Network Working Group T. Dreibholz
Internet-Draft J. Pulinthanath
Intended status: Informational University of Duisburg-Essen
Expires: January 6, 2010 July 5, 2009
Applicability of Reliable Server Pooling for SCTP-Based Endpoint
Mobility
draft-dreibholz-rserpool-applic-mobility-06.txt
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Abstract
This document describes a novel mobility concept based on a
combination of SCTP with Dynamic Address Reconfiguration extension
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and Reliable Server Pooling (RSerPool).
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. Reference Implementation . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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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 [RFC4960] together with its Dynamic
Address Reconfiguration extension (Add-IP, see [RFC5061]), 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 reachable under an additional network-
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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], [RFC5351], [RFC5352], [RFC5353],
[RFC5354], [RFC5355], [RFC5356], 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. Reference Implementation
The RSerPool reference implementation RSPLIB can be found at
[RSerPoolPage]. It supports the functionalities defined by
[RFC5351], [RFC5352], [RFC5353], [RFC5354] and [RFC5356] as well as
the options [I-D.dreibholz-rserpool-asap-hropt],
[I-D.dreibholz-rserpool-enrp-takeover] and
[I-D.dreibholz-rserpool-delay]. An introduction to this
implementation is provided in [Dre2006].
5. Security Considerations
Security considerations for RSerPool systems are described by
[RFC5355].
6. IANA Considerations
This document introduces no additional considerations for IANA.
7. References
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7.1. Normative References
[RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061,
September 2007.
[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.
[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",
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.
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7.2. Informative References
[RSerPoolPage]
Dreibholz, T., "Thomas Dreibholz's RSerPool Page",
URL: http://tdrwww.iem.uni-due.de.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.
[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.
[I-D.dreibholz-rserpool-asap-hropt]
Dreibholz, T., "Handle Resolution Option for ASAP",
draft-dreibholz-rserpool-asap-hropt-04 (work in progress),
January 2009.
[I-D.dreibholz-rserpool-enrp-takeover]
Dreibholz, T. and X. Zhou, "Takeover Suggestion Flag for
the ENRP Handle Update Message",
draft-dreibholz-rserpool-enrp-takeover-01 (work in
progress), January 2009.
[I-D.dreibholz-rserpool-delay]
Dreibholz, T. and X. Zhou, "Definition of a Delay
Measurement Infrastructure and Delay-Sensitive Least-Used
Policy for Reliable Server Pooling",
draft-dreibholz-rserpool-delay-03 (work in progress),
January 2009.
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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/
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@iem.uni-due.de.de
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