RFC 6340

RFC 6340 💖 Textual Conventions for the Representation of Floating-Point Numbers

okay bestie, let's talk about RFC 6340 🦋. It's titled Textual Conventions for the Representation of Floating-Point Numbers, and it's a Standards Track doc from the IETF, published in August 2011. The author is R. Presuhn, writing as Independent, and it's identified by ISSN 2070-1721 ✨. The header doesn't list any RFCs it obsoletes or updates, so it's standing on its own 🧚.

Abstract

This memo defines a Management Information Base (MIB) module containing textual conventions (TCs) to represent floating-point numbers 🌸.

Status of This Memo

This is an Internet Standards Track document 🎀.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741 💅.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6340 🫶.

Copyright Notice

Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License 📜.

Table of Contents

1. Introduction ....................................................2
2. The Internet-Standard Management Framework ......................3
3. Applicability ...................................................3
4. Structure of the MIB Module .....................................4
   4.1. MIB Modules Required for IMPORTS ...........................4
   4.2. Documents Required for REFERENCE Clauses ...................4
5. Definitions .....................................................4
6. Security Considerations .........................................6
7. IANA Considerations .............................................6
8. Contributors ....................................................6
9. References ......................................................7
   9.1. Normative References .......................................7
   9.2. Informative References .....................................7

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1. Introduction 🌈

okay so this memo defines textual conventions for representing floating-point numbers. All of these definitions are in terms of the IEEE "Standard for Floating-Point Arithmetic", IEEE 754-2008 [IEEE.754.2008] 🤓.

IEEE 754-2008 [IEEE.754.2008] provides for a variety of interchange formats for floating-point numbers. The need for three of these, namely:

• 32-bit,
• 64-bit,
• 128-bit,

has been recognized in network management 🍓. For example, Section 4.2.3 of the SMIng Objectives [RFC3216] spells out the need for these three floating-point data types in network management protocols 💜.

picking a floating-point format is a whole thing with lots of considerations and trade-offs 🙈. For an intro to the fundamentals of floating-point representations, see Chapter 4 of [KNUTH]. For a discussion of these issues specifically with respect to the IEEE formats, see [GOLDBERG] ✨.

All of these textual conventions employ the binary interchange format defined in [IEEE.754.2008]. Specifically, this means that for all of them, the highest-order bit of the first byte is the sign bit, with the remaining bits of the octet string corresponding to the exponent and fraction parts, in network byte order 🎀.

2. The Internet-Standard Management Framework 🦋

for a detailed overview of the documents that describe the current Internet-Standard Management Framework, check out section 7 of RFC 3410 [RFC3410] 📚.

Managed objects are accessed via a virtual information store, called the Management Information Base or MIB. MIB objects are generally accessed through the Simple Network Management Protocol (SNMP) 🛰️. Objects in the MIB are defined using the mechanisms in the Structure of Management Information (SMI). This memo specifies a MIB module that is compliant to the SMIv2, which is described in STD 58, RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580 [RFC2580] 💅.

3. Applicability 👑

The following list highlights some of the issues MIB designers need to consider when deciding whether to employ these textual conventions 🧠:

• Floating-point numbers are useful if the number space needs to cover a large dynamic range. For number spaces with a limited range, fixed-point numbers can be more efficient and more precise 🔥.
• Floating-point numbers are typically the wrong answer for data that is truly decimal, or can be handled adequately by re-thinking the units and representing the scaled numbers as integers 🙅‍♀️.
• The SNMP "lexicographical" ordering for INDEX objects using these floating-point textual conventions will simply be that of the octet strings corresponding to the floating-point representations. That will not always reflect the numerical ordering of the corresponding floating-point values. Even if MIB designers take this into account, users might still find the results of a MIB "walk" surprising 😭. Consequently, it is suggested that whenever one of these textual conventions is used for an INDEX object, the DESCRIPTION clause should provide some warning ⚠️.
• Embedded systems sometimes lack floating-point support, which can complicate the implementation of MIB objects using floating-point numbers 🧸.
• In choosing from among the types defined in this memo, MIB designers need to consider both the range and the precision needed. They also need to recognize that it could be inefficient to use, for example, Float128TC when Float64TC would do 💭.
• Since these textual conventions are defined in terms of the OCTET STRING type, the SMI's mechanisms for formally setting range constraints are not available. MIB designers using these textual conventions will need to use DESCRIPTION clauses to spell out any applicable range constraints beyond those implied by the underlying IEEE types 📏.
• Whenever these textual conventions are used in a MIB module, the associated DESCRIPTION clause will need to clearly specify whether denormalized numbers, NaNs ("not a number") or infinities are permitted, along with any special semantics associated with these cases. This is especially important for writeable objects 🚨.

4. Structure of the MIB Module 🧚

This MIB module defines three textual conventions. It defines no MIB objects 🌸.

4.1. MIB Modules Required for IMPORTS 📦

This MIB module employs definitions from [RFC2578] and [RFC2579] 🫧.

4.2. Documents Required for REFERENCE Clauses 📎

This MIB module contains REFERENCE clauses making reference to IEEE 754-2008 [IEEE.754.2008] 🍒.

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okay that's the first chunk, bestie 💖 the actual MIB module definitions in Section 5 and everything after it are coming in part 2 🎀💅

9.2. Informative References 💅

okay so these are the extra-credit reads 📚✨ not required to implement anything, but they're the receipts behind the vibe. bestie, check these out 🫶

• [GOLDBERG] Goldberg, D., "What Every Computer Scientist Should Know About Floating-Point Arithmetic", ACM Computing Surveys Volume 23, Issue 1, March 1991. 🧮💖
• [KNUTH] Knuth, D., "Seminumerical Algorithms", The Art of Computer Programming (Second Edition) Vol. 2, 1981. 🦋
• [RFC3216] Elliott, C., Harrington, D., Jason, J., Schoenwaelder, J., Strauss, F., and W. Weiss, "SMIng Objectives", RFC 3216, December 2001. 🌸
• [RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart, "Introduction and Applicability Statements for Internet-Standard Management Framework", RFC 3410, December 2002. 👑

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Author's Address 🎀

this is who wrote it, the legend Randy Presuhn 🧚💜

Randy Presuhn
San Jose, CA  95120
USA

EMail: randy_presuhn@mindspring.com