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CORE                                                       H. Tschofenig
Internet-Draft                                                  Arm Ltd.
Updates: 8428 (if approved)                                June 18, 2019
Intended status: Standards Track
Expires: December 20, 2019


                Introducing the Local Base Name in SenML
                   draft-tschofenig-core-senml-lbn-00

Abstract

   The Sensor Measurement Lists (SenML) specification defines a format
   for representing simple sensor measurements and device parameters.
   This specification defines a new label to relax the requirement for
   global identification of every measurement.

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   This Internet-Draft will expire on December 20, 2019.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Local Base Name SenML Structure and Semantics . . . . . . . .   4
   4.  CDDL  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Sensor Measurement Lists (SenML) specification, see RFC 8428
   [RFC8428], defines a format for representing simple sensor
   measurements and device parameters.

   Ideally, sensor readings used in the Internet of Things environment
   should be as small as possible.  For this reason the specification
   also defines an encoding of these sensor measurements and device
   parameters in CBOR (on top of other serialization formats).

   A design decision in SenML was, however, that each measurement
   transmitted over the network is self-contained and contains
   information that uniquely identifies and differentiates the sensor
   from all others - not only locally on the device but globally.

   This is accomplished by the combination of two fields, namely the
   'Name' and the 'Base Name' values.  The specification requires the
   concatenation of the Name and the Base Name values to yield the name
   of the sensor and recommends that the concatenated names be
   represented as URIs or URNs.

   Figure 1 is an example taken from RFC 8428.

 [
    {"bn":"urn:dev:ow:10e2073a01080063:","n":"temp","u":"Cel","v":23.1},
    {"n":"label","vs":"Machine Room"},
    {"n":"open","vb":false},
    {"n":"nfc-reader","vd":"aGkgCg"}
 ]

         Figure 1: SenML Example Measurement with Base Name value





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   The global identification of every measurement as it is traveling
   through the network and through different systems has its use case
   and allows easy identification of the source and enables correlation.

   Unfortunately, it also has drawbacks:

   o  The unique identification of the sensor adds a substantial
      overhead, particularly when the sensor identification is verbose.
      Deployed systems, for example, make use of RFC 4122 [RFC4122] Type
      5 Universally Unique IDentifier (UUIDs).

   o  The global identification of every measurements is often
      unnecessary when the SenML is used as a mechanism to represent
      data for device-to-clould communication or cloud-to-gateway
      communication where data is subsequently processed, aggregated or
      otherwise modified.  In such systems, the identification of the
      sensor and the device has its origin in the security context
      rather than in the SenML contained measurment.  LwM2M [LWM2M] is
      an example of such an architecture.

   o  Finally, there are privacy implications of globally identifying
      each measurements and some deployments may prefer better privacy
      protection over ease of correlation.

   This specification therefore updates RFC 8428 and defines a new Local
   Base Name value (lbn) that can be used instead of the Base Name value
   defined in RFC 8428.

   Figure 2 shows an example based on LwM2M use of SenML.

    [
       {"lbn":"/3303/", "n":"0/5700/", "v":25.2},
       {"n":"/1/5700/", "v":5}
    ]

      Figure 2: SenML Example Measurement with Local Base Name value

   Note: In the LwM2M data model objects, object instances, and
   resources are encoded as numerical values.  The value of '3303'
   refers to the Temperature object, '0' and '1' to the two instances of
   the resource '5700' (Sensor Value).  Hence, this measurement
   indicates that the two temperator sensors expose their sensor
   readings.








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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Local Base Name SenML Structure and Semantics

   This specification defines one new lable, the Local Base Name value,
   which is used instead of the Base Name value.  For practical purposes
   the Local Base Name / Name concatination does not need to be a URN or
   a URI because existing data models used in the IoT space do not all
   make use of URIs/URNs.

    +-------------------+-------+------------+------------+------------+
    |          Name     | Label | CBOR Label | JSON Type  | XML Type   |
    +-------------------+-------+------------+------------+------------+
    | Local Base Name   | lbn   |          8 | String     | string     |
    +-------------------+-------+------------+------------+------------+

                   Figure 3: Local Base Name SenML Label

4.  CDDL

   This document defines a new value to be added to the CDDL defined in
   Section 11 of RFC 8428.

   The new key-value-pair is

    lbn => tstr        ; Local Base Name

5.  Security Considerations

   This document inherits the security properties of RFC 8428 but
   improves its privacy features by removing the unique identification
   of the sensor when the Local Base Name value is used instead of the
   Name / Base Name combination.

6.  IANA Considerations

   IANA is asked to register the following new entry in the SenML Labels
   Registry.







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  +-----------------+-------+----+-----------+----------+----+--------------+
  |          Name   | Label | CL | JSON Type | XML Type | EI | Reference    |
  +-----------------+-------+----+-----------+----------+----+--------------+
  | Local Base Name | lbn   |  8 | String    | string   | a  |[[This RFC]]  |
  +-----------------+-------+----+-----------+----------+----+--------------+

                Note that CL = CBOR Label and EI = EXI ID.

7.  Acknowledgements

   The author would like to thank the OMA Device Management and Service
   Enablement working group for their discussion and their input.  In
   particular, I would to thank Ari Keranen, David Navarro, Mojan
   Mohajer and Alan Soloway.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8428]  Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
              Bormann, "Sensor Measurement Lists (SenML)", RFC 8428, DOI
              10.17487/RFC8428, August 2018, <https://www.rfc-
              editor.org/info/rfc8428>.

8.2.  Informative References

   [LWM2M]    Open Mobile Alliance, "Lightweight Machine to Machine
              Technical Specification Version 1.0", February 2017,
              <http://www.openmobilealliance.org/release/LightweightM2M/
              V1_0-20170208-A/
              OMA-TS-LightweightM2M-V1_0-20170208-A.pdf>.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI
              10.17487/RFC4122, July 2005, <https://www.rfc-
              editor.org/info/rfc4122>.








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Author's Address

   Hannes Tschofenig
   Arm Ltd.
   110 Fulbourn Rd
   Cambridge  CB1 9NJ
   UK

   Email: Hannes.tschofenig@arm.com
   URI:   http://www.tschofenig.priv.at









































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