctp]), it is possible for a mobile endpoint to
   inform its peer on address changes.  That is, when a moving mobile
   client gets in the vicinity of an additional radio station, it sends
   an "ASCONF Add Address Request" to tell its peer that it is now



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   reachable under an additional network-layer address.  After that, the
   peer endpoint can use this additional address for a new SCTP path.
   When the first radio station becomes unreachable, the node can send
   an "ASCONF Delete Address Request" to the peer endpoint.  After that,
   the peer removes the corresponding SCTP path to the unusable network-
   layer address.

   The following two cases for handovers are possible:

   o  Make-before-Break: An additional SCTP path can be used before the
      original path becomes unusable.  This case is trivial, since there
      is a continuous connectivity.

   o  Break-before-Make: The original SCTP path becomes unusable before
      a new SCTP path can be used.  For the case that only one endpoint
      performs a handover procedure at the same time, the mobile
      endpoint can always use Add-IP to communicate its new address to
      its peer endpoint.  However, when both endpoints perform a
      handover simultaneously, no endpoint is able to tell its
      corresponding peer the new address.


3.  Solutions for Simultaneous Handovers

3.1.  SCTP with Add-IP and Mobile-IP

   Using SCTP with Add-IP and Mobile IP/Mobile IPv6, the ASCONF messages
   will be sent to the home address of the peer node.  That is, even
   when both nodes are mobile, each endpoint is able to reach its peer
   endpoint using the corresponding home address.  However, this
   solution still requires the full Mobile IP/Mobile IPv6
   infrastructure.

3.2.  SCTP with Add-IP and RSerPool

   Using RSerPool (see [RFC3237], [I-D.ietf-rserpool-arch],
   [I-D.ietf-rserpool-asap], [I-D.ietf-rserpool-enrp],
   [I-D.ietf-rserpool-policies], [I-D.ietf-rserpool-common-param]), at
   least one node registers as a Pool Element (PE) at an ENRP server
   under a Pool Handle (PH) known to both endpoints.  Upon handover, it
   is simply necessary for the PE endpoint to re-register, i.e. to
   update its registration with its new address.  The other endpoint can
   - in the role of a Pool User (PU) - ask an ENRP server for its peer
   node's new addresses.  After the new address is known, it is able to
   create a new SCTP path and continue the communication.

   The usage of RSerPool to provide support for mobile endpoints
   provides the following advantages:



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   o  Simplicity: No Mobile IP/Mobile IPv6 infrastructure is needed.  In
      particular, it is not necessary that the providers of used
      networks (e.g. public WLAN access points, UMTS providers, etc.)
      provide any support for the mobility solution.

   o  Efficiency: No tunnelling of traffic is necessary.

   o  Applicability: All major SCTP implementations already support the
      Dynamic Address Reconfiguration extension.  It is only necessary
      to provide support for RSerPool, e.g. in the form of a userspace
      library, which is much easier to deploy than kernel extensions.

   o  Flexibility: RSerPool provides a complete session layer.  That is,
      providing applications on top of RSerPool makes the support for
      high availability simple.

   A more detailed description of our approach for endpoint mobility, as
   well as a performance analysis using a prototype implementation, can
   be found in our paper [LCN2003].


4.  References

4.1.  Normative References

   [RFC2719]  Ong, L., Rytina, I., Garcia, M., Schwarzbauer, H., Coene,
              L., Lin, H., Juhasz, I., Holdrege, M., and C. Sharp,
              "Framework Architecture for Signaling Transport",
              RFC 2719, October 1999.

   [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.

   [RFC3237]  Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L.,
              Loughney, J., and M. Stillman, "Requirements for Reliable
              Server Pooling", RFC 3237, January 2002.

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

   [RFC3309]  Stone, J., Stewart, R., and D. Otis, "Stream Control
              Transmission Protocol (SCTP) Checksum Change", RFC 3309,
              September 2002.

   [RFC3344]  Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
              August 2002.



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   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

   [I-D.ietf-tsvwg-addip-sctp]
              Stewart, R., "Stream Control Transmission Protocol (SCTP)
              Dynamic Address  Reconfiguration",
              draft-ietf-tsvwg-addip-sctp-22 (work in progress),
              June 2007.

   [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.

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://



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              duepublico.uni-duisburg-essen.de/servlets/DerivateServlet/
              Derivate-16326/Dre2006-final.pdf, March 2007.

   [LCN2003]  Dreibholz, T., Jungmaier, A., and M. Tuexen, "A new Scheme
              for IP-based Internet Mobility", Proceedings of the 28th
              IEEE Local Computer Networks Conference, November 2003.

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

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

   [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.


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/








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

   Phone: +49-201-1837637
   Fax:   +49-201-1837673
   Email: jp@exp-math.uni-essen.de










































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