idnits 2.17.1 draft-bormann-core-senml-versions-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (March 06, 2020) is 1512 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-06) exists of draft-ietf-core-senml-more-units-05 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group C. Bormann 3 Internet-Draft Universitaet Bremen TZI 4 Updates: 8428 (if approved) March 06, 2020 5 Intended status: Standards Track 6 Expires: September 7, 2020 8 SenML Features and Versions 9 draft-bormann-core-senml-versions-01 11 Abstract 13 This short document updates RFC 8428, Sensor Measurement Lists 14 (SenML), by specifying the use of independently selectable "SenML 15 Features" and mapping them to SenML version numbers. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on September 7, 2020. 34 Copyright Notice 36 Copyright (c) 2020 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Feature Codes and the Version number . . . . . . . . . . . . 2 53 3. Features: Reserved0, Reserved1, Reserved2, Reserved3 . . . . 3 54 4. Feature: Secondary Units . . . . . . . . . . . . . . . . . . 3 55 5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 56 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 57 7. Normative References . . . . . . . . . . . . . . . . . . . . 4 58 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 5 59 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 61 1. Introduction 63 The Sensor Measurement Lists (SenML) specification [RFC8428] provides 64 a version number that is initially set to 10, without further 65 specification on the way to make use of different version numbers. 67 The traditional idea of using a version number for evolving an 68 interchange format presupposes a linear progression of that format. 69 A more likely form of evolution of SenML is the addition of 70 independently selectable "features" that can be added to the base 71 version (version 10) in a fashion that these are mostly independent 72 of each other. A recipient of a SenML pack can check the features it 73 implements against those required by the pack, processing the pack 74 only if all required features are provided in the implementation. 76 This short document specifies the use of SenML Features and maps them 77 to SenML version number space, updating [RFC8428]. 79 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 80 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 81 "OPTIONAL" in this document are to be interpreted as described in 82 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 83 capitals, as shown here. 85 Where bit arithmetic is explained, this document uses the notation 86 familiar from the programming language C, except that "**" denotes 87 exponentiation. 89 2. Feature Codes and the Version number 91 The present specification defines "SenML Features", each identified 92 by a "feature name" (a text string) and a "feature code", an unsigned 93 integer less than 53. 95 The specific version of a SenML pack is composed of a set of 96 features. The SenML version number ("bver" field) is then a bitmap 97 of these features, specifically the sum of, for each feature present, 98 two taken to the power of the feature code of that feature. 100 \~~ 52 fc 101 version = > present(fc) x 2 102 /__ fc=0 104 where present(fc) is 1 if the feature with the feature code "fc" is 105 present, 0 otherwise. 107 3. Features: Reserved0, Reserved1, Reserved2, Reserved3 109 For SenML Version 10 as described in [RFC8428], the feature codes 0 110 to 3 are already in use. Reserved1 (1) and Reserved3 (3) are always 111 present and the features Reserved0 (0) and Reserved2 (2) are always 112 absent, yielding a version number of 10 if no other feature is in 113 use. These four reserved feature codes are not to be used with any 114 more specific semantics except in a specification that updates the 115 present specification. 117 4. Feature: Secondary Units 119 The feature "Secondary Units" (code number 4) indicates that 120 secondary unit names [I-D.ietf-core-senml-more-units] MAY be be used 121 in the "u" field of SenML Records, in addition to the primary unit 122 names already allowed by [RFC8428]. 124 Note that the most basic use of this feature simply sets the SenML 125 version number to 26 (10 + 2**4). 127 5. Security Considerations 129 The security considerations of [RFC8428] apply. This specification 130 provides structure to the interpretation of the SenML version number, 131 which poses no additional security considerations except for some 132 potential for surprise that version numbers do not simply increase 133 linearly. 135 6. IANA Considerations 137 IANA is requested to create a new subregistry "SenML features" within 138 the SenML registry [IANA.senml], with the registration policy 139 "specification required" [RFC8126] and the columns: 141 o Feature code (an unsigned integer less than 53) 143 o Feature name (text) 144 o Specification 146 The initial content of this registry is as follows: 148 +--------------+-----------------+---------------+ 149 | Feature code | Feature name | Specification | 150 +--------------+-----------------+---------------+ 151 | 0 | Reserved0 | RFCthis | 152 | 1 | Reserved1 | RFCthis | 153 | 2 | Reserved2 | RFCthis | 154 | 3 | Reserved3 | RFCthis | 155 | 4 | Secondary Units | RFCthis | 156 +--------------+-----------------+---------------+ 158 Table 1: Features defined for SenML at the time of writing 160 As the number of features that can be registered has a hard limit (48 161 codes left at the time of writing), the designated expert is 162 specifically instructed to maintain a frugal regime of code point 163 allocation, keeping code points available for SenML Features that are 164 likely to be useful for non-trivial subsets of the SenML ecosystem. 165 Quantitatively, the expert could for instance steer the allocation to 166 not allocate more than 10 % of the remaining set per year. 168 7. Normative References 170 [I-D.ietf-core-senml-more-units] 171 Bormann, C., "Additional Units for SenML", draft-ietf- 172 core-senml-more-units-05 (work in progress), February 173 2020. 175 [IANA.senml] 176 IANA, "Sensor Measurement Lists (SenML)", 177 . 179 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 180 Requirement Levels", BCP 14, RFC 2119, 181 DOI 10.17487/RFC2119, March 1997, 182 . 184 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 185 Writing an IANA Considerations Section in RFCs", BCP 26, 186 RFC 8126, DOI 10.17487/RFC8126, June 2017, 187 . 189 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 190 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 191 May 2017, . 193 [RFC8428] Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C. 194 Bormann, "Sensor Measurement Lists (SenML)", RFC 8428, 195 DOI 10.17487/RFC8428, August 2018, 196 . 198 Acknowledgements 200 Ari Keranen proposed to use the version number as a bitmap and 201 provided further input on this specification. 203 Author's Address 205 Carsten Bormann 206 Universitaet Bremen TZI 207 Postfach 330440 208 Bremen D-28359 209 Germany 211 Phone: +49-421-218-63921 212 Email: cabo@tzi.org