Network Working Group T. Dreibholz
Internet-Draft University of Duisburg-Essen
Intended status: Experimental X. Zhou
Expires: July 5, 2011 Hainan University
January 01, 2011
Takeover Suggestion Flag for the ENRP Handle Update Message
draft-dreibholz-rserpool-enrp-takeover-05.txt
Abstract
This document describes the Takeover Suggestion Flag for the
ENRP_HANDLE_UPDATE message of the ENRP protocol.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Takeover Suggestion Flag . . . . . . . . . . . . . . . . . . . 3
2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Reference Implementation . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
Reliable Server Pooling as described in [RFC5351] defines protocols
for providing highly available services. The management component
used for pool administration is denoted as ENRP Server or Pool
Registrar (PR). Since a single ENRP server constitutes a single
point of failure, there must be multiple ENRP servers. Servers,
denoted as Pool Elements (PE), use an arbitrary ENRP server for
registration into the pool. The chosen ENRP server becomes the Home
ENRP Server, also denoted as Home PR (PR-H), of the PE. It is
responsible for making the PE identity known to the other ENRP
servers (by using ENRP_HANDLE_UPDATE messages) and also to monitor
the PE health (by using keep-alive messages).
As shown in [AINA2009], the following scenario leads to unbalanced
ENRP server workload: consider a set of multiple ENRP servers with
one subset being unreliable (for example, their network connection
has problems) and some reliable ENRP servers. After a while, the
reliable ENRP server will get the home ENRP server role for almost
all of the PEs, which results in high workload for this ENRP server.
Since the home ENRP server role is more computation-intensive (as
shown by [IJHIT2008]), this leads to highly unbalanced workload for
large RSerPool setups. This unbalanced workload remains, even when
the unreliable ENRP servers become reliable again (for example, when
the network problems have been solved).
1.1. Scope
The Takeover Suggestion Flag defined in this draft defines a flag for
the ENRP_HANDLE_UPDATE message. If the flag is set, the receiving
ENRP server is suggested to take over the PE specified in the
ENRP_HANDLE_UPDATE message.
1.2. Terminology
The terms are commonly identified in related work and can be found in
the RSerPool Overview document RFC 5351 [RFC5351].
1.3. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Takeover Suggestion Flag
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2.1. Definition
In this subsection, only the differences to the ENRP_HANDLE_UPDATE
message defined in [RFC5353] are explained. The following figure
shows the ENRP_HANDLE_UPDATE message:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x04 |0|0|0|0|0|0|0|T| Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sending Server's ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiving Server's ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Update Action | (reserved) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Pool Handle Parameter :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Pool Element Parameter :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
T flag: 1 bit (boolean)
If set, the receiving ENRP server is suggested to take over the PE
specified by the Pool Handle and Pool Element Parameters. It is
RECOMMENDED for the receiving ENRP server to perform this takeover if
it has the resources to do so.
3. 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-delay] and of course the option defined by
this document. An introduction to this implementation is provided in
[Dre2006].
4. Security Considerations
Security considerations for RSerPool systems are described by
[RFC5355].
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5. IANA Considerations
This document does not require additional IANA actions beyond those
already identified in the ENRP and ASAP protocol specifications.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[I-D.dreibholz-rserpool-asap-hropt]
Dreibholz, T., "Handle Resolution Option for ASAP",
draft-dreibholz-rserpool-asap-hropt-07 (work in progress),
July 2010.
[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-06 (work in progress),
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July 2010.
6.2. Informative References
[AINA2009]
Zhou, X., Dreibholz, T., Fa, F., Du, W., and E. Rathgeb,
"Evaluation and Optimization of the Registrar Redundancy
Handling in Reliable Server Pooling Systems",
Proceedings of the IEEE 23rd International Conference on
Advanced Information Networking and Applications (AINA
2009), May 2009.
[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.
[IJHIT2008]
Dreibholz, T. and E. Rathgeb, "An Evalulation of the Pool
Maintenance Overhead in Reliable Server Pooling Systems",
International Journal of Hybrid Information Technology
(IJHIT) Volume 1, Number 2, April 2008.
[RSerPoolPage]
Dreibholz, T., "Thomas Dreibholz's RSerPool Page",
URL: http://tdrwww.iem.uni-due.de.de/dreibholz/rserpool/.
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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Xing Zhou
Hainan University, College of Information Science and Technology
Renmin Avenue 58
570228 Haikou, Hainan
China
Phone: +86-898-66279141
Email: zhouxing@hainu.edu.cn
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