Internet Engineering Task Force (IETF) Y-G. Hong

Internet Engineering Task Force (IETF) Y-G. Hong
Request for Comments: 9453 Daejeon University
Category: Informational C. Gomez
ISSN: 2070-1721 UPC
Y. Choi
ETRI
A. Sangi
Wenzhou-Kean University
S. Chakrabarti
Verizon
September 2023

Applicability and Use Cases for IPv6 over Networks of Resource-
constrained Nodes (6lo)

Abstract

This document describes the applicability of IPv6 over constrained-
node networks (6lo) and provides practical deployment examples. In
addition to IEEE Std 802.15.4, various link-layer technologies are
used as examples, such as ITU-T G.9959 (Z-Wave), Bluetooth Low Energy
(Bluetooth LE), Digital Enhanced Cordless Telecommunications - Ultra
Low Energy (DECT-ULE), Master-Slave/Token Passing (MS/TP), Near Field
Communication (NFC), and Power Line Communication (PLC). This
document targets an audience who would like to understand and
evaluate running end-to-end IPv6 over the constrained-node networks
for local or Internet connectivity.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9453.

Copyright Notice

Copyright (c) 2023 IETF Trust and the persons identified as the
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Table of Contents

1. Introduction
2. 6lo Link-Layer Technologies
2.1. ITU-T G.9959
2.2. Bluetooth LE
2.3. DECT-ULE
2.4. MS/TP
2.5. NFC
2.6. PLC
2.7. Comparison between 6lo Link-Layer Technologies
3. Guidelines for Adopting an IPv6 Stack (6lo)
4. 6lo Deployment Examples
4.1. Wi-SUN Usage of 6lo in Network Layer
4.2. Thread Usage of 6lo in the Network Layer
4.3. G3-PLC Usage of 6lo in Network Layer
4.4. Netricity Usage of 6lo in the Network Layer
5. 6lo Use-Case Examples
5.1. Use Case of ITU-T G.9959: Smart Home
5.2. Use Case of Bluetooth LE: Smartphone-Based Interaction
5.3. Use Case of DECT-ULE: Smart Home
5.4. Use Case of MS/TP: Building Automation Networks
5.5. Use Case of NFC: Alternative Secure Transfer
5.6. Use Case of PLC: Smart Grid
6. IANA Considerations
7. Security Considerations
8. References
8.1. Normative References
8.2. Informative References
Appendix A. Design Space Dimensions for 6lo Deployment
Acknowledgements
Authors' Addresses

1. Introduction

Running IPv6 on constrained-node networks presents challenges due to
the characteristics of these networks, such as small packet size, low
power, low bandwidth, and large number of devices, among others
[RFC4919] [RFC7228]. For example, many IEEE Std 802.15.4 variants
[IEEE-802.15.4] exhibit a frame size of 127 octets, whereas IPv6
requires its underlying layer to support an MTU of 1280 bytes.
Furthermore, those IEEE Std 802.15.4 variants do not offer
fragmentation and reassembly functionality. (It is noted that IEEE
Std 802.15.9-2021 provides a multiplexing and fragmentation layer for
the IEEE Std 802.15.4 [IEEE-802.15.9].) Therefore, an appropriate
adaptation layer supporting fragmentation and reassembly must be
provided below IPv6. Also, the limited IEEE Std 802.15.4 frame size
and low energy consumption requirements motivate the need for packet
header compression. The IETF IPv6 over Low-Power Wireless Personal
Area Network (6LoWPAN) Working Group published a suite of
specifications that provides an adaptation layer to support IPv6 over
IEEE Std 802.15.4 comprising the following functionalities:

* fragmentation and reassembly, address autoconfiguration, and a
frame format [RFC4944]

* IPv6 (and UDP) header compression [RFC6282]

* Neighbor Discovery Optimization for 6LoWPAN [RFC6775] [RFC8505]

As Internet of Things (IoT) services become more popular, the IETF
has defined adaptation layer functionality to support IPv6 over
various link-layer technologies other than IEEE Std 802.15.4, 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). The 6lo adaptation layers use a
variation of the 6LoWPAN stack applied to each particular link-layer
technology.

The 6LoWPAN Working Group produced the document entitled "Design and
Application Spaces for IPv6 over Low-Power Wireless Personal Area
Networks (6LoWPANs)" [RFC6568], which describes potential application
scenarios and use cases for LoWPANs. The present document aims to
provide guidance to an audience that is new to the IPv6 over
constrained-node networks (6lo) concept and want to assess its
application to the constrained-node network of their interest. This
6lo applicability document describes a few sets of practical 6lo
deployment scenarios and use-case examples. In addition, it
considers various network design space dimensions, such as
Deployment, Network Size, Power Source, Connectivity, Multi-Hop
Communication, Traffic pattern, Mobility, and QoS requirements (see
Appendix A).

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

* Various IoT-related wired or wireless link-layer technologies
providing practical information about such technologies.

* General guidelines on how the 6LoWPAN stack can be modified for a
given L2 technology.

* Various 6lo use cases and practical deployment examples.

Note that the use of "master" and "slave" have been retained in this
document to align with use within the industry (e.g., [TIA-485-A] and
[BACnet]).

2. 6lo Link-Layer Technologies

2.1. ITU-T G.9959

The ITU-T G.9959 Recommendation [G.9959] targets LoWPANs 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]. ITU-T G.9959 can be used for smart home applications, and
the transmission range is 100 meters per hop.

2.2. Bluetooth LE

Bluetooth LE was introduced in Bluetooth 4.0, enhanced in Bluetooth
4.1, and developed further in successive versions. The data rate of
Bluetooth LE is 125 kb/s, 500 kb/s, 1 Mb/s, 2 Mb/s; and max
transmission range is around 100 meters (outdoors). The Bluetooth
Special Interest Group (Bluetooth SIG) has also published the
Internet Protocol Support Profile (IPSP). The IPSP enables discovery
of IP-enabled devices and establishment of link-layer connections for
transporting IPv6 packets. IPv6 over Bluetooth LE is dependent on
both Bluetooth 4.1 [BTCorev5.4] and IPSP 1.0 [IPSP] or newer.

Many devices such as mobile phones, notebooks, tablets, and other
handheld computing devices that support Bluetooth 4.0 or subsequent
versions 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. 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 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 has been developed [RFC9159].

2.3. 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 [TS102.939-1]
[TS102.939-2].

The DECT-ULE protocol stack consists of the physical layer operating
at frequencies in the dedicated 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 Frequency-Division Multiplex (FDMA),
Time-Division Multiple Access (TDMA), and Time-Division Duplex (TDD)
techniques. The coverage distance is from 70 meters (indoors) to 600
meters (outdoors).

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 (PPs) attached. The Medium Access Control
(MAC) layer supports classical DECT as this is used for services like
discovery, pairing, and security features. All these features have
been reused from DECT.

The DECT-ULE device can switch to the ULE mode of operation,
utilizing the new Ultra Low Energy (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.

2.4. MS/TP

MS/TP is a 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 mains powered.

b. All MS/TP devices on a segment can communicate directly, so there
are no hidden node issues or mesh routing issues.

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
Universal Asynchronous Receiver Transmitter (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 long range (~1 km), MS/TP can be used to connect
remote devices (such as district heating controllers) to the nearest
building control infrastructure over a single link [RFC8163].

2.5. NFC

NFC technology enables secure interactions between electronic
devices, allowing consumers to perform contactless transactions,
access digital content, and connect electronic devices with a single
touch [LLCP-1.4]. The distance between sender and receiver is 10 cm
or less. NFC complements many popular consumer-level wireless
technologies by utilizing the key elements in existing standards for
contactless card technology.

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 suitable for
establishing connections with other technologies by the simplicity of
touch. In addition to the easy connection and quick transactions,
simple data sharing is available [RFC9428]. NFC can be used for
secure transfer services where privacy is important.

2.6. PLC

PLC is a data transmission technique that utilizes power conductors
as the medium [RFC9354]. Unlike other dedicated communication
infrastructure, power conductors are widely available indoors and
outdoors. Moreover, wired technologies cause less interference to
the radio medium than wireless technologies and are more reliable
than their wireless counterparts.

The table below shows some available open standards defining PLC.

+=============+=================+============+===========+==========+
| PLC Systems | Frequency Range | Type | Data | Distance |
| | | | Rate | |
+=============+=================+============+===========+==========+
| IEEE 1901 | < 100 MHz | Broadband | 200 | 1000 m |
| | | | Mbps | |
+-------------+-----------------+------------+-----------+----------+
| IEEE 1901.1 | < 12 MHz | PLC-IoT | 10 | 2000 m |
| | | | Mbps | |
+-------------+-----------------+------------+-----------+----------+
| IEEE 1901.2 | < 500 kHz | Narrowband | 200 | 3000 m |
| | | | kbps | |
+-------------+-----------------+------------+-----------+----------+
| G3-PLC | < 500 kHz | Narrowband | 234 | 3000 m |
| | | | kbps | |
+-------------+-----------------+------------+-----------+----------+

Table 1: Some Available Open Standards in PLC

IEEE Std 1901 [IEEE-1901] defines a broadband variant of PLC, but it
is only effective within short range. This standard addresses the
requirements of high data rates such as the Internet, HDTV, audio,
and gaming.

IEEE Std 1901.1 [IEEE-1901.1] defines a medium frequency band (less
than 12 MHz) broadband PLC technology for smart grid applications
based on Orthogonal Frequency Division Multiplexing (OFDM). By
achieving an extended communication range with medium speeds, this
standard can be applied in both indoor and outdoor scenarios, such as
Advanced Metering Infrastructure (AMI), street lighting, electric
vehicle charging, and a smart city.

IEEE Std 1901.2 [IEEE-1901.2] defines a narrowband variant of PLC
with a lower data rate but a significantly higher transmission range
that could be used in an indoor or even an outdoor environment. A
typical use case of PLC is a smart grid.

G3-PLC [G3-PLC] is a narrowband PLC technology that is based on the
ITU-T G.9903 Recommendation [G.9903]. The ITU-T G.9903
Recommendation contains the physical layer and data link-layer
specification for the G3-PLC narrowband OFDM power line communication
transceivers, for communications via alternating current and direct
current electric power lines over frequency bands below 500 kHz.

2.7. Comparison between 6lo Link-Layer Technologies

In the above subsections, various 6lo link-layer technologies are
described. The following table shows the dominant parameters of each
use case corresponding to the 6lo link-layer technology.

+=========+========+===========+========+========+========+=========+
| | Z-Wave | Bluetooth |DECT-ULE| MS/TP | NFC | PLC |
| | | LE | | | | |
+=========+========+===========+========+========+========+=========+
| Usage | Home | Interact | Meter |Building| Secure | Smart |
| | Autom. | w/ Smart |Reading | Autom. |Transfer| Grid |
| | | Phone | | | | |
+=========+--------+-----------+--------+--------+--------+---------+
| Topology|L2-mesh | Star & | Star, | MS/TP, | P2P, |Star Tree|
| & | or | Mesh |No mesh |No mesh |L2-mesh | Mesh |
| Subnet |L3-mesh | | | | | |
+=========+--------+-----------+--------+--------+--------+---------+
| Mobility| No | Yes | No | No | Yes | No |
| Req. | | | | | | |
+=========+--------+-----------+--------+--------+--------+---------+
|Buffering| Yes | Yes | Yes | Yes | Yes | Yes |
| Req. | | | | | | |
+=========+--------+-----------+--------+--------+--------+---------+
| Latency,| Yes | Yes | Yes | Yes | Yes | Yes |
| QoS Req.| | | | | | |
+=========+--------+-----------+--------+--------+--------+---------+
| Frequent| No | No | No | Yes | No | No |
| Tx Req. | | | | | | |
+=========+--------+-----------+--------+--------+--------+---------+
| RFC |RFC 7428| RFC 7668 |RFC 8105|RFC 8163|RFC 9428| RFC 9354|
| | | RFC 9159 | | | | |
+=========+--------+-----------+--------+--------+--------+---------+

Table 2: Comparison between 6lo Link-Layer Technologies

3. Guidelines for Adopting an IPv6 Stack (6lo)

6lo aims to reuse and/or adapt existing 6LoWPAN functionality in
order to efficiently support IPv6 over a variety of IoT L2
technologies. The following guideline targets new candidate-
constrained L2 technologies that may be considered for running a
modified 6LoWPAN stack on top. The modification of the 6LoWPAN stack
should be based on the following:

Addressing Model:
The 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.
IPv6 addresses that are derived from an L2 address are specified
in [RFC4944], but there are implications for privacy. The reason
is that the L2 address in 6lo link-layer technologies is a little
short, and devices can become vulnerable to the various threats.
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 addresses, refer to
[RFC8163] for 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 for when to use broadcast, trying to stick
to unicast messaging whenever possible.

MTU Considerations:
The deployment should consider packet maximum transmission unit
(MTU) needs 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 the 6LoWPAN layer may not need to
support fragmentation and reassembly. In fact, for greatest
efficiency, choosing a low-power link layer that can carry
unfragmented application packets would be optimal for packet
transmission if the deployment can afford it. Please refer to 6lo
RFCs [RFC7668], [RFC8163], and [RFC8105] for example guidance.

Mesh or L3 Routing:
6LoWPAN specifications provide mechanisms to support mesh routing
at L2, a configuration called "mesh-under" [RFC6606]. It is also
possible to use an L3 routing protocol in 6LoWPAN, an approach
known as "route-over". [RFC6550] defines RPL, an L3 routing
protocol for low-power and lossy networks using directed acyclic
graphs. 6LoWPAN is routing-protocol-agnostic and does not specify
any particular L2 or L3 routing protocol to use with a 6LoWPAN
stack.

Address Assignment:
6LoWPAN developed a new version of IPv6 Neighbor Discovery
[RFC4861] [RFC4862]. 6LoWPAN Neighbor Discovery [RFC6775]
[RFC8505] inherits from IPv6 Neighbor Discovery for mechanisms
such as Stateless Address Autoconfiguration (SLAAC) and Neighbor
Unreachability Detection (NUD). 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 an RPL network [RFC6550], it is also beneficial to support IP-
in-IP encapsulation [RFC9008]. The 6LoWPAN node should also
support the registration extensions defined in [RFC8505] and use
the mechanism as the default Neighbor Discovery method. It is the
responsibility of the deployment to ensure unique global IPv6
addresses for Internet connectivity. For local-only connectivity,
IPv6 Unique Local Address (ULA) may be used. [RFC6775] and
[RFC8505] specify the 6LoWPAN Border Router (6LBR), which is
responsible for prefix assignment to the 6LoWPAN network. A 6LBR
can be connected to the Internet or to an enterprise network via
one of the interfaces. Please refer to [RFC7668] and [RFC8105]
for examples of address assignment considerations. In addition,
privacy considerations in [RFC8065] must be consulted for
applicability. In certain scenarios, the deployment may not
support IPv6 address autoconfiguration due to regulatory and
business reasons and may choose to offer a separate address
assignment service. Address-Protected Neighbor Discovery
[RFC8928] enables source address validation [RFC6620] and protects
the address ownership against impersonation attacks.

Broadcast Avoidance:
6LoWPAN Neighbor Discovery aims to reduce the amount of multicast
traffic of classic Neighbor Discovery, since IP-level multicast
translates into L2 broadcast in many L2 technologies [RFC6775].
6LoWPAN Neighbor Discovery relies on a proactive registration to
avoid the use of multicast for address resolution. It also uses a
unicast method for Duplicate Address Detection (DAD) and avoids
multicast lookups from all nodes by using non-onlink prefixes.
Router Advertisements (RAs) are also sent in unicast, in response
to Router Solicitations (RSs).

Host-to-Router Interface:
6lo has defined registration extensions for 6LoWPAN Neighbor
Discovery [RFC8505]. This effort provides a host-to-router
interface by which a host can request its router to ensure
reachability for the address registered with the router. Note
that functionality has been developed to ensure that such a host
can benefit from routing services in a RPL network [RFC9010].

Proxy Neighbor Discovery:
Further functionality also allows a device (e.g., an energy-
constrained device that needs to sleep most of the time) to
request proxy Neighbor Discovery services from a 6LoWPAN Backbone
Router (6BBR) [RFC8505] [RFC8929]. The latter RFC federates a
number of links into a multi-link subnet.

Header Compression:
IPv6 header compression [RFC6282] is a vital part of IPv6 over
low-power communication. Examples of header compression over
different link-layer specifications are found in [RFC7668],
[RFC8163], and [RFC8105]. A generic header compression technique
is specified in [RFC7400]. For 6LoWPAN networks where RPL is the
routing protocol, there are 6LoWPAN header compression extensions
that allow compressing the RPL artifacts used when forwarding
packets in the route-over mesh [RFC8138] [RFC9035].

Security and Encryption:
Though 6LoWPAN basic specifications do not address security at the
network layer, the assumption is that L2 security must be present.
Nevertheless, care must be taken since specific L2 technologies
may exhibit security gaps. Typically, 6lo L2 technologies (see
Section 2) offer security properties such as confidentiality and/
or message authentication. In addition, end-to-end security is
highly desirable. Protocols such as DTLS/TLS, as well as Object
Security, are being used in the constrained-node network domain
[SEC-PROT-COMP]. The relevant IETF working groups should be
consulted for application and transport level security. The IETF
has worked on address authentication [RFC8928], and secure
bootstrapping is also being discussed in the IETF. However, there
may be other security mechanisms available in a deployment through
other standards, such as hardware-level security or certificates
for the initial booting process. In order to use security
mechanisms, the implementation needs to be able to afford it in
terms of processing capabilities and energy consumption.

Additional Processing:
[RFC8066] defines guidelines for ESC dispatch octets used in the
6LoWPAN header. The ESC type is defined to use additional
dispatch octets in the 6LoWPAN header. An implementation may take
advantage of the ESC header to offer a deployment-specific
processing of 6LoWPAN packets.

4. 6lo Deployment Examples

4.1. Wi-SUN Usage of 6lo in Network Layer

Wireless Smart Ubiquitous Network (Wi-SUN) [Wi-SUN] is a technology
based on IEEE Std 802.15.4g [IEEE-802.15.4]. Wi-SUN networks support
star and mesh topologies as well as hybrid star/mesh deployments, but
these are typically laid out in a mesh topology where each node
relays data for the network to provide network connectivity. Wi-SUN
networks are deployed on both grid-powered and battery-operated
devices [RFC8376].

The main application domains using Wi-SUN are smart utility and smart
city networks. The Wi-SUN Alliance Field Area Network (FAN)
primarily covers outdoor networks. The Wi-SUN FAN specification
defines an IPv6-based protocol suite that includes TCP/UDP, IPv6, 6lo
adaptation layer, DHCPv6 for IPv6 address management, RPL, and
ICMPv6.

4.2. Thread Usage of 6lo in the Network Layer

Thread is an IPv6-based networking protocol stack built on open
standards, designed for smart home environments, and based on low-
power IEEE Std 802.15.4 mesh networks. Because of its IPv6
foundation, Thread can support existing popular application layers
and IoT platforms, provide end-to-end security, ease development, and
enable flexible designs [Thread].

The Thread specification uses the IEEE Std 802.15.4 [IEEE-802.15.4]
physical and MAC layers operating at 250 kbps in the 2.4 GHz band.

Thread devices use 6LoWPAN, as defined in [RFC4944] and [RFC6282],
for transmission of IPv6 packets over IEEE Std 802.15.4 networks.
Header compression is used within the Thread network, and devices
transmitting messages compress the IPv6 header to minimize the size
of the transmitted packet. The mesh header is supported for link-
layer (i.e., mesh-under) forwarding. The mesh header as used in
Thread also allows efficient end-to-end fragmentation of messages
rather than the hop-by-hop fragmentation specified in [RFC4944].
Mesh-under routing in Thread is based on a distance vector protocol
in a full mesh topology.

4.3. G3-PLC Usage of 6lo in Network Layer

G3-PLC [G3-PLC] is a narrowband PLC technology that is based on the
ITU-T G.9903 Recommendation [G.9903]. G3-PLC supports multi-hop mesh
network topology 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
narrowband PLC technologies. G3-PLC has got massive deployments over
several countries, e.g., Japan and France.

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

* smart metering

* vehicle-to-grid communication

* demand response

* distribution automation

* home/building energy management systems

* smart street lighting

* AMI backbone network

* 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 [RFC9354]. The ESC dispatch type is used in the G3-PLC
to provide fundamental mesh routing and bootstrapping functionalities
[RFC8066].

4.4. Netricity Usage of 6lo in the Network Layer

The Netricity program in the HomePlug Powerline Alliance [NETRICITY]
promotes the adoption of products built on the IEEE Std 1901.2 low-
frequency narrowband PLC standard [IEEE-1901.2], 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 using Netricity are smart grid and smart
cities. This includes, but is not limited to, the following
applications:

* utility grid modernization

* distribution automation

* meter-to-grid connectivity

* microgrids

* grid sensor communications

* load control

* demand response

* net metering

* street lighting control

* photovoltaic panel monitoring

The Netricity system architecture is based on the physical and MAC
layers of IEEE Std 1901.2. Regarding the 6lo adaptation layer and an
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 L3 routing in Netricity uses RPL in non-storing mode with
the MRHOF (Minimum Rank with Hysteresis Objective Function) based on
their own defined Estimated Transmission Time (ETT) metric.

5. 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 section, various 6lo
use cases, which are based on different link-layer technologies, are
described.

5.1. 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 [G.9959].

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

A 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 home appliances on
and off, or the user may control them by pressing a wall switch or
a button on a remote control. Scenes may be programmed so that
the home devices adopt a specific configuration after a given
event. Sensors may also periodically send measurements of several
parameters (e.g., gas presence, light, temperature, humidity),
which are collected at 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 multi-hop paradigm
allows end-to-end connectivity when direct range communication is not
possible.

5.2. 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 interaction between a 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 cellular, a 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 a Body Area Network Based on Bluetooth LE for Fitness

A person wears a smartwatch for fitness purposes. The smartwatch
has several sensors (e.g., heart rate, accelerometer, gyrometer,
GPS, and temperature), 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 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. 6lo enables this use case by
providing efficient end-to-end IPv6 support. 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 of this
document.

5.3. 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 (FP), a
device that typically acts as a base station for wireless telephones.
In this case, additionally, the FP must have a data network
connection. Therefore, DECT-ULE is especially suitable for the
connected home space in application areas such as home automation,
smart metering, safety, and healthcare. Since DECT-ULE uses
dedicated bandwidth, it avoids this coexistence issues suffered by
other technologies that use, for example, Industrial, Scientific, and
Medical (ISM) frequency bands.

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 FP of
the home. The FP 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 FP, 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 FP via
DECT-ULE.

5.4. 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 interconnect 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
fundamental 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. Note that BACnet comprises
various networking solutions other than MS/TP, including the recently
emerged BACnet IP. However, the latter is based on high-speed
Ethernet infrastructure, and it is outside of the constrained-node
network scope.

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.

A multi-zone controller might be implemented as an IP router between
a classical 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, without the line-of-sight
restrictions or hop-by-hop latency of many low-cost wireless
solutions.

5.5. Use Case of NFC: Alternative Secure Transfer

In different applications, a variety of secured data can be handled
and transferred. Depending on the security level of the data,
different transfer methods can be alternatively selected.

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

An older adult who lives alone wears one to several wearable 6lo
devices to measure heartbeat, pulse rate, etc. Other 6lo devices
are densely installed at home for movement detection. A 6LBR at
home will send the sensed information to a connected healthcare
center. Portable base stations with displays 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 becomes a serious
issue in this case, as the sensed data is very personal.

While the older adult is provided audio and video healthcare services
by a tele-assistance based on cellular connections, the older adult
can alternatively use NFC connections to transfer the personal sensed
data to the tele-assistance. Hackers can overhear the data based on
the cellular connection, but they cannot gather the personal data
over the NFC connection.

5.6. Use Case of PLC: Smart Grid

The smart grid concept is based on deploying numerous operational and
energy measuring subsystems in an electricity grid system. It
comprises multiple administrative levels and segments to provide
connectivity among these numerous components. Last mile connectivity
is established over the Low-Voltage segment, whereas connectivity
over electricity distribution takes place over the High-Voltage
segment. Smart grid systems include AMI, Demand Response, Home
Energy Management System, and Wide Area Situational Awareness (WASA),
among others.

Although other wired and wireless technologies are also used in a
smart grid, PLC benefits from reliable data communication over
electrical power lines that are already present, and the deployment
cost can be comparable to wireless technologies. The 6lo-related
scenarios for PLC mainly 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 AMI

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 through a WAN network (e.g.,
Medium-Voltage PLC, Ethernet, or General Packet Radio Service
(GPRS)) for storage and analysis. Two-way communications are
enabled, which means smart meters can perform actions like
notification of electricity charges according to the commands from
the utility company.

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

Example: Use of PLC (IEEE Std 1901.1) for WASA in a Smart Grid

Many subsystems of a smart grid require low data rates, and
narrowband variants (e.g., IEEE Std 1901.1) of PLC fulfill such
requirements. Recently, more complex scenarios are emerging that
require higher data rates.

A WASA subsystem is an appropriate example that collects large
amounts of information about the current state of the grid over a
wide area from electric substations as well as power transmission
lines. The collected feedback is used for monitoring, controlling,
and protecting all the subsystems.

6. IANA Considerations

This document has no IANA actions.

7. Security Considerations

This document does not create security concerns in addition to those
described in the Security Considerations sections of the 6lo
adaptation layers considered in this document [RFC7428], [RFC7668],
[RFC8105], [RFC8163], [RFC9159], [RFC9428], and [RFC9354].

Neighbor Discovery in 6lo links may be susceptible to threats as
detailed in [RFC3756]. Mesh routing is expected to be common in some
6lo networks, such as ITU-T G.9959 networks, Bluetooth LE mesh
networks, and PLC networks. This implies additional threats due to
ad hoc routing as per [KW03]. Most of the L2 technologies considered
in this document (i.e., ITU-T G.9959, Bluetooth LE, DECT-ULE, and
PLC) support link-layer security. Making use of such provisions will
alleviate the threats mentioned above. Note that NFC is often
considered to offer intrinsic security properties due to its short
link range. MS/TP does not support link-layer security, since in its
original BACnet protocol stack, security is provided at the network
layer; thus, alternative security functionality needs to be used for
a 6lo-based protocol stack over MS/TP.

End-to-end communication is expected to be secured by means of common
mechanisms, such as IPsec, DTLS/TLS, Object Security [RFC8613], and
Ephemeral Diffie-Hellman Over COSE (EDHOC) [EDHOC].

The 6lo stack uses the IPv6 addressing model. The implications for
privacy and network performance of using L2-address-derived IPv6
addresses need to be considered [RFC8065].

8. References

8.1. Normative 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,
<https://www.rfc-editor.org/info/rfc4861>.

[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>.

[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,
<https://www.rfc-editor.org/info/rfc4919>.

[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,
<https://www.rfc-editor.org/info/rfc4944>.

[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,
<https://www.rfc-editor.org/info/rfc6568>.

[RFC6606] Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem
Statement and Requirements for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Routing",
RFC 6606, DOI 10.17487/RFC6606, May 2012,
<https://www.rfc-editor.org/info/rfc6606>.

[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014,
<https://www.rfc-editor.org/info/rfc7228>.

[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,
<https://www.rfc-editor.org/info/rfc7428>.

[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,
<https://www.rfc-editor.org/info/rfc7668>.

[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>.

[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.

[RFC9159] Gomez, C., Darroudi, S.M., Savolainen, T., and M. Spoerk,
"IPv6 Mesh over BLUETOOTH(R) Low Energy Using the Internet
Protocol Support Profile (IPSP)", RFC 9159,
DOI 10.17487/RFC9159, December 2021,
<https://www.rfc-editor.org/info/rfc9159>.

[RFC9354] Hou, J., Liu, B., Hong, Y-G., Tang, X., and C. Perkins,
"Transmission of IPv6 Packets over Power Line
Communication (PLC) Networks", RFC 9354,
DOI 10.17487/RFC9354, January 2023,
<https://www.rfc-editor.org/info/rfc9354>.

8.2. Informative References

[BACnet] ASHRAE, "BACnet-A Data Communication Protocol for Building
Automation and Control Networks (ANSI Approved)", ASHRAE
Standard 135-2020, October 2020,
<https://www.techstreet.com/standards/ashrae-
135-2020?product_id=2191852>.

[BTCorev5.4]
Bluetooth, "Core Specification Version 5.4", January 2012,
<https://www.bluetooth.com/specifications/specs/core-
specification-5-4/>.

[EDHOC] Selander, G., Preuß Mattsson, J., and F. Palombini,
"Ephemeral Diffie-Hellman Over COSE (EDHOC)", Work in
Progress, Internet-Draft, draft-ietf-lake-edhoc-22, 25
August 2023, <https://datatracker.ietf.org/doc/html/draft-
ietf-lake-edhoc-22>.

[G.9903] ITU-T, "Narrowband orthogonal frequency division
multiplexing power line communication transceivers for
G3-PLC networks", ITU-T Recommendation G.9903, August
2017, <https://www.itu.int/rec/T-REC-G.9903-201708-I/en>.

[G.9959] ITU-T, "Short range narrow-band digital radiocommunication
transceivers - PHY, MAC, SAR and LLC layer
specifications", ITU-T Recommendation G.9959, January
2015, <https://www.itu.int/rec/T-REC-G.9959-201501-I/en>.

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

[IEEE-1901]
IEEE, "IEEE Standard for Broadband over Power Line
Networks: Medium Access Control and Physical Layer
Specifications", DOI 10.1109/IEEESTD.2010.5678772, IEEE
Std 1901-2010, December 2010,
<https://standards.ieee.org/ieee/1901/4953/>.

[IEEE-1901.1]
IEEE, "IEEE Standard for Medium Frequency (less than 12
MHz) Power Line Communications for Smart Grid
Applications", DOI 10.1109/IEEESTD.2018.8360785, IEEE
Std 1901.1-2018, May 2018,
<https://ieeexplore.ieee.org/document/8360785>.

[IEEE-1901.2]
IEEE, "IEEE Standard for Low-Frequency (less than 500 kHz)
Narrowband Power Line Communications for Smart Grid
Applications", DOI 10.1109/IEEESTD.2013.6679210, IEEE
Std 1901.2-2013, December 2013,
<https://standards.ieee.org/ieee/1901.2/4833/>.

[IEEE-802.15.4]
IEEE, "IEEE Standard for Low-Rate Wireless Networks",
DOI 10.1109/IEEESTD.2020.9144691, IEEE Std 802.15.4-2020,
July 2020,
<https://standards.ieee.org/ieee/802.15.4/7029/>.

[IEEE-802.15.9]
IEEE, "IEEE Standard for Transport of Key Management
Protocol (KMP) Datagrams",
DOI 10.1109/IEEESTD.2022.9690134, IEEE Std 802.15.9-2021,
January 2022,
<https://ieeexplore.ieee.org/document/9690134>.

[IPSP] Bluetooth, "Internet Protocol Support Profile 1.0",
December 2014,
<https://www.bluetooth.com/specifications/specs/internet-
protocol-support-profile-1-0/>.

[KW03] Karlof, C. and D. Wagner, "Secure routing in wireless
sensor networks: attacks and countermeasures", Volume 1,
Issues 2-3, Pages 293-315,
DOI 10.1016/S1570-8705(03)00008-8, September 2003,
<https://doi.org/10.1016/S1570-8705(03)00008-8>.

[LLCP-1.4] NFC Forum, "Logical Link Control Protocol Technical
Specification", Version 1.4, December 2022, <https://nfc-
forum.org/build/specifications/logical-link-control-
protocol-technical-specification/>.

[NETRICITY]
Netricity, "The Netricity program addresses the need for
long range powerline networking for outside-the-home,
smart meter-to-grid, and industrial control applications",
<https://www.netricity.org/>.

[RFC3756] Nikander, P., Ed., Kempf, J., and E. Nordmark, "IPv6
Neighbor Discovery (ND) Trust Models and Threats",
RFC 3756, DOI 10.17487/RFC3756, May 2004,
<https://www.rfc-editor.org/info/rfc3756>.

[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,
<https://www.rfc-editor.org/info/rfc6282>.

[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,
<https://www.rfc-editor.org/info/rfc6550>.

[RFC6620] Nordmark, E., Bagnulo, M., and E. Levy-Abegnoli, "FCFS
SAVI: First-Come, First-Served Source Address Validation
Improvement for Locally Assigned IPv6 Addresses",
RFC 6620, DOI 10.17487/RFC6620, May 2012,
<https://www.rfc-editor.org/info/rfc6620>.

[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,
<https://www.rfc-editor.org/info/rfc6775>.

[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>.

[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,
"IPv6 over Low-Power Wireless Personal Area Network
(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,
April 2017, <https://www.rfc-editor.org/info/rfc8138>.

[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,
<https://www.rfc-editor.org/info/rfc8352>.

[RFC8376] Farrell, S., Ed., "Low-Power Wide Area Network (LPWAN)
Overview", RFC 8376, DOI 10.17487/RFC8376, May 2018,
<https://www.rfc-editor.org/info/rfc8376>.

[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,
<https://www.rfc-editor.org/info/rfc8505>.

[RFC8613] Selander, G., Preuß Mattsson, J., Palombini, F., and L.
Seitz, "Object Security for Constrained RESTful
Environments (OSCORE)", RFC 8613, DOI 10.17487/RFC8613,
July 2019, <https://www.rfc-editor.org/info/rfc8613>.

[RFC8928] Thubert, P., Ed., Sarikaya, B., Sethi, M., and R. Struik,
"Address-Protected Neighbor Discovery for Low-Power and
Lossy Networks", RFC 8928, DOI 10.17487/RFC8928, November
2020, <https://www.rfc-editor.org/info/rfc8928>.

[RFC8929] Thubert, P., Ed., Perkins, C.E., and E. Levy-Abegnoli,
"IPv6 Backbone Router", RFC 8929, DOI 10.17487/RFC8929,
November 2020, <https://www.rfc-editor.org/info/rfc8929>.

[RFC9008] Robles, M.I., Richardson, M., and P. Thubert, "Using RPI
Option Type, Routing Header for Source Routes, and IPv6-
in-IPv6 Encapsulation in the RPL Data Plane", RFC 9008,
DOI 10.17487/RFC9008, April 2021,
<https://www.rfc-editor.org/info/rfc9008>.

[RFC9010] Thubert, P., Ed. and M. Richardson, "Routing for RPL
(Routing Protocol for Low-Power and Lossy Networks)
Leaves", RFC 9010, DOI 10.17487/RFC9010, April 2021,
<https://www.rfc-editor.org/info/rfc9010>.

[RFC9035] Thubert, P., Ed. and L. Zhao, "A Routing Protocol for Low-
Power and Lossy Networks (RPL) Destination-Oriented
Directed Acyclic Graph (DODAG) Configuration Option for
the 6LoWPAN Routing Header", RFC 9035,
DOI 10.17487/RFC9035, April 2021,
<https://www.rfc-editor.org/info/rfc9035>.

[RFC9428] Choi, Y., Ed., Hong, Y., and J. Youn, "Transmission of
IPv6 Packets over Near Field Communication", RFC 9428,
DOI 10.17487/RFC9428, July 2023,
<https://www.rfc-editor.org/info/rfc9428>.

[SEC-PROT-COMP]
Preuß Mattsson, J., Palombini, F., and M. Vučinić,
"Comparison of CoAP Security Protocols", Work in Progress,
Internet-Draft, draft-ietf-iotops-security-protocol-
comparison-02, 11 April 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-iotops-
security-protocol-comparison-02>.

[Thread] Thread, "Resources",
<https://www.threadgroup.org/Support>.

[TIA-485-A]
TIA, "Electrical Characteristics of Generators and
Receivers for Use in Balanced Digital Multipoint Systems",
TIA-485-A, Revision of TIA-485, March 1998,
<https://global.ihs.com/
doc_detail.cfm?item_s_key=00032964>.

[TS102.939-1]
ETSI, "Digital Enhanced Cordless Telecommunications
(DECT); Ultra Low Energy (ULE); Machine to Machine
Communications; Part 1: Home Automation Network (phase
1)", V1.2.1, ETSI-TS 102 939-1, March 2015,
<https://www.etsi.org/deliver/
etsi_ts/102900_102999/10293901/01.02.01_60/
ts_10293901v010201p.pdf>.

[TS102.939-2]
ETSI, "Digital Enhanced Cordless Telecommunications
(DECT); Ultra Low Energy (ULE); Machine to Machine
Communications; Part 2: Home Automation Network (phase
2)", V1.1.1, ETSI TS 102 939-2, March 2015,
<https://www.etsi.org/deliver/
etsi_ts/102900_102999/10293902/01.01.01_60/
ts_10293902v010101p.pdf>.

[Wi-SUN] "Wi-SUN Alliance", <https://www.wi-sun.org>.

Appendix A. Design Space Dimensions for 6lo Deployment

[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 Section 2
of [RFC6568], the following design space dimensions are described:
Deployment, Network Size, Power Source, Connectivity, Multi-Hop
Communication, Traffic Pattern, Mobility, and Quality of Service
(QoS). However, in this document, the following design space
dimensions are considered:

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

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.

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.

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

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

Buffering Requirements:
Some 6lo use case may require a higher data rate than the link-
layer technology support. In this case, a buffering mechanism,
telling the application to throttle its generation of data, and
compression of the data are possible to manage the data.

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

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

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

Reliability and QoS:
Some 6lo use cases require high reliability, for example, real-
time or health-related services.

Traffic Patterns:
6lo use cases may involve various traffic patterns. For example,
some 6lo use cases may require short data lengths and random
transmission. Some 6lo use cases may require continuous data
transmission and discontinuous data transmission.

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

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 that may be tuned
[RFC8352]. Readers are expected to be familiar with the
terminology found in [RFC7228].

Update Firmware Requirements:
Most 6lo use cases will need a mechanism to update firmware. In
these cases, support for over-the-air updates is required,
probably in a broadcast mode when bandwidth is low and the number
of identical devices is high.

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 requirements of the 6lo use cases and
the characteristics of wired and wireless technologies.

Acknowledgements

Carles Gomez has been funded in part by the Spanish Government
through the Jose Castillejo CAS15/00336 grant, the TEC2016-79988-P
grant, and the PID2019-106808RA-I00 grant as well as by Secretaria
d'Universitats i Recerca del Departament d'Empresa i Coneixement de
la Generalitat de Catalunya through grants 2017 SGR 376 and 2021 SGR
00330. 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,
Jianqiang Hou, Kerry Lynn, S.V.R. Anand, and Seyed Mahdi Darroudi
have provided valuable feedback for this document.

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

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
Telecom.

Authors' Addresses

Yong-Geun Hong
Daejeon University
62 Daehak-ro, Dong-gu
Daejeon
34520
South Korea
Phone: +82 42 280 4841
Email: [email protected]

Carles Gomez
Universitat Politecnica de Catalunya
C/Esteve Terradas, 7
08860 Castelldefels
Spain
Email: [email protected]

Younghwan Choi
ETRI
218 Gajeongno, Yuseong
Daejeon
34129
South Korea
Phone: +82 42 860 1429
Email: [email protected]

Abdur Rashid Sangi
Wenzhou-Kean University
88 Daxue Road, Ouhai, Wenzhou
Zhejiang
325060
China
Email: [email protected]

Samita Chakrabarti
Verizon
Bedminster, NJ
United States of America
Email: [email protected]