draft-eckert-ietf-and-energy-overview-06.txt

Network Working Group                                     T. Eckert, Ed.
Internet-Draft                                Futurewei Technologies USA
Intended status: Informational                         M. Boucadair, Ed.
Expires: 9 July 2024                                              Orange
                                                              P. Thubert
                                                     Cisco Systems, Inc.
                                                             J. Tentsura
                                                                  NVIDIA
                                                            C. Pignataro
                                                     NC State University
                                                          6 January 2024


          An Overview of Energy-related Effort within the IETF
                draft-eckert-ietf-and-energy-overview-06

Abstract

   This memo provides an overview of work performed by or proposed
   within the IETF related to energy and/or green: awareness,
   management, control or reduction of consumption of energy, and
   sustainability as it related to the IETF.

   This document is written to help those unfamiliar with that work, but
   interested in it, in the hope to raise more interest in energy-
   related activities within the IETF, such as identifying gaps and
   investigating solutions as appropriate.

   This document captures work until 12/2022, at which time the "IAB
   workshop on Environmental Impact of Internet Applications and
   Systems" revived interest and triggered new work in the topic within
   the IETF/IRTF.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   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
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."




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   This Internet-Draft will expire on 9 July 2024.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Energy Saving: An Introduction  . . . . . . . . . . . . . . .   4
     2.1.  Digitization  . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Energy Saving Through Scale . . . . . . . . . . . . . . .   5
       2.2.1.  An Iconic Example: Telephony  . . . . . . . . . . . .   5
       2.2.2.  The Packet Multiplexing Principle . . . . . . . . . .   5
       2.2.3.  End-to-End Transport  . . . . . . . . . . . . . . . .   5
       2.2.4.  Global vs Restricted Connectivity: The Internet Routing
               Architectures . . . . . . . . . . . . . . . . . . . .   6
       2.2.5.  Freedom to Innovate . . . . . . . . . . . . . . . . .   6
       2.2.6.  End-to-End Encryption . . . . . . . . . . . . . . . .   6
       2.2.7.  Converged Networks  . . . . . . . . . . . . . . . . .   6
         2.2.7.1.  IntServ and DetNet  . . . . . . . . . . . . . . .   7
         2.2.7.2.  DiffServ  . . . . . . . . . . . . . . . . . . . .   7
         2.2.7.3.  SIP . . . . . . . . . . . . . . . . . . . . . . .   8
   3.  Higher or New Energy Consumption  . . . . . . . . . . . . . .   8
   4.  Some Notes on Sustainability  . . . . . . . . . . . . . . . .   9
     4.1.  Follow the Energy Cloud Scheduling  . . . . . . . . . . .   9
     4.2.  Optimize Generated Heat . . . . . . . . . . . . . . . . .  10
     4.3.  Heat Recovery . . . . . . . . . . . . . . . . . . . . . .  10
     4.4.  Telecollaboration . . . . . . . . . . . . . . . . . . . .  10
   5.  Energy Optimization in Specific Networks  . . . . . . . . . .  12
     5.1.  Analysis of Routing Protocol (In)Efficiencies . . . . . .  12
     5.2.  Low Power and Lossy Networks (LLN)  . . . . . . . . . . .  12
       5.2.1.  6LOWPAN WG  . . . . . . . . . . . . . . . . . . . . .  13
       5.2.2.  LPWAN WG  . . . . . . . . . . . . . . . . . . . . . .  14
       5.2.3.  6TISCH WG . . . . . . . . . . . . . . . . . . . . . .  14
       5.2.4.  6LO WG  . . . . . . . . . . . . . . . . . . . . . . .  14
       5.2.5.  ROLL WG . . . . . . . . . . . . . . . . . . . . . . .  14
     5.3.  Constrained Nodes and Networks  . . . . . . . . . . . . .  16
       5.3.1.  LWIG WG . . . . . . . . . . . . . . . . . . . . . . .  16
       5.3.2.  CoRE and CoAP . . . . . . . . . . . . . . . . . . . .  16
       5.3.3.  Satellite Constellations  . . . . . . . . . . . . . .  17



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       5.3.4.  Devices with Batteries  . . . . . . . . . . . . . . .  17
     5.4.  Sample Technical Enablers . . . . . . . . . . . . . . . .  17
       5.4.1.  (IP) Multicast  . . . . . . . . . . . . . . . . . . .  17
         5.4.1.1.  Power Saving with Multicast . . . . . . . . . . .  18
         5.4.1.2.  Power Waste Through Multicast-based Service
                 Coordination  . . . . . . . . . . . . . . . . . . .  19
         5.4.1.3.  Multicast Problems in Wireless Networks . . . . .  19
       5.4.2.  Sleepy Nodes  . . . . . . . . . . . . . . . . . . . .  20
     5.5.  (Lack of) Power Benchmarking Proposals  . . . . . . . . .  22
   6.  Energy Management Networks  . . . . . . . . . . . . . . . . .  22
     6.1.  Smart Grid  . . . . . . . . . . . . . . . . . . . . . . .  22
     6.2.  Synchro Phasor Networks . . . . . . . . . . . . . . . . .  23
   7.  (Limited) Energy Management for Networks  . . . . . . . . . .  24
     7.1.  Some Metrics  . . . . . . . . . . . . . . . . . . . . . .  24
     7.2.  EMAN WG . . . . . . . . . . . . . . . . . . . . . . . . .  24
   8.  Power-Awareness in Forwarding and Routing Protocols . . . . .  26
     8.1.  Power Aware Networks (PANET)  . . . . . . . . . . . . . .  26
     8.2.  SDN-based Semantic Forwarding . . . . . . . . . . . . . .  27
     8.3.  Miscelaneous  . . . . . . . . . . . . . . . . . . . . . .  28
   9.  Gap Analysis  . . . . . . . . . . . . . . . . . . . . . . . .  29
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  29
   11. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . .  29
   12. Informative References  . . . . . . . . . . . . . . . . . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  47

1.  Introduction

   This document summarizes work that has been proposed to or performed
   within the IETF/IRTF.  Particularly, it covers IETF/IRTF RFCs as well
   as ISE RFCs and IETF/IRTF or individual submission drafts that where
   abandoned for various reasons (e.g., lack of momentum, broad scope).

   There are various aspects how a given work relates to energy that are
   classified into categories.  Such a classification does not attempt
   to propose a formal taxonomy, but is used for the sake of better
   readability.  Technologies are listed under a category that is
   specifically significant, for example, by being most narrow.

   This memo usually refers to the technologies by significant early RFC
   or specific draft version, as opposed to the newest.  This is
   contrary to the common practice in IETF documents to refer to the
   newest version.  This approach is meant to allow readers to better
   understand the historic timeline in which a specific technology was
   proposed or introduced.  Especially successful IETF technologies will
   have newer RFC that updates such initial work.






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   This document captures work until 12/2022, at which time the "IAB
   workshop on Environmental Impact of Internet Applications and
   Systems" [I-D.iab-ws-environmental-impacts-report] revived interest
   and highlighted the need for some structured activity within the
   IETF/IRTF.

2.  Energy Saving: An Introduction

   Technologies that simply save energy compared to earlier or other
   alternatives are the broadest and most unspecific category.  In this
   memo such an energy saving simply refers to energy savings in some
   unit of electricity, such as kWh and does not take other aspects of
   energy optimization into account.  See Section 4 for more details.

2.1.  Digitization

   Digitization describes the transformation of processes from non- or
   less digital with networking to more digital with computer-
   networking.  For comparable process results, the digitized option is
   often, but not always, less energy consuming.  Consider, for example,
   the energy consumption in the evolution of messaging starting from
   postal mail and overs telegrams and various other historic form to
   solutions including e-mail utilizing, for example, the IETF "Simple
   Mail Transport Protocol" (SMTP, [RFC822] obsoleted by [RFC2822],
   [RFC5322]), group communications utilizing the IETF "Network News
   Transport Protocol" (NNTP, [RFC3977]) or the almost infinite set of
   communication options built on top of the IETF "HyperText Transport
   Protocol" (HTTP, [RFC2086] and successors), and IETF "HyperText
   Markup Language" (HTML, [RFC1866] superseded by various later version
   of HTML, see [RFC2854]).

   Conventionally, digitization had only "incidental", but not
   "intentional" relationship to energy consumption: If it saved energy,
   this was not a target benefit; in fact, it was not even recognized as
   one until recently.  Instead, the evolution was driven from anything-
   but-energy benefits, but instead utility benefits such as improved
   speed, functionality/flexibility, accessibility, usability,
   scalability, and reduced cost.

   In hindsight though, digitization through IETF technologies and
   specifically the Internet will likely have the largest contribution
   to energy saving amongst all the possible categories, but it is also
   the hardest to pinpoint on any specific technology/RFC.  Instead, it
   is often a combination of the whole stack of deployed protocols and
   operational practices that contributes to energy saving through
   digitization.  It is likely also the biggest overall energy saving
   impact of all possible categories that relate IETF work to energy:




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   The Internet as well as all other IP/MPLS networks are likely the
   biggest energy saving development of the past few decades if only the
   energy consumption of equivalent services is compared.  On the other
   hand, they are also the cause for the biggest new type of new energy
   consumption because of all the new services introduced in the past
   decades with the Internet and the hyper-scaling that the Internet
   affords them.

2.2.  Energy Saving Through Scale

2.2.1.  An Iconic Example: Telephony

   In most cases, energy saving through the use of IETF protocols
   compared to earlier (digitized or non-digitized) solutions is purely
   a result of the reduction in the energy cost per bit over the decades
   in networking.  For example, the energy consumption of digital voice
   telephony through the IETF "Session Initiation Protocol" (SIP,
   [RFC2543] superseded by [RFC3261] and successors) can easily be
   assumed to be more energy efficient on a per voice-minute basis than
   prior voice technologies such as analog or digital "Time Division
   Multiplex" (TDM) telephony solely because of this evolution in mostly
   device as well as physical-layer and link-layer networking
   technologies.

2.2.2.  The Packet Multiplexing Principle

   Nevertheless, it is at the heart of the packet multiplexing model
   employed by the IETF networking protocols IP ([RFC791]) and IPv6
   ([RFC1883] superseded by [RFC2460] and [RFC8200]) to successfully
   support this scaling that brough down the cost per bit through ever
   faster links and network nodes, especially for networks larger than
   building scale networks.  While the IETF protocols have not been the
   first or over their early decades necessarily the most widely
   deployed packet networking protocols, they were the ones who at least
   during the 1990s started to break away from other protocols both in
   scale of deployment, as well as in development of further
   technologies to support this scaling.

2.2.3.  End-to-End Transport

   At the core of scalability, even up to now, is the lightweight per-
   packet-processing enabled through end-to-end congestion loss
   management architecture as embodied through the IETF "Transmission
   Control Protocol" (TCP, [RFC9293]).  This model eliminated more
   expensive per-hop, per-packet processing, such as would be required
   for reliable hop-by-hop forwarding through per-hop ARQ, which was key
   to scaling routers cost effectively.




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2.2.4.  Global vs Restricted Connectivity: The Internet Routing
        Architectures

   The meshed peer-to-peer and transitive routing of the Internet
   enabled through the IETF Border Gateway (Routing) Protocol (BGP,
   [RFC4271] as well as predecessors) is another key factor to
   successful scalability, because it enabled competitive market forces
   to explore markets quickly.

   Prior to the Internet, the public often only had access to highly
   regulated international networking connections through often per-
   country monopoly regulated data networks.

2.2.5.  Freedom to Innovate

   (non-IP) networks often also did not allow as much "freedom-to-
   innovate" (as it is often called in the IETF) for applications
   running over it.  Instead, those networks were exploring the coupling
   of packet transport with higher layer services to allow the network
   operator some degree of revenue sharing with the services running on
   top of it.  Such approaches resulted not only in higher cost of those
   services but also (likely) preferential and (often) exclusionary
   treatment of network traffic not fitting the perceived highest
   revenue service options.

2.2.6.  End-to-End Encryption

   When the same business practices were applied to IP network, it was
   one of the key factors leading to the development of IETF end-to-end
   encryption though protocols such as "Transport Layer Security" (TLS,
   [RFC2246] [RFC4346], [RFC5246], [RFC8446]).  This further
   strengthened the ability to scale service/applications at minimum
   additional cost for the underlying packet transport, arguably driving
   innovation into ever faster networking technology and likely lower
   cost per bit.

2.2.7.  Converged Networks

   Another key factor to support scaling where IETF technologies that
   allowed to multiplex different types of traffic (e.g., real-time vs.
   non-real-time) which previously used separate networks with typically
   incompatible networking technologies.

   Eliminating multiple physical networks with separate routing/
   forwarding nodes and separate links affords significant energy
   savings even at the same generation of speed and hence energy/bit
   simply by avoiding the N-fold production and operations of equipment
   and links.  Of course, originally the CAPEX and OPEX of multiple,



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   technology-diverse networks and host-stacks was the core reason for
   unified networks, and energy saving is in hindsight just incidental
   (as for all other cases mentioned here).

2.2.7.1.  IntServ and DetNet

   The first (non-IETF) widely adopted technology promising converged
   networks was "Asynchronous Transfer Mode" (ATM), which was designed
   and deployed at the end of the 1980s to support specifically
   multiplexing of "Data Voice and Video", where both Voice and Video
   (at that time) required loss-free deterministic bounded latency and
   low-jitter and had therefore their own Time-Division-Multiplex (TDM)
   networks, both separate from so-called Data networks using packet
   multiplexing.  This technology was very expensive on a per-bit basis
   due to its cell-forwarding nature though.

   At the end of the 1980s, it was proven in [BOUNDED_LATENCY] that
   variable length packet multiplexing in network can also support non-
   NP-hard calculations for bounded latency.  This led to the IETF
   "Integrated Services WG" (INTSERV) to support such guaranteed
   throughput and bounded latency traffic via [RFC2212] - and to the
   demise of ATM.

   IntServ has so far seen little traction because it too got superseded
   as explained in the following section - for its original use-cases
   (voice and video).  However, this type of services is being revisited
   for a broader set of use-cases [RFC8575] in the DetNet WG, which
   should enable even further network infrastructure convergence for IoT
   and industrial markets.

2.2.7.2.  DiffServ

   Due to the much higher per-packet processing overhead of INTSERV
   versus regular (so-called Best-Effort) Internet traffic, the INTSERV
   model was already recognized in the 1990s to not support highest-
   scale at lowest cost, leading to the parallel development of the IETF
   "Differentiated Services WG" (DIFFSERV) model defined in [RFC2475].
   This has since then become the dominant technology to support
   multiplexing of applications and services originally not designed for
   the Internet onto a common TCP/IP network infrastructure,
   specifically for voice and video over UDP ([RFC768]) including RTP
   [RFC3550] and SIP.









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2.2.7.3.  SIP

   SIP has most notably in the past two decades eliminated additional
   network infrastructures previously required for (voice) telephony
   services starting in the early 2000 with commercial/enterprise
   deployments and today by removing even the option for any (non-IP/
   SIP) analog or digital (ISDN) telephone service connection, instead
   delivering those purely as services over adaptation interfaces on
   home routers (TBD: Any RFC to cite for those tunneling/adaptation
   services ?).

3.  Higher or New Energy Consumption

   Digitized, network centric workflows may consume more energy than
   their non-digitized counterpart, as may new network centric workflows
   without easy to compare prior workflows.

   In one type of instances, the energy consumption on a per-instance
   basis is lower than in the non-digitized/non-Internet-digitized case,
   but the total number of instances that are (Internet)-digitized is
   orders of magnitudes larger than their alternative options, typically
   because of their higher utility or lower overall cost.

   For example, each instance of (simple text) email consumes less
   energy than sending a letter or postcard.  Even streaming a movie or
   TV series consumes less energy than renting a DVD [DVDvsStreaming].
   Nevertheless, the total amount of instances and in result energy
   consumption for email and streaming easily outranks their predecessor
   technologies.

   While these instances look beneficial from a simple energy
   consumption metric, its overall scale and the resulting energy
   consumption may in itself become an issue, especially when the energy
   demand it creates risks to outstrip the possible energy production,
   short term or long term.  This concern is nowadays often raised
   against the "digital economy", where the network energy consumption
   is typically cited as a small contributor relative to its
   applications, such as what is running in Data Centers (DC).

   In other cases, the energy consumption of digitization requires often
   significantly more than their pre-digitization alternatives.  The
   most well-known example of this are likely crypto-currencies based on
   "proof-of-work" computations (mining), which on a per currency value
   unit can cost from ten to thirty times or more of the energy consumed
   by for example gold mining (very much depending on the highly
   fluctuating price of the crypto currency).  Nevertheless, its overall
   utility compared to such prior currencies or valuables makes it
   highly successful in the market.



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   In general, the digital economy tends to be more energy intensive on
   a per utility/value unit, for example by replacing a lot of manual
   labor with computation), and/or it allows for faster growth of its
   workflows.

   The lower the cost of network traffic, and the more easily accessible
   everywhere network connectivity is, the more competitive and/or
   successful most of these new workflows of the digital economy can be.

   Given how TCP/IP based networks, especially the Internet have
   excelled through their design principles (and success) in this
   reduction of network traffic cost and ubiquitous access over the past
   few decades, as outlined above, one can say that IETF technologies
   and especially the Internet are the most important enabler of the
   digital economy, and the energy consumption it produces.

4.  Some Notes on Sustainability

   Sustainability is the principle to utilize resources in a way that
   they do not diminish or run out over the long term (e.g., ore
   depletion required for building hardware).  Beyond the above covered
   energy saving, sustainability relates with respect to the IETF
   specifically to the use of renewable sources of energy to minimize
   exhaustion of fossil resources, and the impact of IETF technologies
   on global warming to avoid worsening living conditions on the planet.

   While there seems to be no IETF work specifically intending to target
   sustainability, the Internet itself can similarly to how it does for
   digitization play a key role in building sustainable networked IT
   infrastructures.  The following subsections list three exemplary
   areas where global high performance, low-cost Internet networking is
   a key requirement.

4.1.  Follow the Energy Cloud Scheduling

   Renewable energy resources (except for water) do commonly have
   fluctuating energy output.  For example, solar energy output
   correlates to night/day and strength of sunlight.  Cloud Data Centers
   (DC) consume a significant amount of the IT sectors energy.  Some
   workloads may simply be scheduled to consume energy in accordance
   with the amount of available renewable energy at the time, not
   requiring the network.  Significant workloads are not elastic in
   time, such as interactive cloud DC interactive work (cloud based
   applications) or entertainment (gaming, etc.).  These workloads may
   be instantiated or even dynamically (over time) migrate to a DC
   location with sufficient renewable energy and the Internet (or large
   TCP/IP OTT backbone networks) will serve as the fabric to access the
   remote DC and to coordinate the instantiation/migration.



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4.2.  Optimize Generated Heat

   The majority of energy in cloud DCs is normally also wasted as
   exhaust heat, requiring even more energy for cooling.  The warmer the
   location, the more energy needs to be spent for cooling.  For this
   reason, DCs in cooler climates, such as https://greenmountain.no/
   power-and-cooling/, can help to reduce the overall DC energy
   consumption significantly (independent of the energy being consumed
   in the DC to be renewable itself).  The Internet again plays the role
   of providing access to those type of DCs whole location is not
   optimized for consumption but for sustainable generation of compute
   and storage.

4.3.  Heat Recovery

   Exhaust heat, especially from compute in DCs, can be recovered when
   it is coupled to heating systems ranging in size all the way from
   individual family homes through larger buildings (hotels, for
   example) all the way to district heating systems.  A provider of such
   a type of compute-generated heat as a service can sell the compute
   capacity as long as there is cost efficient network connectivity.
   "Cloud & Heat" is an example company offering such infrastructures
   and services https://www.cloudandheat.com/wp-content/
   uploads/2020/02/2020_CloudHeat-Whitepaper-Cost-saving-Potential.pdf.

4.4.  Telecollaboration

   Telecollaboration has a long history in the IETF resulting in
   multiple core technologies over the decades.

   If one considers textual communications via email and netnews (using
   e.g., NNTP) as early forms of Telecollaboration, then
   telecollaboration history through IETF technology reaches back into
   the 1980s and earlier.

   Around 1990, the IETF work on IP Multicast (e.g., [RFC1112] and
   later) enabled the first efficient forms of audio/video group
   collaboration through an overlay network over the Internet called the
   MBone https://en.wikipedia.org/wiki/Mbone which was also used by the
   IETF for more than a decade to provide remote collaboration for its
   own (in-person + remote participation) meetings.

   With the advent of SIP in the early 2000s, commercial
   telecollaboration started to be built most often on SIP based session
   and application protocols with multiple IETF working groups
   contributing to that protocol suite (TBD: how much more example/
   details should we have here).  Using this technology and the
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   life-size video, was/is called Telepresence
   https://en.wikipedia.org/wiki/Telepresence and later to even more
   immersive forms such as AR/VR telecollaboration.

   In 2011, the IETF opened the "Real-Time Communication in Web-
   browsers" (RTCWEB) WG, that towards the end of that decade became the
   most widely supported cross-platform reference for hundreds of
   commercial and free tele-collaboration solutions, including Cisco
   Webex, which is also used by the IETF itself, Zoom, and the
   collaboration suite the IETF most recently uses, Meetecho
   https://www.meetecho.com/en/.

   While the various forms of Telecollaboration are mostly instances of
   digitization, they are discussed under sustainability because of its
   comparison to in-person travel that is not based on simple comparison
   of energy, but nowadays by comparing their impact on global warming,
   a key factor to sustainability.

   Telecollaboration was primarily developed because of the utility for
   the participants - to avoid travel for originally predominantly
   business communications/collaborations.  It saw an extreme increase
   in use (TBD: references) in the Corona Crisis of 2019, when
   especially international travel was often prohibited, and often even
   working from an office.  This forced millions of people to work from
   home and utilizing commercial telecollaboration tools.  It equally
   caused most in-person events that where not cancelled to be moved to
   a telecollaboration platform over the Internet - most of them likely
   relying on RTCWEB protocols.

   Actual energy consumption related comparison between teleconferencing
   and in-person travel is complex but since the last decades is
   commonly based on calculating some form of CO2 emission equivalent of
   the energy consumed, hence comparing not simply the energy
   consumption, but weighing it by the impact the energy consumption has
   on one of the key factors (CO2 emission) known to impact sustainable
   living conditions.

   [VC2014] is a good example of a comparison between travel and
   telecollaboration taking various factors into account and using CO2
   emission equivalents as its core metric.  That paper concludes that
   carbon/ energy cost of telecollaboration could be as little as 7% of
   an in-person meeting.  in-person meeting.  Those numbers have various
   assumptions and change when time-effort of participants is converted
   to carbon/energy costs.  These numbers should even be better today in
   favor of telecollaboration: cost of Internet traffic/bit goes down
   while cost of fossil fuel for travel goes up.





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   Recently, air travel has also come under more scrutiny because the
   greenhouse gas emissions of air travel at the altitudes used by
   commercial aviation has been calculated to have a higher global
   warming impact than simply the amount of CO2 used by the airplane if
   it was exhausted at surface level.  One publicly funded organization
   offering carbon offset services calculates a factor 3 of the CO2
   consumption of an airplane
   https://www.atmosfair.de/de/fliegen_und_klima/flugverkehr_und_klima/
   klimawirkung_flugverkehr/.

   In summary: Telecollaboration has a higher sustainability benefit
   compared to travel than just the comparison of energy consumption
   because of the higher challenge to use renewable energy in
   transportation than in networking, and this is most extreme in the
   case of telecollaboration that replaces air travel because of the
   even higher global warming impact of using fossil fuels in air
   travel.

5.  Energy Optimization in Specific Networks

5.1.  Analysis of Routing Protocol (In)Efficiencies

   At the beginning of much of the following IETF efforts was an
   understanding and analysis that prior protocols for routing and
   subnet management where not able to ideally support evolving network
   and device models: - lower compute performance due to low energy
   (batteries, energy recovery), bitrates especially on radio links, and
   lower memory footprint.

   The two documents from 2008/2009 that capture this analysis/
   understanding are [I-D.levis-roll-overview-protocols] and
   [I-D.ietf-roll-protocols-survey].  The overall challenges also very
   much related to energy of IPv6 over wireless are captured in
   [I-D.thubert-6man-ipv6-over-wireless], which is ongoing work.

5.2.  Low Power and Lossy Networks (LLN)

   Low Power and Lossy Networks (LLNs) are networks in which nodes and/
   or radio links have constraints.  Low power consumption constraints
   in nodes often originate from the need to operate nodes from as long
   as possible from battery and/or energy harvesting such as (today most
   commonly) solar panels associated with the node or ambient energy
   such as energy harvesting from movement for wearable nodes or piezo
   cells to generate energy for mechanically operated nodes such as
   switches.






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   Several IETF WGs have or are producing work is primarily intended wo
   support LLN through multiple layers of the protocol stack.  [RFC8352]
   gives a good overview of the energy consumption related communication
   challenges and solutions produced by the IETF for this space.

   To minimize the energy needs for such nodes, their network data-
   processing mechanisms have to be optimized.  This includes packet
   header compression, fragmentation (to avoid latency through large
   packets at low bitrates, packet bundling to only consume radio energy
   at short time periods, radio energy tuning to just reach the
   destination(s), minimization of multicasting to eliminate need of
   radio receivers to consume energy and so on.  [RFC8352] gives a more
   detailed overview, especially because different L2 technologies such
   as IEEE 802.15.4 type (low power) wireless networks, Bluetooth Low
   Energy (BLE), WLAN (IEEE 802.11) and DEC ULE.

   In the INT area of the IETF, several LLN specific WGs exist(ed):

5.2.1.  6LOWPAN WG

   The "IPv6 over Low power WPAN (Wireless Personal Area Networks)"
   (6lowpan) WG ran from 2005 to 2014 and produced 6 RFC that adopt IPv6
   to IEEE 802.15.4 type (low power) wireless networks by transmission
   procedures [RFC4949], compression of IPv6 (and transport) packet
   headers [RFC6282], modifications for neighbor discovery (ND)
   [RFC6775], as well as 3 informational RFCs about the WPAN space and
   applying IPv6 to it.  Among these, the Problem Statement and
   Requirements [RFC6606] gives details about the power and energy
   approaches and goals.

   "Transmission of IPv6 Packets over IEEE 802.15.4 Networks" [RFC4944],
   "Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based
   Networks" [RFC6282], "Neighbor Discovery Optimization for IPv6 over
   Low-Power Wireless Personal Area Networks (6LoWPANs)" [RFC6775]
   (6LOWPAN-ND).

   It is important to understand the 6LOWPAN Overview, Assumptions,
   Problem Statement, and Goals [RFC4919], including "conserve energy".

   Outside the 6LOWPAN WG, [RFC9139] connects Information-Centric
   Networking (ICN) to Low-Power Wireless Personal Area Networks
   (LoWPANs).









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5.2.2.  LPWAN WG

   Since 2014 and before 2023, the "IPv6 over Low Power Wide-Area
   Networks" (LPWAN) WG has produced 4 RFC for low-power wide area
   networks, such as LoRaWAN https://en.wikipedia.org/wiki/LoRa, with
   three Standards-Track RFC documents, [RFC8724], [RFC8824], and
   [RFC9011].

5.2.3.  6TISCH WG

   Since 2013, the "IPv6 over the TSCH mode of IEEE 802.15.4e" (6tisch)
   WG has produced 7 RFC for a version of 802.15.4 called the "Time-
   Slotted Channel Hopping Mode" (TSCH), which supports deterministic
   latency and lower energy consumption through the use of scheduling
   traffic into well-defined time slots, thereby also optimizing/
   minimizing energy consumption when compared to 802.15.4 without TSCH.

5.2.4.  6LO WG

   Since 2013, the "IPv6 over Networks of Resource-constrained Nodes"
   (6lo) WG has generalized the work of 6lowpan for LLN in general,
   producing 17 RFC for IPv6-over-l2foo adaptation layer specifications,
   information models, cross-adaptation layer specification (such as
   header specifications) and maintenance and informational documents
   for other pre-existing IETF work in this space.

   Notably, a key specification produced is [RFC7668], "IPv6 over
   BLUETOOTH(R) Low Energy", using IPv6 over Low-power Wireless Personal
   Area Network (6LoWPAN) techniques, as well as the related [RFC9159]
   for the formation of extended topologies, an IPv6 mesh over Bluetooth
   LE links.

   From a management perspective, produced [RFC7388], LOWPAN MIB, as
   well as several specific improvements around power such as [RFC7973],
   [RFC8025], [RFC8928], [RFC8931], and [RFC9034].

   Finally, the 6LO WG also produced [RFC8105], IPv6 over DECT Ultra-Low
   Energy, and [RFC9354], IPv6 over Power Line Communication (PLC).

5.2.5.  ROLL WG

   In the RouTinG (RTG) area of the IETF, the "Routing Over Low power
   and Lossy networks" (ROLL) WG has produced since 2008 23 RFC.
   Initially it produced requirement RFCs of different type of "Low-
   power and Lossy Networks": urban: [RFC5548], industrial [RFC5673],
   home automation [RFC5826] and building automation [RFC5867].





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   Since then, its work is mostly focused on the "IPv6 Routing Protocol
   for Low-Power and Lossy Networks" (RPL) [RFC6550] [RFC6551]
   [RFC6552], which is used in a wide variety of the above-described
   IPv6 instances of LLN networks and which are discussed in two ROLL
   applicability statement RFCs, "Applicability Statement: The Use of
   the Routing Protocol for Low-Power and Lossy Networks (RPL) Protocol
   Suite in Home Automation and Building Control" [RFC7733] and
   "Applicability Statement for the Routing Protocol for Low-Power and
   Lossy Networks (RPL) in Advanced Metering Infrastructure (AMI)
   Networks" [RFC8036].  Further, some RPL RFCs were progressed in the
   6MAN WG, such as [RFC6553], RPL Option for Carrying RPL Information
   in Data-Plane Datagrams, and [RFC6554], IPv6 Routing Header for
   Source Routes with RPL.  [RFC7416] covers a Security Threat Analysis
   for RPLs, which is also relevant to energy efforts.

   The ROLL WG also wrote a more generic RFC for LLN, "Terms Used in
   Routing for Low-Power and Lossy Networks" [RFC7102].  RPL has a
   highly configurable set of functions to support (energy) constrained
   networks.  Unconstrained root node(s), typically edge routers between
   the RPL network and a backbone network calculate "Destination-
   Oriented Directed Acyclic Graphs" (DODAG) and can use strict hop-by-
   hop source routing with dedicated IPv6 routing headers [RFC8138]
   [RFC9008] to minimize constrained nodes routing related compute and
   memory requirements.  "The Trickle Algorithm" [RFC6206] allows to
   minimize routing related packets through automatic lazy updates.
   While RPL is naturally a mesh network routing protocol, where all
   nodes are usually expected to be able to participate in it, RPL also
   supports even more lightweight leave nodes [RFC9010].

   The 2013 [I-D.ajunior-energy-awareness-00] proposes the introducing
   of energy related parameters into RPL to support calculation/
   selection of most energy efficient paths.  The 2017 "An energy
   optimization routing scheme for LLSs",
   [I-D.wang-roll-energy-optimization-scheme] observed that DODAGs in
   RPL tend to require more energy in nodes closer to the root and
   proposed specific optimizations to reduce this problem.  Neither of
   these drafts proceeded in the IETF.

   While original use-cases for RPL where energy and size limited
   networks, its design is to a large extend not scale limited.  Because
   of this, and due to its reduced compute/memory requirements for the
   same size networks compared to other routing protocols, especially
   the so-called link-state "Interior Gateway routing Protocols" (IGP),
   such as most commonly used protocols ISIS ([RFC1142] superseded by
   [ISO10589-Second-Edition]) and OSPF [RFC2328], RPL has also
   proliferated into use-cases for non-constrained networks, for example
   to support the largest possible networks automatically, such as in
   [RFC8994].



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5.3.  Constrained Nodes and Networks

   (Power) constrained nodes and/or networks exist in a much broader
   variety than coupled with low-power and lossy networks.  For example,
   Wi-Fi and cellular mobile network connections are not considered to
   be lossy networks, and personal mobile nodes with both connections
   are order of magnitude less constrained than nodes typically attached
   to LLN network.  Therefore, broader work in the IETF than focused
   primarily on LLN typically uses just the term lightweight or
   constrained (nodes and networks).

5.3.1.  LWIG WG

   Since 2013, the "Light-Weight Implementation Guidance" (lwig) WG is
   has produced 6 informational RFC on the groups subject, much of which
   indirectly supports implementing power efficient network
   implementations via lightweight nodes/links, but it also addressed
   the topic explicitly including via the aforementioned [RFC8352] and
   [RFC9178], "Building Power-Efficient Constrained Application Protocol
   (CoAP) Devices for Cellular Networks".

   Further, the LWIG WG produced [RFC7228], "Terminology for
   Constrained-Node Networks", which includes important energy and power
   definitions of terms.  These include scaling properties, classes of
   energy limitation, and strategies for using power for communication.
   It also produced [RFC9006], giving guidance on TCP usage for saving
   energy.

5.3.2.  CoRE and CoAP

   In the APPlication (APP) area of the IETF, the "Constrained RESTful
   Environments" (core) WG has produced since 2010 21 RFC, most of them
   for or related to "The Constrained Application Protocol" (CoAP)
   [RFC6690], which can best be described as a replacement for HTTP for
   constrained environment, using UDP instead of TCP and DTLS instead of
   TLS, compact binary message formats instead of human readable textual
   formats, RESTful message exchange semantic instead of a broader set
   of options (in HTTP), but also more functionality such as (multicast)
   discovery and directory services, therefore providing a more
   comprehensive set of common application functions with more compact
   on-the-wire/radio encoding than its unconstrained alternatives.
   "Object Security for Constrained RESTful Environments" (OSCORE),
   [RFC8613] is a further product of the CoRE WG providing a more
   message layer based, more lightweight security alternative to DTLS.







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   While originally designed for LLN, CoAP is transcending LLN and
   equally becoming ubicuitous in unconstrained environments such as
   wired/ethernet industrial Machine 2 Machine (M2M) communications,
   because of simplicity, flexibility and relying on the single set of
   protocols supporting the widest range of deployment scenarios.

   In the SECurity (SEC) area of the IETF, the "Authentication and
   Authorization for Constrained Environments" (ace) working group has
   since 2014 produced 4 RFC for security functions in constrained
   environments, for example CoAP based variations of prior HTTPS
   protocols such as EST-coaps [RFC9148] for HTTPS based EST [RFC7030].
   Constrained node support in cryptography especially entails support
   for Elliptic Curve (EC) public keys due to their shorter key sizes
   and lower compute requirements compared to RSA public keys with same
   cryptographic strength.  While the benefits of EC over RSA where
   making them preferred, this "additional market space" (constrained
   node) benefit helped in their faster market proliferation even beyond
   constrained networks.

5.3.3.  Satellite Constellations

   Emerging communication infrastructures may have specific requirements
   on power consumption.  Such requirements should be taken into account
   when designing/customizing techniques (e.g., routing) to be enabled
   in such networks.  For example,
   [I-D.lhan-problems-requirements-satellite-net] identifies a set of
   requirements (including power) for satellite constellations.

5.3.4.  Devices with Batteries

   Many IETF protocols (e.g., [RFC3948]) were designed to accommodate
   the presence of middleboxes mainly by encouraging clients to issue
   frequent keepalives.  Such strategy has implication on battery-
   supplied devices.  In order to optimize battery consumption for such
   devices, [RFC6887] specifies a deterministic method so that client
   can control state in the network, including their lifetime.
   Keepalive alive messages may this be optimized as a function of the
   network policies.

   A_REC#2 of [RFC7849] further insist on the importance of saving
   battery exacerbated by keep-alive messages and recommends the support
   of collaborative means to control state in the network rather than
   relying on heuristics.

5.4.  Sample Technical Enablers

5.4.1.  (IP) Multicast




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5.4.1.1.  Power Saving with Multicast

   IP Multicast was introduced with [RFC1112] and today also called "Any
   Source Multicast" (ASM) has various protocols go through the
   standardization process in the IETF across multiple working groups.
   There are also MPLS and BIER multicast protocols from the IETF
   developed in the equally named WGs.

   These three, network layer multicast technologies can be a power
   saving technologies when used to distribute data because they reduce
   the number of packets that need to be sent across the network
   (through in-network-replication where needed).  Because most current
   link and router technologies do not allow to actually save
   significant amounts of energy on lower than maximum utilization,
   these benefits are often only theoretical though.  Software routers
   are the ones most likely to expose energy consumption somewhat
   proportional to their throughput for just the forwarding (CPU) chip.

   Likewise, in large backbone networks, IP multicast can free up
   bandwidth to be used for other traffic, such as unicast traffic,
   which may allow to avoid upgrades to faster and potentially more
   power consuming routers/links.  Today, these benefits too are most
   often overcompensated for by lower per-bit energy consumption of
   newer generations of routers and links though.

   Multicasting can also save energy on the transmitting station across
   radio links, compared to replicated unicast traffic, but this is
   rarely significant, because except for fully battery powered mesh
   network, there are typically non-energy-constrained nodes, such as
   (commonly) the wired access-points in Wi-Fi networks.

   In result, today multicasting has typically no significant power
   saving benefits with available network technologies.  Instead, it is
   used (for data distribution) when the amount of traffic that a
   unicast solution alternative (with so-called ingress replication) is
   not possible due to the total amount of traffic generated.  This
   includes wireless/radio networks, where equally airtime is the
   limiting factor.

   As an additional pointer, [RFC7731] defined the Multicast Protocol
   for Low-Power and Lossy Networks (MPL).










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5.4.1.2.  Power Waste Through Multicast-based Service Coordination

   (IP) multicast is often not used to distribute data requested by
   receivers, but also coordination type functions such as service or
   resource announcement, discovery or selection.  These multicast
   messages may not carry a lot of data, but they cause recurring, often
   periodic packets to be sent across a domain and waste energy because
   of various ill-advised designs, including, but not limited to the
   following issues:

   (a) The receivers of such packets may not even need to receive them,
   but the protocol shares a multicast group with another protocol that
   the client does need to receive.

   (b) The receiver should not need to receive the packet as far as
   multicast is concerned, but the underlying link-layer technology
   still makes the receiver consume the packet at link-layer.

   (c) The information received is not new, but just periodically
   refreshed.

   (d) The packet was originated for a service selection by a client,
   and the receiving device is even responding, but the client then
   chooses to select another device for the service/resource.

   These problems are specifically problematic in the presence of so-
   called "sleepy" nodes Section 5.4.2 that need to wake up to receive
   such packets (unnecessarily).  It is worse, when the network itself
   is an LLN network where the forwarders themselves are power
   constrained and for example periodic multicasting of such
   coordination packets wastes energy on those forwarders as well -
   compared to better alternatives.

   In 2006, the IETF published "Source Specific Multicast" (SSM)
   [RFC4607], a variation of IP Multicast that does not allow to perform
   these type of coordination functions but is only meant for (and
   useable for) actual data distribution.  SSM was introduced for other
   reasons than the above-described power related issues though, but
   deprecating the use of ASM is one way to avoid/minimize its ill-
   advised use with these type of coordination functions, when energy
   efficiency is an issue.  [RFC8815] is an example for deprecating ASM
   for other reasons in Service Provider networks.

5.4.1.3.  Multicast Problems in Wireless Networks

   [RFC9119] covers multicast challenges and solutions (proposals) for
   IP Multicast over Wi-Fi.  With respect to power consumption, it
   discusses the following aspects:



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   (a) Unnecessary wake-up of power constrained Wi-Fi Stations (STA)
   nodes can be minimized by wireless Access Points (APs) that buffer
   multicast packets so they are sent only periodically when those nodes
   wake up.

   (b) Wi-Fi access points with "Multiple Input Multiple Output" (MIMO)
   antenna diversity focus sent packets in a way that they are not
   "broadcast" to all receivers within a particular maximum distance
   from the AP, making Wi-Fi multicast transmission even less desirable.

   (c) It lists the most widely deployed protocols using aforementioned
   coordination via IP multicast and describes their specific challenges
   and possible improvements.

   (d) Existing proprietary conversion of Wi-Fi multicast to Wi-Fi
   unicast packets.

   [I-D.desmouceaux-ipv6-mcast-wifi-power-usage] focuses on IPv6-related
   concerns of multicast traffic in large wireless network.  This
   document provides as set of statistics and the induced device power
   consumption of such flows.

5.4.2.  Sleepy Nodes

   Sleepy nodes are one of the most common design solutions in support
   of power saving.  This includes LLN level constrained nodes, but also
   nodes with significant battery capacity, such as mobile phones,
   tablets and notebooks, because battery lifetime has long since been a
   key selling factor.  In result, vendors do attempt to optimize power
   consumption across all hardware and software components of such
   nodes, including the interface hardware and protocols used across the
   nodes Wi-Fi and mobile radios.

   Restating from [I-D.bormann-core-roadmap-05]: CoAP has basic support
   for sleepy nodes by allowing caching of resource information in (non-
   sleepy) proxy nodes.  [RFC7641] enhances this support by enabling
   sleepy nodes to update caching intermediaries on their own schedule.
   Around 2012/2013, there was significant review of further review of
   further support for sleepy nodes in CoAP, resulting in a long list of
   drafts, whose sleepy nodes benefits are discussed in
   [I-D.bormann-core-roadmap-05]: [I-D.vial-core-mirror-server],
   [I-D.vial-core-mirror-proxy], [I-D.fossati-core-publish-option],
   [I-D.giacomin-core-sleepy-option], [I-D.castellani-core-alive],
   [I-D.rahman-core-sleepy-problem-statement], [I-D.rahman-core-sleepy],
   [I-D.rahman-core-sleepy-nodes-do-we-need],
   [I-D.fossati-core-monitor-option].  None of these drafts proceeded
   though.




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   One partial solution to some sleepy node issues related to their
   energy consumption, especially the ones caused by the use of
   multicast Section 5.4.1.2, Section 5.4.1.3 is the use of the
   "Constrained RESTful Environments (CoRE) Resource Directory" (CoRE-
   RD) [RFC9176].  It allows for sleepy nodes to register discover and
   register resources via unicast and avoids waking up sleepy nodes when
   they are not selected by a resource consumer.

   A partial alternative to CoRE-RD is the "DNS-Based Service Discovery"
   {DNS-SD} [RFC6763] combined with for example "Service Registration
   Protocol for DNS-Based Service Discovery" [I-D.ietf-dnssd-srp].
   Services can be seen as a subset of resources, and in networks where
   DNS has to be supported anyhow for other reasons, DNS-SD may be a
   sufficient alternative to CoRE-RD.  It is used for example in Thread
   https://en.wikipedia.org/wiki/Thread_(network_protocol) for this
   purpose and the only multicast based coordination is the one to
   establish network wide parameters, such as the address(es) of DNS-SD
   server(s).

   "Building Power-Efficient Constrained Application Protocol (CoAP)
   Devices for Cellular Networks" [RFC9178] discusses sleepy devices,
   especially the use of CoAP PubSub [I-D.ietf-core-coap-pubsub] as a
   mechanism to build proxies for sleepy devices.  "Sensor Measurement
   Lists (SenML)", normalized proxy infrastructures are best built with
   published data models, such as "Sensor Measurement Lists" (SenML)
   [RFC8428] for sensors, likely the largest number of sleepy devices,
   especially in LLN.

   "Reducing Energy Consumption of Router Advertisements", [RFC7772]
   eliminates/reduces the energy impact for sleepy nodes of the
   ubiquitous IPv6 "Neighbor Discovery" (ND) protocol by giving
   recommends for replacing multicast "Router Advertisement" (RA)
   messages with so-called directed unicast versions, therefore not
   waking up sleepy nodes (with an IP multicast RA message).  This was
   already allowed in ND [RFC4861], but not recommended as the default.
   Note that [RFC7772] does not provide all the energy related
   optimizations of ND as developed by 6LoWPAN through [RFC6775], later
   updated by [RFC8505] is 6LO.
   [I-D.chakrabarti-nordmark-energy-aware-nd] proposes generalizations
   for those applications for to all IPv6 links, but was not further
   pursued by the IETF so far.










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5.5.  (Lack of) Power Benchmarking Proposals

   [I-D.petrescu-v6ops-ipv6-power-ipv4] presented some measurement
   results of the power consumption when using IPv6 vs IPv4 with a focus
   on mobile devices.  Such measurements are not backed with formal
   benchmarking methodologies so that solid and reliable references are
   set to compare and interpret data.

   https://www.ietf.org/proceedings/103/slides/slides-103-saag-iot-
   benchmarking-00 presented a benchmark example but with a focus on
   power cost of encryption.

6.  Energy Management Networks

   The use of IETF protocol networks in networks that operate power
   consumption and production is another broad area of digitization.

6.1.  Smart Grid

   "Smart Grid" is the most well-known instance of such energy
   management networks.  According to https://en.wikipedia.org/wiki/
   Smart_grid, the term covers aspects mostly centered around
   intelligent measured and controlled consumption of energy.  This
   includes "Advanced Metering Infrastructure" / "Smart Meters", remote
   controllable "distribution boards", "circuit breakers", "load
   control" and "smart appliances".  Use cases for the "Smart Grid"
   include for example timed and measured operations of home devices
   such as washers or charging cars, when energy consumption is below
   average.

   The 2011 "Internet Protocols for the Smart Grid" [RFC6272] is a quite
   comprehensive (66 page) overview of all IETF protocols considered to
   be necessary or beneficial for Smart Grid networks.  This document
   was written in response to interest by the (not-yet-smart grid)
   community in utilizing the IETF TCP/IP technologies to evolve
   previously non-TCP/IP network, and the risk that unnecessary
   reinvention of the wheel/protocols would be done by that community
   instead of reusing what was already well specified by the IETF.













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   Most of the overview in this document is not specific to networks
   used for Smart Grid applications but just summarized in the document
   for the above-described outreach and education to the community.  The
   aspects most specific to Smart Grids is the back in 2011 still
   somewhat in its infancy adaptation of IPv6 network technologies to
   LLN networks (see Section 5.2): smart meters, circuit breakers, load
   measurement devices, car chargers and so on - all those devices would
   most likely be connected to the network via a low-power radio
   networks, which ideally would utilize IPv6 directly.  Support for LLN
   networks with IPv6 has well improved in IETF specifications in the
   past decade.

6.2.  Synchro Phasor Networks

   Power output of multiple power plants/generators into the same power
   grid needs to be synchronized by power levels based on consumption
   and power phase (50/60Hz depending on continent) to avoid that energy
   created out-of-phase is not only wasted, but would actually burn out
   power lines or create permanent damage in power generators.  When
   generators go out-of-sync, they have to be emergency switched off,
   resulting in (rolling-)blackouts, worsening the conditions beyond its
   likely root-cause such as a single overloaded limited region.

   Synchro Phasor Networks are networks whose goal it is to support
   synchronization of power generators across a power grid, ultimately
   also permitting to build larger and more resilient power grids.
   "Power Measurement Units" (PMU) are their core sensing elements.
   Since about 2012? these networks have started to move from
   traditional SCADA towards more TCP/IP based networking and
   application technologies "to improve power system reliability and
   visibility through wide area measurement and control, by fostering
   the use and capabilities of synchrophasor technology"
   (www.naspi.org).

   With their fast control loop reaction time and measurement
   requirements, they also benefit from reliable, fast propagation of
   PMU data as well as stricter clock synchronization than most Smart
   Grid applications.  For example, transmission lines expand under heat
   that s caused by electrical load and/or environmental temperature by
   as much as 30% (between coldest and hottest or highest-load times),
   impacting the necessary phase relationship of power generation on
   either end (speed of light propagation speed based on effective
   length of contracted/expanded wire).

   The length of transmission wires can be measured from data sent
   across the transmission lines and measuring their propagation latency
   with the help of accurate clock synchronization between sender and
   receiver(s), using for example network-based clock synchronization



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   protocols.  The IETF "Network Time Protocol version 4" (NTPv4),
   [RFC5905] is one option for this.  The IEEE PTP protocol is often
   preferred though because it specifies better how measurements can be
   integrated at the hardware level of Ethernet interfaces, thus
   allowing easier to achieve higher accuracy, such as Maximum Time
   Interval (MTIE) errors of less than 1 msec.  See for example
   [NASPICLOCK].

   The "North American SynchroPhasor Initiative" (NASPI),
   https://www.naspi.org is an example organization in support of
   synchrophasor networking.  It is an ongoing project by the USA
   "Department of Energy" (DoE).

7.  (Limited) Energy Management for Networks

7.1.  Some Metrics

   A 2010-2013 draft [I-D.manral-bmwg-power-usage], which was not
   adopted discussed and proposed metrics for power consumption that
   where intended to be used for benchmarking.

   The later work in Section 7.2 referred instead to other metrics for
   measuring power consumption from other SDOs.

   A 2011-2012 draft [I-D.jennings-energy-pricing], which was not
   adopted, discusses and proposes a data model to communicate time-
   varying cost of energy in support of enabling time-shifting of
   network attached or managed equipment consumption of power.

7.2.  EMAN WG

   While the IETF did specify a few MIBs with aspects related to of
   power management, it was only with the formation of the "Energy
   Management" (EMAN) WG which ran from 2010 to 2015 and released 7 RFC,
   that the IETF produced a comprehensive set of MIB based publications
   for managing energy/power for network equipment and associated
   devices and integrated prior scattered power management related work
   in the IETF.

   EMAN produced (solely) a set of data/information models (MIBs).  It
   does not introduce any new protocol/stacks nor does it address
   "questions regarding Smart Grid, electricity producers, and
   distributors" (from [RFC7603]).








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   [I-D.claise-power-management-arch] describes the initial EMAN
   architecture as envisioned by some of the core contributors to the
   WG.  It was rewritten in EMAN as the "Energy Management Framework"
   [RFC7326].  "Requirements for Energy Management" are defined in
   [RFC6988].

   According to [RFC7326], "the (EMAN) framework presents a physical
   reference model and information model.  The information model
   consists of an Energy Management Domain as a set of Energy Objects.
   Each Energy Object can be attributed with identity, classification,
   and context.  Energy Objects can be monitored and controlled with
   respect to power, Power State, energy, demand, Power Attributes, and
   battery.  Additionally, the framework models relationships and
   capabilities between Energy Objects."

   One category of use-cases of particular interest to network equipment
   vendors was and is the management of "Power over Ethernet" via the
   EMAN framework, measuring and controlling ethernet connected devices
   through their PoE supplied power.  Besides industrial, surveillance
   cameras and office equipment, such as Wi-Fi access points and phones,
   PoE is also positioned as a new approach for replacing most in-
   building automation components including security control for doors/
   windows, as well as environmental controls and lighting through the
   use of an in-ceiling, PoE enabled IP/ethernet infrastructure.

   EMAN produced version 4 of the "Entity MIB" (ENTITY-MIB) [RFC6933],
   primarily to introduce globally unique UUIDs for physical entities
   that allows to better link across different entities, such as a PoE
   port on an ethernet switch and the device connected to that switch
   port.

   The "Monitoring and Control MIB for Power and Energy" [RFC7460]
   specifies a MIB for monitoring for Power State and energy consumption
   of networked.  The document discusses the link with other MIBs such
   as the ENTITY-MIB, the ENTITY-SENSOR-MIB [RFC3433] for which it is
   amending missing accuracy information to meet IEC power monitoring
   requirements, the "Power Ethernet MIB" (POWER-ETHERNET-MIB) [RFC3621]
   to manage PoE, and the pre-existing IETF MIB for Uninterruptable
   Power Supplies (UPS) (UPS-MIB) [RFC1628], allowing for example to
   build control systems that manage shutdowns of devices in case of
   power failure based on UPS battery capacity and device consumptions/
   priorities.  Similarly, the EMAN "Definition of Managed Objects for
   Battery Monitoring" [RFC7577] defines objects to support battery
   monitoring in managed devices.  It is important to note that, outside
   the EMAN WG and as an Independent Submission, [RFC9271] specifies
   "Uninterruptible Power Supply (UPS) Management Protocol -- Commands
   and Responses".




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   The pre-existing IETF "Entity State MIB" (ENTITY-STATE-MIB) [RFC4268]
   allows to specify the operational state of entities specified via the
   ENTITY-MIB respective to their power consumption and operational
   capabilities (e.g.: "coldStandby", "hotStandby", "ready" etc.).
   Devices can also act as proxies to provide a MIB interfaces for
   monitoring and control of power for other devices, that may use other
   protocols, such as in case of a home gateway interfacing with various
   vendor specific protocols of home equipment.

   The EMAN "Energy Object Context MIB" [RFC7461] defines the ENERGY-
   OBJECT-CONTEXT-MIB and IANA-ENERGY-RELATION-MIB, both of which serve
   to "address device identification, context information, and the
   energy relationships between devices" according to [RFC7461].

   To automatically discover and negotiate PoE power consumption between
   switch and client, non-IETF technologies, such as IEEE "Link Layer
   Discovery Protocol" (LLDP) and proprietary MIBs for it, such as LLDP-
   EXT-MED-MIB can be used.

   Finally, the "Energy Management (EMAN) Applicability Statement"
   [RFC7603] provides an overview of EMAN with a user/operator
   perspective, also reviewing a range of typical scenarios it can
   support as well as how it could/can link to a variety of pre-
   existing, non-IETF standards relevant for power management.  Such
   intended applicability includes home, core, and DC networks.

   There are currently no YANG equivalent modules.  Such modules would
   not only be designed to echo the EMAN MIBs but would also allow to
   control dedicated power optimization engines instead of relying upon
   static and frozen vendor-specific optimization.

8.  Power-Awareness in Forwarding and Routing Protocols

8.1.  Power Aware Networks (PANET)

   In 2013/2014, some drafts proposed how networks themselves,
   specifically those of Internet Service Providers (ISP) could
   dynamically regulate their power consumption based on the required
   performance, for example by switching off or low-powering non-needed
   components (links, nodes, linecards) or changing speeds on links, or
   reducing clock-rates of processing elements, and/or routing traffic
   to utilize as few components as will support the required
   performance.  The authors called this "Power Aware Networks" (PANET),
   even though no awareness of actual power consumption is required in
   this approach.






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   The 2013 "Power-Aware Networks (PANET): Problem Statement"
   [I-D.zhang-panet-problem-statement] gives an overview of this
   concept, and so does "Power-aware Routing and Traffic Engineering:
   Requirements, Approaches, and Issues", [I-D.zhang-greennet] from the
   same year.

   The 2014 [I-D.retana-rtgwg-eacp] exemplifies the concept and
   discusses key challenges such as the reduced resilience against
   errors when redundant components are switched off, the risk of
   increased stretch (path length) and therefore latency under partial
   network component shutdown or down-speeding, as well as the idea of
   saving energy through (periodic) microsleeps such as possible with
   "Energy Efficient Ethernet" https://en.wikipedia.org/wiki/Energy-
   Efficient_Ethernet links.  The 2013 draft "Reducing Power Consumption
   using BGP with power source data",
   [I-D.mjsraman-panet-inter-as-power-source] proposed BGP attributes to
   allow calculation of power efficient (or for example green) paths.

   One core market driver for this work where rolling blackouts that
   especially affected India at the time of these drafts, raising the
   desire to be for example reducing the total power consumption of a
   network in times of such energy emergencies.

   While there was technical interest in the IETF, the market
   significance for the vendors mostly present in the IETF was
   considered as not to be important enough.  Likewise, traditional
   routers, unlike for example todays standard PC hardware designs do
   exhibit little power savings upon shutdown of components such as
   line-cards or interfaces.

   In addition, an SDN / controller-based solution where relatively in
   their infancy back in 2013/2014, and technologies that would allow
   for SDN controller to have resilient (self-healing) connectivity such
   as described in [RFC8368]/[RFC8994] was also not available, making
   the risk of severely impacting network reliability one of the key
   factors for this PANET work to not proceed so far.

8.2.  SDN-based Semantic Forwarding

   Recently, [I-D.boucadair-irtf-sdn-and-semantic-routing] provided the
   following feature as an example of capabilities that can be offered
   by appropriate control of forwarding elements:









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   Energy-efficient Forwarding: An important effort was made in the past
   to optimize the energy consumption of network elements.  However,
   such optimization is node-specific and no standardized means to
   optimize the energy consumption at the scale of the network have been
   defined.  For example, many nodes (also, service cards) are deployed
   as backups.

   A controller-based approach can be implemented so that the route
   selection process optimizes the overall energy consumption of a path.
   Such a process takes into account the current load, avoids waking
   nodes/cards for handling "sparse" traffic (i.e., a minor portion of
   the total traffic), considers node-specific data (e.g., [RFC7460]),
   etc.  This off-line Semantic Routing approach will transition
   specific cards/nodes to "idle" and wake them as appropriate, etc.,
   without breaking service objectives.  Moreover, such an approach will
   have to maintain an up-to-date topology even if a node is in an
   "idle" state (such nodes may be removed from adjacency tables if they
   don't participate in routing advertisements).

8.3.  Miscelaneous

   The non-adopted, expired 2013 draft
   [I-D.okamoto-ccamp-midori-gmpls-extension-reqs] discusses power
   awareness in routing in conjunction with Traffic Engineering
   (tunnels), specifically in the context of Generalized MPLS (GMPLS),
   e.g.: various L2 technologies such as switched optical fiber
   networks.  It primarily claims the issue that the existing management
   objects are not sufficient to express energy management related
   aspects, and thus do not allow to build energy conscious policies
   into PCE for such GMPLS networks.

   The non-adopted 2013 "Requirements for an Energy-Efficient Network
   System", [I-D.suzuki-eens-requirements] proposes a signaling of
   network capacity towards DC, for example based on load or network
   energy management in support of appropriate performance control (such
   as VM migration) the DC - or vice versa (DC load-based traffic
   engineering in the network to support that DC load).

   The non-adopted 2013 "Building power optimal Multicast Trees"
   [I-D.mjsraman-rtgwg-pim-power] proposes that (PIM based) IP Multicast
   routing could perform local routing choices in the case of "Equal
   Cost MultiPath" (ECMP) "Reverse Path Forwarding" (RPF) alternatives
   based on the energy that would be consumed in the router, such as
   when one ECMP alternative would use a more power efficient linecard
   or when one ECMP choice was on the same linecard as the interfaces to
   which the packets would need to be routed (and therefore avoiding to
   forward the packet across separate ingress and egress linecards).




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9.  Gap Analysis

   The 2013 "Towards an Energy-Efficient Internet"
   [I-D.winter-energy-efficient-internet] summarizes some of the same
   work items as this document (as written back in 2013) and lists
   additional more non-adopted drafts.  It also identifies three areas
   of gaps, that it suggests the IETF to work on: "Load-adaptive
   Resource Management", "Energy-efficient Protocol Design" and "Energy-
   efficiency Metrics and Standard Benchmarking Methodologies".

   Some aspects for those areas of gaps where partially tackled by later
   work in the IETF, but broadly speaking, most of those areas remain
   open to a wide range of possible further IETF/IRTF work.

10.  Acknowledgments

   Thanks for Fred Baker for his review and suggestions.

11.  Changelog

   [RFC-Editor: this section to be removed in final document.]

   The master for this document is hosted at http://github.com/toerless/
   energy.  Please submit Issues and/or Pull-requests for proposed
   changes or join the team of authors and edit yourself.

   00: Initial version

   01: Added Co-author (Mohamed Boucadair) - long list of typo fixes,
   editorial improvements in abstract, introduction and other chapters.
   Added section on satellite networks, devices with batteries, power
   benchmarking and SDN-based forwarding semantics.

   02: Minor text edits (med), add pointer to additional draft (med),
   Added co-author pascal (tte),

   03: Added Jeff Tentsura as co-author

   04: Various textual fixups, added new versions of RFC for references
   using obsoleted RFCs, so that both original and latest are
   referenced.

   05: Added pointers on analysis and limit scope of document to
   12/2022.

   06: Full review and throughout addition of references and context on
   energy and power-related IETF work, full editorial pass.  New co-
   author.



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12.  Informative References

   [BOUNDED_LATENCY]
              Cruz, R.L., "A calculus for network delay. I. Network
              elements in isolation", DOI 10.1109/18.61109,
              IEEE Transactions on Information Theory ( Volume: 37,
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   [DVDvsStreaming]
              Zielinski, S., "Streaming a Movie Uses Less Energy Than
              Watching a DVD", May 2014,
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              movie-less-energy-dvd-180951586>.

   [I-D.ajunior-energy-awareness-00]
              Junior, A. and R. C. Sofia, "Energy-awareness metrics
              global applicability guidelines", Work in Progress,
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              October 2012, <https://datatracker.ietf.org/doc/html/
              draft-ajunior-energy-awareness-00>.

   [I-D.bormann-core-roadmap-05]
              Bormann, C., "CoRE Roadmap and Implementation Guide", Work
              in Progress, Internet-Draft, draft-bormann-core-roadmap-
              05, 21 October 2013,
              <https://datatracker.ietf.org/doc/html/draft-bormann-core-
              roadmap-05>.

   [I-D.boucadair-irtf-sdn-and-semantic-routing]
              Boucadair, M., Trossen, D., and A. Farrel, "Considerations
              for the use of SDN in Semantic Routing Networks", Work in
              Progress, Internet-Draft, draft-boucadair-irtf-sdn-and-
              semantic-routing-01, 31 May 2022,
              <https://datatracker.ietf.org/doc/html/draft-boucadair-
              irtf-sdn-and-semantic-routing-01>.

   [I-D.castellani-core-alive]
              Castellani, A. P. and S. Loreto, "CoAP Alive Message",
              Work in Progress, Internet-Draft, draft-castellani-core-
              alive-00, 29 March 2012,
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              core-alive-00>.

   [I-D.chakrabarti-nordmark-energy-aware-nd]
              Chakrabarti, S., Nordmark, E., and M. Cullen, "Energy
              Aware IPv6 Neighbor Discovery Optimizations", Work in
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              energy-aware-nd-02, 12 March 2012,
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              Claise, B., Parello, J., and B. Schoening, "Power
              Management Architecture", Work in Progress, Internet-
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              2010, <https://datatracker.ietf.org/doc/html/draft-claise-
              power-management-arch-02>.

   [I-D.desmouceaux-ipv6-mcast-wifi-power-usage]
              Desmouceaux, Y., "Power consumption due to IPv6 multicast
              on WiFi devices", Work in Progress, Internet-Draft, draft-
              desmouceaux-ipv6-mcast-wifi-power-usage-01, 1 August 2014,
              <https://datatracker.ietf.org/doc/html/draft-desmouceaux-
              ipv6-mcast-wifi-power-usage-01>.

   [I-D.fossati-core-monitor-option]
              Fossati, T., Giacomin, P., and S. Loreto, "Monitor Option
              for CoAP", Work in Progress, Internet-Draft, draft-
              fossati-core-monitor-option-00, 9 July 2012,
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              monitor-option-00>.

   [I-D.fossati-core-publish-option]
              Fossati, T., Giacomin, P., and S. Loreto, "Publish Option
              for CoAP", Work in Progress, Internet-Draft, draft-
              fossati-core-publish-option-03, 6 January 2014,
              <https://datatracker.ietf.org/doc/html/draft-fossati-core-
              publish-option-03>.

   [I-D.giacomin-core-sleepy-option]
              Fossati, T., Giacomin, P., Loreto, S., and M. Rossini,
              "Sleepy Option for CoAP", Work in Progress, Internet-
              Draft, draft-giacomin-core-sleepy-option-00, 29 February
              2012, <https://datatracker.ietf.org/doc/html/draft-
              giacomin-core-sleepy-option-00>.

   [I-D.iab-ws-environmental-impacts-report]
              Arkko, J., Perkins, C., and S. Krishnan, "Report from the
              IAB Workshop on Environmental Impact of Internet
              Applications and Systems, 2022", Work in Progress,
              Internet-Draft, draft-iab-ws-environmental-impacts-report-
              03, 23 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-iab-ws-
              environmental-impacts-report-03>.




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   [I-D.ietf-core-coap-pubsub]
              Jimenez, J., Koster, M., and A. Keränen, "A publish-
              subscribe architecture for the Constrained Application
              Protocol (CoAP)", Work in Progress, Internet-Draft, draft-
              ietf-core-coap-pubsub-13, 20 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-core-
              coap-pubsub-13>.

   [I-D.ietf-dnssd-srp]
              Lemon, T. and S. Cheshire, "Service Registration Protocol
              for DNS-Based Service Discovery", Work in Progress,
              Internet-Draft, draft-ietf-dnssd-srp-23, 4 August 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-dnssd-
              srp-23>.

   [I-D.ietf-roll-protocols-survey]
              Tavakoli, A. and S. Dawson-Haggerty, "Overview of Existing
              Routing Protocols for Low Power and Lossy Networks", Work
              in Progress, Internet-Draft, draft-ietf-roll-protocols-
              survey-07, 24 April 2009,
              <https://datatracker.ietf.org/doc/html/draft-ietf-roll-
              protocols-survey-07>.

   [I-D.ietf-tcpm-rfc793bis]
              Eddy, W., "Transmission Control Protocol (TCP)", Work in
              Progress, Internet-Draft, draft-ietf-tcpm-rfc793bis-28, 7
              March 2022, <https://datatracker.ietf.org/doc/html/draft-
              ietf-tcpm-rfc793bis-28>.

   [I-D.jennings-energy-pricing]
              Jennings, C. F. and B. Nordman, "Communication of Energy
              Price Information", Work in Progress, Internet-Draft,
              draft-jennings-energy-pricing-01, 10 July 2011,
              <https://datatracker.ietf.org/doc/html/draft-jennings-
              energy-pricing-01>.

   [I-D.levis-roll-overview-protocols]
              Jp, V., "Overview of Existing Routing Protocols for Low
              Power and Lossy Networks", Work in Progress, Internet-
              Draft, draft-levis-roll-overview-protocols-00, 12 February
              2008, <https://datatracker.ietf.org/doc/html/draft-levis-
              roll-overview-protocols-00>.









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   [I-D.lhan-problems-requirements-satellite-net]
              Han, L., Li, R., Retana, A., Chen, M., Su, L., and T.
              Jiang, "Problems and Requirements of Satellite
              Constellation for Internet", Work in Progress, Internet-
              Draft, draft-lhan-problems-requirements-satellite-net-06,
              4 January 2024, <https://datatracker.ietf.org/doc/html/
              draft-lhan-problems-requirements-satellite-net-06>.

   [I-D.manral-bmwg-power-usage]
              Manral, V., Sharma, P., Banerjee, S., and Y. Ping,
              "Benchmarking Power usage of networking devices", Work in
              Progress, Internet-Draft, draft-manral-bmwg-power-usage-
              04, 12 March 2013, <https://datatracker.ietf.org/doc/html/
              draft-manral-bmwg-power-usage-04>.

   [I-D.mjsraman-panet-inter-as-power-source]
              Raman, S., Venkataswami, B. V., Raina, G., and K.
              Veezhinathan, "Reducing Power Consumption using BGP with
              power source data", Work in Progress, Internet-Draft,
              draft-mjsraman-panet-inter-as-power-source-00, 25 January
              2013, <https://datatracker.ietf.org/doc/html/draft-
              mjsraman-panet-inter-as-power-source-00>.

   [I-D.mjsraman-rtgwg-pim-power]
              Raman, S., Venkataswami, B. V., Raina, G., and V. Srini,
              "Building power optimal Multicast Trees", Work in
              Progress, Internet-Draft, draft-mjsraman-rtgwg-pim-power-
              02, 27 March 2012, <https://datatracker.ietf.org/doc/html/
              draft-mjsraman-rtgwg-pim-power-02>.

   [I-D.okamoto-ccamp-midori-gmpls-extension-reqs]
              Okamoto, S., "Requirements of GMPLS Extensions for Energy
              Efficient Traffic Engineering", Work in Progress,
              Internet-Draft, draft-okamoto-ccamp-midori-gmpls-
              extension-reqs-02, 14 March 2013,
              <https://datatracker.ietf.org/doc/html/draft-okamoto-
              ccamp-midori-gmpls-extension-reqs-02>.

   [I-D.petrescu-v6ops-ipv6-power-ipv4]
              Petrescu, A., Saïd, S. B. H., Philippot, O., and T.
              Vincent, "Power Consumption of IPv6 vs IPv4 in
              Smartphone", Work in Progress, Internet-Draft, draft-
              petrescu-v6ops-ipv6-power-ipv4-00, 13 March 2017,
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              v6ops-ipv6-power-ipv4-00>.






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   [I-D.rahman-core-sleepy]
              Rahman, A., "Enhanced Sleepy Node Support for CoAP", Work
              in Progress, Internet-Draft, draft-rahman-core-sleepy-05,
              11 February 2014, <https://datatracker.ietf.org/doc/html/
              draft-rahman-core-sleepy-05>.

   [I-D.rahman-core-sleepy-nodes-do-we-need]
              Rahman, A., "Sleepy Devices: Do we need to Support them in
              CORE?", Work in Progress, Internet-Draft, draft-rahman-
              core-sleepy-nodes-do-we-need-01, 11 February 2014,
              <https://datatracker.ietf.org/doc/html/draft-rahman-core-
              sleepy-nodes-do-we-need-01>.

   [I-D.rahman-core-sleepy-problem-statement]
              Rahman, A., Fossati, T., Loreto, S., and M. Vial, "Sleepy
              Devices in CoAP - Problem Statement", Work in Progress,
              Internet-Draft, draft-rahman-core-sleepy-problem-
              statement-01, 21 October 2012,
              <https://datatracker.ietf.org/doc/html/draft-rahman-core-
              sleepy-problem-statement-01>.

   [I-D.retana-rtgwg-eacp]
              Retana, A., White, R., and M. Paul, "A Framework for
              Energy Aware Control Planes", Work in Progress, Internet-
              Draft, draft-retana-rtgwg-eacp-07, 24 August 2023,
              <https://datatracker.ietf.org/doc/html/draft-retana-rtgwg-
              eacp-07>.

   [I-D.suzuki-eens-requirements]
              Suzuki, T. and T. Tarui, "Requirements for an Energy-
              Efficient Network System", Work in Progress, Internet-
              Draft, draft-suzuki-eens-requirements-00, 15 October 2012,
              <https://datatracker.ietf.org/doc/html/draft-suzuki-eens-
              requirements-00>.

   [I-D.thubert-6man-ipv6-over-wireless]
              Thubert, P. and M. Richardson, "Architecture and Framework
              for IPv6 over Non-Broadcast Access", Work in Progress,
              Internet-Draft, draft-thubert-6man-ipv6-over-wireless-15,
              8 March 2023, <https://datatracker.ietf.org/doc/html/
              draft-thubert-6man-ipv6-over-wireless-15>.

   [I-D.vial-core-mirror-proxy]
              Vial, M., "CoRE Mirror Server", Work in Progress,
              Internet-Draft, draft-vial-core-mirror-proxy-01, 13 July
              2012, <https://datatracker.ietf.org/doc/html/draft-vial-
              core-mirror-proxy-01>.




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   [I-D.vial-core-mirror-server]
              Vial, M., "CoRE Mirror Server", Work in Progress,
              Internet-Draft, draft-vial-core-mirror-server-01, 10 April
              2013, <https://datatracker.ietf.org/doc/html/draft-vial-
              core-mirror-server-01>.

   [I-D.wang-roll-energy-optimization-scheme]
              Wang, H., Wei, M., Li, S., Huang, Q., Wang, P., and C.
              Wang, "An energy optimization routing scheme for LLSs",
              Work in Progress, Internet-Draft, draft-wang-roll-energy-
              optimization-scheme-00, 21 February 2017,
              <https://datatracker.ietf.org/doc/html/draft-wang-roll-
              energy-optimization-scheme-00>.

   [I-D.winter-energy-efficient-internet]
              Winter, R., Jeong, S., and J. Choi, "Towards an Energy-
              Efficient Internet", Work in Progress, Internet-Draft,
              draft-winter-energy-efficient-internet-01, 22 October
              2012, <https://datatracker.ietf.org/doc/html/draft-winter-
              energy-efficient-internet-01>.

   [I-D.zhang-greennet]
              Zhang, B., Shi, J., Dong, J., and M. Zhang, "Power-aware
              Routing and Traffic Engineering: Requirements, Approaches,
              and Issues", Work in Progress, Internet-Draft, draft-
              zhang-greennet-01, 10 January 2013,
              <https://datatracker.ietf.org/doc/html/draft-zhang-
              greennet-01>.

   [I-D.zhang-panet-problem-statement]
              Zhang, B., Shi, J., Dong, J., Zhang, M., and M. Boucadair,
              "Power-Aware Networks (PANET): Problem Statement", Work in
              Progress, Internet-Draft, draft-zhang-panet-problem-
              statement-03, 15 October 2013,
              <https://datatracker.ietf.org/doc/html/draft-zhang-panet-
              problem-statement-03>.

   [ISO10589-Second-Edition]
              Standardization, I. O. for., "Intermediate system to
              Intermediate system intra-domain routeing information
              exchange protocol for use in conjunction with the protocol
              for providing the connectionless-mode Network Service (ISO
              8473)", ISO ISO/IEC 10589:2002, Second Edition, Nov.
              2002., n.d..

   [NASPICLOCK]
              Force, N. T. S. T., "Time Synchronization in the Electric
              Power System", March 2017,



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              <https://www.naspi.org/sites/default/files/
              reference_documents/tstf_electric_power_system_report_pnnl
              _26331_march_2017_0.pdf>.

   [RFC1112]  Deering, S., "Host extensions for IP multicasting", STD 5,
              RFC 1112, DOI 10.17487/RFC1112, August 1989,
              <https://www.rfc-editor.org/rfc/rfc1112>.

   [RFC1142]  Oran, D., Ed., "OSI IS-IS Intra-domain Routing Protocol",
              RFC 1142, DOI 10.17487/RFC1142, February 1990,
              <https://www.rfc-editor.org/rfc/rfc1142>.

   [RFC1628]  Case, J., Ed., "UPS Management Information Base",
              RFC 1628, DOI 10.17487/RFC1628, May 1994,
              <https://www.rfc-editor.org/rfc/rfc1628>.

   [RFC1866]  Berners-Lee, T. and D. Connolly, "Hypertext Markup
              Language - 2.0", RFC 1866, DOI 10.17487/RFC1866, November
              1995, <https://www.rfc-editor.org/rfc/rfc1866>.

   [RFC1883]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 1883, DOI 10.17487/RFC1883,
              December 1995, <https://www.rfc-editor.org/rfc/rfc1883>.

   [RFC2086]  Myers, J., "IMAP4 ACL extension", RFC 2086,
              DOI 10.17487/RFC2086, January 1997,
              <https://www.rfc-editor.org/rfc/rfc2086>.

   [RFC2212]  Shenker, S., Partridge, C., and R. Guerin, "Specification
              of Guaranteed Quality of Service", RFC 2212,
              DOI 10.17487/RFC2212, September 1997,
              <https://www.rfc-editor.org/rfc/rfc2212>.

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, DOI 10.17487/RFC2246, January 1999,
              <https://www.rfc-editor.org/rfc/rfc2246>.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <https://www.rfc-editor.org/rfc/rfc2328>.

   [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/rfc/rfc2460>.







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   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
              <https://www.rfc-editor.org/rfc/rfc2475>.

   [RFC2543]  Handley, M., Schulzrinne, H., Schooler, E., and J.
              Rosenberg, "SIP: Session Initiation Protocol", RFC 2543,
              DOI 10.17487/RFC2543, March 1999,
              <https://www.rfc-editor.org/rfc/rfc2543>.

   [RFC2822]  Resnick, P., Ed., "Internet Message Format", RFC 2822,
              DOI 10.17487/RFC2822, April 2001,
              <https://www.rfc-editor.org/rfc/rfc2822>.

   [RFC2854]  Connolly, D. and L. Masinter, "The 'text/html' Media
              Type", RFC 2854, DOI 10.17487/RFC2854, June 2000,
              <https://www.rfc-editor.org/rfc/rfc2854>.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <https://www.rfc-editor.org/rfc/rfc3261>.

   [RFC3433]  Bierman, A., Romascanu, D., and K.C. Norseth, "Entity
              Sensor Management Information Base", RFC 3433,
              DOI 10.17487/RFC3433, December 2002,
              <https://www.rfc-editor.org/rfc/rfc3433>.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <https://www.rfc-editor.org/rfc/rfc3550>.

   [RFC3621]  Berger, A. and D. Romascanu, "Power Ethernet MIB",
              RFC 3621, DOI 10.17487/RFC3621, December 2003,
              <https://www.rfc-editor.org/rfc/rfc3621>.

   [RFC3948]  Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
              Stenberg, "UDP Encapsulation of IPsec ESP Packets",
              RFC 3948, DOI 10.17487/RFC3948, January 2005,
              <https://www.rfc-editor.org/rfc/rfc3948>.

   [RFC3977]  Feather, C., "Network News Transfer Protocol (NNTP)",
              RFC 3977, DOI 10.17487/RFC3977, October 2006,
              <https://www.rfc-editor.org/rfc/rfc3977>.





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   [RFC4268]  Chisholm, S. and D. Perkins, "Entity State MIB", RFC 4268,
              DOI 10.17487/RFC4268, November 2005,
              <https://www.rfc-editor.org/rfc/rfc4268>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/rfc/rfc4271>.

   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346,
              DOI 10.17487/RFC4346, April 2006,
              <https://www.rfc-editor.org/rfc/rfc4346>.

   [RFC4607]  Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
              <https://www.rfc-editor.org/rfc/rfc4607>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <https://www.rfc-editor.org/rfc/rfc4861>.

   [RFC4919]  Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
              over Low-Power Wireless Personal Area Networks (6LoWPANs):
              Overview, Assumptions, Problem Statement, and Goals",
              RFC 4919, DOI 10.17487/RFC4919, August 2007,
              <https://www.rfc-editor.org/rfc/rfc4919>.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
              <https://www.rfc-editor.org/rfc/rfc4944>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <https://www.rfc-editor.org/rfc/rfc4949>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/rfc/rfc5246>.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              DOI 10.17487/RFC5322, October 2008,
              <https://www.rfc-editor.org/rfc/rfc5322>.





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   [RFC5548]  Dohler, M., Ed., Watteyne, T., Ed., Winter, T., Ed., and
              D. Barthel, Ed., "Routing Requirements for Urban Low-Power
              and Lossy Networks", RFC 5548, DOI 10.17487/RFC5548, May
              2009, <https://www.rfc-editor.org/rfc/rfc5548>.

   [RFC5673]  Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T.
              Phinney, "Industrial Routing Requirements in Low-Power and
              Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October
              2009, <https://www.rfc-editor.org/rfc/rfc5673>.

   [RFC5826]  Brandt, A., Buron, J., and G. Porcu, "Home Automation
              Routing Requirements in Low-Power and Lossy Networks",
              RFC 5826, DOI 10.17487/RFC5826, April 2010,
              <https://www.rfc-editor.org/rfc/rfc5826>.

   [RFC5867]  Martocci, J., Ed., De Mil, P., Riou, N., and W. Vermeylen,
              "Building Automation Routing Requirements in Low-Power and
              Lossy Networks", RFC 5867, DOI 10.17487/RFC5867, June
              2010, <https://www.rfc-editor.org/rfc/rfc5867>.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
              <https://www.rfc-editor.org/rfc/rfc5905>.

   [RFC6206]  Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
              "The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
              March 2011, <https://www.rfc-editor.org/rfc/rfc6206>.

   [RFC6272]  Baker, F. and D. Meyer, "Internet Protocols for the Smart
              Grid", RFC 6272, DOI 10.17487/RFC6272, June 2011,
              <https://www.rfc-editor.org/rfc/rfc6272>.

   [RFC6282]  Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              DOI 10.17487/RFC6282, September 2011,
              <https://www.rfc-editor.org/rfc/rfc6282>.

   [RFC6550]  Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
              Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
              JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
              Low-Power and Lossy Networks", RFC 6550,
              DOI 10.17487/RFC6550, March 2012,
              <https://www.rfc-editor.org/rfc/rfc6550>.







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   [RFC6551]  Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
              and D. Barthel, "Routing Metrics Used for Path Calculation
              in Low-Power and Lossy Networks", RFC 6551,
              DOI 10.17487/RFC6551, March 2012,
              <https://www.rfc-editor.org/rfc/rfc6551>.

   [RFC6552]  Thubert, P., Ed., "Objective Function Zero for the Routing
              Protocol for Low-Power and Lossy Networks (RPL)",
              RFC 6552, DOI 10.17487/RFC6552, March 2012,
              <https://www.rfc-editor.org/rfc/rfc6552>.

   [RFC6553]  Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
              Power and Lossy Networks (RPL) Option for Carrying RPL
              Information in Data-Plane Datagrams", RFC 6553,
              DOI 10.17487/RFC6553, March 2012,
              <https://www.rfc-editor.org/rfc/rfc6553>.

   [RFC6554]  Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
              Routing Header for Source Routes with the Routing Protocol
              for Low-Power and Lossy Networks (RPL)", RFC 6554,
              DOI 10.17487/RFC6554, March 2012,
              <https://www.rfc-editor.org/rfc/rfc6554>.

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

   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link
              Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
              <https://www.rfc-editor.org/rfc/rfc6690>.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <https://www.rfc-editor.org/rfc/rfc6763>.

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,
              <https://www.rfc-editor.org/rfc/rfc6775>.

   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              DOI 10.17487/RFC6887, April 2013,
              <https://www.rfc-editor.org/rfc/rfc6887>.




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   [RFC6933]  Bierman, A., Romascanu, D., Quittek, J., and M.
              Chandramouli, "Entity MIB (Version 4)", RFC 6933,
              DOI 10.17487/RFC6933, May 2013,
              <https://www.rfc-editor.org/rfc/rfc6933>.

   [RFC6988]  Quittek, J., Ed., Chandramouli, M., Winter, R., Dietz, T.,
              and B. Claise, "Requirements for Energy Management",
              RFC 6988, DOI 10.17487/RFC6988, September 2013,
              <https://www.rfc-editor.org/rfc/rfc6988>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/rfc/rfc7030>.

   [RFC7102]  Vasseur, JP., "Terms Used in Routing for Low-Power and
              Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
              2014, <https://www.rfc-editor.org/rfc/rfc7102>.

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

   [RFC7326]  Parello, J., Claise, B., Schoening, B., and J. Quittek,
              "Energy Management Framework", RFC 7326,
              DOI 10.17487/RFC7326, September 2014,
              <https://www.rfc-editor.org/rfc/rfc7326>.

   [RFC7388]  Schoenwaelder, J., Sehgal, A., Tsou, T., and C. Zhou,
              "Definition of Managed Objects for IPv6 over Low-Power
              Wireless Personal Area Networks (6LoWPANs)", RFC 7388,
              DOI 10.17487/RFC7388, October 2014,
              <https://www.rfc-editor.org/rfc/rfc7388>.

   [RFC7416]  Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A.,
              and M. Richardson, Ed., "A Security Threat Analysis for
              the Routing Protocol for Low-Power and Lossy Networks
              (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015,
              <https://www.rfc-editor.org/rfc/rfc7416>.

   [RFC7460]  Chandramouli, M., Claise, B., Schoening, B., Quittek, J.,
              and T. Dietz, "Monitoring and Control MIB for Power and
              Energy", RFC 7460, DOI 10.17487/RFC7460, March 2015,
              <https://www.rfc-editor.org/rfc/rfc7460>.






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   [RFC7461]  Parello, J., Claise, B., and M. Chandramouli, "Energy
              Object Context MIB", RFC 7461, DOI 10.17487/RFC7461, March
              2015, <https://www.rfc-editor.org/rfc/rfc7461>.

   [RFC7577]  Quittek, J., Winter, R., and T. Dietz, "Definition of
              Managed Objects for Battery Monitoring", RFC 7577,
              DOI 10.17487/RFC7577, July 2015,
              <https://www.rfc-editor.org/rfc/rfc7577>.

   [RFC7603]  Schoening, B., Chandramouli, M., and B. Nordman, "Energy
              Management (EMAN) Applicability Statement", RFC 7603,
              DOI 10.17487/RFC7603, August 2015,
              <https://www.rfc-editor.org/rfc/rfc7603>.

   [RFC7641]  Hartke, K., "Observing Resources in the Constrained
              Application Protocol (CoAP)", RFC 7641,
              DOI 10.17487/RFC7641, September 2015,
              <https://www.rfc-editor.org/rfc/rfc7641>.

   [RFC7668]  Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
              Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low
              Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015,
              <https://www.rfc-editor.org/rfc/rfc7668>.

   [RFC768]   Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/rfc/rfc768>.

   [RFC7731]  Hui, J. and R. Kelsey, "Multicast Protocol for Low-Power
              and Lossy Networks (MPL)", RFC 7731, DOI 10.17487/RFC7731,
              February 2016, <https://www.rfc-editor.org/rfc/rfc7731>.

   [RFC7733]  Brandt, A., Baccelli, E., Cragie, R., and P. van der Stok,
              "Applicability Statement: The Use of the Routing Protocol
              for Low-Power and Lossy Networks (RPL) Protocol Suite in
              Home Automation and Building Control", RFC 7733,
              DOI 10.17487/RFC7733, February 2016,
              <https://www.rfc-editor.org/rfc/rfc7733>.

   [RFC7772]  Yourtchenko, A. and L. Colitti, "Reducing Energy
              Consumption of Router Advertisements", BCP 202, RFC 7772,
              DOI 10.17487/RFC7772, February 2016,
              <https://www.rfc-editor.org/rfc/rfc7772>.








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   [RFC7849]  Binet, D., Boucadair, M., Vizdal, A., Chen, G., Heatley,
              N., Chandler, R., Michaud, D., Lopez, D., and W. Haeffner,
              "An IPv6 Profile for 3GPP Mobile Devices", RFC 7849,
              DOI 10.17487/RFC7849, May 2016,
              <https://www.rfc-editor.org/rfc/rfc7849>.

   [RFC791]   Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <https://www.rfc-editor.org/rfc/rfc791>.

   [RFC793]   Postel, J., "Transmission Control Protocol", RFC 793,
              DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/rfc/rfc793>.

   [RFC7973]  Droms, R. and P. Duffy, "Assignment of an Ethertype for
              IPv6 with Low-Power Wireless Personal Area Network
              (LoWPAN) Encapsulation", RFC 7973, DOI 10.17487/RFC7973,
              November 2016, <https://www.rfc-editor.org/rfc/rfc7973>.

   [RFC8025]  Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power
              Wireless Personal Area Network (6LoWPAN) Paging Dispatch",
              RFC 8025, DOI 10.17487/RFC8025, November 2016,
              <https://www.rfc-editor.org/rfc/rfc8025>.

   [RFC8036]  Cam-Winget, N., Ed., Hui, J., and D. Popa, "Applicability
              Statement for the Routing Protocol for Low-Power and Lossy
              Networks (RPL) in Advanced Metering Infrastructure (AMI)
              Networks", RFC 8036, DOI 10.17487/RFC8036, January 2017,
              <https://www.rfc-editor.org/rfc/rfc8036>.

   [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/rfc/rfc8105>.

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

   [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/rfc/rfc8200>.






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   [RFC822]   Crocker, D., "STANDARD FOR THE FORMAT OF ARPA INTERNET
              TEXT MESSAGES", STD 11, RFC 822, DOI 10.17487/RFC0822,
              August 1982, <https://www.rfc-editor.org/rfc/rfc822>.

   [RFC8352]  Gomez, C., Kovatsch, M., Tian, H., and Z. Cao, Ed.,
              "Energy-Efficient Features of Internet of Things
              Protocols", RFC 8352, DOI 10.17487/RFC8352, April 2018,
              <https://www.rfc-editor.org/rfc/rfc8352>.

   [RFC8368]  Eckert, T., Ed. and M. Behringer, "Using an Autonomic
              Control Plane for Stable Connectivity of Network
              Operations, Administration, and Maintenance (OAM)",
              RFC 8368, DOI 10.17487/RFC8368, May 2018,
              <https://www.rfc-editor.org/rfc/rfc8368>.

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

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/rfc/rfc8446>.

   [RFC8505]  Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
              Perkins, "Registration Extensions for IPv6 over Low-Power
              Wireless Personal Area Network (6LoWPAN) Neighbor
              Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
              <https://www.rfc-editor.org/rfc/rfc8505>.

   [RFC8575]  Jiang, Y., Ed., Liu, X., Xu, J., and R. Cummings, Ed.,
              "YANG Data Model for the Precision Time Protocol (PTP)",
              RFC 8575, DOI 10.17487/RFC8575, May 2019,
              <https://www.rfc-editor.org/rfc/rfc8575>.

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

   [RFC8724]  Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
              Zuniga, "SCHC: Generic Framework for Static Context Header
              Compression and Fragmentation", RFC 8724,
              DOI 10.17487/RFC8724, April 2020,
              <https://www.rfc-editor.org/rfc/rfc8724>.






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   [RFC8815]  Abrahamsson, M., Chown, T., Giuliano, L., and T. Eckert,
              "Deprecating Any-Source Multicast (ASM) for Interdomain
              Multicast", BCP 229, RFC 8815, DOI 10.17487/RFC8815,
              August 2020, <https://www.rfc-editor.org/rfc/rfc8815>.

   [RFC8824]  Minaburo, A., Toutain, L., and R. Andreasen, "Static
              Context Header Compression (SCHC) for the Constrained
              Application Protocol (CoAP)", RFC 8824,
              DOI 10.17487/RFC8824, June 2021,
              <https://www.rfc-editor.org/rfc/rfc8824>.

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

   [RFC8931]  Thubert, P., Ed., "IPv6 over Low-Power Wireless Personal
              Area Network (6LoWPAN) Selective Fragment Recovery",
              RFC 8931, DOI 10.17487/RFC8931, November 2020,
              <https://www.rfc-editor.org/rfc/rfc8931>.

   [RFC8994]  Eckert, T., Ed., Behringer, M., Ed., and S. Bjarnason, "An
              Autonomic Control Plane (ACP)", RFC 8994,
              DOI 10.17487/RFC8994, May 2021,
              <https://www.rfc-editor.org/rfc/rfc8994>.

   [RFC9006]  Gomez, C., Crowcroft, J., and M. Scharf, "TCP Usage
              Guidance in the Internet of Things (IoT)", RFC 9006,
              DOI 10.17487/RFC9006, March 2021,
              <https://www.rfc-editor.org/rfc/rfc9006>.

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

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

   [RFC9011]  Gimenez, O., Ed. and I. Petrov, Ed., "Static Context
              Header Compression and Fragmentation (SCHC) over LoRaWAN",
              RFC 9011, DOI 10.17487/RFC9011, April 2021,
              <https://www.rfc-editor.org/rfc/rfc9011>.





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   [RFC9034]  Thomas, L., Anamalamudi, S., Anand, S.V.R., Hegde, M., and
              C. Perkins, "Packet Delivery Deadline Time in the Routing
              Header for IPv6 over Low-Power Wireless Personal Area
              Networks (6LoWPANs)", RFC 9034, DOI 10.17487/RFC9034, June
              2021, <https://www.rfc-editor.org/rfc/rfc9034>.

   [RFC9119]  Perkins, C., McBride, M., Stanley, D., Kumari, W., and JC.
              Zúñiga, "Multicast Considerations over IEEE 802 Wireless
              Media", RFC 9119, DOI 10.17487/RFC9119, October 2021,
              <https://www.rfc-editor.org/rfc/rfc9119>.

   [RFC9139]  Gündoğan, C., Schmidt, T., Wählisch, M., Scherb, C.,
              Marxer, C., and C. Tschudin, "Information-Centric
              Networking (ICN) Adaptation to Low-Power Wireless Personal
              Area Networks (LoWPANs)", RFC 9139, DOI 10.17487/RFC9139,
              November 2021, <https://www.rfc-editor.org/rfc/rfc9139>.

   [RFC9148]  van der Stok, P., Kampanakis, P., Richardson, M., and S.
              Raza, "EST-coaps: Enrollment over Secure Transport with
              the Secure Constrained Application Protocol", RFC 9148,
              DOI 10.17487/RFC9148, April 2022,
              <https://www.rfc-editor.org/rfc/rfc9148>.

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

   [RFC9176]  Amsüss, C., Ed., Shelby, Z., Koster, M., Bormann, C., and
              P. van der Stok, "Constrained RESTful Environments (CoRE)
              Resource Directory", RFC 9176, DOI 10.17487/RFC9176, April
              2022, <https://www.rfc-editor.org/rfc/rfc9176>.

   [RFC9178]  Arkko, J., Eriksson, A., and A. Keränen, "Building Power-
              Efficient Constrained Application Protocol (CoAP) Devices
              for Cellular Networks", RFC 9178, DOI 10.17487/RFC9178,
              May 2022, <https://www.rfc-editor.org/rfc/rfc9178>.

   [RFC9271]  Price, R., Ed., "Uninterruptible Power Supply (UPS)
              Management Protocol -- Commands and Responses", RFC 9271,
              DOI 10.17487/RFC9271, August 2022,
              <https://www.rfc-editor.org/rfc/rfc9271>.

   [RFC9293]  Eddy, W., Ed., "Transmission Control Protocol (TCP)",
              STD 7, RFC 9293, DOI 10.17487/RFC9293, August 2022,
              <https://www.rfc-editor.org/rfc/rfc9293>.




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

   [VC2014]   Ong, D., Moors, T., and V. Sivaraman, "Comparison of the
              energy, carbon and time costs of videoconferencing and in-
              person meetings", DOI 10.1016/j.comcom.2014.02.009, 2014,
              <https://www.sciencedirect.com/science/article/pii/
              S0140366414000620>.

Authors' Addresses

   Toerless Eckert (editor)
   Futurewei Technologies USA
   2220 Central Expressway
   Santa Clara,  CA 95050
   United States of America
   Email: tte@cs.fau.de


   Mohamed Boucadair (editor)
   Orange
   35000 Rennes
   France
   Email: mohamed.boucadair@orange.com


   Pascal Thubert
   Cisco Systems, Inc.
   45 Allee des Ormes - BP1200, Building D
   06254 MOUGINS Sophia Antipolis
   France
   Phone: +33 497 23 26 34
   Email: pthubert@cisco.com


   Jeff Tentsura
   NVIDIA
   United States of America
   Email: jefftant.ietf@gmail.com


   Carlos Pignataro
   NC State University
   United States of America
   Email: cpignata@gmail.com



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