rfc1404.txt
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Network Working Group B. Stockman
Request for Comments: 1404 NORDUnet/SUNET
January 1993
A Model for Common Operational Statistics
Status of the Memo
This memo provides information for the Internet community. It does
not specify an Internet standard. 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, storage formats and presentation formats.
Acknowledgements
The author would like to thank the members of the Operational
Statistics Working Group of the IETF whose efforts made this memo
possible.
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 ..................................... 7
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
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
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RFC 1404 Operational Statistics January 1993
3.4.1 Chosen Metrics .......................................... 10
4. Polling Frequencies ..................................... 11
4.1 Variables Needing High Resolution Polling ............... 11
4.2 Variables not Needing High Resolution Polling ........... 11
5. Pre-Processing of Raw Statistical Data .................. 12
5.1 Optimizing and Concentrating Data to Resources .......... 12
5.2 Aggregation of Data ..................................... 12
6. Storing of Statistical Data ............................. 13
6.1 The Storage Format ...................................... 13
6.1.1 The Label Section ....................................... 14
6.1.2 The Device Section ...................................... 14
6.1.3 The Data Section ........................................ 16
6.2 Storage Requirement Estimations ......................... 17
7. Report Formats .......................................... 18
7.1 Report Types and Contents ............................... 18
7.2 Contents of the Reports ................................. 18
7.2.1 Offered Load by Link .................................... 18
7.2.2 Offered Load by Customer ................................ 18
7.2.3 Resource Utilization Reporting .......................... 19
7.2.3.1 Utilization as Maximum Peak Behavior .................... 19
7.2.3.2 Utilization as Frequency Distribution of Peaks .......... 19
8. Considerations for Future Development ................... 20
8.1 A Client/Server Based Statistical Exchange System ....... 20
8.2 Inclusion of Variables not in the Internet Standard MIB . 20
8.3 Detailed Resource Utilization Statistics ................ 20
Appendix A Some formulas for statistical aggregation ........... 21
Appendix B An example .......................................... 24
Security Considerations ......................................... 27
Author's Address ................................................ 27
1. Introduction
Today it is not uncommon for many network administrations to collect
and archive network management metrics that indicate network
utilization, growth, and outages. The primary goal is to facilitate
near-term problem isolation and longer-term network planning within
the organization. There is also the larger goal of cooperative
problem isolation and network planning between network
administrations. This larger goal is likely to become increasingly
important as the Internet continues to grow.
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 makes it difficult
to compare data between networks. Plus, there is not common
agreement on what metrics should be regularly collected or how they
should be displayed.
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RFC 1404 Operational Statistics January 1993
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 storage format to facilitate the usage of these data by
common presentation tools.
4) Common presentation formats.
Under this Operational Statistics model, collection tools will
collect and store data in a given format to be retrieved later by
presentation tools displaying the data in a predefined way. (See
figure below.)
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RFC 1404 Operational Statistics January 1993
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 1404 Operational Statistics January 1993
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
conforming to this model.
The model defines a minimal set of metrics, how these metrics should
gathered and stored. Finally the model gives recommendations on the
content and the layout of statistical reports making it possible to
easily compare networks statistics between NOCs.
The primary purpose of this model is to define ways and methods on
how NOCs could most effectively share their operational statistics.
One intention with this model is to specify a baseline capability
that NOCs conforming to the this model may support with a minimal
development effort and a 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.
3. The definition of methods and formats for generating
reports.
The model indicates that old tools used today could be retrofitted
into the new paradigm. This could be done by providing conversion-
filters between the old and the new environment tools. In this sense
this model intends to advocate the development of public domain
software for use by participating NOCs.
One basic idea with 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
The intention here is to define a minimal set of metrics that easily
could be gathered using standard SNMP based network management tools.
These metrics should hence be available as variables in the Internet
Standard MIB.
If the Internet Standard MIB is changed also this minimal set of
metrics could be reconsidered as there are many metrics viewed as
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RFC 1404 Operational Statistics January 1993
important but currently not being defined in the standard MIB. For
some metrics being highly desirable to collect there are currently no
way to get them into the Internet Standard MIB as these metrics
probably are not possible to retrieve using SNMP. Tools and methods
in gathering such metrics should be explicitly defined 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 intention is to minimize
redundant information by using a single header structure where all
information relevant to a certain set of statistical data is stored.
This header section will give information on when and where the
corresponding statistical data where collected.
2.3 Reports
Some basic classes of reports are suggested with regards to different
views of network behavior. For this reason reports on totals of
octets and packets over some period in time are regarded as essential
to give an overall view of the traffic flows in a network.
Differentiation between application and protocols to give ideas on
which type of traffic is dominant is regarded as needed. Finally
reports on resource utilization are recommended..
Depending on the intention with a report the timeperiod over which it
spans may vary. For capacity planning there may be a need for longer
term reports while in engineering and operation there may be
sufficient with reports on weekly or daily basis.
2.4 Security Issues
There are legal, ethical and political concerns of data sharing.
People are concerned about showing data that may make one of the
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 must
be collected from all of the involved sites and it must be collected
at the same interval. To prevent vendors from getting an unfair
performance information, certain data must not be made available.
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RFC 1404 Operational Statistics January 1993
3. Categorization of Metrics
3.1 Overview
This section gives a classification of metrics with regard to scope
and easiness of retrieve. A recommendation of a minimal set of
metrics is given. The 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:
- Utilization metrics
- Performance metrics
- Availability metrics
- Stability metrics
3.2.1. Utilization Metrics
These category describes different aspects of the total traffic being
forwarded through the network. Possible metrics are:
- Total input and output packets and octets.
- Various peak metrics.
- Per protocol and per application metrics.
3.2.2 Performance Metrics
These metrics describes the quality of service such as delays and
congestion situations. Possible metrics are:
- RTT metrics on different protocol layers.
- Number of collisions on a bus network
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