Network Working Group T. Dreibholz
Internet-Draft University of Duisburg-Essen
Expires: October 10, 2005 L. Coene
Siemens
P. Conrad
University of Delaware
April 08, 2005
Reliable Server Pooling Applicability for IP Flow Information Exchange
draft-coene-rserpool-applic-ipfix-01.txt
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Abstract
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 [6]
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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 [4])
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
control.
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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 [9] 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] Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L., Loughney,
J., and M. Stillman, "Requirements for Reliable Server
Pooling", RFC 3237, January 2002.
[2] Bradner, S., "Intellectual Property Rights in IETF Technology",
RFC 3668, February 2004.
[3] 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.
[4] Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, "Aggregate
Server Access Protocol (ASAP)", draft-ietf-rserpool-asap-11
(work in progress), February 2005.
[5] Xie, Q., Stewart, R., Stillman, M., and M. Tuexen, "Enpoint
Handlespace Redundancy Protocol (ENRP)",
draft-ietf-rserpool-enrp-11 (work in progress), February 2005.
[6] 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.
[7] 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.
[8] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. Conrad,
"Stream Control Transmission Protocol (SCTP) Partial
Reliability Extension", RFC 3758, May 2004.
[9] Coene, L., "Stream Control Transmission Protocol Applicability
Statement", RFC 3257, April 2002.
[10] Conrad, P. and P. Lei, "Services Provided By Reliable Server
Pooling", draft-ietf-rserpool-service-01 (work in progress),
June 2004.
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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@exp-math.uni-essen.de
URI: http://www.exp-math.uni-essen.de/~dreibh/
Lode Coene
Siemens
Atealaan 32
Herentals 2200
Belgium
Phone: +32-14-252081
Email: lode.coene@siemens.com
Phillip Conrad
University of Delaware
103 Smith Hall
Newark DE 19716
USA
Phone: +1 302 831 8622
Email: conrad@acm.org
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