rfc1857.txt
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Network Working Group M. LambertRequest For Comments: 1857 Pittsburgh Supercomputing CenterObsoletes: 1404 October 1995Category: Informational A Model for Common Operational StatisticsStatus 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 .. 9Lambert Informational [Page 1] 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 ................................................ 271. 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.Lambert Informational [Page 2] 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.)Lambert Informational [Page 3] RFC 1857 Operational Statistics October 1995The 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) ! !-------------------!Lambert Informational [Page 4] 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.Lambert Informational [Page 5] 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.Lambert Informational [Page 6] RFC 1857 Operational Statistics October 19953. Categorization of Metrics3.1. 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 metrics3.2.1. 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 metrics3.2.2. 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⌨️ 快捷键说明
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