draft-ietf-lwig-energy-efficient-08.txt   rfc8352.txt 
Internet Engineering Task Force C. Gomez Internet Engineering Task Force (IETF) C. Gomez
Internet-Draft Universitat Politecnica de Catalunya Request for Comments: 8352 UPC
Intended status: Informational M. Kovatsch Category: Informational M. Kovatsch
Expires: April 24, 2018 ETH Zurich ISSN: 2070-1721 ETH Zurich
H. Tian H. Tian
China Academy of Telecommunication Research China Academy of Telecommunication Research
Z. Cao, Ed. Z. Cao, Ed.
Huawei Technologies Huawei Technologies
October 21, 2017 April 2018
Energy-Efficient Features of Internet of Things Protocols Energy-Efficient Features of Internet of Things Protocols
draft-ietf-lwig-energy-efficient-08
Abstract Abstract
This document describes the challenges for energy-efficient protocol This document describes the challenges for energy-efficient protocol
operation on constrained devices and the current practices used to operation on constrained devices and the current practices used to
overcome those challenges. It summarizes the main link-layer overcome those challenges. It summarizes the main link-layer
techniques used for energy-efficient networking, and it highlights techniques used for energy-efficient networking, and it highlights
the impact of such techniques on the upper layer protocols so that the impact of such techniques on the upper-layer protocols so that
they can together achieve an energy efficient behavior. The document they can together achieve an energy-efficient behavior. The document
also provides an overview of energy-efficient mechanisms available at also provides an overview of energy-efficient mechanisms available at
each layer of the IETF protocol suite specified for constrained node each layer of the IETF protocol suite specified for constrained-node
networks. networks.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." 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.
This Internet-Draft will expire on April 24, 2018. 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/rfc8352.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Medium Access Control and Radio Duty Cycling . . . . . . . . 5 3. Medium Access Control and Radio Duty Cycling . . . . . . . . 6
3.1. Radio Duty Cycling techniques . . . . . . . . . . . . . . 6 3.1. Techniques for Radio Duty Cycling . . . . . . . . . . . . 6
3.2. Latency and buffering . . . . . . . . . . . . . . . . . . 7 3.2. Latency and Buffering . . . . . . . . . . . . . . . . . . 7
3.3. Throughput . . . . . . . . . . . . . . . . . . . . . . . 7 3.3. Throughput . . . . . . . . . . . . . . . . . . . . . . . 8
3.4. Radio interface tuning . . . . . . . . . . . . . . . . . 8 3.4. Radio Interface Tuning . . . . . . . . . . . . . . . . . 8
3.5. Packet bundling . . . . . . . . . . . . . . . . . . . . . 8 3.5. Packet Bundling . . . . . . . . . . . . . . . . . . . . . 8
3.6. Power save services available in example low-power radios 8 3.6. Power Save Services Available in Example Low-Power Radios 8
3.6.1. Power Save Services Provided by IEEE 802.11 . . . . . 8 3.6.1. Power Save Services Provided by IEEE 802.11 . . . . . 8
3.6.2. Power Save Services Provided by Bluetooth LE . . . . 9 3.6.2. Power Save Services Provided by Bluetooth LE . . . . 10
3.6.3. Power Save Services in IEEE 802.15.4 . . . . . . . . 10 3.6.3. Power Save Services in IEEE 802.15.4 . . . . . . . . 11
3.6.4. Power Save Services in DECT ULE . . . . . . . . . . . 12 3.6.4. Power Save Services in DECT ULE . . . . . . . . . . . 12
4. IP Adaptation and Transport Layer . . . . . . . . . . . . . . 14 4. IP Adaptation and Transport Layer . . . . . . . . . . . . . . 14
5. Routing Protocols . . . . . . . . . . . . . . . . . . . . . . 15 5. Routing Protocols . . . . . . . . . . . . . . . . . . . . . . 15
6. Application Layer . . . . . . . . . . . . . . . . . . . . . . 16 6. Application Layer . . . . . . . . . . . . . . . . . . . . . . 16
6.1. Energy efficient features in CoAP . . . . . . . . . . . . 16 6.1. Energy-Efficient Features in CoAP . . . . . . . . . . . . 16
6.2. Sleepy node support . . . . . . . . . . . . . . . . . . . 16 6.2. Sleepy Node Support . . . . . . . . . . . . . . . . . . . 17
6.3. CoAP timers . . . . . . . . . . . . . . . . . . . . . . . 17 6.3. CoAP Timers . . . . . . . . . . . . . . . . . . . . . . . 17
6.4. Data compression . . . . . . . . . . . . . . . . . . . . 17 6.4. Data Compression . . . . . . . . . . . . . . . . . . . . 18
7. Summary and Conclusions . . . . . . . . . . . . . . . . . . . 18 7. Summary and Conclusions . . . . . . . . . . . . . . . . . . . 18
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
11. Security Considerations . . . . . . . . . . . . . . . . . . . 19 10.1. Normative References . . . . . . . . . . . . . . . . . . 19
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 10.2. Informative References . . . . . . . . . . . . . . . . . 22
12.1. Normative References . . . . . . . . . . . . . . . . . . 19 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 23
12.2. Informative References . . . . . . . . . . . . . . . . . 21 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
Network systems for physical world monitoring contain many battery- Network systems for monitoring the physical world contain many
powered or energy-harvesting devices. For example, in an battery-powered or energy-harvesting devices. For example, in an
environmental monitoring system, or a temperature and humidity environmental monitoring system or a temperature and humidity
monitoring system, there may not be always-on and sustained power monitoring system, there may not be always on and sustained power
supplies for the potentially large number of constrained devices. In supplies for the potentially large number of constrained devices. In
such deployment scenarios, it is necessary to optimize the energy such deployment scenarios, it is necessary to optimize the energy
consumption of the constrained devices. In this document we describe consumption of the constrained devices. In this document, we
techniques that are in common use at Layer 2 and at Layer 3, and we describe techniques that are in common use at Layer 2 and at Layer 3,
indicate the need for higher-layer awareness of lower-layer features. and we indicate the need for higher-layer awareness of lower-layer
features.
Many research efforts have studied this "energy efficiency" problem. Many research efforts have studied this "energy efficiency" problem.
Most of this research has focused on how to optimize the system's Most of this research has focused on how to optimize the system's
power consumption in certain deployment scenarios, or how an existing power consumption in certain deployment scenarios or how an existing
network function such as routing or security could be more energy- network function such as routing or security could be more energy
efficient. Only few efforts have focused on energy-efficient designs efficient. Only few efforts have focused on energy-efficient designs
for IETF protocols and standardized network stacks for such for IETF protocols and standardized network stacks for such
constrained devices [I-D.kovatsch-lwig-class1-coap]. constrained devices [CLASS1-CoAP].
The IETF has developed a suite of Internet protocols suitable for The IETF has developed a suite of Internet protocols suitable for
such constrained devices, including IPv6 over Low-Power Wireless such constrained devices, including IPv6 over Low-Power Wireless
Personal Area Networks (6LoWPAN) [RFC6282],[RFC6775],[RFC4944], the Personal Area Networks (6LoWPAN) [RFC6282] [RFC6775] [RFC4944], the
IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL)
[RFC6550], and the Constrained Application Protocol (CoAP) [RFC7252]. [RFC6550], and the Constrained Application Protocol (CoAP) [RFC7252].
This document tries to summarize the design considerations for making This document tries to summarize the design considerations for making
the IETF constrained protocol suite as energy-efficient as possible. the IETF constrained protocol suite as energy efficient as possible.
While this document does not provide detailed and systematic While this document does not provide detailed and systematic
solutions to the energy efficiency problem, it summarizes the design solutions to the energy-efficiency problem, it summarizes the design
efforts and analyzes the design space of this problem. In efforts and analyzes the design space of this problem. In
particular, it provides an overview of the techniques used by the particular, it provides an overview of the techniques used by the
lower layers to save energy and how these may impact on the upper lower layers to save energy and how these may impact on the upper
layers. Cross-layer interaction is therefore considered in this layers. Cross-layer interaction is therefore considered in this
document from this specific point of view. Providing further design document from this specific point of view. Providing further design
recommendations that go beyond the layered protocol architecture is recommendations that go beyond the layered protocol architecture is
out of the scope of this document. out of the scope of this document.
After reviewing the energy-efficient designs of each layer, we After reviewing the energy-efficient designs of each layer, we
summarize the document by presenting some overall conclusions. summarize the document by presenting some overall conclusions.
Though the lower layer communication optimization is the key part of Though the lower-layer communication optimization is the key part of
energy efficient design, the protocol design at the upper layers is energy-efficient design, the protocol design at the upper layers is
also important to make the device energy-efficient. also important to make the device energy efficient.
1.1. Terminology 1.1. Terminology
Terms used in this document are defined in [RFC7228] Terms used in this document are defined in [RFC7228] [CNN-TERMS].
[I-D.bormann-lwig-7228bis].
2. Overview 2. Overview
The IETF has developed protocols to enable end-to-end IP The IETF has developed protocols to enable end-to-end IP
communication between constrained nodes and fully capable nodes. communication between constrained nodes and fully capable nodes.
This work has expedited the evolution of the traditional Internet This work has expedited the evolution of the traditional Internet
protocol stack to a light-weight Internet protocol stack. As shown protocol stack to a lightweight Internet protocol stack. As shown in
in Figure 1 below, the IETF has developed CoAP as the application Figure 1 below, the IETF has developed CoAP as the application layer
layer and 6LoWPAN as the adaption layer to run IPv6 over IEEE and 6LoWPAN as the adaption layer to run IPv6 over IEEE 802.15.4
802.15.4 and Bluetooth Low-Energy, with the support of routing by RPL [IEEE802.15.4] and Bluetooth Low Energy (also referred to as
and efficient neighbor discovery by 6LoWPAN-ND. 6LoWPAN is currently Bluetooth LE and BTLE), with the support of routing by RPL and
being adapted by the 6lo working group to support IPv6 over various efficient neighbor discovery by 6LoWPAN Neighbor Discovery (6LoWPAN-
other technologies, such as ITU-T G.9959 [G9959], DECT ULE [TS102], ND). 6LoWPAN is currently being adapted by the 6lo Working Group to
MS/TP-BACnet [MSTP], and Near Field Communication (NFC) [NFC]. support IPv6 over various other technologies, such as ITU-T G.9959
[G9959], Digital Enhanced Cordless Telecommunications Ultra Low
Energy (DECT ULE) [TS102], Building Automation and Control Networks
Master-Slave/Token-Passing (BACnet MS/TP) [MSTP], and Near Field
Communication [NFC].
+-----+ +-----+ +-----+ +------+ +-----+ +-----+ +-----+ +------+
|HTTP | | FTP | |SNMP | | CoAP | |HTTP | | FTP | |SNMP | | CoAP |
+-----+ +-----+ +-----+ +------+ +-----+ +-----+ +-----+ +------+
\ / / / \ \ / / / \
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| TCP | | UDP | | TCP | | UDP | | TCP | | UDP | | TCP | | UDP |
+-----+ +-----+ ===> +-----+ +-----+ +-----+ +-----+ ===> +-----+ +-----+
\ / \ / \ / \ /
+-----+ +------+ +-------+ +------+ +-----+ +-----+ +------+ +-------+ +------+ +-----+
skipping to change at page 4, line 33 skipping to change at page 4, line 43
+-----+ +------+ +-------+ +------+ +-----+ +-----+ +------+ +-------+ +------+ +-----+
| | | |
+-------+ +-------+ +----------+ +-------+ +-------+ +----------+
|MAC/PHY| | 6Lo |--|6LoWPAN-ND| |MAC/PHY| | 6Lo |--|6LoWPAN-ND|
+-------+ +-------+ +----------+ +-------+ +-------+ +----------+
| |
+-------+ +-------+
|MAC/PHY| |MAC/PHY|
+-------+ +-------+
Figure 1: Traditional and Light-weight Internet Protocol Stack Figure 1: Traditional and Lightweight Internet Protocol Stack
There are numerous published studies reporting comprehensive There are numerous published studies reporting comprehensive
measurements of wireless communication platforms [Powertrace]. As an measurements of wireless communication platforms [Powertrace]. As an
example, below we list the energy consumption profile of the most example, below we list the energy-consumption profile of the most
common operations involved in communication on a prevalent sensor common operations involved in communication on a prevalent sensor
node platform. The measurement was based on the Tmote Sky with node platform. The measurement was based on the Tmote Sky with
ContikiMAC [ContikiMAC] as the radio duty cycling algorithm. From ContikiMAC [ContikiMAC] as the Radio Duty Cycling algorithm. From
this and many other measurement reports (e.g.[AN079]), we can see this and many other measurement reports (e.g., [AN079]), we can see
that the energy consumption of optimized transmission and reception that the energy consumption of optimized transmission and reception
are in the same order. For IEEE 802.15.4 and Ultra WideBand (UWB) are in the same order. For IEEE 802.15.4 [IEEE802.15.4] and Ultra
links, transmitting may actually be even cheaper than receiving. It WideBand (UWB) links, transmitting may actually be even cheaper than
also shows that broadcast and non-synchronized communication receiving. It also shows that broadcast and non-synchronized
transmissions are energy costly because they need to acquire the communication transmissions are energy costly because they need to
medium for a long time. acquire the medium for a long time.
+---------------------------------------+---------------+ +---------------------------------------+---------------+
| Activity | Energy (uJ) | | Activity | Energy |
| | (microjoules) |
+---------------------------------------+---------------+ +---------------------------------------+---------------+
| Broadcast reception | 178 | | Broadcast reception | 178 |
+---------------------------------------+---------------+ +---------------------------------------+---------------+
| Unicast reception | 222 | | Unicast reception | 222 |
+---------------------------------------+---------------+ +---------------------------------------+---------------+
| Broadcast transmission | 1790 | | Broadcast transmission | 1790 |
+---------------------------------------+---------------+ +---------------------------------------+---------------+
| Non-synchronized unicast transmission | 1090 | | Non-synchronized unicast transmission | 1090 |
+---------------------------------------+---------------+ +---------------------------------------+---------------+
| Synchronized unicast transmission | 120 | | Synchronized unicast transmission | 120 |
+---------------------------------------+---------------+ +---------------------------------------+---------------+
| Unicast TX to awake receiver | 96 | | Unicast TX to awake receiver | 96 |
+---------------------------------------+---------------+ +---------------------------------------+---------------+
| Listening (for 1000 ms) | 63000 | | Listening (for 1000 ms) | 63000 |
+---------------------------------------+---------------+ +---------------------------------------+---------------+
Figure 2: Power consumption of common operations involved in Figure 2: Power Consumption of Common Operations Involved in
communication on the Tmote Sky with ContikiMAC Communication on the Tmote Sky with ContikiMAC
At the Physical layer, one approach that may allow reducing energy At the Physical layer, one approach that may reduce the energy
consumption of a device that uses a wireless interface is based on consumption of a device that uses a wireless interface is based on
reducing the device transmit power level as long as the intended next reducing the device transmit power level, as long as the intended
hop(s) are still within range of the device. In some cases, if node next hop(s) is still within range of the device. In some cases, if
A has to transmit a message to node B, a solution to reduce node A node A has to transmit a message to node B, a solution to reduce node
transmit power is to leverage an intermediate device, e.g. node C as A transmit power is to leverage an intermediate device, e.g., node C
a message forwarder. Let d be the distance between node A and node as a message forwarder. Let d be the distance between node A and
B. Assuming free-space propagation, where path loss is proportional node B. Assuming free-space propagation, where path loss is
to d^2, if node C is placed right in the middle of the path between A proportional to d^2, if node C is placed right in the middle of the
and B (that is, at a distance d/2 from both node A and node B), the path between A and B (that is, at a distance d/2 from both node A and
minimum transmit power to be used by node A (and by node C) is node B), the minimum transmit power to be used by node A (and by node
reduced by a factor of 4. However, this solution requires additional C) is reduced by a factor of 4. However, this solution requires
devices, it requires a routing solution, and it also increases additional devices, it requires a routing solution, and it also
transmission delay between A and B. increases transmission delay between A and B.
3. Medium Access Control and Radio Duty Cycling 3. Medium Access Control and Radio Duty Cycling
In networks, communication and power consumption are interdependent. In networks, communication and power consumption are interdependent.
The communication device is typically the most power-consuming The communication device is typically the most power-consuming
component, but merely refraining from transmissions is not enough to component, but merely refraining from transmissions is not enough to
achieve a low power consumption: the radio may consume as much power achieve a low power consumption: the radio may consume as much power
in listen mode as when actively transmitting. This illustrates the in listen mode as when actively transmitting. This illustrates the
key problem known as idle listening, whereby the radio of a device key problem known as idle listening, whereby the radio of a device
may be in receive mode (ready to receive any message), even if no may be in receive mode (ready to receive any message), even if no
message is being transmitted to that device. Idle listening can message is being transmitted to that device. Idle listening can
consume a huge amount of energy unnecessarily. To reduce power consume a huge amount of energy unnecessarily. To reduce power
consumption, the radio must be switched completely off -- duty-cycled consumption, the radio must be switched completely off -- duty-cycled
-- as much as possible. By applying duty-cycling, the lifetime of a -- as much as possible. By applying duty cycling, the lifetime of a
device operating on a common button battery may be on the order of device operating on a common button battery may be on the order of
years, whereas otherwise the battery may be exhausted in a few days years, whereas otherwise the battery may be exhausted in a few days
or even hours. Duty-cycling is a technique generally employed by or even hours. Duty cycling is a technique generally employed by
devices that use the P1 strategy [RFC7228], which need to be able to devices that use the P1 strategy [RFC7228], which need to be able to
communicate on a relatively frequent basis. Note that a more communicate on a relatively frequent basis. Note that a more
aggressive approach to save energy relies on the P0, Normally-off aggressive approach to save energy relies on the P0 (Normally-off)
strategy, whereby devices sleep for very long periods and communicate strategy, whereby devices sleep for very long periods and communicate
infrequently, even though they spend energy in network reattachment infrequently, even though they spend energy in network reattachment
procedures. procedures.
From the perspective of Medium Access Control (MAC) and Radio Duty From the perspective of Medium Access Control (MAC) and Radio Duty
Cycling (RDC), all upper layer protocols, such as routing, RESTful Cycling (RDC), all upper-layer protocols, such as routing, RESTful
communication, adaptation, and management flows, are applications. communication, adaptation, and management flows, are applications.
Since the duty cycling algorithm is the key to energy-efficiency of Since the duty-cycling algorithm is the key to energy efficiency of
the wireless medium, it synchronizes transmission and/or reception the wireless medium, it synchronizes transmission and/or reception
requests from the higher layers. requests from the higher layers.
MAC and RDC are not in the scope of the IETF, yet lower layer MAC and RDC are not in the scope of the IETF, yet lower-layer
designers and chipset manufacturers take great care to save energy. designers and chipset manufacturers take great care to save energy.
By knowing the behaviors of these lower layers, IETF engineers can By knowing the behaviors of these lower layers, engineers can design
design protocols that work well with them. The IETF protocols to be protocols that work well with them. The IETF protocols to be
discussed in the following sections are the customers of the lower discussed in the following sections are the customers of the lower
layers. layers.
3.1. Radio Duty Cycling techniques 3.1. Techniques for Radio Duty Cycling
This subsection describes three main three RDC techniques. Note that This subsection describes three main RDC techniques. Note that more
more than one of these techniques may be available or can even be than one of these techniques may be available or can even be combined
combined in a specific radio technology: in a specific radio technology:
a) Channel sampling. In this solution, the radio interface of a a) Channel sampling: In this solution, the radio interface of a
device periodically monitors the channel for very short time device periodically monitors the channel for very short time
intervals (i.e. with a low duty cycle) with the aim of detecting intervals (i.e., with a low duty cycle) with the aim of detecting
incoming transmissions. In order to make sure that a receiver can incoming transmissions. In order to make sure that a receiver
correctly receive a transmitted data unit, the sender may prepend a can correctly receive a transmitted data unit, the sender may
preamble of a duration at least the sampling period to the data unit prepend a preamble of a duration at least the sampling period to
to be sent. Another option for the sender is to repeatedly transmit the data unit to be sent. Another option for the sender is to
the data unit, instead of sending a preamble before the data unit. repeatedly transmit the data unit instead of sending a preamble
Once a transmission is detected by a receiver, the receiver may stay before the data unit. Once a transmission is detected by a
awake until the complete reception of the data unit. Examples of receiver, the receiver may stay awake until the complete
radio technologies that use preamble sampling include ContikiMAC, the reception of the data unit. Examples of radio technologies that
Coordinated Sampled Listening (CSL) mode of IEEE 802.15.4e, and the use preamble sampling include ContikiMAC, the Coordinated Sampled
Frequently Listening (FL) mode of ITU-T G.9959 [G9959]. Listening (CSL) mode of IEEE 802.15.4e [IEEE802.15.4], and the
Frequently Listening (FL) mode of ITU-T G.9959 [G9959].
b) Scheduled transmissions. This approach allows a device to know b) Scheduled transmissions: This approach allows a device to know
the particular time at which it should be awake (during some time the particular time at which it should be awake (during some time
interval) in order to receive data. Otherwise, the device may remain interval) in order to receive data. Otherwise, the device may
in sleep mode. The decision on the times at which communication is remain in sleep mode. The decision on the times at which
attempted relies on some form of negotation between the involved communication is attempted relies on some form of negotiation
devices. Such negotiation may be performed per transmission or per between the involved devices. Such negotiation may be performed
session/connection. Bluetooth Low Energy (Bluetooth LE) is an per transmission or per session/connection. Bluetooth Low Energy
example of a radio technology based on this mechanism. (Bluetooth LE) is an example of a radio technology based on this
mechanism.
c) Listen after send. This technique allows a node to remain in c) Listen after send: This technique allows a node to remain in
sleep mode by default, wake up and poll a sender (which must be ready sleep mode by default, then wake up and poll a sender (which must
to receive a poll message) for pending transmissions. After sending be ready to receive a poll message) for pending transmissions.
the poll message, the node remains in receive mode, ready for a After sending the poll message, the node remains in receive mode
potential incoming transmission. After a certain time interval, the and is ready for a potential incoming transmission. After a
node may go back to sleep. For example, the Receiver Initiated certain time interval, the node may go back to sleep. For
Transmission (RIT) mode of 802.15.4e, and the transmission of data example, this technique is used in the Receiver Initiated
between a coordinator and a device in IEEE 802.15.4-2003 use this Transmission (RIT) mode of IEEE 802.15.4e [IEEE802.15.4] and in
technique. the transmission of data between a coordinator and a device in
the 2003 version of IEEE 802.15.4 [IEEE802.15.4].
3.2. Latency and buffering 3.2. Latency and Buffering
The latency of a data unit transmission to a duty-cycled device is The latency of a data unit transmission to a duty-cycled device is
equal to or greater than the latency of transmitting to an always-on equal to or greater than the latency of transmitting to an always-on
device. Therefore, duty-cycling leads to a trade-off between energy device. Therefore, duty cycling leads to a trade-off between energy
consumption and latency. Note that in addition to a latency consumption and latency. Note that in addition to a latency
increase, RDC may introduce latency variance, since the latency increase, RDC may introduce latency variance since the latency
increase is a random variable (which is uniformly distributed if increase is a random variable (which is uniformly distributed if duty
duty-cycling follows a periodical behavior). cycling follows a periodic behavior).
On the other hand, due to the latency increase of duty-cycling, a On the other hand, due to the latency increase introduced by duty
sender waiting for a transmission opportunity may need to store cycling, a sender waiting for a transmission opportunity may need to
subsequent outgoing packets in a buffer, increasing memory store subsequent outgoing packets in a buffer. This buffering would
requirements and potentially incurring queuing waiting time that increase memory requirements and potentially incur queuing wait
contributes to the packet's overall delay and increases the times. Such wait times would in turn contribute to packet
probability of buffer overflow, leading to losses. transmission delay and increase the probability of buffer overflow,
leading to losses.
3.3. Throughput 3.3. Throughput
Although throughput is not typically a key concern in constrained Although throughput is not typically a key concern in constrained-
node network applications, it is indeed important in some services in node network applications, it is indeed important in some services in
such networks, such as over-the-air software updates or when off-line such networks, such as over-the-air software updates or when off-line
sensors accumulate measurements that have to be quickly transferred sensors accumulate measurements that have to be quickly transferred
when there is an opportunity for connectivity. when there is an opportunity for connectivity.
Since RDC introduces inactive intervals in energy-constrained Since RDC introduces inactive intervals in energy-constrained
devices, it reduces the throughput that can be achieved when devices, it reduces the throughput that can be achieved when
communicating with such devices. There exists a trade-off between communicating with such devices. There exists a trade-off between
the achievable throughput and energy consumption. the achievable throughput and energy consumption.
3.4. Radio interface tuning 3.4. Radio Interface Tuning
The parameters controlling the radio duty cycle have to be carefully The parameters controlling the radio duty cycle have to be carefully
tuned to achieve the intended application and/or network tuned to achieve the intended application and/or network
requirements. On the other hand, upper layers should take into requirements. On the other hand, upper layers should take into
account the expected latency and/or throughput behavior due to RDC. account the expected latency and/or throughput behavior due to RDC.
The next subsection provides details on key parameters controlling The next subsection provides details on key parameters controlling
RDC mechanisms, and thus fundamental trade-offs, for various examples RDC mechanisms, and thus fundamental trade-offs, for various examples
of relevant low-power radio technologies. of relevant low-power radio technologies.
3.5. Packet bundling 3.5. Packet Bundling
Another technique that may be useful to increase communication energy Another technique that may be useful to increase communication energy
efficiency is packet bundling. This technique, which is available in efficiency is packet bundling. This technique, which is available in
several radio interfaces (e.g. LTE and some 802.11 variants), allows several radio interfaces (e.g., LTE and some 802.11 variants), allows
to aggregate several small packets into a single large packet. for aggregation of several small packets into a single large packet.
Header and communication overhead is therefore reduced. Header and communication overhead is therefore reduced.
3.6. Power save services available in example low-power radios 3.6. Power Save Services Available in Example Low-Power Radios
This subsection presents power save services and techniques used in a This subsection presents power save services and techniques used in a
few relevant examples of wireless low-power radios: IEEE 802.11, few relevant examples of wireless low-power radios: IEEE 802.11
Bluetooth LE and IEEE 802.15.4. For a more detailed overview of each [IEEE802.11], Bluetooth LE, and IEEE 802.15.4 [IEEE802.15.4]. For a
technology, the reader may refer to the literature or to the more detailed overview of each technology, the reader may refer to
corresponding specifications. the literature or to the corresponding specifications.
3.6.1. Power Save Services Provided by IEEE 802.11 3.6.1. Power Save Services Provided by IEEE 802.11
IEEE 802.11 defines the Power Save Mode (PSM) whereby a station may IEEE 802.11 [IEEE802.11] defines the Power Save Mode (PSM) whereby a
indicate to an Access Point (AP) that it will enter a sleep mode station may indicate to an Access Point (AP) that it will enter a
state. While the station is sleeping, the AP buffers any frames that sleep mode state. While the station is sleeping, the AP buffers any
should be sent to the sleeping station. The station wakes up every frames that should be sent to the sleeping station. The station
Listen Interval (which can be a multiple of the Beacon Interval) in wakes up every listen interval (which can be a multiple of the beacon
order to receive beacons. The AP signals in the beacon whether there interval) in order to receive beacons. The AP signals, by means of a
is data pending for the station or not. If there are not frames to beacon field, whether there is data pending for the station or not.
be sent to the station, the latter may get back to sleep mode.
Otherwise, the station may send a message requesting the transmission
of the buffered data and stay awake in receive mode.
IEEE 802.11v [IEEE80211v] further defines mechanisms and services for If there are not frames to be sent to the station, the latter may get
power save of stations/nodes that include flexible multicast service back to sleep mode. Otherwise, the station may send a message
(FMS), proxy ARP advertisement, extended sleep modes, and traffic requesting the transmission of the buffered data and stay awake in
filtering. Upper layer protocols knowledge of such capabilities receive mode.
provided by the lower layer enables better interworking.
IEEE 802.11v [IEEE802.11] further defines mechanisms and services for
power save of stations/nodes that include Flexible Multicast Service
(FMS), Proxy ARP advertisement, extended sleep modes, and traffic
filtering. Upper-layer protocol's knowledge of such capabilities,
provided by the lower layer, enables better interworking.
These services include: These services include:
Proxy ARP: The Proxy ARP capability enables an Access Point (AP) to Proxy ARP: The Proxy ARP capability enables an Access Point (AP) to
indicate that the non-AP station (STA) will not receive ARP frames. indicate that the non-AP station (STA) will not receive ARP
The Proxy ARP capability enables the non-AP STA to remain in power- frames. The Proxy ARP capability enables the non-AP STA to remain
save for longer periods of time. in power save mode for longer periods of time.
Basic Service Set (BSS) Max Idle Period management enables an AP to Basic Service Set (BSS) Max Idle Period Management: Enables an AP to
indicate a time period during which the AP does not disassociate a indicate a time period during which the AP does not disassociate a
STA due to non-receipt of frames from the STA. This supports STA due to non-receipt of frames from the STA. This supports
improved STA power saving and AP resource management. improved STA power saving and AP resource management.
FMS: A service in which a non-access point (non-AP) STA can request a FMS: A service in which a non-AP STA can request a multicast
multicast delivery interval longer than the delivery traffic delivery interval longer than the Delivery Traffic Indication
indication message (DTIM) interval for the purposes of lengthening Message (DTIM) interval for the purposes of lengthening the period
the period of time a STA may be in a power save state. of time a STA may be in a power save state.
Traffic Filtering Service (TFS): A service provided by an access Traffic Filtering Service (TFS): A service provided by an AP to a
point (AP) to a non-AP STA that can reduce the number of frames sent non-AP STA that can reduce the number of frames sent to the STA by
to the STA by dropping individually addressed frames that do not dropping individually addressed frames that do not match traffic
match traffic filters specified by the STA. filters specified by the STA.
Using the above services provided by the lower layer, the constrained Using the above services provided by the lower layer, the constrained
nodes can achieve either client initiated power save (via TFS) or nodes can achieve either client-initiated power save (via TFS) or
network assisted power save (Proxy-ARP, BSS Max Idel Period and FMS). network-assisted power save (Proxy ARP, BSS Max Idle Period, and
FMS).
Upper layer protocols should synchronize with the parameters such as Upper-layer protocols should synchronize with the parameters such as
FMS interval and BSS MAX Idle Period, so that the wireless FMS interval and BSS MAX Idle Period so that the wireless
transmissions are not triggered periodically. transmissions are not triggered periodically.
3.6.2. Power Save Services Provided by Bluetooth LE 3.6.2. Power Save Services Provided by Bluetooth LE
Bluetooth LE is a wireless low-power communications technology that Bluetooth LE is a wireless low-power communications technology that
is the hallmark component of the Bluetooth 4.0, 4.1, and 4.2 is the hallmark component of the Bluetooth 4.0, 4.1, and 4.2
specifications [Bluetooth42]. BT-LE has been designed for the goal specifications [Bluetooth42]. BTLE has been designed for the goal of
of ultra-low-power consumption. IPv6 can be run IPv6 over Bluetooth ultra-low power consumption. IPv6 can be run IPv6 over Bluetooth LE
LE networks by using a 6LoWPAN variant adapted to BT-LE [RFC7668]. networks by using a 6LoWPAN variant adapted to BTLE [RFC7668].
Bluetooth LE networks comprise a master and one or more slaves which Bluetooth LE networks comprise a master and one or more slaves, which
are connected to the master. The Bluetooth LE master is assumed to are connected to the master. The Bluetooth LE master is assumed to
be a relatively powerful device, whereas a slave is typically a be a relatively powerful device, whereas a slave is typically a
constrained device (e.g. a class 1 device). constrained device (e.g., a Class 1 device).
Medium access in Bluetooth LE is based on a Time Division Multiple Medium access in Bluetooth LE is based on a Time-Division Multiple
Access (TDMA) scheme which is coordinated by the master. This device Access (TDMA) scheme that is coordinated by the master. This device
determines the start of connection events, in which communication determines the start of connection events in which communication
between the master and a slave takes place. At the beginning of a between the master and a slave takes place. At the beginning of a
connection event, the master sends a poll message, which may connection event, the master sends a poll message, which may
encapsulate data, to the slave. The latter must send a response, encapsulate data, to the slave. The latter must send a response,
which may also contain data. The master and the slave may continue which may also contain data. The master and the slave may continue
exchanging data until the end of the connection event. The next exchanging data until the end of the connection event. The next
opportunity for communication between the master and the slave will opportunity for communication between the master and the slave will
be in the next connection event scheduled for the slave. be in the next connection event scheduled for the slave.
The time between consecutive connection events is defined by the The time between consecutive connection events is defined by the
connInterval parameter, which may range between 7.5 ms and 4 s. The connInterval parameter, which may range between 7.5 ms and 4 s. The
slave may remain in sleep mode since the end of its last connection slave may remain in sleep mode from the end of its last connection
event until the beginning of its next connection event. Therefore, event until the beginning of its next connection event. Therefore,
Bluetooth LE is duty-cycled by design. Furthermore, after having Bluetooth LE is duty-cycled by design. Furthermore, after having
replied to the master, a slave is not required to listen to the replied to the master, a slave is not required to listen to the
master (and thus may keep the radio in sleep mode) for master (and thus may keep the radio in sleep mode) for
connSlaveLatency consecutive connection events. connSlaveLatency is connSlaveLatency consecutive connection events. connSlaveLatency is
an integer parameter between 0 and 499 which should not cause link an integer parameter between 0 and 499 that should not cause link
inactivity for more than connSupervisionTimeout time. The inactivity for more than connSupervisionTimeout time. The
connSupervisionTimeout parameter is in the range between 100 ms and connSupervisionTimeout parameter is in the range between 100 ms and
32 s. 32 s.
Upper layer protocols should take into account the medium access and Upper-layer protocols should take into account the medium access and
duty-cycling behavior of Bluetooth LE. In particular, connInterval, duty-cycling behavior of Bluetooth LE. In particular, connInterval,
connSlaveLatency and connSupervisionTimeout determine the time connSlaveLatency, and connSupervisionTimeout determine the time
between two consecutive connection events for a given slave. The between two consecutive connection events for a given slave. The
upper layer packet generation pattern and rate should be consistent upper-layer packet generation pattern and rate should be consistent
with the settings of the aforementioned parameters (and vice versa). with the settings of the aforementioned parameters (and vice versa).
For example, assume connInterval=4 seconds, connSlaveLatency=7 and For example, assume connInterval = 4 seconds, connSlaveLatency =
connSupervisionTimeout=32 seconds. With these settings, 7 seconds, and connSupervisionTimeout = 32 seconds. With these
communication opportunities between a master and a slave will occur settings, communication opportunities between a master and a slave
during a given interval every 32 seconds. Duration of the interval will occur during a given interval every 32 seconds. Duration of the
will depend on several factors, including number of connected slaves, interval will depend on several factors, including number of
amount of data to be transmitted, etc. In the worst case, only one connected slaves, amount of data to be transmitted, etc. In the
data unit can be sent from master to slave and vice versa every 32 worst case, only one data unit can be sent from master to slave (and
seconds. vice versa) every 32 seconds.
3.6.3. Power Save Services in IEEE 802.15.4 3.6.3. Power Save Services in IEEE 802.15.4
IEEE 802.15.4 is a family of standard radio interfaces for low-rate, IEEE 802.15.4 [IEEE802.15.4] is a family of standard radio interfaces
low-power wireless networking [fifteendotfour]. Since the for low-rate, low-power wireless networking. Since the publication
publication of its first version in 2003, IEEE 802.15.4 has become of its first version in 2003, IEEE 802.15.4 [IEEE802.15.4] has become
the de-facto choice for a wide range of constrained node network the de facto choice for a wide range of constrained-node network
application domains and has been a primary target technology of application domains and has been a primary target technology of
various IETF working groups such as 6LoWPAN [RFC6282], [RFC6775], various IETF working groups such as 6LoWPAN [RFC6282] [RFC6775]
[RFC4944] and 6TiSCH [I-D.ietf-6tisch-architecture]. IEEE 802.15.4 [RFC4944] and 6TiSCH [ARCH-6TiSCH]. IEEE 802.15.4 [IEEE802.15.4]
specifies a variety of related PHY and MAC layer functionalites. specifies a variety of related Physical layer (PHY) and MAC layer
functionalities.
IEEE 802.15.4 defines three roles called device, coordinator and IEEE 802.15.4 [IEEE802.15.4] defines three roles called device,
Personal Area Network (PAN) coordinator. The device role is adequate coordinator, and Personal Area Network (PAN) coordinator. The device
for nodes that do not implement the complete IEEE 802.15.4 role is adequate for nodes that do not implement the complete IEEE
functionality, and is mainly targeted for constrained nodes with a 802.15.4 [IEEE802.15.4] functionality and is mainly targeted for
limited energy source. The coordinator role includes synchronization constrained nodes with a limited energy source. The coordinator role
capabilities and is suitable for nodes that do not suffer severe includes synchronization capabilities and is suitable for nodes that
constraints (e.g. a mains-powered node). The PAN coordinator is a do not suffer severe constraints (e.g., a mains-powered node). The
special type of coordinator that acts as a principal controller in an PAN coordinator is a special type of coordinator that acts as a
IEEE 802.15.4 network. principal controller in an IEEE 802.15.4 [IEEE802.15.4] network.
IEEE 802.15.4 defines two main types of networks depending on their IEEE 802.15.4 [IEEE802.15.4] defines two main types of networks
configuration: beacon-enabled and nonbeacon-enabled networks. In the depending on their configuration: beacon-enabled and non-beacon-
first network type, coordinators periodically transmit beacons. The enabled networks. In the first network type, coordinators
time between beacons is divided in three main parts: the Contention periodically transmit beacons. The time between beacons is divided
Access Period (CAP), the Contention Free Period (CFP) and an inactive in three main parts: the Contention Access Period (CAP), the
period. In the first period, nodes use slotted Carrier Sense Contention Free Period (CFP), and an inactive period. In the first
Multiple Access / Collision Avoidance (CSMA/CA) for data period, nodes use slotted Carrier Sense Multiple Access with
communication. In the second one, a TDMA scheme controls medium Collision Avoidance (CSMA/CA) for data communication. In the second
access. During the idle period, communication does not take place, one, a TDMA scheme controls medium access. During the idle period,
thus the inactive period is a good opportunity for nodes to turn the communication does not take place, and thus the inactive period is a
radio off and save energy. The coordinator announces in each beacon good opportunity for nodes to turn the radio off and save energy.
the list of nodes for which data will be sent in the subsequent The coordinator announces in each beacon the list of nodes for which
period. Therefore, devices may remain in sleep mode by default and data will be sent in the subsequent period. Therefore, devices may
wake up periodically to listen to the beacons sent by their remain in sleep mode by default and wake up periodically to listen to
coordinator. If a device wants to transmit data, or learns from a the beacons sent by their coordinator. If a device wants to transmit
beacon that it is an intended destination, then it will exchange data, or learns from a beacon that it is an intended destination,
messages with the coordinator (and thus consume energy). An then it will exchange messages with the coordinator (and thus consume
underlying assumption is that when a message is sent to a energy). An underlying assumption is that when a message is sent to
coordinator, the radio of the coordinator will be ready to receive a coordinator, the radio of the coordinator will be ready to receive
the message. the message.
The beacon interval and the duration of the beacon interval active The beacon interval and the duration of the active portion of the
portion (i.e. the CAP and the CFP), and thus the duty cycle, can be beacon interval (i.e., the CAP and the CFP), and thus the duty cycle,
configured. The parameters that control these times are called can be configured. The parameters that control these times are
macBeaconOrder and macSuperframeOrder, respectively. As an example, called macBeaconOrder and macSuperframeOrder, respectively. As an
when IEEE 802.15.4 operates in the 2.4 GHz PHY, both times can be example, when IEEE 802.15.4 [IEEE802.15.4] operates in the 2.4 GHz
(independently) set to values in the range between 15.36 ms and 251.6 PHY, both times can be (independently) set to values in the range
seconds. between 15.36 ms and 251.6 s.
In the beaconless mode, nodes use unslotted CSMA/CA for data In the beaconless mode, nodes use unslotted CSMA/CA for data
transmission. The device may be in sleep mode by default and may transmission. The device may be in sleep mode by default and may
activate its radio to either i) request to the coordinator whether activate its radio to either i) request to the coordinator whether
there is pending data for the device, or ii) to transmit data to the there is pending data for the device, or to ii) transmit data to the
coordinator. The wake-up pattern of the device, if any, is out of coordinator. The wake-up pattern of the device, if any, is out of
the scope of IEEE 802.15.4. the scope of IEEE 802.15.4 [IEEE802.15.4].
Communication between the two ends of an IEEE 802.15.4 link may also Communication between the two ends of an IEEE 802.15.4 [IEEE802.15.4]
take place in a peer-to-peer configuration, whereby both link ends link may also take place in a peer-to-peer configuration, whereby
assume the same role. In this case, data transmission can happen at both link ends assume the same role. In this case, data transmission
any moment. Nodes must have their radio in receive mode, and be can happen at any moment. Nodes must have their radio in receive
ready to listen to the medium by default (which for battery-enabled mode and be ready to listen to the medium by default (which for
nodes may lead to a quick battery depletion), or apply battery-enabled nodes may lead to a quick battery depletion) or apply
synchronization techniques. The latter are out of the scope of IEEE synchronization techniques. The latter are out of the scope of IEEE
802.15.4. 802.15.4 [IEEE802.15.4].
The main MAC layer IEEE 802.15.4 amendment to date is IEEE 802.15.4e. The main MAC layer IEEE 802.15.4 [IEEE802.15.4] amendment to date is
This amendment includes various new MAC layer modes, some of which IEEE 802.15.4e. This amendment includes various new MAC layer modes,
include mechanisms for low energy consumption. Among these, the some of which include mechanisms for low energy consumption. Among
Time-Slotted Channel Hopping (TSCH) is an outstanding mode which these, the Time-Slotted Channel Hopping (TSCH) is an outstanding mode
offers robust features for industrial environments, among others. In that offers robust features for industrial environments, among
order to provide the functionality needed to enable IPv6 over TSCH, others. In order to provide the functionality needed to enable IPv6
the 6TiSCH working group was created. TSCH is based on a TDMA over TSCH, the 6TiSCH Working Group was created. TSCH is based on a
schedule whereby a set of time slots are used for frame transmission TDMA schedule whereby a set of timeslots are used for frame
and reception, and other time slots are unscheduled. The latter time transmission and reception, and other timeslots are unscheduled. The
slots may be used by a dynamic scheduling mechanism, otherwise nodes latter timeslots may be used by a dynamic scheduling mechanism,
may keep the radio off during the unscheduled time slots, thus saving otherwise, nodes may keep the radio off during the unscheduled
energy. The minimal schedule configuration specified in timeslots, thus saving energy. The minimal schedule configuration
[I-D.ietf-6tisch-minimal] comprises 101 time slots; 95 of these time specified in [RFC8180] comprises 101 timeslots; 95 of these timeslots
slots are unscheduled and the time slot duration is 15 ms. are unscheduled and the timeslot duration is 15 ms.
The previously mentioned CSL and RIT are also 802.15.4e modes The previously mentioned CSL and RIT are also 802.15.4e modes
designed for low energy. designed for low energy.
3.6.4. Power Save Services in DECT ULE 3.6.4. Power Save Services in DECT ULE
DECT Ultra Low Energy (DECT ULE) is a wireless technology building on DECT Ultra Low Energy (DECT ULE) is a wireless technology building on
the key fundamentals of traditional DECT / CAT-iq [EN300] but with the key fundamentals of traditional DECT / Cordless Advanced
specific changes to significantly reduce the power consumption at the Technology - internet and quality (CAT-iq) [EN300] but with specific
expense of data throughput [TS102]. DECT ULE devices typically changes to significantly reduce the power consumption at the expense
operate on special power optimized silicon, but can connect to a DECT of data throughput [TS102]. DECT ULE devices typically operate on
Gateway supporting traditional DECT / CAT-iq for cordless telephony special power-optimized silicon but can connect to a DECT Gateway
and data as well as the DECT ULE extensions. IPv6 can be run over supporting traditional DECT/CAT-iq for cordless telephony and data as
DECT ULE by using a 6LoWPAN variant [I-D.ietf-6lo-dect-ule]. well as the DECT ULE extensions. IPv6 can be run over DECT ULE by
using a 6LoWPAN variant [RFC8105].
DECT defines two major roles: the Portable Part (PP) is the power DECT defines two major roles: the Portable Part (PP) is the power
constrained device, while the Fixed Part (FP) is the Gateway or base constrained device while the Fixed Part (FP) is the Gateway or base
station in a star topology. DECT operates in license free and station in a star topology. Because TDMA/FDMA and Time-Division
reserved frequency bands based on TDMA/FDMA and TDD using dynamic Duplex (TDD) using dynamic channel allocation for interference, DECT
channel allocation for interference avoidance. It provides good operates in license-free and reserved frequency bands. It provides
indoor (~50 m) and outdoor (~300 m) coverage. It uses a frame length good indoor (~50 m) and outdoor (~300 m) coverage. It uses a frame
of 10 ms divided into 24 timeslots, and it supports connection length of 10 ms divided into 24 timeslots, and it supports
oriented, packet data and connection-less services. connection-oriented packet data and connection-less services.
The FP usually transmits a so-called dummy bearer (beacon) that is The FP usually transmits a so-called dummy bearer (beacon) that is
used to broadcast synchronization, system and paging information. used to broadcast synchronization, system, and paging information.
The slot/carrier position of this dummy bearer can automatically be The slot/carrier position of this dummy bearer can automatically be
reallocated in order to avoid mutual interference with other DECT reallocated in order to avoid mutual interference with other DECT
signals. signals.
At the MAC level DECT ULE communications between FP and PP are At the MAC level, DECT ULE communications between FP and PP are
initiated by the PP. A FP can initiate communication indirectly by initiated by the PP. An FP can initiate communication indirectly by
sending paging signal to a PP. The PP determines the timeslot and sending a paging signal to a PP. The PP determines the timeslot and
frequency on which the communication between FP and PP takes place. frequency in which the communication between FP and PP takes place.
The PP verifies the radio timeslot/frequency position is unoccupied The PP verifies the radio timeslot/frequency position is unoccupied
before it initiates its transmitter. An access-request message, before it initiates its transmitter. An access-request message,
which usually carries data, is sent to the FP. The FP sends a which usually carries data, is sent to the FP. The FP sends a
confirm message, which also may carry data. More data can be sent in confirm message, which also may carry data. More data can be sent in
subsequent frames. A MAC level automatic retransmission scheme subsequent frames. A MAC-level automatic retransmission scheme
significantly improves data transfer reliability. A segmentation and significantly improves the reliability of data transfer. A
reassembly scheme supports transfer of larger higher layer SDUs and segmentation and reassembly scheme supports transfer of larger,
provides data integrity check. The DECT ULE packet data service higher-layer Service Data Units (SDUs) and provides data integrity
ensures data integrity, proper sequencing, duplicate protection, but checks. The DECT ULE packet data service ensures data integrity,
not guaranteed delivery. Higher layers protocols have to take this proper sequencing, and duplicate protection but not guaranteed
into consideration. delivery. Higher-layer protocols have to take this into
consideration.
The FP may send paging information to PPs to trigger connection setup The FP may send paging information to PPs to trigger connection setup
and indicate the required service type. The interval between paging and indicate the required service type. The interval between paging
information to a specific PP can be defined in range 10 ms to 327 information to a specific PP can be defined in the range of 10 ms to
seconds. The PP may enter sleep mode to save power. The listening 327 s. The PP may enter sleep mode to save power. The listening
interval is defined by the PP application. For short sleep intervals interval is defined by the PP application. For short sleep intervals
(below ~10 seconds) the PP may be able to retain synchronization to (below ~10 seconds), the PP may be able to retain synchronization to
the FP dummy bearer and only turn on the receiver during the expected the FP dummy bearer and only turn on the receiver during the expected
timeslot. For longer sleep intervals the PP can't keep timeslot. For longer sleep intervals, the PP can't keep
synchronization and has to search for and resynchronize to the FP synchronization and has to search for, and resynchronize to, the FP
dummybearer. Hence, longer sleep interval reduces the average energy dummy bearer. Hence, longer sleep intervals reduce the average
consumption, but adds a energy consumption penalty for acquiring energy consumption but add an energy consumption penalty for
synchronization to the FP dummy bearer. The PP can obtain all acquiring synchronization to the FP dummy bearer. The PP can obtain
information to determine paging and acquire synchronization all information to determine paging and acquire synchronization
information in a single reception of one full timeslot. information in a single reception of one full timeslot.
Packet data latency is normally 30 ms for short packets (below or Packet data latency is normally 30 ms for short packets (below or
equal to 32 octets), however if retry and back-off scenarios occur, equal to 32 octets), however, if retry and back-off scenarios occur,
the latency is increased. The latency can actually be reduced to the latency is increased. The latency can actually be reduced to
about 10 ms by doing energy consuming RSSI scanning in advance. In about 10 ms by doing energy consuming Received Signal Strength
the direction from FP to PP the latency is usually increased by the Indication (RSSI) scanning in advance. In the direction from FP to
used paging interval and the sleep interval. The MAC layer can PP, the latency is usually increased by the used paging interval and
piggyback commands to improve efficiency (reduce latency) of higher the sleep interval. The MAC layer can piggyback commands to improve
layer protocols. Such commands can instruct the PP to initiate a new efficiency (reduce latency) of higher-layer protocols. Such commands
packet transfer in N frames without the need for resynchronization can instruct the PP to initiate a new packet transfer in N frames
and listening to paging or instruct the PP to stay in a higher duty without the need for resynchronization and can listen to paging or
cycle paging detection mode. instruct the PP to stay in a higher duty-cycle paging detection mode.
The DECT ULE technology allows per PP configuration of paging The DECT ULE technology allows a per-PP configuration of paging
interval, MTU size, reassembly window size and higher layer service interval, MTU size, reassembly window size, and higher-layer service
negotiation and protocol. negotiation and protocol.
4. IP Adaptation and Transport Layer 4. IP Adaptation and Transport Layer
6LoWPAN provides an adaptation layer designed to support IPv6 over 6LoWPAN provides an adaptation layer designed to support IPv6 over
IEEE 802.15.4. 6LoWPAN affects the energy-efficiency problem in three IEEE 802.15.4 [IEEE802.15.4]. 6LoWPAN affects the energy-efficiency
aspects, as follows. problem in three aspects, as follows.
First, 6LoWPAN provides one fragmentation and reassembly mechanism First, 6LoWPAN provides one fragmentation and reassembly mechanism,
which is aimed at solving the packet size issue in IPv6 and could which is aimed at solving the packet size issue in IPv6 and could
also affect energy-efficiency. IPv6 requires that every link in the also affect energy efficiency. IPv6 requires that every link in the
internet have an MTU of 1280 octets or greater. On any link that Internet have an MTU of 1280 octets or greater. On any link that
cannot convey a 1280-octet packet in one piece, link-specific cannot convey a 1280-octet packet in one piece, link-specific
fragmentation and reassembly must be provided at a layer below IPv6 fragmentation and reassembly must be provided at a layer below IPv6
[RFC2460]. 6LoWPAN provides fragmentation and reassembly below the [RFC8200]. 6LoWPAN provides fragmentation and reassembly below the
IP layer to solve the problem. One of the benefits from placing IP layer to solve the problem. One of the benefits from placing
fragmentation at a lower layer such as the 6LoWPAN layer is that it fragmentation at a lower layer such as the 6LoWPAN layer is that it
can avoid the presence of more IP headers, because fragmentation at can avoid the presence of more IP headers because fragmentation at
the IP layer will produce more IP packets, each one carrying its own the IP layer will produce more IP packets, each one carrying its own
IP header. However, performance can be severely affected if, after IP header. However, performance can be severely affected if, after
IP layer fragmentation, then 6LoWPAN fragmentation happens as well IP layer fragmentation, then 6LoWPAN fragmentation happens as well
(e.g. when the upper layer is not aware of the existence of the (e.g., when the upper layer is not aware of the existence of the
fragmentation at the 6LoWPAN layer). One solution is to require fragmentation at the 6LoWPAN layer). One solution is to require that
higher layers awareness of lower layer features and generate small the higher layers have an awareness of the lower-layer features and
enough packets to avoid fragmentation. In this regard, the Block generate small enough packets to avoid fragmentation. In this
option in CoAP can be useful when CoAP is used at the application regard, the Block option in CoAP can be useful when CoAP is used at
layer [RFC 7959]. the application layer [RFC7959].
Secondly, 6LoWPAN swaps computing with communication. 6LoWPAN applies Secondly, 6LoWPAN swaps computing with communication. 6LoWPAN applies
compression of the IPv6 header. Subject to the packet size limit of compression of the IPv6 header. Subject to the packet size limit of
IEEE 802.15.4, 40 octets long IPv6 header and 8 octets or 20 octets IEEE 802.15.4 [IEEE802.15.4], a 40-octet-long IPv6 header and an 8 or
long UDP and TCP header will consume even more packet space than the 20-octet-long UDP and TCP header will consume even more packet space
data itself. 6LoWPAN provides IPv6 and UDP header compression at the than the data itself. 6LoWPAN provides IPv6 and UDP header
adaptation layer. Therefore, a lower amount of data will be handled compression at the adaptation layer. Therefore, a lower amount of
by the lower layers, whereas both the sender and receiver will spend data will be handled by the lower layers, whereas both the sender and
more computing power on the compression and decompression of the receiver will spend more computing power on the compression and
packets over the air. Compression can also be performed at higher decompression of the packets over the air. Compression can also be
layers (see Section 6.4). performed at higher layers (see Section 6.4).
Finally, the 6LoWPAN working group developed the energy-efficient Finally, the 6LoWPAN Working Group developed the energy-efficient
Neighbor Discovery called 6LoWPAN-ND, which is an energy efficient Neighbor Discovery called 6LoWPAN-ND, which is an energy-efficient
replacement of the IPv6 ND in constrained environments. IPv6 replacement of the IPv6 ND in constrained environments. IPv6
Neighbor Discovery was not designed for non-transitive wireless Neighbor Discovery was not designed for non-transitive wireless
links, as its heavy use of multicast makes it inefficient and links, as its heavy use of multicast makes it inefficient and
sometimes impractical in a low-power and lossy network. 6LoWPAN-ND sometimes impractical in a low-power and lossy network. 6LoWPAN-ND
describes simple optimizations to IPv6 Neighbor Discovery, its describes simple optimizations to IPv6 Neighbor Discovery, its
addressing mechanisms, and duplicate address detection for Low-power addressing mechanisms, and duplicate address detection for Low-Power
Wireless Personal Area Networks and similar networks. However, Wireless Personal Area Networks and similar networks. However,
6LoWPAN ND does not modify Neighbor Unreachability Detection (NUD) 6LoWPAN-ND does not modify Neighbor Unreachability Detection (NUD)
timeouts, which are very short (by default three transmissions spaced timeouts, which are very short (by default three transmissions spaced
one second apart). NUD timeout settings should be tuned taking into 1 second apart). NUD timeout settings should be tuned to take into
account the latency that may be introduced by duty-cycled mechanisms account the latency that may be introduced by duty-cycled mechanisms
at the link layer, or alternative, less impatient NUD algorithms at the link layer or the alternative, less impatient NUD algorithms
should be considered [I-D.ietf-6man-impatient-nud]. should be considered [RFC7048].
IPv6 underlies the higher layer protocols, including both TCP/UDP IPv6 underlies the higher-layer protocols, including both TCP/UDP
transport and applications. By design, the higher-layer protocols do transport and applications. By design, the higher-layer protocols do
not typically have specific information about the lower layers, and not typically have specific information about the lower layers and
thus cannot solve the energy-efficiency problem. thus cannot solve the energy-efficiency problem.
The network stack can be designed to save computing power. For The network stack can be designed to save computing power. For
example the Contiki implementation has multiple cross layer example, the Contiki implementation has multiple cross-layer
optimizations for buffers and energy management, e.g., the computing optimizations for buffers and energy management, e.g., the computing
and validation of UDP/TCP checksums without the need of reading IP and validation of UDP/TCP checksums without the need of reading IP
headers from a different layer. These optimizations are software headers from a different layer. These optimizations are software
implementation techniques, and out of the scope of IETF and the LWIG implementation techniques and are out of the scope of the IETF and
working group. the LWIG Working Group.
5. Routing Protocols 5. Routing Protocols
RPL [RFC6550] is a routing protocol designed by the IETF for RPL [RFC6550] is a routing protocol designed by the IETF for
constrained environments. RPL exchanges messages periodically and constrained environments. RPL exchanges messages periodically and
keeps routing states for each destination. RPL is optimized for the keeps routing states for each destination. RPL is optimized for the
many-to-one communication pattern, where network nodes primarily send many-to-one communication pattern (where network nodes primarily send
data towards the border router, but has provisions for any-to-any data towards the border router) but has provisions for any-to-any
routing as well. routing as well.
The authors of the Powertrace tool [Powertrace] studied the power The authors of the Powertrace tool [Powertrace] studied the power
profile of RPL. Their analysis divides the routing protocol into profile of RPL. Their analysis divides the routing protocol into
control and data traffic. The control plane carries ICMP messages to control and data traffic. The control plane carries ICMP messages to
establish and maintain the routing states. The data plane carries establish and maintain the routing states. The data plane carries
any application that uses RPL for routing packets. The study has any application that uses RPL for routing packets. The study has
shown that the power consumption of the control traffic goes down shown that the power consumption of the control traffic goes down
over time in a relatively stable network. The study also reflects over time in a relatively stable network. The study also reflects
that the routing protocol should keep the control traffic as low as that the routing protocol should keep the control traffic as low as
possible to make it energy-friendly. The amount of RPL control possible to make it energy friendly. The amount of RPL control
traffic can be tuned by setting the Trickle [RFC6206] algorithm traffic can be tuned by setting the Trickle [RFC6206] algorithm
parameters (i.e. Imin, Imax and k) to appropriate values. However, parameters (i.e., Imin, Imax, and k) to appropriate values. However,
there exists a trade-off between energy consumption and other there exists a trade-off between energy consumption and other
performance parameters such as network convergence time and performance parameters such as network convergence time and
robustness. robustness.
RFC 6551 [RFC6551] defines routing metrics and constraints to be used RFC 6551 [RFC6551] defines routing metrics and constraints to be used
by RPL in route computation. Among others, RFC 6551 specifies a Node by RPL in route computation. Among others, RFC 6551 specifies a Node
Energy object that allows to provide information related to node Energy object that allows to provide information related to node
energy, such as the energy source type or the estimated percentage of energy, such as the energy source type or the estimated percentage of
remaining energy. Appropriate use of energy-based routing metrics remaining energy. Appropriate use of energy-based routing metrics
may help to balance energy consumption of network nodes, minimize may help to balance energy consumption of network nodes, minimize
network partitioning and increase network lifetime. network partitioning, and increase network lifetime.
6. Application Layer 6. Application Layer
6.1. Energy efficient features in CoAP 6.1. Energy-Efficient Features in CoAP
CoAP [RFC7252] is designed as a RESTful application protocol, CoAP [RFC7252] is designed as a RESTful application protocol that
connecting the services of smart devices to the World Wide Web. CoAP connects the services of smart devices to the World Wide Web. CoAP
is not a chatty protocol. It provides basic communication services is not a chatty protocol. It provides basic communication services
such as service discovery and GET/POST/PUT/DELETE methods with a such as service discovery and GET/POST/PUT/DELETE methods with a
binary header. binary header.
Energy efficiency is part of the CoAP protocol design. CoAP uses a Energy efficiency is part of the CoAP protocol design. CoAP uses a
fixed-length binary header of only four bytes that may be followed by fixed-length binary header of only four bytes that may be followed by
binary options. To reduce regular and frequent queries of the binary options. To reduce regular and frequent queries of the
resources, CoAP provides an observe mode, in which the requester resources, CoAP provides an observe mode in which the requester
registers its interest of a certain resource and the responder will registers its interest of a certain resource and the responder will
report the value whenever it was updated. This reduces the request report the value whenever it was updated. This reduces the request/
response round trips while keeping information exchange a ubiquitous response round trips while keeping information exchange an ubiquitous
service; an energy-constrained server can remain in sleep mode during service; an energy-constrained server can remain in sleep mode during
the period between observe notification transmissions. the period between observe notification transmissions.
Furthermore, [RFC7252] defines CoAP proxies which can cache resource Furthermore, [RFC7252] defines CoAP proxies that can cache resource
representations previously provided by sleepy CoAP servers. The representations previously provided by sleepy CoAP servers. The
proxies themselves may respond to client requests if the proxies themselves may respond to client requests if the
corresponding server is sleeping and the resource representation is corresponding server is sleeping and the resource representation is
recent enough. Otherwise, a proxy may attempt to obtain the resource recent enough. Otherwise, a proxy may attempt to obtain the resource
from the sleepy server. from the sleepy server.
CoAP proxy and cache functionality may also be used to perform data CoAP proxy and cache functionality may also be used to perform data
aggregation. This technique allows a node to receive data messages aggregation. This technique allows a node to receive data messages
(e.g. carrying sensor readings) from other nodes in the network, (e.g., carrying sensor readings) from other nodes in the network,
perform an operation based on the content in those messages, and perform an operation based on the content in those messages, and
transmit the result of the operation. Such operation may simply be transmit the result of the operation. Such operation may simply be
intended to use one packet to carry the readings transported in intended to use one packet to carry the readings transported in
several packets (which reduces header and transmission overhead), or several packets (which reduces header and transmission overhead), or
it may be a more sophisticated operation, possibly based on it may be a more sophisticated operation, possibly based on
mathematical, logical or filtering principles (which reduces the mathematical, logical, or filtering principles (which reduces the
payload size to be transmitted). payload size to be transmitted).
6.2. Sleepy node support 6.2. Sleepy Node Support
Beyond these features of CoAP, there have been a number of proposals Beyond these features of CoAP, there have been a number of proposals
to further support sleepy nodes at the application layer by to further support sleepy nodes at the application layer by
leveraging CoAP mechanisms. A good summary of such proposals can be leveraging CoAP mechanisms. A good summary of such proposals can be
found in [I-D.rahman-core-sleepy-nodes-do-we-need], while an example found in [SLEEPY-DEVICES], while an example application (in the
application (in the context of illustrating several security context of illustrating several security mechanisms) in a scenario
mechanisms) in a scenario with sleepy devices has been described with sleepy devices has been described [CRYPTO-SENSORS]. Approaches
[I-D.ietf-lwig-crypto-sensors]. Approaches to support sleepy nodes to support sleepy nodes include exploiting the use of proxies,
include exploiting the use of proxies, leveraging the Resource leveraging the resource directory [CoRE-RD], or signaling when a node
Directory [I-D.ietf-core-resource-directory] or signaling when a node
is awake to the interested nodes. Recent work defines publish- is awake to the interested nodes. Recent work defines publish-
subscribe and message queuing extensions to CoAP and the Resource subscribe and message queuing extensions to CoAP and the resource
Directory in order to support devices that spend most of their time directory in order to support devices that spend most of their time
in asleep [I-D.ietf-core-coap-pubsub]. Notably, this work has been asleep [CoAP-BROKER]. Notably, this work has been adopted by the
adopted by the CoRE Working Group. CoRE Working Group.
In addition to the work within the scope of CoAP to support sleepy In addition to the work within the scope of CoAP to support sleepy
nodes, other specifications define application layer functionality nodes, other specifications define application-layer functionality
for the same purpose. The Lightweight Machine-to-Machine (LWM2M) for the same purpose. The Lightweight Machine-to-Machine (LwM2M)
specification from the Open Mobile Alliance (OMA) defines a Queue specification from the Open Mobile Alliance (OMA) defines a queue
Mode whereby an LWM2M Server queues requests to an LWM2M Client until mode whereby an LwM2M Server queues requests to an LwM2M Client until
the latter (which may often stay in sleep mode) is online. LWM2M the latter (which may often stay in sleep mode) is online. LwM2M
functionality operates on top of CoAP. functionality operates on top of CoAP.
oneM2M defines a CoAP binding with an application layer mechanism for oneM2M defines a CoAP binding with an application-layer mechanism for
sleepy nodes [oneM2M]. sleepy nodes [oneM2M].
6.3. CoAP timers 6.3. CoAP Timers
CoAP offers mechanisms for reliable communication between two CoAP CoAP offers mechanisms for reliable communication between two CoAP
endpoints. A CoAP message may be signaled as a confirmable (CON) endpoints. A CoAP message may be signaled as a confirmable (CON)
message, and an acknowledgment (ACK) is issued by the receiver if the message, and an acknowledgment (ACK) is issued by the receiver if the
CON message is correctly received. The sender starts a CON message is correctly received. The sender starts a
Retransmission TimeOut (RTO) for every CON message sent. The initial Retransmission Timeout (RTO) for every CON message sent. The initial
RTO value is chosen randomly between 2 and 3 s. If an RTO expires, RTO value is chosen randomly between 2 and 3 s. If an RTO expires,
the new RTO value is doubled (unless a limit on the number of the new RTO value is doubled (unless a limit on the number of
retransmissions has been reached). Since duty-cycling at the link retransmissions has been reached). Since duty cycling at the link
layer may lead to long latency (i.e. even greater than the initial layer may lead to long latency (i.e., even greater than the initial
RTO value), CoAP RTO parameters should be tuned accordingly in order RTO value), CoAP RTO parameters should be tuned accordingly in order
to avoid spurious RTOs which would unnecessarily waste node energy to avoid spurious RTOs that would unnecessarily waste node energy and
and other resources. On the other hand, note that CoAP can also run other resources. On the other hand, note that CoAP can also run on
on top of TCP [I-D.ietf-core-coap-tcp-tls]. In that case, similar top of TCP [RFC8323]. In that case, similar guidance applies to TCP
guidance applies to TCP timers, albeit with greater motivation to timers, albeit with greater motivation to carefully configure TCP RTO
carefully configure TCP RTO parameters, since [RFC6298] reduced the parameters since [RFC6298] reduced the default initial TCP RTO to 1
default initial TCP RTO to 1 second, which may interact more second, which may interact more negatively with duty-cycled links
negatively with duty-cycled links than default CoAP RTO values. than default CoAP RTO values.
6.4. Data compression 6.4. Data Compression
Another method intended to reduce the size of the data units to be Another method intended to reduce the size of the data units to be
communicated in constrained-node networks is data compression, which communicated in constrained-node networks is data compression, which
allows to encode data using less bits than the original data allows to encode data using fewer bits than the original data
representation. Data compression is more efficient at higher layers, representation. Data compression is more efficient at higher layers,
particularly before encryption is used. In fact, encryption particularly before encryption is used. In fact, encryption
mechanisms may generate an output that does not contain redundancy, mechanisms may generate an output that does not contain redundancy,
making it almost impossible to reduce the data representation size. making it almost impossible to reduce the data representation size.
In CoAP, messages may be encrypted by using DTLS (or TLS when CoAP In CoAP, messages may be encrypted by using Datagram Transport Layer
over TCP is used), which is the default mechanism for securing CoAP Security (DTLS) or TLS when CoAP over TCP is used, which is the
exchanges. default mechanism for securing CoAP exchanges.
7. Summary and Conclusions 7. Summary and Conclusions
We summarize the key takeaways in this document: We summarize the key takeaways of this document:
a. Internet protocols designed by IETF can be considered as the a. Internet protocols designed by the IETF can be considered the
customer of the lower layers (PHY, MAC, and Duty-cycling). To customer of the lower layers (PHY, MAC, and duty cycling). To
reduce power consumption, it is recommended that Layer 3 designs reduce power consumption, it is recommended that Layer 3 designs
should operate based on awareness of lower-level parameters should operate based on awareness of lower-level parameters
rather than treating the lower layer as a black box (Sections 4, rather than treating the lower layer as a black box (see Sections
5 and 6). 4, 5, and 6).
b. It is always useful to compress the protocol headers in order to b. It is always useful to compress the protocol headers in order to
reduce the transmission/reception power. This design principle reduce the transmission/reception power. This design principle
has been employed by many protocols in 6Lo and CoRE working group has been employed by many protocols in the 6lo and CoRE Working
(Sections 4 and 6). Groups (see Sections 4 and 6).
c. Broadcast and non-synchronized transmissions consume more than c. Broadcast and non-synchronized transmissions consume more than
other TX/RX operations. If protocols must use these ways to other TX/RX operations. If protocols must use these ways to
collect information, reduction of their usage by aggregating collect information, reduction of their usage by aggregating
similar messages together will be helpful in saving power similar messages together will be helpful in saving power (see
(Sections 2 and 6.1). Sections 2 and 6.1).
d. Saving power by sleeping as much as possible is used widely d. Saving power by sleeping as much as possible is used widely
(Section 3). (Section 3).
8. Contributors 8. IANA Considerations
Jens T. Petersen, RTX, contributed the section on power save
services in DECT ULE.
9. Acknowledgments
Carles Gomez has been supported by the Spanish Government, FEDER and
the ERDF through projects TEC2012-32531 and TEC2016-79988-P.
Authors would like to thank the review and feedback from a number of
experts in this area: Carsten Bormann, Ari Keranen, Hannes
Tschofenig, Dominique Barthel, Bernie Volz and Charlie Perkins.
The text of this document was improved based on IESG Document Editing
session during IETF87. Thanks to Ted Lemon and Joel Jaeglli for
initiating and facilitating this editing session.
10. IANA Considerations
This document has no IANA requests. This document has no IANA actions.
11. Security Considerations 9. Security Considerations
This document discusses the energy efficient protocol design, and This document discusses energy-efficient protocol design and does not
does not incur any changes or challenges on security issues besides incur any changes or challenges on security issues besides what the
what the protocol specifications have analyzed. protocol specifications have analyzed.
12. References 10. References
12.1. Normative References 10.1. Normative References
[Bluetooth42] [Bluetooth42]
Bluetooth Special Interest Group, "Bluetooth Core Bluetooth Special Interest Group, "Core Version 4.2",
Specification Version 4.2", December 2014, available from "Legacy Core Specifications", December
<https://www.bluetooth.org/en-us/specification/ 2014, <https://www.bluetooth.com/specifications/
adopted-specifications>. bluetooth-core-specification/legacy-specifications>.
[EN300] ETSI, "Digital Enhanced Cordless Telecommunications [EN300] ETSI, "Digital Enhanced Cordless Telecommunications
(DECT); Common Interface (CI)", March 2015, (DECT); Common Interface (CI); Part 1: Overview", ETSI EN
300 175-1 V2.6.1, July 2015,
<https://www.etsi.org/deliver/ <https://www.etsi.org/deliver/
etsi_en/300100_300199/30017501/02.06.01_60/ etsi_en/300100_300199/30017501/02.06.01_60/
en_30017501v020601p.pdf>. en_30017501v020601p.pdf>.
[fifteendotfour] [G9959] ITU-T, "Short range narrow-band digital radiocommunication
IEEE Computer Society, "IEEE Std. 802.15.4-2015 IEEE transceivers - PHY, MAC, SAR and LLC layer
Standard for Local and metropolitan area networks--Part specifications", ITU-T Recommendation G.9959, January
15.4: Low-Rate Wireless Personal Area Networks (LR- 2015, <http://www.itu.int/rec/T-REC-G.9959>.
WPANs)", 2015, <https://standards.ieee.org/findstds/
standard/802.15.4-2015.html>.
[G9959] International Telecommunication Union, "Short range [IEEE802.11]
narrow-band digital radiocommunication transceivers - PHY IEEE, "IEEE Standard for Information technology--
and MAC layer specifications, ITU-T Recommendation Telecommunications and information exchange between
G.9959", January 2015, systems Local and metropolitan area networks--Specific
<http://www.itu.int/rec/T-REC-G.9959>. requirements - Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications",
IEEE 802.11, DOI 10.1109/IEEESTD.2016.7786995,
<http://ieeexplore.ieee.org/document/7786995/versions>.
[IEEE80211v] [IEEE802.15.4]
IEEE, "Part 11: Wireless LAN Medium Access Control (MAC) IEEE, "IEEE Standard for Low-Rate Wireless Networks",
and Physical Layer (PHY) specifications, Amendment 8: IEEE IEEE 802.15.4, DOI 10.1109/IEEESTD.2016.7460875,
802.11 Wireless Network Management.", February 2012. <https://standards.ieee.org/findstds/
standard/802.15.4-2015.html>.
[MSTP] ANSI/ASHRAE, "Addenda: BACnet -- A Data Communication [MSTP] ANSI/ASHRAE, "Addenda: BACnet -- A Data Communication
Protocol for Building Automation and Control Networks, Protocol for Building Automation and Control Networks
ANSI/ASHRAE Addenda an, at, au, av, aw, ax, and az to ANSI/ASHRAE Addenda an, at, au, av, aw, ax, and az to
ANSI/ASHRAE Standard 135-2012", July 2014, ANSI/ASHRAE Standard 135-2012", July 2014,
<https://www.ashrae.org/File%20Library/docLib/StdsAddenda/ <https://www.ashrae.org/technical-resources/standards-and-
07-31-2014_135_2012_an_at_au_av_aw_ax_az_Final.pdf>. guidelines/standards-addenda/
addenda-to-standard-135-2012>.
[NFC] NFC Forum, "NFC Logical Link Control Protocol version 1.3, [NFC] NFC Forum, "NFC Logical Link Control Protocol", Technical
NFC Forum Technical Specification", March 2016. Specification, Version 1.3, March 2016.
[oneM2M] oneM2M, "oneM2M specifications", [oneM2M] oneM2M, "oneM2M - Published Specifications",
<http://www.onem2m.org/technical/published-documents>. <http://www.onem2m.org/technical/published-documents>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4 "Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<https://www.rfc-editor.org/info/rfc4944>. <https://www.rfc-editor.org/info/rfc4944>.
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206, "The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
March 2011, <https://www.rfc-editor.org/info/rfc6206>. March 2011, <https://www.rfc-editor.org/info/rfc6206>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
skipping to change at page 21, line 26 skipping to change at page 21, line 32
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014, DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>. <https://www.rfc-editor.org/info/rfc7252>.
[RFC7668] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B., [RFC7668] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low
Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015, Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015,
<https://www.rfc-editor.org/info/rfc7668>. <https://www.rfc-editor.org/info/rfc7668>.
[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>.
[TS102] ETSI, "Digital Enhanced Cordless Telecommunications [TS102] ETSI, "Digital Enhanced Cordless Telecommunications
(DECT); Ultra Low Energy (ULE); Machine to Machine (DECT); Ultra Low Energy (ULE); Machine to Machine
Communications; Part 2: Home Automation Network (phase 2", Communications; Part 2: Home Automation Network (phase 2",
March 2015, <https://www.etsi.org/deliver/ ETSI TS 102 939-2 V1.1.1, March 2015,
<https://www.etsi.org/deliver/
etsi_ts/102900_102999/10293902/01.01.01_60/ etsi_ts/102900_102999/10293902/01.01.01_60/
ts_10293902v010101p.pdf>. ts_10293902v010101p.pdf>.
12.2. Informative References 10.2. Informative References
[AN079] Kim, C., "Measuring Power Consumption of CC2530 With [AN079] Kim, C., "Measuring Power Consumption of CC2530 With
Z-Stack", September 2012, Z-Stack", Application Note AN079, SWRA292, September 2012,
<http://www.ti.com/lit/an/swra292/swra292.pdf>. <http://www.ti.com/lit/an/swra292/swra292.pdf>.
[ContikiMAC] [ARCH-6TiSCH]
Dunkels, A., "The ContikiMAC Radio Duty Cycling Protocol,
SICS Technical Report T2011:13", December 2011,
<https://www.mysciencework.com/publication/download/2f406d
3c4cc1eda32a234f7a1ad2cc3b/7eb199e4f8b00857e21af2b7d2b31c0
d>.
[I-D.bormann-lwig-7228bis]
Bormann, C., Ersue, M., Keranen, A., and C. Gomez,
"Terminology for Constrained-Node Networks", draft-
bormann-lwig-7228bis-01 (work in progress), May 2017.
[I-D.ietf-6lo-dect-ule]
Mariager, P., Petersen, J., Shelby, Z., Logt, M., and D.
Barthel, "Transmission of IPv6 Packets over DECT Ultra Low
Energy", draft-ietf-6lo-dect-ule-09 (work in progress),
December 2016.
[I-D.ietf-6man-impatient-nud]
Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
Detection is too impatient", draft-ietf-6man-impatient-
nud-07 (work in progress), October 2013.
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-12 (work of IEEE 802.15.4", Work in Progress, draft-ietf-6tisch-
in progress), August 2017. architecture-13, November 2017.
[I-D.ietf-6tisch-minimal] [CLASS1-CoAP]
Vilajosana, X., Pister, K., and T. Watteyne, "Minimal Kovatsch, M., "Implementing CoAP for Class 1 Devices",
6TiSCH Configuration", draft-ietf-6tisch-minimal-21 (work Work in Progress, draft-kovatsch-lwig-class1-coap-00,
in progress), February 2017. October 2012.
[I-D.ietf-core-coap-pubsub] [CNN-TERMS]
Bormann, C., Ersue, M., Keranen, A., and C. Gomez,
"Terminology for Constrained-Node Networks", Work in
Progress, draft-bormann-lwig-7228bis-02, October 2017.
[CoAP-BROKER]
Koster, M., Keranen, A., and J. Jimenez, "Publish- Koster, M., Keranen, A., and J. Jimenez, "Publish-
Subscribe Broker for the Constrained Application Protocol Subscribe Broker for the Constrained Application Protocol
(CoAP)", draft-ietf-core-coap-pubsub-02 (work in (CoAP)", Work in Progress, draft-ietf-core-coap-pubsub-04,
progress), July 2017. March 2018.
[I-D.ietf-core-coap-tcp-tls] [ContikiMAC]
Bormann, C., Lemay, S., Tschofenig, H., Hartke, K., Dunkels, A., "The ContikiMAC Radio Duty Cycling Protocol",
Silverajan, B., and B. Raymor, "CoAP (Constrained SICS Technical Report T2011:13, December 2011,
Application Protocol) over TCP, TLS, and WebSockets", <http://soda.swedishict.se/5128/>.
draft-ietf-core-coap-tcp-tls-09 (work in progress), May
2017.
[I-D.ietf-core-resource-directory] [CoRE-RD] Shelby, Z., Koster, M., Bormann, C., Stok, P., and C.
Shelby, Z., Koster, M., Bormann, C., Stok, P., and C. Amsuess, Ed., "CoRE Resource Directory", Work in
Amsuess, "CoRE Resource Directory", draft-ietf-core- Progress, draft-ietf-core-resource-directory-13, March
resource-directory-11 (work in progress), July 2017. 2018.
[I-D.ietf-lwig-crypto-sensors] [CRYPTO-SENSORS]
Sethi, M., Arkko, J., Keranen, A., and H. Back, "Practical Sethi, M., Arkko, J., Keranen, A., and H. Back, "Practical
Considerations and Implementation Experiences in Securing Considerations and Implementation Experiences in Securing
Smart Object Networks", draft-ietf-lwig-crypto-sensors-04 Smart Object Networks", Work in Progress, draft-ietf-lwig-
(work in progress), August 2017. crypto-sensors-06, February 2018.
[I-D.kovatsch-lwig-class1-coap] [Powertrace]
Kovatsch, M., "Implementing CoAP for Class 1 Devices", Dunkels, A., Eriksson, J., Finne, N., and N. Tsiftes,
draft-kovatsch-lwig-class1-coap-00 (work in progress), "Powertrace: Network-level Power Profiling for Low-power
October 2012. Wireless Networks", SICS Technical Report T2011:05, March
2011, <http://soda.swedishict.se/4112/>.
[I-D.rahman-core-sleepy-nodes-do-we-need] [RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
Detection Is Too Impatient", RFC 7048,
DOI 10.17487/RFC7048, January 2014,
<https://www.rfc-editor.org/info/rfc7048>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/info/rfc7959>.
[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>.
[RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal
IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH)
Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180,
May 2017, <https://www.rfc-editor.org/info/rfc8180>.
[RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
Application Protocol) over TCP, TLS, and WebSockets",
RFC 8323, DOI 10.17487/RFC8323, February 2018,
<https://www.rfc-editor.org/info/rfc8323>.
[SLEEPY-DEVICES]
Rahman, A., "Sleepy Devices: Do we need to Support them in Rahman, A., "Sleepy Devices: Do we need to Support them in
CORE?", draft-rahman-core-sleepy-nodes-do-we-need-01 (work CORE?", Work in Progress, draft-rahman-core-sleepy-nodes-
in progress), February 2014. do-we-need-01, February 2014.
[Powertrace] Acknowledgments
Dunkels, Eriksson, Finne, and Tsiftes, "Powertrace:
Network-level Power Profiling for Low-power Wireless Carles Gomez has been supported by the Spanish Government, FEDER, and
Networks", March 2011, <https://core.ac.uk/download/ the ERDF through projects TEC2012-32531 and TEC2016-79988-P.
pdf/11435067.pdf?repositoryId=362>.
The authors would like to give thanks for the review and feedback
from a number of experts in this area: Carsten Bormann, Ari Keranen,
Hannes Tschofenig, Dominique Barthel, Bernie Volz, and Charlie
Perkins.
The text of this document was improved based on an IESG document
editing session during IETF 87. Thanks to Ted Lemon and Joel Jaeggli
for initiating and facilitating this editing session.
Contributors
Jens T. Petersen, RTX, contributed the section on power save services
in DECT ULE.
Authors' Addresses Authors' Addresses
Carles Gomez Carles Gomez
Universitat Politecnica de Catalunya Universitat Politecnica de Catalunya
C/Esteve Terradas, 7 C/Esteve Terradas, 7
Castelldefels 08860 Castelldefels 08860
Spain Spain
Email: carlesgo@entel.upc.edu Email: carlesgo@entel.upc.edu
Matthias Kovatsch Matthias Kovatsch
ETH Zurich ETH Zurich
Universitaetstrasse 6 Universitaetstrasse 6
Zurich, CH-8092 Zurich, CH-8092
Switzerland Switzerland
Email: kovatsch@inf.ethz.ch Email: ietf@kovatsch.net
Hui Tian Hui Tian
China Academy of Telecommunication Research China Academy of Telecommunication Research
Huayuanbeilu No.52 Huayuanbeilu No. 52
Beijing, Haidian District 100191 Beijing, Haidian District 100191
China China
Email: tianhui@ritt.cn Email: tianhui@ritt.cn
Zhen Cao (editor) Zhen Cao (editor)
Huawei Technologies Huawei Technologies
China China
Email: zhencao.ietf@gmail.com Email: zhencao.ietf@gmail.com
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