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rfc:rfc3593

Network Working Group K. Tesink, Ed. Request for Comments: 3593 Telcordia Technologies Obsoletes: 2493 September 2003 Category: Standards Track

   Textual Conventions for MIB Modules Using Performance History
                    Based on 15 Minute Intervals

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

 This document defines a set of Textual Conventions for MIB modules
 that make use of performance history data based on 15 minute
 intervals.
 This memo replaces RFC 2493.  Changes relative to RFC 2493 are
 summarized in the MIB module's REVISION clause.

Table of Contents

 1.  Introduction .................................................  2
 2.  Note on Invalid Data and Proxies .............................  2
 3.  Note on xyzTimeElapsed .......................................  3
 4.  Note on xyzValidIntervals ....................................  3
 5.  Definitions ..................................................  4
 6.  Acknowledgments ..............................................  8
 7.  References ...................................................  8
     7.1.  Normative References ...................................  8
     7.2.  Informative References .................................  8
 8.  Security Considerations ......................................  9
 9.  Intellectual Property Statement ..............................  9
 10. Editor's Address .............................................  9
 11. Full Copyright Statement ..................................... 10

Tesink Standards Track [Page 1] RFC 3593 15 Minute Based Performance History TCs September 2003

1. Introduction

 In cases where a manager must obtain performance history data about
 the behavior of equipment it manages, several strategies can be
 followed in the design of a MIB that represents the managed
 equipment, including:
 0  The agent counts events on a continuous basis and, whenever
    desired, the manager obtains the value of the event counter and
    adjusts its understanding of the history of events at the agent.
 0  The agent allocates events to 'buckets' where each bucket
    represents an interval of time.
 Telecommunications equipment often makes use of the latter strategy.
 See [3][4][5][7][8] for examples.  In particular, for this equipment
 it is common that history data is maintained by the agent in terms of
 fifteen minute intervals.
 This memo does not attempt to compare the relative merits of
 different strategies used to obtain history data.  Differences may
 include polling policy, the amount of management traffic between
 manager and agent, agent simplicity, and 'data currentness' of the
 data obtained by the manager.  MIB designers should consider these
 aspects when choosing a particular strategy in a MIB design.
 Instead, this memo provides definitions that can be used in MIB
 modules that require history data based on fifteen minute intervals.
 When designing a MIB module, it is often useful to define new types
 similar to those defined in the SMI [2].  In comparison to a type
 defined in the SMI, each of these new types has a different name, a
 similar syntax, but more precise semantics.  These newly defined
 types are termed textual conventions, and are used for the
 convenience of humans reading the MIB module.  This is done through
 Textual Conventions as defined in RFC 2579 [1].  It is the purpose of
 this document to define the set of textual conventions to be used
 when performance history based on 15 minute intervals is kept.  The
 performance history textual conventions defined in this memo are
 based on 32 bit counts.  For high capacity performance history counts
 see [9].

2. Note on Invalid Data and Proxies

 In this document, the word proxy indicates an application which
 receives SNMP messages and replies to them on behalf of the devices
 where the actual implementation resides, e.g., DS3/E3 interfaces.
 The proxy will have already collected the information about the
 DS3/E3 interfaces into its local database and may not necessarily

Tesink Standards Track [Page 2] RFC 3593 15 Minute Based Performance History TCs September 2003

 forward requests to the actual DS3/E3 interface.  It is expected in
 such an application that there are periods of time where the proxy is
 not communicating with the DS3/E3 interfaces.  In these instances,
 the proxy will not necessarily have up-to-date configuration
 information, and will most likely have missed the collection of some
 data.  Missed data collection may result in some intervals in the
 interval table being unavailable.

3. Note on xyzTimeElapsed

 While xyzTimeElapsed is defined as having a maximum, there may be
 cases (e.g., an adjustment in the system's time-of-day clock) where
 the actual value of the current interval would exceed this maximum
 value.
 Suppose that an agent which aligns its 15-minute measurement
 intervals to 15-minute time-of-day ("wall clock") boundaries has a
 time-of-day clock that systematically gains time, and that a manager
 periodically corrects the clock by setting it back.
 It is assumed that the agent's time-of-day clock is reasonably
 accurate, say within a few seconds per day.  Thus, the manager's
 periodic clock adjustments will normally be small, and if done
 frequently enough, need not ever exceed 10 seconds.  In this case,
 all interval durations will be within the allowed tolerance and none
 need be marked invalid, _if_ the ANSI procedure of ending measurement
 intervals at 15-minute time-of-day boundaries is followed [6].
 If the time-of-day clock is systematically adjusted in small
 increments, then always ending measurement intervals at 15-minute
 time-of-day boundaries will result, in the long term, in the correct
 number of intervals with the correct average duration, irrespective
 of whether the clock is moved ahead or moved back.  Thus, if for some
 reason, such as an adjustment in the system's time-of-day clock, the
 current interval exceeds the maximum value, it is considered
 acceptable that the agent will return the maximum value.

4. Note on xyzValidIntervals

 The overall constraint on <n> is 1 =< n =< 96.  Any additional
 constraints on n must be defined in the DESCRIPTION clause (e.g., see
 [5]).

Tesink Standards Track [Page 3] RFC 3593 15 Minute Based Performance History TCs September 2003

5. Definitions

 PerfHist-TC-MIB DEFINITIONS ::= BEGIN
 IMPORTS
    MODULE-IDENTITY,
    Gauge32, mib-2
        FROM SNMPv2-SMI
    TEXTUAL-CONVENTION
        FROM SNMPv2-TC;
 perfHistTCMIB MODULE-IDENTITY
      LAST-UPDATED "200308130000Z"
      ORGANIZATION "IETF AToM MIB WG"
      CONTACT-INFO
         "WG charter:
            http://www.ietf.org/html.charters/atommib-charter.html
          Mailing Lists:
            General Discussion: atommib@research.telcordia.com
            To Subscribe: atommib-request@research.telcordia.com
          Editor:  Kaj Tesink
          Postal:  Telcordia Technologies
                   331 Newman Springs Road
                   Red Bank, NJ 07701
                   USA
          Tel:     +1 732 758 5254
          E-mail:  kaj@research.telcordia.com"
      DESCRIPTION
       "This MIB Module provides Textual Conventions
        to be used by systems supporting 15 minute
        based performance history counts.
        Copyright (C) The Internet Society (2003).
        This version of this MIB module is part of
        RFC 3593;  see the RFC itself for full
        legal notices."
      REVISION      "200308130000Z"
      DESCRIPTION
       "Contact information and references updated.
        No technical changes have been applied.
        Published as RFC 3593."
      REVISION      "199811071100Z"
      DESCRIPTION
       "The RFC 2493 version of this MIB module."
      ::= { mib-2 58 }

Tesink Standards Track [Page 4] RFC 3593 15 Minute Based Performance History TCs September 2003

  1. - The Textual Conventions defined below are organized
  2. - alphabetically
  1. - Use of these TCs assumes the following:
  2. - 0 The agent supports 15 minute based history
  3. - counters.
  4. - 0 The agent is capable of keeping a history of n
  5. - intervals of 15 minute performance data. The
  6. - value of n is defined by the specific MIB
  7. - module but shall be 0 < n =< 96.
  8. - 0 The agent may optionally support performance
  9. - data aggregating the history intervals.
  10. - 0 The agent will keep separate tables for the
  11. - current interval, the history intervals, and
  12. - the total aggregates.
  13. - 0 The agent will keep the following objects.
  14. - If performance data is kept for multiple instances
  15. - of a measured entity, then
  16. - these objects are applied to each instance of
  17. - the measured entity (e.g., interfaces).
  18. -
  19. - xyzTimeElapsed OBJECT-TYPE
  20. - SYNTAX INTEGER (0..899)
  21. - MAX-ACCESS read-only
  22. - STATUS current
  23. - DESCRIPTION
  24. - "The number of seconds that have elapsed since
  25. - the beginning of the current measurement period.
  26. - If, for some reason, such as an adjustment in the
  27. - system's time-of-day clock, the current interval
  28. - exceeds the maximum value, the agent will return
  29. - the maximum value."
  30. - ::= { xxx }
  1. - xyzValidIntervals OBJECT-TYPE
  2. - SYNTAX INTEGER (0..<n>)
  3. - MAX-ACCESS read-only
  4. - STATUS current
  5. - DESCRIPTION
  6. - "The number of previous near end intervals
  7. - for which data was collected.
  8. - [ The overall constraint on <n> is 1 =< n =< 96; ]
  9. - [ Define any additional constraints on <n> here. ]
  10. - The value will be <n> unless the measurement was
  11. - (re-)started within the last (<n>*15) minutes, in which
  12. - case the value will be the number of complete 15
  13. - minute intervals for which the agent has at least
  14. - some data. In certain cases (e.g., in the case

Tesink Standards Track [Page 5] RFC 3593 15 Minute Based Performance History TCs September 2003

  1. - where the agent is a proxy) it is possible that some
  2. - intervals are unavailable. In this case, this
  3. - interval is the maximum interval number for
  4. - which data is available."
  5. - ::= { xxx }
  1. - xyzInvalidIntervals OBJECT-TYPE
  2. - SYNTAX INTEGER (0..<n>)
  3. - MAX-ACCESS read-only
  4. - STATUS current
  5. - DESCRIPTION
  6. - "The number of intervals in the range from
  7. - 0 to xyzValidIntervals for which no
  8. - data is available. This object will typically
  9. - be zero except in cases where the data for some
  10. - intervals are not available (e.g., in proxy
  11. - situations)."
  12. - ::= { xxx }
 PerfCurrentCount ::= TEXTUAL-CONVENTION
       STATUS  current
       DESCRIPTION
          "A counter associated with a
           performance measurement in a current 15
           minute measurement interval.  The value
           of this counter starts from zero and is
           increased when associated events occur,
           until the end of the 15 minute interval.
           At that time the value of the counter is
           stored in the first 15 minute history
           interval, and the CurrentCount is
           restarted at zero.  In the
           case where the agent has no valid data
           available for the current interval the
           corresponding object instance is not
           available and upon a retrieval request
           a corresponding error message shall be
           returned to indicate that this instance
           does not exist (for example, a noSuchName
           error for SNMPv1 and a noSuchInstance for
           SNMPv2 GET operation)."
        SYNTAX  Gauge32

Tesink Standards Track [Page 6] RFC 3593 15 Minute Based Performance History TCs September 2003

 PerfIntervalCount ::= TEXTUAL-CONVENTION
       STATUS  current
       DESCRIPTION
          "A counter associated with a
           performance measurement in a previous
           15 minute measurement interval.  In the
           case where the agent has no valid data
           available for a particular interval the
           corresponding object instance is not
           available and upon a retrieval request
           a corresponding error message shall be
           returned to indicate that this instance
           does not exist (for example, a noSuchName
           error for SNMPv1 and a noSuchInstance for
           SNMPv2 GET operation).
           In a system supporting
           a history of n intervals with
           IntervalCount(1) and IntervalCount(n) the
           most and least recent intervals
           respectively, the following applies at
           the end of a 15 minute interval:
           - discard the value of IntervalCount(n)
           - the value of IntervalCount(i) becomes that
             of IntervalCount(i-1) for n >= i > 1
           - the value of IntervalCount(1) becomes that
             of CurrentCount
           - the TotalCount, if supported, is adjusted."
        SYNTAX  Gauge32
 PerfTotalCount ::= TEXTUAL-CONVENTION
       STATUS  current
       DESCRIPTION
          "A counter associated with a
           performance measurements aggregating the
           previous valid 15 minute measurement
           intervals.  (Intervals for which no valid
           data was available are not counted)"
        SYNTAX  Gauge32
 END

Tesink Standards Track [Page 7] RFC 3593 15 Minute Based Performance History TCs September 2003

6. Acknowledgments

 This document is a product of the AToM MIB Working Group.  The editor
 would like to acknowledge Mike Heard for his many valuable
 contributions to this memo.

7. References

7.1. Normative References

 [1]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
      M. and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
      RFC 2579, April 1999.
 [2]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
      M. and S. Waldbusser, "Structure of Management Information
      Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.

7.2. Informative References

 [3]  Fowler, D., "Definitions of Managed Objects for the DS1, E1, DS2
      and E2 Interface Types", RFC 2495, January 1999.
 [4]  Fowler, D., "Definitions of Managed Objects for the DS3/E3
      Interface Type", RFC 2496, January 1999.
 [5]  Tesink, K., "Definitions of Managed Objects for the Synchronous
      Optical Network/Synchronous Digital Hierarchy (SONET/SDH)
      Interface Type", RFC 3592, September 2003.
 [6]  American National Standard for Telecommunications - Digital
      Hierarchy - Layer 1 In-Service Digital Transmission Performance
      Monitoring, ANSI T1.231-1997, September 1997.
 [7]  Bathrick, G. and F. Ly, "Definitions of Managed Objects for the
      ADSL Lines", RFC 2662, August 1999.
 [8]  Ray, B., and R. Abbi, "Definitions of Managed Objects for High
      Bit-Rate DSL - 2nd generation (HDSL2) and Single-Pair High-Speed
      Digital Subscriber Line (SHDSL) Lines", RFC 3276, May 2002.
 [9]  Ray, B. and R. Abbi, "High Capacity Textual Conventions for MIB
      Modules Using Performance History Based on 15 Minute Intervals",
      Work in Progress.

Tesink Standards Track [Page 8] RFC 3593 15 Minute Based Performance History TCs September 2003

8. Security Considerations

 This memo defines textual conventions for use in other MIB modules.
 Security issues for these MIB modules are addressed in the memos
 defining those modules.

9. Intellectual Property Statement

 The IETF takes no position regarding the validity or scope of any
 intellectual property or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; neither does it represent that it
 has made any effort to identify any such rights.  Information on the
 IETF's procedures with respect to rights in standards-track and
 standards-related documentation can be found in BCP-11.  Copies of
 claims of rights made available for publication and any assurances of
 licenses to be made available, or the result of an attempt made to
 obtain a general license or permission for the use of such
 proprietary rights by implementors or users of this specification can
 be obtained from the IETF Secretariat.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights which may cover technology that may be required to practice
 this standard.  Please address the information to the IETF Executive
 Director.

10. Editor's Address

 Kaj Tesink
 Telcordia Technologies
 331 Newman Springs Road
 P.O. Box 7020
 Red Bank, NJ  07701-7020
 Phone: +1 732 758 5254
 EMail: kaj@research.telcordia.com

Tesink Standards Track [Page 9] RFC 3593 15 Minute Based Performance History TCs September 2003

11. Full Copyright Statement

 Copyright (C) The Internet Society (2003).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Tesink Standards Track [Page 10]

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