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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'IEEE.754.2008' Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Presuhn 3 Internet-Draft None 4 Intended status: Standards Track December 9, 2010 5 Expires: June 12, 2011 7 Textual Conventions for the Representation of Floating-Point Numbers 8 draft-presuhn-floats-03.txt 10 Abstract 12 This memo defines a Management Information Base (MIB) module 13 containing textual conventions (TCs) to represent floating-point 14 numbers. 16 Status of this Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on June 12, 2011. 33 Copyright Notice 35 Copyright (c) 2010 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. The Internet-Standard Management Framework . . . . . . . . . . 4 52 3. Structure of the MIB Module . . . . . . . . . . . . . . . . . . 4 53 3.1. MIB modules required for IMPORTS . . . . . . . . . . . . . 4 54 3.2. Documents required for REFERENCE clauses . . . . . . . . . 4 55 4. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 4 56 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 57 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 58 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 7 59 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 60 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 61 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 62 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 64 1. Introduction 66 This memo defines textual conventions for the representation of 67 floating-point numbers. All of these definitions are in terms of the 68 IEEE Standard for Floating-Point Arithmetic, IEEE 754-2008 69 [IEEE.754.2008]. 71 The IEEE Standard for Floating-Point Arithmetic, IEEE 754-2008 72 [IEEE.754.2008], provides for a variety of interchange formats for 73 floating point numbers. The need for three of these, namely 75 o 32-bit, 77 o 64-bit, 79 o 128-bit, 81 has been recognized in network management. For example, Section 82 4.2.3 of the SMIng Objectives [RFC3216] elaborates the need for these 83 three floating-point data types in network management protocols. 85 The selection of a floating-point format involves many considerations 86 and trade-offs. For an introduction to the fundamentals of floating- 87 point representations see chapter 4 of [KNUTH]. The following list 88 highlights some of the issues MIB designers need to consider: 90 o Floating point numbers are useful if the number space needs to 91 cover a large dynamic range. For number spaces with a limited 92 range, fixed point numbers can be more efficient and more precise. 94 o Floating point numbers are the typically the wrong answer for data 95 that is truly decimal or can be handled adequately by re-thinking 96 the units and representing the scaled numbers as integers. 98 o The SNMP "lexicographical" ordering for INDEX objects using these 99 floating point textual conventions will simply be that of the 100 octet strings corresponding to the floating point representations, 101 which will not in general reflect the numerical ordering of the 102 corresponding floating point values. 104 o Embedded systems sometimes lack floating point support, which can 105 complicate the implementation of MIB objects using floating point 106 numbers. 108 o In choosing from among the types defined in this memo, MIB 109 designers need to consider both the range and the precision 110 needed, as well as recognize that it could be inefficient to use, 111 for example, Float128TC when Float64TC would do. 113 o Since these textual conventions are defined in terms of the OCTET 114 STRING type, the SMI's mechanisms for formally setting range 115 constraints are not available. MIB designers using these textual 116 conventions will need to use DESCRIPTION clauses to spell out any 117 applicable range constraints beyond those implied by the 118 underlying IEEE types. 120 2. The Internet-Standard Management Framework 122 For a detailed overview of the documents that describe the current 123 Internet-Standard Management Framework, please refer to section 7 of 124 RFC 3410 [RFC3410]. 126 Managed objects are accessed via a virtual information store, termed 127 the Management Information Base or MIB. MIB objects are generally 128 accessed through the Simple Network Management Protocol (SNMP). 129 Objects in the MIB are defined using the mechanisms defined in the 130 Structure of Management Information (SMI). This memo specifies a MIB 131 module that is compliant to the SMIv2, which is described in STD 58, 132 RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580 133 [RFC2580]. 135 3. Structure of the MIB Module 137 This MIB module defines three textual conventions. It defines no MIB 138 objects. 140 3.1. MIB modules required for IMPORTS 142 This MIB module employs definitions from [RFC2578] and [RFC2579]. 144 3.2. Documents required for REFERENCE clauses 146 This MIB module contains REFERENCE clauses making reference to IEEE 147 754-2008 [IEEE.754.2008]. 149 4. Definitions 151 FLOAT-TC-MIB DEFINITIONS ::= BEGIN 153 IMPORTS 154 MODULE-IDENTITY, 155 mib-2 FROM SNMPv2-SMI 156 TEXTUAL-CONVENTION FROM SNMPv2-TC; 158 floatTcMIB MODULE-IDENTITY 159 LAST-UPDATED "201012050000Z" -- 05 December, 2010 160 ORGANIZATION "None" 161 CONTACT-INFO "Randy Presuhn 162 Email: randy_presuhn@mindspring.com" 164 DESCRIPTION "Textual conventions for the representation 165 of floating-point numbers. 167 Copyright (c) 2010 IETF Trust and the persons 168 identified as the document authors. All rights 169 reserved. 171 Redistribution and use in source and binary forms, 172 with or without modification, is permitted pursuant 173 to, and subject to the license terms contained in, 174 the Simplified BSD License set forth in Section 175 4.c of the IETF Trust's Legal Provisions Relating 176 to IETF Documents 177 (http://trustee.ietf.org/license-info). 179 This version of this MIB module is part of RFC XXXX; 180 see the RFC itself for full legal notices." 182 REVISION "201012050000Z" 183 DESCRIPTION "Initial version, published as RFC XXXX." 184 ::= { mib-2 XXX } 185 -- RFC Ed.: replace XXX with IANA-assigned number & remove this note 186 -- RFC Ed.: replace XXXX with the RFC number & remove this note 188 Float32TC ::= TEXTUAL-CONVENTION 189 STATUS current 190 DESCRIPTION 191 "This type represents a 32-bit (4-octet) IEEE 192 floating-point number in binary interchange format." 193 REFERENCE 194 "IEEE Standard for Binary Floating-Point Arithmetic, 195 Standard 754-2008" 196 SYNTAX OCTET STRING (SIZE(4)) 198 Float64TC ::= TEXTUAL-CONVENTION 199 STATUS current 200 DESCRIPTION 201 "This type represents a 64-bit (8-octet) IEEE 202 floating-point number in binary interchange format." 204 REFERENCE 205 "IEEE Standard for Binary Floating-Point Arithmetic, 206 Standard 754-2008" 207 SYNTAX OCTET STRING (SIZE(8)) 209 Float128TC ::= TEXTUAL-CONVENTION 210 STATUS current 211 DESCRIPTION 212 "This type represents a 128-bit (16-octet) IEEE 213 floating-point number in binary interchange format." 214 REFERENCE 215 "IEEE Standard for Binary Floating-Point Arithmetic, 216 Standard 754-2008" 217 SYNTAX OCTET STRING (SIZE(16)) 219 END 221 5. Security Considerations 223 This module does not define any management objects. Instead, it 224 defines a set of textual conventions that can be used by other MIB 225 modules to define management objects. 227 Meaningful security considerations can only be written in the MIB 228 modules that define management objects. Therefore, this memo has no 229 impact on the security of the Internet. 231 6. IANA Considerations 233 The MIB module in this document uses the following IANA-assigned 234 OBJECT IDENTIFIER value recorded in the SMI Numbers registry: 236 Descriptor OBJECT IDENTIFIER value 237 ---------- ----------------------- 238 floatTcMIB { mib-2 XXX } 240 Editor's Note (to be removed prior to publication): the IANA is 241 requested to assign a value for "XXX" under the 'mib-2' subtree and 242 to record the assignment in the SMI Numbers registry. When the 243 assignment has been made, the RFC Editor is asked to replace "XXX" 244 (here and in the MIB module) with the assigned value and to remove 245 this note. 247 7. Contributors 249 The following people provided helpful comments during the development 250 of this document: 252 o Andy Bierman 254 o Juergen Quittek 256 o Juergen Schoenwaeder 258 o Robert Story 260 8. References 262 8.1. Normative References 264 [IEEE.754.2008] 265 Institute of Electrical and Electronics Engineers, 266 "Standard for Binary Floating-Point Arithmetic", 267 IEEE Standard 754, August 2008. 269 [RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J. 270 Schoenwaelder, Ed., "Structure of Management Information 271 Version 2 (SMIv2)", STD 58, RFC 2578, April 1999. 273 [RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J. 274 Schoenwaelder, Ed., "Textual Conventions for SMIv2", 275 STD 58, RFC 2579, April 1999. 277 [RFC2580] McCloghrie, K., Perkins, D., and J. Schoenwaelder, 278 "Conformance Statements for SMIv2", STD 58, RFC 2580, 279 April 1999. 281 8.2. Informative References 283 [KNUTH] Knuth, D., "Seminumerical Algorithms", The Art of Computer 284 Programming (Second Edition) Vol. 2, 1981. 286 [RFC3216] Elliott, C., Harrington, D., Jason, J., Schoenwaelder, J., 287 Strauss, F., and W. Weiss, "SMIng Objectives", RFC 3216, 288 December 2001. 290 [RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart, 291 "Introduction and Applicability Statements for Internet- 292 Standard Management Framework", RFC 3410, December 2002. 294 Author's Address 296 Randy Presuhn 297 None 298 San Jose, CA 95120 299 USA 301 Email: randy_presuhn@mindspring.com