draft-eckert-ietf-and-energy-overview-00.txt

Network Working Group                                          T. Eckert
Internet-Draft                                Futurewei Technologies USA
Intended status: Informational                              20 June 2022
Expires: 22 December 2022


                     IETF and Energy - an overview
                 draft-eckert-ietf-and-energy-overview-00

Abstract

   This memo attempts to provide an overview of work performed by or
   proposed to the IETF relates 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 the work but
   interested in it, in the hope to raise interest in energy related
   activites in the IETF, such as identifyng gaps and working on
   solution opportunities.

   In general, this document attempts to summarize existing work.  On
   occasion it elaborates more details in support of better
   understanding the energy relationship of specific technologies, when
   this background can not be found from existing draft/RFCs.

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."

   This Internet-Draft will expire on 22 December 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Energy saving . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Digitization  . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Energy saving through scale . . . . . . . . . . . . . . .   4
       2.2.1.  An example: Telephony . . . . . . . . . . . . . . . .   5
       2.2.2.  The packet multiplexing principle . . . . . . . . . .   5
       2.2.3.  End-to-end transport  . . . . . . . . . . . . . . . .   5
       2.2.4.  Internet routing architecture . . . . . . . . . . . .   5
       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  . . . . . . . . . . . . . . .   6
         2.2.7.2.  DiffServ  . . . . . . . . . . . . . . . . . . . .   7
         2.2.7.3.  SIP . . . . . . . . . . . . . . . . . . . . . . .   7
   3.  Higher or new energy consumption  . . . . . . . . . . . . . .   7
   4.  Sustainability  . . . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Follow the energy cloud scheduling  . . . . . . . . . . .   9
     4.2.  Minimize generated heat . . . . . . . . . . . . . . . . .   9
     4.3.  Heat recovery . . . . . . . . . . . . . . . . . . . . . .  10
     4.4.  Telecollaboration . . . . . . . . . . . . . . . . . . . .  10
   5.  Energy saving in networks and nodes . . . . . . . . . . . . .  12
     5.1.  Low Power and Lossy Networks (LLN)  . . . . . . . . . . .  12
       5.1.1.  6LOWPAN WG  . . . . . . . . . . . . . . . . . . . . .  12
       5.1.2.  LPWAN WG  . . . . . . . . . . . . . . . . . . . . . .  13
       5.1.3.  6TISCH WG . . . . . . . . . . . . . . . . . . . . . .  13
       5.1.4.  6LO WG  . . . . . . . . . . . . . . . . . . . . . . .  13
       5.1.5.  ROLL WG . . . . . . . . . . . . . . . . . . . . . . .  13
     5.2.  Constrained Nodes and Networks  . . . . . . . . . . . . .  14
       5.2.1.  LWIG WG . . . . . . . . . . . . . . . . . . . . . . .  15
       5.2.2.  CORE and CoAP . . . . . . . . . . . . . . . . . . . .  15
     5.3.  Selected cross-WG technologies  . . . . . . . . . . . . .  15
       5.3.1.  (IP) Multicast  . . . . . . . . . . . . . . . . . . .  16
         5.3.1.1.  Power saving with multicast . . . . . . . . . . .  16
         5.3.1.2.  Power waste through multicast based service
                 coordination  . . . . . . . . . . . . . . . . . . .  16
         5.3.1.3.  Multicast problems with WiFi  . . . . . . . . . .  17
       5.3.2.  Sleepy nodes  . . . . . . . . . . . . . . . . . . . .  18
   6.  Energy Management Networks  . . . . . . . . . . . . . . . . .  19
     6.1.  Smart Grid  . . . . . . . . . . . . . . . . . . . . . . .  19
     6.2.  Syncro Phasor Networks  . . . . . . . . . . . . . . . . .  20



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   7.  Energy Management in Networks . . . . . . . . . . . . . . . .  21
     7.1.  Metrics and costs . . . . . . . . . . . . . . . . . . . .  21
     7.2.  EMAN WG . . . . . . . . . . . . . . . . . . . . . . . . .  22
   8.  Power awareness in network forwarding and routing
           protocols . . . . . . . . . . . . . . . . . . . . . . . .  23
     8.1.  Power Aware Networks (PANET)  . . . . . . . . . . . . . .  23
     8.2.  Other . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   9.  Gaps  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   10. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   11. Informative References  . . . . . . . . . . . . . . . . . . .  25
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  37

1.  Introduction

   This document summarizes work that has been proposed to or performed
   by the IETF.  This means that it covers IETF RFC as well as
   individual submission RFC and IETF or individual submission drafts
   that where abandoned.  For this document, IETF also includes work
   proposed to or performed by the IRTF.  All this is loosely referred
   to as 'IETF work' in this memo.

   There are various aspects how work can relate to energy.  This
   document does not attempt to propose a taxonomy or ontology, but it
   is nevertheless structured around various classifictions.  Many
   technologies discussed will fall into multiple categories.  Each is
   listed under a category that is specifically significant for example
   by being most narrow.

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

2.  Energy saving

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








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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
   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]), group communications utiziling
   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] and successors).

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

   In hindsight though, digitization through IETF technologies and
   specifically the Internet will likely have the largest contribution
   to energy saving amonst 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:

   The Internet as well as all other TCP/IP 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










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2.2.1.  An 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] 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] and successors) 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 where the ones who at least during the 1990th 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 emobodied through the IETF "Transport
   Control Protocol" (TCP, [RFC793] and successors).  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.

2.2.4.  Internet routing architecture

   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.




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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 where 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, resulting not only in higher cost of those services but
   also 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 where 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] and its successors).  This further strengthened the ability
   to scale service/applications at minimum additional cost for the
   underlying packet transport, arguably driving innvoation 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 (such as "Voice,
   Video and Data") which previously used/required 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,
   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) wider adopted technology promising converged
   networks was "Asynchronuous Transfer Mode" (ATM), which was designed
   and deployed at the end of the 1980th 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.



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   At the end of the 1980th, it was proven (TBD: need to find the
   reference, cedric knows..) that variable length packet multiplexing
   in network can also support non-NP-hard calculations for bounded
   latency.  This lead 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
   superceeded as explained in the following section - for its original
   use-cases (voice and video).  However this type of services are 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 INSERV
   versus standard (so-called Best-Effort) Internet traffic, the INTSERV
   model was already recognized in the 1990th to not support highest-
   scale at lowest cost, leading to the parallel development of the IETF
   "Differentated 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.

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 worklows
   without easy to compare prior workflows.








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   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)-digitzed is
   orders of magnituedes 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
   (https://www.smithsonianmag.com/science-nature/streaming-movie-less-
   energy-dvd-180951586).  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 10..30 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.

   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.



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4.  Sustainability

   Sustainability is the principle to utilize resources in a way that
   they do not diminish or run out over the long term.  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 fossile 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 (TBD: did we miss anything ?), the Internet itself can
   similarily to how it does for digitization play a key role in
   building sustainable networked IT infrastructures.  The following
   subsections list three examples 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.

4.2.  Minimize generated heat

   The mayority of energy in cloud DC 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, DC 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 DC whole location is not optimized for
   consumption but for sustainable generation of compute and storage.







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4.3.  Heat recovery

   Exhaust heat, especially from compute in DC, can be recovered when it
   is coupled to heating systems ranging in size all the way from
   individual familys home through larger buildings (hotels etc.) all
   the way to district heating systems.  A provider of such 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 netwnews (using
   e.g.: NNTP) as early forms of Telecollaboration, then
   telecollaboration history through IETF technology reaches back into
   the 1980th 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 2000, 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
   Internet, the immersive nature of telecollaboration was brought to
   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 standard for hundreds of
   commercial and free tele-collaboration solutions, including Cisco
   Webex, which is also used by the IETF itself, Zoom and the new IETF
   collaboration suite MeetEcho (TBD: good references here ?).






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   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 fator 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 fossile fuel for travel goes up.

   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 air plane if
   it was exhausted at surface level.  One publically funded
   organization offering carbon offset services calculates a factor 3 of
   the CO2 consumption of an air plane
   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



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   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 fossile fuels in air
   travel.

5.  Energy saving in networks and nodes

5.1.  Low Power and Lossy Networks (LLN)

   Low Power and Lossy Networks are networks in which nodes and/or radio
   links have constraints.  Low poer 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.

   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
   engergy at short time periods, radio energy tuning to just reach the
   destination(s), minimization of of multicasting to eliminate need of
   radio receivers to consume energy and so on.  [RFC8352] gives a more
   detailled overview, especially because different L2 technologies such
   as IEEE 802.15.4 type (low power) wireless networks, Bluetooth Low
   Energy (BLE), WiFi (IEEE 802.11) and DEC ULE.

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

5.1.1.  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.  "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



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   (6LoWPANs)" [RFC6775] (6LOWPAN-ND).

5.1.2.  LPWAN WG

   Since 2014, 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, [RFC8724],
   [RFC8824], [RFC9011].

5.1.3.  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.

5.1.4.  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.

5.1.5.  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].

   Since then its work is mostly focussed on the "IPv6 Routing Protocol
   for Low-Power and Lossy Networks" (RPL) [RFC6550], 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].

   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



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   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 [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] 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].

5.2.  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
   WiFi and mobile network connections are not considered to be lossy
   networks, and personal mobile nodes with either connections are order
   of magnitude less constrained than nodes typically attached to LLN
   network.  Therefore, broader work in the IETF than focussed primarily
   on LLN typically uses just the term light-weight or constrained
   (nodes and networks).











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5.2.1.  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".

5.2.2.  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 readible 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.

   While originally designed for LLN, CoAP is transcending LLN and
   equally becoming standards 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.  Selected cross-WG technologies




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5.3.1.  (IP) Multicast

5.3.1.1.  Power saving with multicast

   IP Multicast was introduced with [RFC1112] and today also called "Any
   Source Multicast" (ASM) has various protocols standardized 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 somwhat
   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 WiFi 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 alternatice (with so-called ingres replication) is
   not possible due to the total amount of traffic generated.  This
   includes wireless/radio networks, where equally airtime is the
   limiting factor.

5.3.1.2.  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



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   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 5.3.2 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 forwaders as well -
   compared to better alternatives.

   In 2006, the IETF standardized "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.

5.3.1.3.  Multicast problems with WiFi

   [RFC9119] covers multicast challenges and solution (proposals) for IP
   Multicast over WiFi.  With respect to power consumption, it discusses
   the following aspects.

   (a) Unnecessary wake-up of power constrained WiFi 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.






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   (b) WiFi 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 WiFi 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 WiFi multicast to WiFi unicast
   packets.

5.3.2.  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 WiFi 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.

   One partial solution to some sleepy node issues related to their
   energy consumption, especially the ones caused by the use of
   multicast Section 5.3.1.2, Section 5.3.1.3 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 resouce consumer.






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   An 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)", Standardized proxy infrastructures are best built
   with standard 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].
   [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.

6.  Energy Management Networks

   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 applicances".  Use cases for the "Smart Grid"
   include for example timed and measured operations of home devices



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   such as washers or charging cars, when energy consumption os 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.

   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 avbove 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 5.1 below): 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.  Syncro 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.

   Syncro Phasor Networks are networks whose goal it is to support
   synchronziation 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 sensoring 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).






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   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 hotted/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
   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 Syncro Phasor Initiative" (NASPI),
   https://www.naspi.org is an example organization in support of syncro
   phasor networking.  It is an ongoing project by the USA "Department
   of Energy" (DoE).

7.  Energy Management in Networks

7.1.  Metrics and costs

   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 pre-existing
   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.









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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 standards 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]).

   [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 managment 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 WiFi 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.






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   The "Monitoring and Control MIB for Power and Energy" [RFC7460] is a
   new EMAN MIB, linking against various pre-existing and new EMAN MIBs;
   the ENTITY-MIB, the ENTITY-SENSOR-MIB [RFC3433] for which it is
   amending missing accuracy information to meet IEC power monitoring
   requirements, the pre-existing IETF "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 poweer failure based on UPS battery capacity
   and device consumptions/priorities.  Similarily, the EMAN "Definition
   of Managed Objects for Battery Monitoring" [RFC7577] defines objects
   to support battery monitoring in managed devices.

   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 ot 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.

8.  Power awareness in network forwarding and routing protocols

8.1.  Power Aware Networks (PANET)

   In 2013/2014, some drafts discussed/proposed how networks themselves,
   specifically those of Internet Service Providers (ISP) could become
   "power aware" to the extend that its power consumption could be
   regulated (or self-regulate) based on the current required
   performance of the network and/or available power, by reducing excess
   (or too power expensive) network capacity through switching-off/low-



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   powering components such as redundant routers, linecards, interfaces
   or links, or reducing power consumption by reducing bitrates on
   links.

   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 downspeeding, 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.











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8.2.  Other

   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.: varous L2 technologies such as switched optical fiber networks.
   It primarily claims the issue that the existing management objects
   are not sufficient to express energy managemenet 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 ingres and egres linecards).

9.  Gaps

   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.  Summary

   TBD

11.  Informative References



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   [I-D.ajunior-energy-awareness-00]
              Junior, A. and R. C. Sofia, "Energy-awareness metrics
              global applicability guidelines", Work in Progress,
              Internet-Draft, draft-ajunior-energy-awareness-00, 16
              October 2012, <https://www.ietf.org/archive/id/draft-
              ajunior-energy-awareness-00.txt>.

   [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://www.ietf.org/archive/id/
              draft-bormann-core-roadmap-05.txt>.

   [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, <https://www.ietf.org/archive/id/
              draft-castellani-core-alive-00.txt>.

   [I-D.chakrabarti-nordmark-energy-aware-nd]
              Chakrabarti, S., Nordmark, E., and M. Wasserman, "Energy
              Aware IPv6 Neighbor Discovery Optimizations", Work in
              Progress, Internet-Draft, draft-chakrabarti-nordmark-
              energy-aware-nd-02, 12 March 2012,
              <https://www.ietf.org/archive/id/draft-chakrabarti-
              nordmark-energy-aware-nd-02.txt>.

   [I-D.claise-power-management-arch]
              Claise, B., Parello, J., and B. Schoening, "Power
              Management Architecture", Work in Progress, Internet-
              Draft, draft-claise-power-management-arch-02, 22 October
              2010, <https://www.ietf.org/archive/id/draft-claise-power-
              management-arch-02.txt>.

   [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,
              <https://www.ietf.org/archive/id/draft-fossati-core-
              monitor-option-00.txt>.

   [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://www.ietf.org/archive/id/draft-fossati-core-
              publish-option-03.txt>.




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   [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://www.ietf.org/archive/id/draft-giacomin-
              core-sleepy-option-00.txt>.

   [I-D.ietf-core-coap-pubsub]
              Koster, M., Keranen, A., and J. Jimenez, "Publish-
              Subscribe Broker for the Constrained Application Protocol
              (CoAP)", Work in Progress, Internet-Draft, draft-ietf-
              core-coap-pubsub-10, 4 May 2022,
              <https://www.ietf.org/archive/id/draft-ietf-core-coap-
              pubsub-10.txt>.

   [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-13, 24 April 2022,
              <https://www.ietf.org/archive/id/draft-ietf-dnssd-srp-
              13.txt>.

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

   [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://www.ietf.org/archive/id/draft-
              manral-bmwg-power-usage-04.txt>.

   [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://www.ietf.org/archive/id/draft-mjsraman-
              panet-inter-as-power-source-00.txt>.








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   [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://www.ietf.org/archive/id/draft-
              mjsraman-rtgwg-pim-power-02.txt>.

   [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://www.ietf.org/archive/id/draft-okamoto-ccamp-
              midori-gmpls-extension-reqs-02.txt>.

   [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://www.ietf.org/archive/id/draft-
              rahman-core-sleepy-05.txt>.

   [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://www.ietf.org/archive/id/draft-rahman-core-sleepy-
              nodes-do-we-need-01.txt>.

   [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://www.ietf.org/archive/id/draft-rahman-core-sleepy-
              problem-statement-01.txt>.

   [I-D.retana-rtgwg-eacp]
              Retana, A., White, R., and M. Paul, "A Framework and
              Requirements for Energy Aware Control Planes", Work in
              Progress, Internet-Draft, draft-retana-rtgwg-eacp-03, 24
              October 2014, <https://www.ietf.org/archive/id/draft-
              retana-rtgwg-eacp-03.txt>.









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   [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://www.ietf.org/archive/id/draft-suzuki-eens-
              requirements-00.txt>.

   [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://www.ietf.org/archive/id/draft-vial-core-
              mirror-proxy-01.txt>.

   [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://www.ietf.org/archive/id/draft-vial-core-
              mirror-server-01.txt>.

   [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://www.ietf.org/archive/id/draft-wang-roll-energy-
              optimization-scheme-00.txt>.

   [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://www.ietf.org/archive/id/draft-winter-
              energy-efficient-internet-01.txt>.

   [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://www.ietf.org/archive/id/draft-zhang-greennet-
              01.txt>.










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   [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://www.ietf.org/archive/id/draft-zhang-panet-
              problem-statement-03.txt>.

   [NASPICLOCK]
              Force, N. T. S. T., "Time Synchronization in the Electric
              Power System", March 2017,
              <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/info/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/info/rfc1142>.

   [RFC1628]  Case, J., Ed., "UPS Management Information Base",
              RFC 1628, DOI 10.17487/RFC1628, May 1994,
              <https://www.rfc-editor.org/info/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/info/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/info/rfc1883>.

   [RFC2086]  Myers, J., "IMAP4 ACL extension", RFC 2086,
              DOI 10.17487/RFC2086, January 1997,
              <https://www.rfc-editor.org/info/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/info/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/info/rfc2246>.




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

   [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/info/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/info/rfc2543>.

   [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/info/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/info/rfc3550>.

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

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

   [RFC4268]  Chisholm, S. and D. Perkins, "Entity State MIB", RFC 4268,
              DOI 10.17487/RFC4268, November 2005,
              <https://www.rfc-editor.org/info/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/info/rfc4271>.

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







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

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

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

   [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/info/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/info/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/info/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/info/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/info/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/info/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/info/rfc6272>.





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

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

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

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <https://www.rfc-editor.org/info/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/info/rfc6775>.

   [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/info/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/info/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/info/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/info/rfc7102>.







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   [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/info/rfc7326>.

   [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/info/rfc7460>.

   [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/info/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/info/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/info/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/info/rfc7641>.

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

   [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/info/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/info/rfc7772>.

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



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   [RFC793]   Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [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/info/rfc8036>.

   [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/info/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/info/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/info/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/info/rfc8428>.

   [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/info/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/info/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/info/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/info/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/info/rfc8824>.

   [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/info/rfc8994>.

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

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

   [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/info/rfc9011>.

   [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/info/rfc9119>.

   [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/info/rfc9148>.

   [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/info/rfc9176>.




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   [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/info/rfc9178>.

   [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>.

Author's Address

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
































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