Network Working Group T. Dreibholz
Internet-Draft J. Pulinthanath
Expires: September 25, 2006 University of Duisburg-Essen
Mar 24, 2006
Applicability of Reliable Server Pooling for SCTP-Based Endpoint
Mobility
draft-dreibholz-rserpool-applic-mobility-00.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on September 25, 2006.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document describes a novel mobility concept based on a
combination of SCTP with Dynamic Address Reconfiguration extension
and Reliable Server Pooling (RSerPool).
Dreibholz & Pulinthanath Expires September 25, 2006 [Page 1]
Internet-Draft SCTP Mobility with RSerPool Mar 2006
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).
Dreibholz & Pulinthanath Expires September 25, 2006 [Page 2]
Internet-Draft SCTP Mobility with RSerPool Mar 2006
2. Existing Mobility Solutions
2.1. Mobile IP and Mobile IPv6
In the concept of Mobile IP [10] 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 tunneled 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 [11] is an extension of Mobile IP. In Mobile IPv6, the
FA is not needed. The packets will be tunneled 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 [6], [9]) together with its Dynamic
Address Reconfiguration extension (Add-IP, see [12]), 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-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.
Dreibholz & Pulinthanath Expires September 25, 2006 [Page 3]
Internet-Draft SCTP Mobility with RSerPool Mar 2006
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 [7], [13], [14], [15], [17], [16]), 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:
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 tunneling of traffic is necessary.
o Deployability: 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 [1].
Dreibholz & Pulinthanath Expires September 25, 2006 [Page 4]
Internet-Draft SCTP Mobility with RSerPool Mar 2006
4. Normative References
[1] 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.
[2] Dreibholz, T., "An efficient approach for state sharing in
server pools", Proceedings of the 27th IEEE Local Computer
Networks Conference, October 2002.
[3] Dreibholz, T. and E. Rathgeb, "An Application Demonstration of
the Reliable Server Pooling Framework", Proceedings of the 24th
IEEE Infocom, March 2005.
[4] Dreibholz, T. and E. Rathgeb, "Implementing the Reliable Server
Pooling Framework", Proceedings of the 8th IEEE International
Conference on Telecommunications, June 2005.
[5] 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.
[6] 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.
[7] Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L., Loughney,
J., and M. Stillman, "Requirements for Reliable Server
Pooling", RFC 3237, January 2002.
[8] Coene, L., "Stream Control Transmission Protocol Applicability
Statement", RFC 3257, April 2002.
[9] Stone, J., Stewart, R., and D. Otis, "Stream Control
Transmission Protocol (SCTP) Checksum Change", RFC 3309,
September 2002.
[10] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[11] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[12] Stewart, R., "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration",
draft-ietf-tsvwg-addip-sctp-14 (work in progress), March 2006.
Dreibholz & Pulinthanath Expires September 25, 2006 [Page 5]
Internet-Draft SCTP Mobility with RSerPool Mar 2006
[13] Tuexen, M., "Architecture for Reliable Server Pooling",
draft-ietf-rserpool-arch-10 (work in progress), July 2005.
[14] Stewart, R., "Aggregate Server Access Protocol (ASAP)",
draft-ietf-rserpool-asap-13 (work in progress), February 2006.
[15] Stewart, R., "Endpoint Handlespace Redundancy Protocol (ENRP)",
draft-ietf-rserpool-enrp-13 (work in progress), February 2006.
[16] Stewart, R., "Aggregate Server Access Protocol (ASAP) and
Endpoint Handlespace Redundancy Protocol (ENRP) Parameters",
draft-ietf-rserpool-common-param-10 (work in progress),
February 2006.
[17] Tuexen, M. and T. Dreibholz, "Reliable Server Pooling
Policies", draft-ietf-rserpool-policies-02 (work in progress),
February 2006.
[18] Conrad, P. and P. Lei, "Services Provided By Reliable Server
Pooling", draft-ietf-rserpool-service-02 (work in progress),
October 2005.
[19] Dreibholz, T., "Thomas Dreibholz's RSerPool Page",
URL: http://tdrwww.exp-math.uni-essen.de/dreibholz/rserpool/.
Dreibholz & Pulinthanath Expires September 25, 2006 [Page 6]
Internet-Draft SCTP Mobility with RSerPool Mar 2006
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@exp-math.uni-essen.de
URI: http://www.exp-math.uni-essen.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@exp-math.uni-essen.de
Dreibholz & Pulinthanath Expires September 25, 2006 [Page 7]
Internet-Draft SCTP Mobility with RSerPool Mar 2006
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Dreibholz & Pulinthanath Expires September 25, 2006 [Page 8]