Network Working Group Y. Kikuchi
Internet-Draft Kochi University of Technology
Intended status: Informational S. Matsushima
Expires: January 9, 2009 Softbank Telecom Corp.
K. Nagami
Intec Netcore Inc.
S. Uda
Japan Advanced Institute of
Science and Technology
Jul 08, 2008
Requirements of One-way Passive Measurement for End-to-End Quality
draft-kikuchi-passive-measure-reqs-00.txt
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Abstract
This draft describes the necessary requirements to passively measure
end-to-end quality and to monitor them via applicable ways. This
feature is crucial for Service Providers (SPs), especially who
provide transports with Service Level Agreements (SLAs).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3
2. Service Model . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Active vs. Passive . . . . . . . . . . . . . . . . . . . . 6
4.2. Quality Evaluation . . . . . . . . . . . . . . . . . . . . 6
4.3. Getting Quality Information . . . . . . . . . . . . . . . 6
4.4. Overhead Consideration . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 12
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1. Introduction
This draft describes the necessary requirements to passively measure
end-to-end quality and to monitor them via applicable ways.
Measuring end-to-end quality in passive ways is necessary for Service
Providers (SPs) who provide transport to users. However, the
standards do not define the measurement and monitoring of a network,
which is helpful when the SPs want to know the quality of their end-
to-end traffic. Therefore, measurement and monitoring standards need
to be defined.
1.1. Requirements notation
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].
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2. Service Model
Figure 1 shows that SP X and SP Y provide a transport between user A
and user B using some ISPs. Let SP X and SP Y "Transport Service
Providers" (TSPs) here because they should be distinguished from the
intermediate ISPs. The users construct an application over the
transport. The TSPs may apply two or more routes to provide one
transport.
USER A ................. Application ................ USER B
| |
(SLA) (SLA)
| |
TSP X >>................ Transport ................>> TSP Y
| |
*-> ISP 1_1 -> ISP 1_2 -> ... -> ISP 1_n1 ->*
| |
*-> ISP 2_1 -> ISP 2_2 -> ... -> ISP 2_n2 ->*
: :
*-> ISP m_1 -> ISP m_2 -> ... -> ISP m_nm ->*
Figure 1: Service Model
The TSPs maintain reachability and some required quality of the
transport of IP datagrams to users. There must be Service Level
Agreements (SLAs) in the contract between the TSPs and thier users.
The SLAs specify the level that the TSPs must maintain, which are
sets of measurable characteristics such as total unavailable time in
a month, loss of packets and some qualities for real time
applications.
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3. Motivations
TSPs need to know the quality of their traffic in order to know
whether the traffic in a normal state or not. The measured quality
could be important information to trace down the cause of the trouble
when an application is not working properly. Without the necessary
information, it is difficult for TSPs to determine whether problems
come from the user, the TSPs, or the intermediate ISPs.
The quality measurement is specially required by TSPs when they have
SLAs to their customers. They must be aware of the status of
underlying traffic well and must report it as an evidence of quality
to the users.
TSPs also need to know the quality of a transport when they have
multiple paths to serve the transport. TSPs may be able to serve an
appropriate transport to users by selecting a better quality path.
In addition, the TSPs may be able to distribute the load of a
transport to different paths.
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4. Requirements
This section describes each requirement necessary to measure one-way
end-to-end quality for TSPs.
The quality should be measured for transports in operation because
the measured quality is used to maintain the transports to report
regarding to the SLA and to select the best path. The measurement
would be used not only for testing and benchmarking but also for the
daily operational tool. Therefore, the requirements are from
operational points of view.
4.1. Active vs. Passive
There are two ways to measure the quality of transports, one is
active and the other is passive. Active measurement uses additional
probing packets to determine the quality of the tranports. Passive
measurement uses the traffic packets to measure quality.
From the TSPs point of view, passive measurement should be supported.
Because SLAs should refer to the users' transports, the measurement
should be determined passively rather than actively.
4.2. Quality Evaluation
The standard that define a passive measurement of transports must
contain two elements, one is `WHAT' type of quality the protocol
measure, or `metrics', and the other is `HOW' the protocol evaluate
the quality.
The most basic metric is to detect whether the packets in a transport
are in-sequence or out-of-sequence. Measurement of types of out-of-
sequence packets are also basic metrics, such as lost, duplication
and reordering in a transport.
It is required to disable the measurement function for avoiding the
measurement overhead in case when TSPs need not to measure the
quality. See also the discussion in the Section 4.4.
4.3. Getting Quality Information
The measurement mechanisms must define how to monitor the result of
the quality of transports, such as SNMP [RFC3411]. The parameters
used in the measurement mechanisms might be modified by TSPs'
operators. Moreover, they may notify exceptional situations and
illegal operations to the operators.
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4.4. Overhead Consideration
Protocol designers should take into account the computing and space
costs of the implementations where the standard defines the
measurement and monitoring. This includes overhead of traffic
transmission, which may reflect the cost of equipment introductions
and operational expenses. The designers should not adopt non-
scalable mechanisms and should pay particular attention to resource
consumption sensitive protocols such as mobile protocols.
We should adopt a simplified determination in some cases when both a
precise complex determination and a simpler one exist. Sometimes it
is sufficient for operators to show an approximate degree different
from the normal operation rather than a precise state.
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5. Security Considerations
Not yet.
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Appendix A. Acknowledgements
The authors would like to thank for helpful discussions in TEReCo 2.0
research project sponsored in part by the ministry of internal
affairs and communications Japan (SCOPE 072309007).
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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.
6.2. Informative References
[RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
December 2002.
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Authors' Addresses
Yutaka Kikuchi
Kochi University of Technology
306B Research Collaboration Center
185 Miyanokuchi, Tosayamada-cho
Kami-shi, Kochi 782-0003
JP
Phone: +81-887-57-2068
Email: yu@kikuken.org
Satoru Matsushima
Softbank Telecom Corp.
1-9-1 Higashi-Shinbashi
Minato-ku, Tokyo
JP
Email: satoru@ft.solteria.net
Ken-ichi Nagami
Intec Netcore Inc.
1-3-3 Shin-suna
Koto-ku, Tokyo
JP
Phone: +81-3-5565-5069
Email: nagami@inetcore.com
Satoshi Uda
Japan Advanced Institute of Science and Technology
1-1 Asahi-dai
Nomi-shi, Ishikawa-ken 923-1292
JP
Email: zin@jaist.ac.jp
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