6Lo Working Group                                              Y-G. Hong
Internet-Draft                                                      ETRI
Intended status: Informational                                  C. Gomez
Expires: May 7, 2020                                                 UPC
                                                               Y-H. Choi
                                                               AR. Sangi
                                         Huaiyin Institute of Technology
                                                             T. Aanstoot
                                                                Modio AB
                                                          S. Chakrabarti
                                                        November 4, 2019

  IPv6 over Constrained Node Networks (6lo) Applicability & Use cases


   This document describes the applicability of IPv6 over constrained
   node networks (6lo) and provides practical deployment examples.  In
   addition to IEEE 802.15.4, various link layer technologies such as
   ITU-T G.9959 (Z-Wave), BLE, DECT-ULE, MS/TP, NFC, and PLC (IEEE
   1901.2) are used as examples.  The document targets an audience who
   like to understand and evaluate running end-to-end IPv6 over the
   constrained node networks connecting devices to each other or to
   other devices on the Internet (e.g. cloud infrastructure).

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   working documents as Internet-Drafts.  The list of current Internet-
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 7, 2020.

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Copyright Notice

   Copyright (c) 2019 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
   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions and Terminology . . . . . . . . . . . . . . . . .   4
   3.  6lo Link layer technologies . . . . . . . . . . . . . . . . .   4
     3.1.  ITU-T G.9959  . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Bluetooth LE  . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  DECT-ULE  . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  MS/TP . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.5.  NFC . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.6.  PLC . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.7.  Comparison between 6lo Link layer technologies  . . . . .   7
   4.  6lo Deployment Scenarios  . . . . . . . . . . . . . . . . . .   8
     4.1.  G3-PLC usage of 6lo in network layer  . . . . . . . . . .   8
     4.2.  Netricity usage of 6lo in network layer . . . . . . . . .   9
   5.  Guidelines for adopting IPv6 stack (6lo/6LoWPAN)  . . . . . .  10
   6.  6lo Use Case Examples . . . . . . . . . . . . . . . . . . . .  12
     6.1.  Use case of ITU-T G.9959: Smart Home  . . . . . . . . . .  12
     6.2.  Use case of Bluetooth LE: Smartphone-based Interaction  .  13
     6.3.  Use case of DECT-ULE: Smart Home  . . . . . . . . . . . .  14
     6.4.  Use case of MS/TP: Building Automation Networks . . . . .  14
     6.5.  Use case of NFC: Alternative Secure Transfer  . . . . . .  15
     6.6.  Use case of PLC: Smart Grid . . . . . . . . . . . . . . .  15
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     10.2.  Informative References . . . . . . . . . . . . . . . . .  19
   Appendix A.  Design Space Dimensions for 6lo Deployment . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

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1.  Introduction

   Running IPv6 on constrained node networks has different features from
   general node networks due to the characteristics of constrained node
   networks such as small packet size, short link-layer address, low
   bandwidth, network topology, low power, low cost, and large number of
   devices [RFC4919][RFC7228].  For example, some IEEE 802.15.4 link
   layers[IEEE802154] have a frame size of 127 octets and IPv6 requires
   the layer below to support an MTU of 1280 bytes, therefore an
   appropriate fragmentation and reassembly adaptation layer must be
   provided at the layer below IPv6.  Also, the limited size of IEEE
   802.15.4 frame and low energy consumption requirements make the need
   for header compression.  The IETF 6LoPWAN (IPv6 over Low powerWPAN)
   working group published an adaptation layer for sending IPv6 packets
   over IEEE 802.15.4 [RFC4944], which includes a compression format for
   IPv6 datagrams over IEEE 802.15.4-based networks [RFC6282], and
   Neighbor Discovery Optimization for 6LoPWAN [RFC6775].

   As IoT (Internet of Things) services become more popular, IPv6 over
   various link layer technologies such as Bluetooth Low Energy
   (Bluetooth LE), ITU-T G.9959 (Z-Wave), Digital Enhanced Cordless
   Telecommunications - Ultra Low Energy (DECT-ULE), Master-Slave/Token
   Passing (MS/TP), Near Field Communication (NFC), and Power Line
   Communication (PLC) have been defined at IETF 6lo working
   group[IETF_6lo].  IPv6 stacks for constrained node networks use a
   variation of the 6LoWPAN stack applied to each particular link layer

   In the 6LoPWAN working group, the [RFC6568], "Design and Application
   Spaces for 6LoWPANs" was published and it describes potential
   application scenarios and use cases for low-power wireless personal
   area networks.  Hence, this 6lo applicability document aims to
   provide guidance to an audience who are new to IPv6-over-low-power
   networks concept and want to assess if variance of 6LoWPAN stack
   (6lo) can be applied to the constrained layer two (L2) network of
   their interest.  This 6lo applicability document puts together
   various design space dimensions such as deployment, network size,
   power source, connectivity, multi-hop communication, traffic pattern,
   security level, mobility, and QoS requirements etc.  In addition, it
   describes a few set of 6LoPWAN application scenarios and practical
   deployment as examples.

   This document provides the applicability and use cases of 6lo,
   considering the following aspects:

   o  6lo applicability and use cases MAY be uniquely different from
      those of 6LoWPAN defined for IEEE 802.15.4.

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   o  It SHOULD cover various IoT related wire/wireless link layer
      technologies providing practical information of such technologies.

   o  A general guideline on how the 6LoWPAN stack can be modified for a
      given L2 technology.

   o  Example use cases and practical deployment examples.

2.  Conventions and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  6lo Link layer technologies

3.1.  ITU-T G.9959

   The ITU-T G.9959 Recommendation [G.9959] targets low-power Personal
   Area Networks (PANs), and defines physical layer and link layer
   functionality.  Physical layers of 9.6 kbit/s, 40 kbit/s and 100
   kbit/s are supported.  G.9959 defines how a unique 32-bit HomeID
   network identifier is assigned by a network controller and how an
   8-bit NodeID host identifier is allocated to each node.  NodeIDs are
   unique within the network identified by the HomeID.  The G.9959
   HomeID represents an IPv6 subnet that is identified by one or more
   IPv6 prefixes [RFC7428].  The ITU-T G.9959 can be used for smart home

3.2.  Bluetooth LE

   Bluetooth LE was introduced in Bluetooth 4.0, enhanced in Bluetooth
   4.1, and developed even further in successive versions.  Bluetooth
   SIG has also published Internet Protocol Support Profile (IPSP).  The
   IPSP enables discovery of IP-enabled devices and establishment of
   link-layer connection for transporting IPv6 packets.  IPv6 over
   Bluetooth LE is dependent on both Bluetooth 4.1 and IPSP 1.0 or

   Many Devices such as mobile phones, notebooks, tablets and other
   handheld computing devices which support Bluetooth 4.0 or subsequent
   chipsets also support the low-energy variant of Bluetooth.  Bluetooth
   LE is also being included in many different types of accessories that
   collaborate with mobile devices such as phones, tablets and notebook
   computers.  An example of a use case for a Bluetooth LE accessory is
   a heart rate monitor that sends data via the mobile phone to a server
   on the Internet [RFC7668].  A typical usage of Bluetooth LE is
   smartphone-based interaction with constrained devices.  Bluetooth LE

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   was originally designed to enable star topology networks.  However,
   recent Bluetooth versions support the formation of extended
   topologies, and IPv6 support for mesh networks of Bluetooth LE
   devices is being developed [I-D.ietf-6lo-blemesh]

3.3.  DECT-ULE

   DECT ULE is a low power air interface technology that is designed to
   support both circuit switched services, such as voice communication,
   and packet mode data services at modest data rate.

   The DECT ULE protocol stack consists of the PHY layer operating at
   frequencies in the 1880 - 1920 MHz frequency band depending on the
   region and uses a symbol rate of 1.152 Mbps.  Radio bearers are
   allocated by use of FDMA/TDMA/TDD techniques.

   In its generic network topology, DECT is defined as a cellular
   network technology.  However, the most common configuration is a star
   network with a single Fixed Part (FP) defining the network with a
   number of Portable Parts (PP) attached.  The MAC layer supports
   traditional DECT as this is used for services like discovery,
   pairing, security features etc.  All these features have been reused
   from DECT.

   The DECT ULE device can switch to the ULE mode of operation,
   utilizing the new ULE MAC layer features.  The DECT ULE Data Link
   Control (DLC) provides multiplexing as well as segmentation and re-
   assembly for larger packets from layers above.  The DECT ULE layer
   also implements per-message authentication and encryption.  The DLC
   layer ensures packet integrity and preserves packet order, but
   delivery is based on best effort.

   The current DECT ULE MAC layer standard supports low bandwidth data
   broadcast.  However the usage of this broadcast service has not yet
   been standardized for higher layers [RFC8105].  DECT-ULE can be used
   for smart metering in a home.

3.4.  MS/TP

   Master-Slave/Token-Passing (MS/TP) is a Medium Access Control (MAC)
   protocol for the RS-485 [TIA-485-A] physical layer and is used
   primarily in building automation networks.

   An MS/TP device is typically based on a low-cost microcontroller with
   limited processing power and memory.  These constraints, together
   with low data rates and a small MAC address space, are similar to
   those faced in 6LoWPAN networks.  MS/TP differs significantly from
   6LoWPAN in at least three respects: a) MS/TP devices are typically

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   mains powered, b) all MS/TP devices on a segment can communicate
   directly so there are no hidden node or mesh routing issues, and c)
   the latest MS/TP specification provides support for large payloads,
   eliminating the need for fragmentation and reassembly below IPv6.

   MS/TP is designed to enable multidrop networks over shielded twisted
   pair wiring.  It can support network segments up to 1000 meters in
   length at a data rate of 115.2 kbit/s or segments up to 1200 meters
   in length at lower bit rates.  An MS/TP interface requires only a
   UART, an RS-485 [TIA-485-A] transceiver with a driver that can be
   disabled, and a 5 ms resolution timer.  The MS/TP MAC is typically
   implemented in software.

   Because of its superior "range" (~1 km) compared to many low power
   wireless data links, MS/TP may be suitable to connect remote devices
   (such as district heating controllers) to the nearest building
   control infrastructure over a single link [RFC8163].  MS/TP can be
   used for building automation networks.

3.5.  NFC

   NFC technology enables simple and safe two-way interactions between
   electronic devices, allowing consumers to perform contactless
   transactions, access digital content, and connect electronic devices
   with a single touch.  NFC complements many popular consumer level
   wireless technologies, by utilizing the key elements in existing
   standards for contactless card technology (ISO/IEC 14443 A&B and
   JIS-X 6319-4).  NFC can be compatible with existing contactless card
   infrastructure and it enables a consumer to utilize one device across
   different systems.

   Extending the capability of contactless card technology, NFC also
   enables devices to share information at a distance that is less than
   10 cm with a maximum communication speed of 424 kbps.  Users can
   share business cards, make transactions, access information from a
   smart poster or provide credentials for access control systems with a
   simple touch.

   NFC's bidirectional communication ability is ideal for establishing
   connections with other technologies by the simplicity of touch.  In
   addition to the easy connection and quick transactions, simple data
   sharing is also available [I-D.ietf-6lo-nfc].  NFC can be used for
   secure transfer in healthcare services.

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3.6.  PLC

   PLC is a data transmission technique that utilizes power conductors
   as medium.  Unlike other dedicated communication infrastructure,
   power conductors are widely available indoors and outdoors.
   Moreover, wired technologies are more susceptible to cause
   interference but are more reliable than their wireless counterparts.
   PLC is a data transmission technique that utilizes power conductors
   as medium[I-D.ietf-6lo-plc].

   The below table shows some available open standards defining PLC.

   | PLC Systems | Frequency Range |    Type    | Data Rate | Distance |
   |   IEEE1901  |     <100MHz     | Broadband  |  200Mbps  |  1000m   |
   |             |                 |            |           |          |
   |  IEEE1901.1 |      <15MHz     |  PLC-IoT   |   10Mbps  |  2000m   |
   |             |                 |            |           |          |
   |  IEEE1901.2 |     <500kHz     | Narrowband |  200Kbps  |  3000m   |

               Table 1: Some Available Open Standards in PLC

   [IEEE1901] defines a broadband variant of PLC but is effective within
   short range.  This standard addresses the requirements of
   applications with high data rate such as: Internet, HDTV, Audio,
   Gaming etc.  Broadband operates on OFDM (Orthogonal Frequency
   Division Multiplexing) modulation.

   [IEEE1901.2] defines a narrowband variant of PLC with less data rate
   but significantly higher transmission range that could be used in an
   indoor or even an outdoor environment.  It is applicable to typical
   IoT applications such as: Building Automation, Renewable Energy,
   Advanced Metering, Street Lighting, Electric Vehicle, Smart Grid etc.
   Moreover, IEEE 1901.2 standard is based on the 802.15.4 MAC sub-layer
   and fully endorses the security scheme defined in 802.15.4 [RFC8036].
   A typical use case of PLC is smart grid.

3.7.  Comparison between 6lo Link layer technologies

   In above clauses, various 6lo Link layer technologies and a possible
   candidate are described.  The following table shows that dominant
   paramters of each use case corresponding to the 6lo link layer

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|              |  Z-Wave |   BLE   | DECT-ULE|  MS/TP  |   NFC   |   PLC   |
|              |  Home   | Interact|         | Building| Health- |         |
|     Usage    |  Auto-  | w/ Smart|  Meter  |  Auto-  |  care   |  Smart  |
|              | mation  |  Phone  | Reading | mation  | Service |  Grid   |
|   Topology   | L2-mesh |  Star   |  Star   |  MS/TP  |  P2P    |  Star   |
|      &       |    or   |    &    |         |         |         |  Tree   |
|    Subnet    | L3-mesh |  Mesh   | No mesh | No mesh | L2-mesh |  Mesh   |
|              |         |         |         |         |         |         |
|   Mobility   |   No    |   Low   |   No    |   No    | Moderate|   No    |
|  Requirement |         |         |         |         |         |         |
|              |  High + |         |  High + |  High + |         |  High + |
|   Security   | Privacy |Partially| Privacy | Authen. |  High   | Encrypt.|
|  Requirement | required|         | required| required|         | required|
|              |         |         |         |         |         |         |
|   Buffering  |   Low   |   Low   |   Low   |   Low   |   Low   |   Low   |
|  Requirement |         |         |         |         |         |         |
|   Latency,   |         |         |         |         |         |         |
|     QoS      |   High  |   Low   |   Low   |   High  |   High  |   Low   |
|  Requirement |         |         |         |         |         |         |
|              |         |         |         |         |         |         |
|     Data     | Infrequ-| Infrequ-| Infrequ-| Frequent|  Small  | Infrequ-|
|     Rate     |   ent   |   ent   |   ent   |         |         |   ent   |
|     RFC #    |         |         |         |         |  draft- |  draft- |
|      or      | RFC7428 | RFC7668 | RFC8105 | RFC8163 | ietf-6lo| ietf-6lo|
|     Draft    |         |         |         |         |   -nfc  |   -plc  |

            Table 2: Comparison between 6lo Link layer technologies

4.  6lo Deployment Scenarios

4.1.  G3-PLC usage of 6lo in network layer

   G3-PLC [G3-PLC] is a narrow-band PLC technology that is based on
   ITU-T G.9903 Recommendation [G.9903].  G3-PLC supports multi-hop mesh
   network, and facilitates highly-reliable, long-range communication.
   With the abilities to support IPv6 and to cross transformers, G3-PLC
   is regarded as one of the next-generation NB-PLC technologies.

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   G3-PLC has got massive deployments over several countries, e.g.
   Japan and France.

   The main application domains targeted by G3-PLC are smart grid and
   smart cities.  This includes, but is not limited to the following

   o  Smart Metering

   o  Vehicle-to-Grid Communication

   o  Demand Response (DR)

   o  Distribution Automation

   o  Home/Building Energy Management Systems

   o  Smart Street Lighting

   o  Advanced Metering Infrastructure (AMI) backbone network

   o  Wind/Solar Farm Monitoring

   In the G3-PLC specification, the 6lo adaption layer utilizes the
   6LoWPAN functions (e.g. header compression, fragmentation and
   reassembly).  However, due to the different characteristics of the
   PLC media, the 6LoWPAN adaptation layer cannot perfectly fulfill the
   requirements[I-D.ietf-6lo-plc].  The ESC dispatch type is used in the
   G3-PLC to provide native mesh routing and bootstrapping

4.2.  Netricity usage of 6lo in network layer

   The Netricity program in HomePlug Powerline Alliance [NETRICITY]
   promotes the adoption of products built on the IEEE 1901.2 Low-
   Frequency Narrow-Band PLC standard, which provides for urban and long
   distance communications and propagation through transformers of the
   distribution network using frequencies below 500 kHz.  The technology
   also addresses requirements that assure communication privacy and
   secure networks.

   The main application domains targeted by Netricity are smart grid and
   smart cities.  This includes, but is not limited to the following

   o  Utility grid modernization

   o  Distribution automation

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   o  Meter-to-Grid connectivity

   o  Micro-grids

   o  Grid sensor communications

   o  Load control

   o  Demand response

   o  Net metering

   o  Street Lighting control

   o  Photovoltaic panel monitoring

   Netricity system architecture is based on the PHY and MAC layers of
   IEEE 1901.2 PLC standard.  Regarding the 6lo adaptation layer and
   IPv6 network layer, Netricity utilizes IPv6 protocol suite including
   6lo/6LoWPAN header compression, DHCPv6 for IP address management, RPL
   routing protocol, ICMPv6, and unicast/multicast forwarding.  Note
   that the layer 3 routing in Netricity uses RPL in non-storing mode
   with the MRHOF objective function based on the own defined Estimated
   Transmission Time (ETT) metric.

5.  Guidelines for adopting IPv6 stack (6lo/6LoWPAN)

   The following guideline targets new candidate constrained L2
   technologies that may be considered for running modified 6LoWPAN
   stack on top.  The modification of 6LoWPAN stack should be based on
   the following:

   o  Addressing Model: Addressing model determines whether the device
      is capable of forming IPv6 Link-local and global addresses and
      what is the best way to derive the IPv6 addresses for the
      constrained L2 devices.  Whether the device is capable of forming
      IPv6 Link-local and global addresses, L2-address-derived IPv6
      addresses are specified in [RFC4944], but there exist implications
      for privacy.  For global usage, a unique IPv6 address must be
      derived using an assigned prefix and a unique interface ID.
      [RFC8065] provides such guidelines.  For MAC derived IPv6 address,
      please refer to [RFC8163] for IPv6 address mapping examples.
      Broadcast and multicast support are dependent on the L2 networks.
      Most low-power L2 implementations map multicast to broadcast
      networks.  So care must be taken in the design when to use
      broadcast and try to stick to unicast messaging whenever possible.

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   o  MTU Considerations: The deployment SHOULD consider their need for
      maximum transmission unit (MTU) of a packet over the link layer
      and should consider if fragmentation and reassembly of packets are
      needed at the 6LoWPAN layer.  For example, if the link layer
      supports fragmentation and reassembly of packets, then 6LoWPAN
      layer may skip supporting fragmentation/reassembly.  In fact, for
      most efficiency, choosing a low-power link layer that can carry
      unfragmented application packets would be optimum for packet
      transmission if the deployment can afford it.  Please refer to 6lo
      RFCs [RFC7668], [RFC8163], [RFC8105] for example guidance.

   o  Mesh or L3-Routing: 6LoWPAN specifications do provide mechanisms
      to support for mesh routing at L2.  [RFC6550] defines layer three
      (L3) routing for low power lossy networks using directed graphs.
      6LoWPAN is routing protocol agnostic and other L2 or L3 routing
      protocols can be run using a 6LoWPAN stack.

   o  Address Assignment: 6LoWPAN developed a new version of IPv6
      Neighbor Discovery[RFC4861][RFC4862] that relies on a proactive
      registration to avoid the use of multicast. 6LoWPAN Neighbor
      Discovery[RFC6775][RFC8505] inherits from IPv6 Neighbor Discovery
      for mechanisms such as Stateless Address Autoconfiguration(SLAAC)
      and Neighbor Unreachability Detection(NUD), but uses a unicast
      method for Duplicate Address Detection(DAD), and avoids multicast
      lookups from all nodes by using non-onlink prefixes.  A 6LoWPAN
      Node is also expected to be an IPv6 host per[RFC8200] which means
      it should ignore consumed routing headers and Hop-by-Hop options;
      when operating in a RPL network[RFC6550], it is also beneficial to
      support IP-in-IP encapsulation [I-D.ietf-roll-useofrplinfo].  The
      6LoWPWAN Node should also support [RFC8505] and use it as the
      default Neighbor Discovery method.  It is the responsibility of
      the deployment to ensure unique global IPv6 addresses for the
      Internet connectivity.  For local-only connectivity IPv6 ULA may
      be used.  [RFC6775] specifies the 6LoWPAN border router(6LBR)
      which is responsible for prefix assignment to the 6lo/6LoWPAN
      network. 6LBR can be connected to the Internet or Enterprise
      network via its one of the interfaces.  Please refer to [RFC7668]
      and [RFC8105] for examples of address assignment considerations.
      In addition, privacy considerations [RFC8065] must be consulted
      for applicability.  In certain scenarios, the deployment may not
      support autoconfiguration of IPv6 addressing due to regulatory and
      business reasons and may choose to offer a separate address
      assignment service.

   o  Header Compression: IPv6 header compression [RFC6282] is a vital
      part of IPv6 over low power communication.  Examples of header
      compression for different link-layers specifications are found in

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      [RFC7668], [RFC8163], [RFC8105].  A generic header compression
      technique is specified in [RFC7400].

   o  Security and Encryption: Though 6LoWPAN basic specifications do
      not address security at the network layer, the assumption is that
      L2 security must be present.  In addition, application level
      security is highly desirable.  The working groups [IETF_ace] and
      [IETF_core] should be consulted for application and transport
      level security. 6lo working group is working on address
      authentication [I-D.ietf-6lo-ap-nd] and secure bootstrapping is
      also being discussed at IETF.  However, there may be different
      levels of security available in a deployment through other
      standards such as hardware level security or certificates for
      initial booting process.  Encryption is important if the
      implementation can afford it.

   o  Additional processing: [RFC8066] defines guidelines for ESC
      dispatch octets use in the 6LoWPAN header.  An implementation may
      take advantage of ESC header to offer a deployment specific
      processing of 6LoWPAN packets.

6.  6lo Use Case Examples

   As IPv6 stacks for constrained node networks use a variation of the
   6LoWPAN stack applied to each particular link layer technology,
   various 6lo use cases can be provided.  In this clause, various 6lo
   use cases which are based on each particular link layer technology
   are described.

6.1.  Use case of ITU-T G.9959: Smart Home

   Z-Wave is one of the main technologies that may be used to enable
   smart home applications.  Born as a proprietary technology, Z-Wave
   was specifically designed for this particular use case.  Recently,
   the Z-Wave radio interface (physical and MAC layers) has been
   standardized as the ITU-T G.9959 specification.

   Example: Use of ITU-T G.9959 for Home Automation

   Variety of home devices (e.g. light dimmers/switches, plugs,
   thermostats, blinds/curtains and remote controls) are augmented with
   ITU-T G.9959 interfaces.  A user may turn on/off or may control home
   appliances by pressing a wall switch or by pressing a button in a
   remote control.  Scenes may be programmed, so that after a given
   event, the home devices adopt a specific configuration.  Sensors may
   also periodically send measurements of several parameters (e.g. gas
   presence, light, temperature, humidity, etc.) which are collected at

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   a sink device, or may generate commands for actuators (e.g. a smoke
   sensor may send an alarm message to a safety system).

   The devices involved in the described scenario are nodes of a network
   that follows the mesh topology, which is suitable for path diversity
   to face indoor multipath propagation issues.  The multihop paradigm
   allows end-to-end connectivity when direct range communication is not
   possible.  Security support is required, specially for safety-related
   communication.  When a user interaction (e.g. a button press)
   triggers a message that encapsulates a command, if the message is
   lost, the user may have to perform further interactions to achieve
   the desired effect (e.g. a light is turned off).  A reaction to a
   user interaction will be perceived by the user as immediate as long
   as the reaction takes place within 0.5 seconds [RFC5826].

6.2.  Use case of Bluetooth LE: Smartphone-based Interaction

   The key feature behind the current high Bluetooth LE momentum is its
   support in a large majority of smartphones in the market.  Bluetooth
   LE can be used to allow the interaction between the smartphone and
   surrounding sensors or actuators.  Furthermore, Bluetooth LE is also
   the main radio interface currently available in wearables.  Since a
   smartphone typically has several radio interfaces that provide
   Internet access, such as Wi-Fi or 4G, the smartphone can act as a
   gateway for nearby devices such as sensors, actuators or wearables.
   Bluetooth LE may be used in several domains, including healthcare,
   sports/wellness and home automation.

   Example: Use of Bluetooth LE-based Body Area Network for fitness

   A person wears a smartwatch for fitness purposes.  The smartwatch has
   several sensors (e.g. heart rate, accelerometer, gyrometer, GPS,
   temperature, etc.), a display, and a Bluetooth LE radio interface.
   The smartwatch can show fitness-related statistics on its display.
   However, when a paired smartphone is in the range of the smartwatch,
   the latter can report almost real-time measurements of its sensors to
   the smartphone, which can forward the data to a cloud service on the
   Internet.  In addition, the smartwatch can receive notifications
   (e.g. alarm signals) from the cloud service via the smartphone.  On
   the other hand, the smartphone may locally generate messages for the
   smartwatch, such as e-mail reception or calendar notifications.

   The functionality supported by the smartwatch may be complemented by
   other devices such as other on-body sensors, wireless headsets or
   head-mounted displays.  All such devices may connect to the
   smartphone creating a star topology network whereby the smartphone is
   the central component.  Support for extended network topologies (e.g.
   mesh networks) is being developed as of the writing.

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6.3.  Use case of DECT-ULE: Smart Home

   DECT is a technology widely used for wireless telephone
   communications in residential scenarios.  Since DECT-ULE is a low-
   power variant of DECT, DECT-ULE can be used to connect constrained
   devices such as sensors and actuators to a Fixed Part, a device that
   typically acts as a base station for wireless telephones.  Therefore,
   DECT-ULE is specially suitable for the connected home space in
   application areas such as home automation, smart metering, safety,
   healthcare, etc.

   Example: Use of DECT-ULE for Smart Metering

   The smart electricity meter of a home is equipped with a DECT-ULE
   transceiver.  This device is in the coverage range of the Fixed Part
   of the home.  The Fixed Part can act as a router connected to the
   Internet.  This way, the smart meter can transmit electricity
   consumption readings through the DECT-ULE link with the Fixed Part,
   and the latter can forward such readings to the utility company using
   Wide Area Network (WAN) links.  The meter can also receive queries
   from the utility company or from an advanced energy control system
   controlled by the user, which may also be connected to the Fixed Part
   via DECT-ULE.

6.4.  Use case of MS/TP: Building Automation Networks

   The primary use case for IPv6 over MS/TP (6LoBAC) is in building
   automation networks.  [BACnet] is the open international standard
   protocol for building automation, and MS/TP is defined in [BACnet]
   Clause 9.  MS/TP was designed to be a low cost multi-drop field bus
   to inter-connect the most numerous elements (sensors and actuators)
   of a building automation network to their controllers.  A key aspect
   of 6LoBAC is that it is designed to co-exist with BACnet MS/TP on the
   same link, easing the ultimate transition of some BACnet networks to
   native end-to-end IPv6 transport protocols.  New applications for
   6LoBAC may be found in other domains where low cost, long distance,
   and low latency are required.

   Example: Use of 6LoBAC in Building Automation Networks

   The majority of installations for MS/TP are for "terminal" or
   "unitary" controllers, i.e. single zone or room controllers that may
   connect to HVAC or other controls such as lighting or blinds.  The
   economics of daisy-chaining a single twisted-pair between multiple
   devices is often preferred over home-run Cat-5 style wiring.

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   A multi-zone controller might be implemented as an IP router between
   a traditional Ethernet link and several 6LoBAC links, fanning out to
   multiple terminal controllers.

   The superior distance capabilities of MS/TP (~1 km) compared to other
   6lo media may suggest its use in applications to connect remote
   devices to the nearest building infrastructure. for example, remote
   pumping or measuring stations with moderate bandwidth requirements
   can benefit from the low cost and robust capabilities of MS/TP over
   other wired technologies such as DSL, and without the line-of-site
   restrictions or hop-by-hop latency of many low cost wireless

6.5.  Use case of NFC: Alternative Secure Transfer

   According to applications, various secured data can be handled and
   transferred.  Depending on security level of the data, methods for
   transfer can be alternatively selected.

   Example: Use of NFC for Secure Transfer in Healthcare Services with

   A senior citizen who lives alone wears one to several wearable 6lo
   devices to measure heartbeat, pulse rate, etc.  The 6lo devices are
   densely installed at home for movement detection.  An LoWPAN Border
   Router (LBR) at home will send the sensed information to a connected
   healthcare center.  Portable base stations with LCDs may be used to
   check the data at home, as well.  Data is gathered in both periodic
   and event-driven fashion.  In this application, event-driven data can
   be very time-critical.  In addition, privacy also becomes a serious
   issue in this case, as the sensed data is very personal.

   While the senior citizen is provided audio and video healthcare
   services by a tele-assistance based on LTE connections, the senior
   citizen can alternatively use NFC connections to transfer the
   personal sensed data to the tele-assistance.  At this moment, hidden
   hackers can overhear the data based on the LTE connection, but they
   cannot gather the personal data over the NFC connection.

6.6.  Use case of PLC: Smart Grid

   Smart grid concept is based on numerous operational and energy
   measuring sub-systems of an electric grid.  It comprises of multiple
   administrative levels/segments to provide connectivity among these
   numerous components.  Last mile connectivity is established over LV
   segment, whereas connectivity over electricity distribution takes
   place in HV segment.

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   Although other wired and wireless technologies are also used in Smart
   Grid (Advance Metering Infrastructure - AMI, Demand Response - DR,
   Home Energy Management System - HEMS, Wide Area Situational Awareness
   - WASA etc), PLC enjoys the advantage of existing (power conductor)
   medium and better reliable data communication.  PLC is a promising
   wired communication technology in that the electrical power lines are
   already there and the deployment cost can be comparable to wireless
   technologies.  The 6lo related scenarios lie in the low voltage PLC
   networks with most applications in the area of Advanced Metering
   Infrastructure, Vehicle-to-Grid communications, in-home energy
   management and smart street lighting.

   Example: Use of PLC for Advanced Metering Infrastructure

   Household electricity meters transmit time-based data of electric
   power consumption through PLC.  Data concentrators receive all the
   meter data in their corresponding living districts and send them to
   the Meter Data Management System (MDMS) through WAN network (e.g.
   Medium-Voltage PLC, Ethernet or GPRS) for storage and analysis.  Two-
   way communications are enabled which means smart meters can do
   actions like notification of electricity charges according to the
   commands from the utility company.

   With the existing power line infrastructure as communication medium,
   cost on building up the PLC network is naturally saved, and more
   importantly, labor operational costs can be minimized from a long-
   term perspective.  Furthermore, this AMI application speeds up
   electricity charge, reduces losses by restraining power theft and
   helps to manage the health of the grid based on line loss analysis.

   Example: Use of PLC (IEEE1901.1) for WASA in Smart Grid

   Many sub-systems of Smart Grid require low data rate and narrowband
   variant (IEEE1901.2) of PLC fulfils such requirements.  Recently,
   more complex scenarios are emerging that require higher data rates.

   WASA sub-system is an appropriate example that collects large amount
   of information about the current state of the grid over wide area
   from electric substations as well as power transmission lines.  The
   collected feedback is used for monitoring, controlling and protecting
   all the sub-systems.

7.  IANA Considerations

   There are no IANA considerations related to this document.

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8.  Security Considerations

   Security considerations are not directly applicable to this document.
   The use cases will use the security requirements described in the
   protocol specifications.

9.  Acknowledgements

   Carles Gomez has been funded in part by the Spanish Government
   through the Jose Castillejo CAS15/00336 grant, and through the
   TEC2016-79988-P grant.  His contribution to this work has been
   carried out in part during his stay as a visiting scholar at the
   Computer Laboratory of the University of Cambridge.

   Thomas Watteyne, Pascal Thubert, Xavier Vilajosana, Daniel Migault,
   and Jianqiang HOU have provided valuable feedback for this draft.

   Das Subir and Michel Veillette have provided valuable information of
   jupiterMesh and Paul Duffy has provided valuable information of Wi-
   SUN for this draft.  Also, Jianqiang Hou has provided valuable
   information of G3-PLC and Netricity for this draft.  Kerry Lynn and
   Dave Robin have provided valuable information of MS/TP and practical
   use case of MS/TP for this draft.

   Deoknyong Ko has provided relevant text of LTE-MTC and he shared his
   experience to deploy IPv6 and 6lo technologies over LTE MTC in SK

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC4919]  Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
              over Low-Power Wireless Personal Area Networks (6LoWPANs):
              Overview, Assumptions, Problem Statement, and Goals",
              RFC 4919, DOI 10.17487/RFC4919, August 2007,

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,

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   [RFC5826]  Brandt, A., Buron, J., and G. Porcu, "Home Automation
              Routing Requirements in Low-Power and Lossy Networks",
              RFC 5826, DOI 10.17487/RFC5826, April 2010,

   [RFC6282]  Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              DOI 10.17487/RFC6282, September 2011,

   [RFC6550]  Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
              Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
              JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
              Low-Power and Lossy Networks", RFC 6550,
              DOI 10.17487/RFC6550, March 2012,

   [RFC6568]  Kim, E., Kaspar, D., and JP. Vasseur, "Design and
              Application Spaces for IPv6 over Low-Power Wireless
              Personal Area Networks (6LoWPANs)", RFC 6568,
              DOI 10.17487/RFC6568, April 2012,

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,

   [RFC7400]  Bormann, C., "6LoWPAN-GHC: Generic Header Compression for
              IPv6 over Low-Power Wireless Personal Area Networks
              (6LoWPANs)", RFC 7400, DOI 10.17487/RFC7400, November
              2014, <https://www.rfc-editor.org/info/rfc7400>.

   [RFC7428]  Brandt, A. and J. Buron, "Transmission of IPv6 Packets
              over ITU-T G.9959 Networks", RFC 7428,
              DOI 10.17487/RFC7428, February 2015,

   [RFC7668]  Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
              Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low
              Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015,

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   [RFC8036]  Cam-Winget, N., Ed., Hui, J., and D. Popa, "Applicability
              Statement for the Routing Protocol for Low-Power and Lossy
              Networks (RPL) in Advanced Metering Infrastructure (AMI)
              Networks", RFC 8036, DOI 10.17487/RFC8036, January 2017,

   [RFC8065]  Thaler, D., "Privacy Considerations for IPv6 Adaptation-
              Layer Mechanisms", RFC 8065, DOI 10.17487/RFC8065,
              February 2017, <https://www.rfc-editor.org/info/rfc8065>.

   [RFC8066]  Chakrabarti, S., Montenegro, G., Droms, R., and J.
              Woodyatt, "IPv6 over Low-Power Wireless Personal Area
              Network (6LoWPAN) ESC Dispatch Code Points and
              Guidelines", RFC 8066, DOI 10.17487/RFC8066, February
              2017, <https://www.rfc-editor.org/info/rfc8066>.

   [RFC8105]  Mariager, P., Petersen, J., Ed., Shelby, Z., Van de Logt,
              M., and D. Barthel, "Transmission of IPv6 Packets over
              Digital Enhanced Cordless Telecommunications (DECT) Ultra
              Low Energy (ULE)", RFC 8105, DOI 10.17487/RFC8105, May
              2017, <https://www.rfc-editor.org/info/rfc8105>.

   [RFC8163]  Lynn, K., Ed., Martocci, J., Neilson, C., and S.
              Donaldson, "Transmission of IPv6 over Master-Slave/Token-
              Passing (MS/TP) Networks", RFC 8163, DOI 10.17487/RFC8163,
              May 2017, <https://www.rfc-editor.org/info/rfc8163>.

   [RFC8352]  Gomez, C., Kovatsch, M., Tian, H., and Z. Cao, Ed.,
              "Energy-Efficient Features of Internet of Things
              Protocols", RFC 8352, DOI 10.17487/RFC8352, April 2018,

   [RFC8505]  Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
              Perkins, "Registration Extensions for IPv6 over Low-Power
              Wireless Personal Area Network (6LoWPAN) Neighbor
              Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,

10.2.  Informative References

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,

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   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,

              Choi, Y., Hong, Y., Youn, J., Kim, D., and J. Choi,
              "Transmission of IPv6 Packets over Near Field
              Communication", draft-ietf-6lo-nfc-15 (work in progress),
              July 2019.

              Gomez, C., Darroudi, S., Savolainen, T., and M. Spoerk,
              "IPv6 Mesh over BLUETOOTH(R) Low Energy using IPSP",
              draft-ietf-6lo-blemesh-06 (work in progress), September

              Hou, J., Liu, B., Hong, Y., Tang, X., and C. Perkins,
              "Transmission of IPv6 Packets over PLC Networks", draft-
              ietf-6lo-plc-00 (work in progress), February 2019.

              Robles, I., Richardson, M., and P. Thubert, "Using RPL
              Option Type, Routing Header for Source Routes and IPv6-in-
              IPv6 encapsulation in the RPL Data Plane", draft-ietf-
              roll-useofrplinfo-31 (work in progress), August 2019.

              Thubert, P., Sarikaya, B., Sethi, M., and R. Struik,
              "Address Protected Neighbor Discovery for Low-power and
              Lossy Networks", draft-ietf-6lo-ap-nd-12 (work in
              progress), April 2019.

              "IETF IPv6 over Networks of Resource-constrained Nodes
              (6lo) working group",

              "IETF Authentication and Authorization for Constrained
              Environments (ace) working group",

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              "IETF Constrained RESTful Environments (core) working
              group", <https://datatracker.ietf.org/wg/core/charter/>.

              IEEE standard for Information Technology, "IEEE Std.
              802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
              and Physical Layer (PHY) Specifications for Low-Rate
              Wireless Personal Area Networks".

              "TIA, "Electrical Characteristics of Generators and
              Receivers for Use in Balanced Digital Multipoint Systems",
              TIA-485-A (Revision of TIA-485)", March 2003,

   [G3-PLC]   "G3-PLC Alliance", <http://www.g3-plc.com/home/>.

              "Netricity program in HomePlug Powerline Alliance",

   [G.9959]   "International Telecommunication Union, "Short range
              narrow-band digital radiocommunication transceivers - PHY
              and MAC layer specifications", ITU-T Recommendation",
              January 2015.

   [G.9903]   "International Telecommunication Union, "Narrowband
              orthogonal frequency division multiplexing power line
              communication transceivers for G3-PLC networks", ITU-T
              Recommendation", August 2017.

              "IEEE Standard, IEEE Std. 1901-2010 - IEEE Standard for
              Broadband over Power Line Networks: Medium Access Control
              and Physical Layer Specifications", 2010,

              "IEEE Standard, IEEE Std. 1901.2-2013 - IEEE Standard for
              Low-Frequency (less than 500 kHz) Narrowband Power Line
              Communications for Smart Grid Applications", 2013,

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   [BACnet]   "ASHRAE, "BACnet-A Data Communication Protocol for
              Building Automation and Control Networks", ANSI/ASHRAE
              Standard 135-2016", January 2016,

Appendix A.  Design Space Dimensions for 6lo Deployment

   The [RFC6568] lists the dimensions used to describe the design space
   of wireless sensor networks in the context of the 6LoWPAN working
   group.  The design space is already limited by the unique
   characteristics of a LoWPAN (e.g. low power, short range, low bit
   rate).  In [RFC6568], the following design space dimensions are
   described: Deployment, Network size, Power source, Connectivity,
   Multi-hop communication, Traffic pattern, Mobility, Quality of
   Service (QoS).  However, in this document, the following design space
   dimensions are considered:

   o  Deployment/Bootstrapping: 6lo nodes can be connected randomly, or
      in an organized manner.  The bootstrapping has different
      characteristics for each link layer technology.

   o  Topology: Topology of 6lo networks may inherently follow the
      characteristics of each link layer technology.  Point-to-point,
      star, tree or mesh topologies can be configured, depending on the
      link layer technology considered.

   o  L2-Mesh or L3-Mesh: L2-mesh and L3-mesh may inherently follow the
      characteristics of each link layer technology.  Some link layer
      technologies may support L2-mesh and some may not support.

   o  Multi-link subnet, single subnet: The selection of multi-link
      subnet and single subnet depends on connectivity and the number of
      6lo nodes.

   o  Data rate: Typically, the link layer technologies of 6lo have low
      rate of data transmission.  But, by adjusting the MTU, it can
      deliver higher upper layer data rate.

   o  Buffering requirements: Some 6lo use case may require more data
      rate than the link layer technology support.  In this case, a
      buffering mechanism to manage the data is required.

   o  Security and Privacy Requirements: Some 6lo use case can involve
      transferring some important and personal data between 6lo nodes.
      In this case, high-level security support is required.

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   o  Mobility across 6lo networks and subnets: The movement of 6lo
      nodes depends on the 6lo use case.  If the 6lo nodes can move or
      moved around, a mobility management mechanism is required.

   o  Time synchronization requirements: The requirement of time
      synchronization of the upper layer service is dependent on the 6lo
      use case.  For some 6lo use case related to health service, the
      measured data must be recorded with exact time and must be
      transferred with time synchronization.

   o  Reliability and QoS: Some 6lo use case requires high reliability,
      for example real-time service or health-related services.

   o  Traffic patterns: 6lo use cases may involve various traffic
      patterns.  For example, some 6lo use case may require short data
      length and random transmission.  Some 6lo use case may require
      continuous data and periodic data transmission.

   o  Security Bootstrapping: Without the external operations, 6lo nodes
      must have the security bootstrapping mechanism.

   o  Power use strategy: to enable certain use cases, there may be
      requirements on the class of energy availability and the strategy
      followed for using power for communication [RFC7228].  Each link
      layer technology defines a particular power use strategy which may
      be tuned [RFC8352].  Readers are expected to be familiar with
      [RFC7228] terminology.

   o  Update firmware requirements: Most 6lo use cases will need a
      mechanism for updating firmware.  In these cases support for over
      the air updates are required, probably in a broadcast mode when
      bandwith is low and the number of identical devices is high.

   o  Wired vs. Wireless: Plenty of 6lo link layer technologies are
      wireless, except MS/TP and PLC.  The selection of wired or
      wireless link layer technology is mainly dependent on the
      requirement of 6lo use cases and the characteristics of wired/
      wireless technologies.  For example, some 6lo use cases may
      require easy and quick deployment, whereas others may need a
      continuous source of power.

Authors' Addresses

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   Yong-Geun Hong
   161 Gajeong-Dong Yuseung-Gu
   Daejeon  305-700

   Phone: +82 42 860 6557
   Email: yghong@etri.re.kr

   Carles Gomez
   Universitat Politecnica de Catalunya/Fundacio i2cat
   C/Esteve Terradas, 7
   Castelldefels  08860

   Email: carlesgo@entel.upc.edu

   Younghwan Choi
   218 Gajeongno, Yuseong
   Daejeon  305-700

   Phone: +82 42 860 1429
   Email: yhc@etri.re.kr

   Abdur Rashid Sangi
   Huaiyin Institute of Technology
   No.89 North Beijing Road, Qinghe District
   Huaian  223001
   P.R. China

   Email: sangi_bahrian@yahoo.com

   Take Aanstoot
   Modio AB
   S:t Larsgatan 15, 582 24

   Email: take@modio.se

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   Samita Chakrabarti
   San Jose, CA

   Email: samitac.ietf@gmail.com

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