rfc1857.txt
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Network Working Group M. Lambert
Request For Comments: 1857 Pittsburgh Supercomputing Center
Obsoletes: 1404 October 1995
Category: Informational
A Model for Common Operational Statistics
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
This memo describes a model for operational statistics in the
Internet. It gives recommendations for metrics, measurements,
polling periods and presentation formats and defines a format for the
exchange of operational statistics.
Acknowledgements
The author would like to thank the members of the Operational
Statistics Working Group of the IETF whose efforts made this memo
possible, particularly Bernhard Stockman, author of RFC 1404, and
Nevil Brownlee, who produced the revised BNF description of the
model. Wherever possible, their text has been changed as little as
feasible.
Table of Contents
1. Introduction ............................................. 2
2. The Model ................................................ 5
2.1 Metrics and Polling Periods .............................. 5
2.2 Format for Storing Collected Data ........................ 6
2.3 Reports .................................................. 6
2.4 Security Issues .......................................... 6
3. Categorization of Metrics ................................ 7
3.1 Overview ................................................. 7
3.2 Categorization of Metrics Based on Measurement Areas ..... 7
3.2.1 Utilization Metrics ...................................... 7
3.2.2 Performance Metrics ...................................... 7
3.2.3 Availability Metrics ..................................... 8
3.2.4 Stability Metrics ........................................ 8
3.3 Categorization Based on Availability of Metrics .......... 8
3.3.1 Per Interface Variables Already in Standard MIB .......... 8
3.3.2 Per Interface Variables in Private Enterprise MIB ........ 9
3.3.3 Per interface Variables Needing High Resolution Polling .. 9
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RFC 1857 Operational Statistics October 1995
3.3.4 Per Interface Variables not in any MIB ................... 9
3.3.5 Per Node Variables ....................................... 9
3.3.6 Metrics not being Retrievable with SNMP ................. 10
3.4 Recommended Metrics ..................................... 10
4. Polling Frequencies ..................................... 10
4.1 Variables Needing High Resolution Polling ............... 11
4.2 Variables not Needing High Resolution Polling ........... 11
5. Pre-Processing of Raw Statistical Data .................. 11
5.1 Optimizing and Concentrating Data to Resources .......... 11
5.2 Aggregation of Data ..................................... 12
6. Storing of Statistical Data ............................. 12
6.1 The Storage Format ...................................... 13
6.1.1 The Label Section ....................................... 14
6.1.2 The Device Section ...................................... 15
6.1.3 The Data Section ........................................ 17
6.2 Storage Requirement Estimations ......................... 17
7. Report Formats .......................................... 18
7.1 Report Types and Contents ............................... 18
7.2 Contents of the Reports ................................. 19
7.2.1 Offered Load by Link .................................... 19
7.2.2 Offered Load by Customer ................................ 19
7.2.3 Resource Utilization Reporting .......................... 20
7.2.3.1 Utilization as Maximum Peak Behavior .................... 20
7.2.3.2 Utilization as Frequency Distribution of Peaks .......... 20
8. Considerations for Future Development ................... 20
8.1 A Client/Server Based Statistical Exchange System ....... 21
8.2 Inclusion of Variables not in the Internet Standard MIB . 21
8.3 Detailed Resource Utilization Statistics ................ 21
Appendix A Some formulas for statistical aggregation ........... 22
Appendix B An example .......................................... 24
Security Considerations ......................................... 27
Author's Address ................................................ 27
1. Introduction
Many network administrations commonly collect and archive network
management metrics that indicate network utilization, growth and
reliability. The primary goals of this activity are to facilitate
near-term problem isolation and longer-term network planning within
the organization. There is also the broader goal of cooperative
problem isolation and network planning among network administrations.
This broader goal is likely to become increasingly important as the
Internet continues to grow, particularly as the number of Internet
service providers expands and the quality of service between
providers becomes more of a concern.
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RFC 1857 Operational Statistics October 1995
There exist a variety of network management tools for the collection
and presentation of network management metrics. However, different
kinds of measurement and presentation techniques make it difficult
to compare data among networks. In addition, there is not general
agreement on what metrics should be regularly collected or how they
should be displayed.
There needs to be an agreed-upon model for
1) A minimal set of common network management metrics to satisfy
the goals stated above,
2) Tools for collecting these metrics,
3) A common interchange format to facilitate the usage of these
data by common presentation tools and
4) Common presentation formats.
Under this Operational Statistics model, collection tools will
collect and store data to be retrieved later in a given format by
presentation tools displaying the data in a predefined way. (See
figure below.)
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RFC 1857 Operational Statistics October 1995
The Operational Statistics Model
(Collection of common metrics, by commonly available tools, stored in
a common format, displayed in common formats by commonly available
presentation tools.)
!-----------------------!
! Network !
!---+---------------+---!
/ \
/ \
/ \
--------+------ ----+---------
! New ! ! Old !
! Collection ! ! Collection !
! Tool ! ! Tool !
!---------+---! !------+-----!
\ !
\ !-------+--------!
\ ! Post-Processor !
\ !--+-------------!
\ /
\ /
\ /
!--+-------+---!
! Common !
! Statistics !
! Database !
!-+--------+---!
/ \
/ \
/ \
/ !-+-------------!
/ ! Pre-Processor !
/ !-------+-------!
!-----------+--! !
! New ! !-------+-------!
! Presentation ! ! Old !
! Tool ! ! Presentation !
!---------+----! ! Tool !
\ !--+------------!
\ /
\ /
!-+---------------+-!
! Graphical Output !
! (e.g., to paper !
! or X Window) !
!-------------------!
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RFC 1857 Operational Statistics October 1995
This memo gives an overview of this model for common operational
statistics. The model defines the gathering, storing and presentation
of network operational statistics and classifies the types of
information that should be available at each network operation center
(NOC) conforming to this model.
The model defines a minimal set of metrics and discusses how these
metrics should be gathered and stored. It gives recommendations for
the content and layout of statistical reports which make possible the
easy comparison of network statistics among NOCs.
The primary purpose of this model is to define mechanisms by which
NOCs could share most effectively their operational statistics. One
intent of this model is to specify a baseline capability that NOCs
conforming to the model may support with minimal development effort
and minimal ongoing effort.
2. The Model
The model defines three areas of interest on which all underlying
concepts are based:
1) The definition of a minimal set of metrics to be gathered,
2) The definition of a format for storing collected statistical
data and
3) The definition of methods and formats for generating reports.
The model indicates that old tools currently in use could be
retrofitted into the new paradigm. This could be done by providing
conversion filters between old and new tools. In this sense this
model intends to advocate the development of freely redistributable
software for use by participating NOCs.
One basic idea of the model is that statistical data stored at one
place could be retrieved and displayed at some other place.
2.1. Metrics and Polling Periods
Here the value is 0.
The intent here is to define a minimal set of metrics that could be
gathered easily using standard SNMP-based network management tools.
Thus, these metrics should be available as variables in the Internet
Standard MIB.
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RFC 1857 Operational Statistics October 1995
If the Internet Standard MIB were changed, this minimal set of
metrics should be reconsidered, as there are many metrics regarded
as important, but not currently defined in the standard MIB.
Some metrics which are highly desirable to collect are probably not
retrievable using SNMP. Therefore, tools and methods for gathering
such metrics should be defined explicitly if such metrics are to be
considered. This is, however, outside of the scope of this memo.
2.2. Format for Storing Collected Data
A format for storing data is defined. The intent is to minimize
redundant information by using a single header structure wherein all
information relevant to a certain set of statistical data is stored.
This header section will give information about when and where the
corresponding statistical data were collected.
2.3. Reports
Some basic classes of reports are suggested, addressing different
views of network behavior. Reports of total octets and packets over
some time period are regarded as essential to give an overall view of
the traffic flow in a network. Differentiation between applications
and protocols is regarded as needed to give ideas on which type of
traffic is dominant. Reports on resource utilization are
recommended.
The time period which a report spans may vary depending on its
intent. In engineering and operations daily or weekly reports may be
sufficient, whereas for capacity planning there may be a need for
longer-term reports.
2.4. Security Issues
There are legal, ethical and political concerns about data sharing.
People, in particular Network Service Providers, are concerned about
showing data that may make one of their networks look bad.
For this reason there is a need to insure integrity, conformity and
confidentiality of the shared data. To be useful, the same data
should be collected from all involved sites and it should be
collected at the same interval.
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RFC 1857 Operational Statistics October 1995
3. Categorization of Metrics
3.1. Overview
This section gives a classification of metrics with regard to scope
and ease of retrieval. A recommendation of a minimal set of metrics
is given. This section also gives some hints on metrics to be
considered for future inclusion when available in the network
management environment. Finally some thoughts on storage requirements
are presented.
3.2. Categorization of Metrics Based on Measurement Areas
The metrics used in evaluating network traffic could be classified
into (at least) four major categories:
o Utilization metrics
o Performance metrics
o Availability metrics
o Stability metrics
3.2.1. Utilization Metrics
This category describes different aspects of the total traffic being
forwarded through the network. Possible metrics include:
o Total input and output packets and octets
o Various peak metrics
o Per protocol and per application metrics
3.2.2. Performance Metrics
These metrics relate to quality of service issues such as delays and
congestion situations. Possible metrics include:
o RTT metrics on different protocol layers
o Number of collisions on a bus network
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