Network Working Group R. Presuhn
Internet-Draft None
Intended status: Standards Track June 15, 2011
Expires: December 17, 2011

Textual Conventions for the Representation of Floating-Point Numbers
draft-ietf-opsawg-mib-floats-02.txt

Abstract

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

Status of this Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on December 17, 2011.

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

This memo defines textual conventions for the representation of floating-point numbers. All of these definitions are in terms of the IEEE Standard for Floating-Point Arithmetic, IEEE 754-2008 [IEEE.754.2008].

The IEEE Standard for Floating-Point Arithmetic, IEEE 754-2008 [IEEE.754.2008], provides for a variety of interchange formats for floating point numbers. The need for three of these, namely [RFC3216] elaborates the need for these three floating-point data types in network management protocols.

has been recognized in network management. For example, Section 4.2.3 of the SMIng Objectives

The selection of a floating-point format involves many considerations and trade-offs. For an introduction to the fundamentals of floating-point representations see chapter 4 of [KNUTH], and for a 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, please refer to section 7 of RFC 3410 [RFC3410].

Managed objects are accessed via a virtual information store, termed 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 defined 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:

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].

5. Definitions


FLOAT-TC-MIB DEFINITIONS ::= BEGIN

IMPORTS
    MODULE-IDENTITY,
    mib-2                                 FROM SNMPv2-SMI  -- RFC 2578
    TEXTUAL-CONVENTION			  FROM SNMPv2-TC;  -- RFC 2579

floatTcMIB    MODULE-IDENTITY
    LAST-UPDATED "201106010000Z"          -- June 1, 2011
    ORGANIZATION "None"
    CONTACT-INFO "Randy Presuhn
                  Email: randy_presuhn@mindspring.com"

    DESCRIPTION  "Textual conventions for the representation
		  of floating-point numbers.

                  Copyright (c) 2010 IETF Trust and the persons
                  identified as the document authors.  All rights
                  reserved.

                  Redistribution and use in source and binary forms,
                  with or without modification, is permitted pursuant
                  to, and subject to the license terms contained in,
                  the Simplified BSD License set forth in Section
                  4.c of the IETF Trust's Legal Provisions Relating
                  to IETF Documents
                  (http://trustee.ietf.org/license-info).

                  This version of this MIB module is part of RFC XXXX;
                  see the RFC itself for full legal notices."

    REVISION     "201106010000Z"          -- June 1, 2011
    DESCRIPTION  "Initial version, published as RFC XXXX."
     ::= { mib-2 XXX }
-- RFC Ed.: replace XXX with IANA-assigned number & remove this note
-- RFC Ed.: replace XXXX with the RFC number & remove this note

Float32TC ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION  "This type represents a 32-bit (4-octet) IEEE
	          floating-point number in binary interchange format."
    REFERENCE    "IEEE Standard for Floating-Point Arithmetic,
                  Standard 754-2008"
    SYNTAX       OCTET STRING (SIZE(4))


Float64TC ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION  "This type represents a 64-bit (8-octet) IEEE
                  floating-point number in binary interchange format."
    REFERENCE    "IEEE Standard for Floating-Point Arithmetic,
                  Standard 754-2008"
    SYNTAX       OCTET STRING (SIZE(8))


Float128TC ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION  "This type represents a 128-bit (16-octet) IEEE
                  floating-point number in binary interchange format."
    REFERENCE    "IEEE Standard for Floating-Point Arithmetic,
                  Standard 754-2008"
    SYNTAX       OCTET STRING (SIZE(16))

END
                

6. Security Considerations

This module does not define any management objects. Instead, it defines a set of textual conventions that can be used by other MIB modules to define management objects.

Meaningful security considerations can only be written in the MIB modules that define management objects. Therefore, this memo has no impact on the security of the Internet.

7. IANA Considerations

The MIB module in this document uses the following IANA-assigned OBJECT IDENTIFIER value recorded in the SMI Numbers registry:

      
   Descriptor        OBJECT IDENTIFIER value
   ----------        -----------------------
   floatTcMIB        { mib-2 XXX }

      

Editor's Note (to be removed prior to publication): the IANA is requested to assign a value for "XXX" under the 'mib-2' subtree and to record the assignment in the SMI Numbers registry. When the assignment has been made, the RFC Editor is asked to replace "XXX" (here and in the MIB module) with the assigned value and to remove this note.

8. Contributors

The following people provided helpful comments during the development of this document:

9. References

9.1. Normative References

[RFC2578] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
[RFC2579] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999.
[RFC2580] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Conformance Statements for SMIv2", STD 58, RFC 2580, April 1999.
[IEEE.754.2008] Institute of Electrical and Electronics Engineers , "Standard for Floating-Point Arithmetic", IEEE Standard 754, August 2008.

9.2. Informative References

[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.
[KNUTH] Knuth, D., "Seminumerical Algorithms", The Art of Computer Programming (Second Edition) Vol. 2, 1981.
[GOLDBERG] Goldberg, D., "What Every Computer Scientist Should Know About Floating-Point Arithmetic ", ACM Computing Surveys Volume 23, Issue 1, March 1991.

Author's Address

Randy Presuhn None San José, CA 95120 USA EMail: randy_presuhn@mindspring.com