RFC 2493
Textual Conventions for MIB Modules Using Performance History Based on 15 Minute Intervals
Part 1 of 2 💖
Status of this Memo 📜
okay so this is an Internet standards track protocol doc for the Internet community, and it's literally asking for discussion and suggestions for improvements 💅 For the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1). Distribution of this memo is unlimited 🌈
Copyright Notice ©️
Copyright (C) The Internet Society (1999). All Rights Reserved. 🫶
Abstract ✨
This document defines a set of Textual Conventions for MIB modules that use performance history data based on 15 minute intervals 🦋
1. Table of Contents 📑
1 Table of Contents ..................................... 1
2 Introduction .......................................... 1
3 Note on Invalid Data and Proxy ........................ 2
4 Note on xyzTimeElapsed ................................ 3
5 Note on xyzValidIntervals ............................. 3
6 Definitions ........................................... 3
7 Acknowledgments ....................................... 7
8 References ............................................ 7
9 Security Considerations ............................... 8
10 IANA Considerations .................................. 8
11 Author's Address ..................................... 8
12 Intellectual Property ................................ 8
13 Full Copyright Statement ............................. 92. Introduction 🌸
okay so picture this: a manager needs performance history data about how its equipment has been behaving 👀 There are a couple of ways to design a MIB (the thing that represents the managed equipment) to handle that, including:
- The agent counts events continuously, and whenever the manager wants, it grabs the value of the event counter and updates its own understanding of the event history at the agent. 🔢
- The agent sorts events into "buckets," where each bucket stands for a span of time. 🪣
Telecom equipment usually goes with the second approach, see [3][4][5] for examples. Specifically, for that kind of equipment, history data is typically kept by the agent in fifteen minute intervals ⏱️
This memo isn't trying to decide which strategy is the best one 🙅♀️ There are differences to think about, like polling policy, how much management traffic goes between manager and agent, how simple the agent is, and the "data currentness" of what the manager gets back. MIB designers should weigh these when they pick a strategy for their design. What this memo does instead is give you definitions you can use in MIB modules that need history data based on fifteen minute intervals 💜
When you're designing a MIB module, it's super useful to define new types that look like the ones in the SMI [2]. Compared to an SMI type, each of these new types has a different name, a similar syntax, but more precise semantics. These are called textual conventions, and they're there for the humans reading the MIB module 🧠 That's done through Textual Conventions as defined in RFC1903[1]. So the whole purpose of this document is to define the set of textual conventions you should use when performance history based on 15 minute intervals is kept. For an example, see the Trunk MIB modules [3][4][5] ✨
3. Note on Invalid Data and Proxy 🧚
In this document, the word proxy means an application that receives SNMP messages and replies to them on behalf of the devices where the actual implementation lives, like DS3/E3 interfaces 🛰️ The proxy will have already collected the information about those DS3/E3 interfaces into its local database, and it might not necessarily forward requests to the actual DS3/E3 interface. In an application like this, it's expected that there will be periods of time when the proxy isn't communicating with the DS3/E3 interfaces. During those times, the proxy won't necessarily have up-to-date configuration information, and it will most likely have missed the collection of some data. Missed data collection can make some intervals in the interval table unavailable 🙈
4. Note on xyzTimeElapsed 🕰️
Okay, so xyzTimeElapsed is defined as having a maximum, but there can be cases (like an adjustment to the system's time-of-day clock) where the actual value of the current interval would go over that maximum 😭
Say an agent lines up its 15-minute measurement intervals to 15-minute time-of-day ("wall clock") boundaries, and its time-of-day clock systematically gains time. Meanwhile, a manager periodically corrects the clock by setting it back 🔁
It's assumed that the agent's time-of-day clock is reasonably accurate, say within a few seconds per day. So the manager's periodic clock adjustments will normally be small, and if they're done often enough, they don't ever need to exceed 10 seconds. In that case, all interval durations stay within the allowed tolerance and none need to 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 gets systematically adjusted in small increments, then always ending measurement intervals at 15-minute time-of-day boundaries will, in the long term, give you the correct number of intervals with the correct average duration. That's true whether the clock is moved ahead or moved back 🦋 So if the current interval exceeds the maximum value for some reason (like an adjustment to the system's time-of-day clock), it's considered acceptable for the agent to return the maximum value 🫶
5. 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]) 💖
⋯ to be continued in part 2 🎀
6. Definitions 🎀
Okay bestie, here's the actual MIB module. It's basically a toolkit of textual conventions for 15 minute performance history counts, and the comments up top explain how the agent is expected to behave 💅
PerfHist-TC-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY,
Gauge32, mib-2
FROM SNMPv2-SMI
TEXTUAL-CONVENTION
FROM SNMPv2-TC;
perfHistTCMIB MODULE-IDENTITY
LAST-UPDATED "9811071100Z"
ORGANIZATION "IETF AToMMIB and TrunkMIB WGs"
CONTACT-INFO
"Kaj Tesink
Postal: Bellcore
331 Newman Springs Road
Red Bank, NJ 07701
USA
Tel: +1 732 758 5254
Fax: +1 732 758 2269
E-mail: kaj@bellcore.com"
DESCRIPTION
"This MIB Module provides Textual Conventions
to be used by systems supporting 15 minute
based performance history counts."
::= { mib-2 58 }
-- The Textual Conventions defined below are organized
-- alphabetically
-- Use of these TCs assumes the following:
-- 0 The agent supports 15 minute based history
-- counters.
-- 0 The agent is capable of keeping a history of n
-- intervals of 15 minute performance data. The
-- value of n is defined by the specific MIB
-- module but shall be 0 < n =< 96.
-- 0 The agent may optionally support performance
-- data aggregating the history intervals.
-- 0 The agent will keep separate tables for the
-- current interval, the history intervals, and
-- the total aggregates.
-- 0 The agent will keep the following objects.
-- If performance data is kept for multiple instances
-- of a measured entity, then
-- these objects are applied to each instance of
-- the measured entity (e.g., interfaces).
--
-- xyzTimeElapsed OBJECT-TYPE
-- SYNTAX INTEGER (0..899)
-- MAX-ACCESS read-only
-- STATUS current
-- DESCRIPTION
-- "The number of seconds that have elapsed since
-- the beginning of the current measurement period.
-- If, for some reason, such as an adjustment in the
-- system's time-of-day clock, the current interval
-- exceeds the maximum value, the agent will return
-- the maximum value."
-- ::= { xxx }
-- xyzValidIntervals OBJECT-TYPE
-- SYNTAX INTEGER (0..<n>)
-- MAX-ACCESS read-only
-- STATUS current
-- DESCRIPTION
-- "The number of previous near end intervals
-- for which data was collected.
-- [ The overall constraint on <n> is 1 =< n =< 96; ]
-- [ Define any additional constraints on <n> here. ]
-- The value will be <n> unless the measurement was
-- (re-)started within the last (<n>*15) minutes, in which
-- case the value will be the number of complete 15
-- minute intervals for which the agent has at least
-- some data. In certain cases (e.g., in the case
-- where the agent is a proxy) it is possible that some
-- intervals are unavailable. In this case, this
-- interval is the maximum interval number for
-- which data is available."
-- ::= { xxx }
-- xyzInvalidIntervals OBJECT-TYPE
-- SYNTAX INTEGER (0..<n>)
-- MAX-ACCESS read-only
-- STATUS current
-- DESCRIPTION
-- "The number of intervals in the range from
-- 0 to xyzValidIntervals for which no
-- data is available. This object will typically
-- be zero except in cases where the data for some
-- intervals are not available (e.g., in proxy
-- situations)."
-- ::= { 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
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
END7. Acknowledgments 🫶
This one's a group project 🌈 The document is a product of the AToMMIB and TrunkMIB Working Groups, so big thanks to them.
8. References 📚
- [1] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Textual Conventions for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1903, January 1996.
- [2] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Structure of Management Information for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1902, January 1996.
- [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 SONET/SDH Interface Type", Work in Progress.
- [6] American National Standard for Telecommunications - Digital Hierarchy - Layer 1 In-Service Digital Transmission Performance Monitoring, ANSI T1.231-1997, September 1997.
9. Security Considerations 🔐
Okay, this part is serious, so listen up 🙈 This memo only defines textual conventions for use in other MIB modules. That means the security issues for these MIB modules are handled in the memos that define those modules, not here. Go check those documents before you deploy anything, periodt.
10. IANA Considerations 🧚
Before this memo gets published as an RFC, IANA is asked to make a suitable OBJECT IDENTIFIER assignment. Easy ask, very important vibe ✨
11. Author's Address 💌
Kaj Tesink
Bellcore
331 Newman Springs Road
P.O. Box 7020
Red Bank, NJ 07701-7020
Phone: (732) 758-5254
EMail: kaj@bellcore.com12. Intellectual Property ⚖️
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. It also doesn't 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.
13. Full Copyright Statement ©️
Copyright (C) The Internet Society (1999). 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.
📦 where this page comes from
- ietf: rfc2493 1999-01
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms