rfc9845v1.txt   rfc9845.txt 
Internet Research Task Force (IRTF) A. Clemm, Ed. Internet Research Task Force (IRTF) A. Clemm, Ed.
Request for Comments: 9845 Independent Request for Comments: 9845 Sympotech
Category: Informational C. Pignataro, Ed. Category: Informational C. Pignataro, Ed.
ISSN: 2070-1721 NC State University ISSN: 2070-1721 NC State University & Blue Fern Consulting
C. Westphal C. Westphal
University of California, Santa Cruz
L. Ciavaglia L. Ciavaglia
Nokia Nokia
J. Tantsura J. Tantsura
Nvidia Nvidia
M-P. Odini M-P. Odini
August 2025 September 2025
Challenges and Opportunities in Management for Green Networking Challenges and Opportunities in Management for Green Networking
Abstract Abstract
Reducing humankind's environmental footprint and making technology Reducing humankind's environmental footprint and making technology
more environmentally sustainable are among the biggest challenges of more environmentally sustainable are among the biggest challenges of
our age. Networks play an important part in this challenge. On one our age. Networks play an important part in this challenge. On one
hand, they enable applications that help to reduce this footprint. hand, they enable applications that help to reduce this footprint.
On the other hand, they contribute to this footprint themselves in no On the other hand, they significantly contribute to this footprint
insignificant way. Therefore, methods to make networking technology themselves. Therefore, methods to make networking technology itself
itself "greener" and to manage and operate networks in ways that "greener" and to manage and operate networks in ways that reduce
reduce their environmental footprint without impacting their utility their environmental footprint without impacting their utility need to
need to be explored. This document outlines a corresponding set of be explored. This document outlines a corresponding set of
opportunities, along with associated research challenges, for opportunities, along with associated research challenges, for
networking technology in general and management technology in networking technology in general and management technology in
particular to become "greener", i.e., more sustainable, with reduced particular to become greener, i.e., more sustainable, with reduced
greenhouse gas emissions and less negative impact on the environment. greenhouse gas emissions and less negative impact on the environment.
This document is a product of the Network Management Research Group This document is a product of the Network Management Research Group
(NMRG) of the Internet Research Task Force (IRTF). This document (NMRG) of the Internet Research Task Force (IRTF). This document
reflects the consensus of the research group. It is not a candidate reflects the consensus of the research group. It is not a candidate
for any level of Internet Standard and is published for informational for any level of Internet Standard and is published for informational
purposes. purposes.
Status of This Memo Status of This Memo
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Climate change and the need to curb greenhouse gas (GHG) emissions Climate change and the need to curb greenhouse gas (GHG) emissions
have been recognized by the United Nations and by most governments as have been recognized by the United Nations and by most governments as
one of the big challenges of our time. As a result, curbing those one of the big challenges of our time. As a result, curbing those
emissions is becoming increasingly important for society and for many emissions is becoming increasingly important for society and for many
industries. The networking industry is no exception. industries. The networking industry is no exception.
The science behind greenhouse gas emissions and their relationship The science behind greenhouse gas emissions and their relationship
with climate change is complex. However, there is overwhelming with climate change is complex. However, there is overwhelming
scientific consensus pointing toward a clear correlation between scientific consensus pointing toward a clear correlation between
climate change and a rising amount of greenhouse gases in the climate change and a rising amount of greenhouse gases in the
atmosphere. One greenhouse gas of particular concern, but by no atmosphere. When we say 'greenhouse gases' or GHG, we are referring
means the only one, is carbon dioxide (CO2). Carbon dioxide is to gases in the Earth's atmosphere that trap heat and contribute to
emitted in the process of burning fuels to generate energy that is the greenhouse effect. They include carbon dioxide (CO2), methane
used, for example, to power electrical devices such as networking (CH4), nitrous oxide (N2O), and fluorinated gases (as covered under
equipment. Notable here is the use of fossil fuels (such as oil, the Kyoto Protocol and Paris Agreement). In terms of emissions from
which releases CO2 that has long been removed from the earth's human activity, the dominant greenhouse gas is carbon dioxide (CO2).
atmosphere), as opposed to the use of renewable or sustainable fuels CO2 is emitted in the process of burning fuels to generate energy
that do not "add" to the amount of CO2 in the atmosphere. There are that is used, for example, to power electrical devices such as
additional gases associated with electricity generation, in networking equipment. Those fuels often include fossil fuels (such
particular methane (CH4) and nitrous oxide (N2O). Although they as oil), which releases CO2 that had long been removed from the
exist in smaller quantities, they have an even higher Global Warming earth's atmosphere, as opposed to the use of renewable or sustainable
Potential (GWP). fuels that do not "add" to the amount of CO2 in the atmosphere.
Other GHGs such as CH4 and N2O are associated with electricity
generation as well. Although they are emitted in smaller quantities,
they have an even higher Global Warming Potential (GWP). To
facilitate accounting for them, they are collectively simply
converted into CO2 equivalents (CO2e).
Greenhouse gas emissions are in turn correlated with the need to Greenhouse gas emissions are in turn correlated with the need to
power technology, including networks. Reducing those emissions can power technology, including networks. Reducing those emissions can
be achieved by reducing the amount of fossil fuels needed to generate be achieved by reducing the amount of fossil fuels needed to generate
the energy that is needed to power those networks. This can be the energy that is needed to power those networks. This can be
achieved by improving the energy mix to include increasing amounts of achieved by improving the energy mix to include increasing amounts of
low-carbon and/or renewable (and hence sustainable) energy sources, low-carbon and/or renewable (and hence sustainable) energy sources,
such as wind or solar. It can also be achieved by increasing energy such as wind or solar. It can also be achieved by increasing energy
savings and improving energy efficiency so that the same outcomes are savings and improving energy efficiency so that the same outcomes are
achieved while consuming less energy in the first place. achieved while consuming less energy in the first place.
The amount of greenhouse gases that an activity adds to the The amount of greenhouse gases that an activity adds to the
atmosphere, such as CO2 that is emitted in burning fossil fuels to atmosphere, such as CO2 that is emitted in burning fossil fuels to
generate the required energy, is also referred to as the "greenhouse generate the required energy, is also referred to as the "greenhouse
footprint" or the "carbon footprint" (accounting for greenhouses footprint" or the "carbon footprint" (accounting for greenhouse gases
gases other than CO2 in terms of CO2 equivalents). Reducing this other than CO2 in terms of CO2 equivalents). Reducing this footprint
footprint to net zero is hence a major sustainability goal. However, to net zero is hence a major sustainability goal. However,
sustainability encompasses other factors beyond carbon, such as the sustainability encompasses other factors beyond carbon, such as the
sustainable use of other natural resources, the preservation of sustainable use of other natural resources, the preservation of
natural habitats and biodiversity, and the avoidance of any form of natural habitats and biodiversity, and the avoidance of any form of
pollution. pollution.
In the context of this document, we refer to networking technology In the context of this document, we refer to networking technology
that helps to improve its own networking sustainability as "green". that helps to improve its own networking sustainability as "green".
Green, in that sense, includes technology that helps to lower Green, in that sense, includes technology that helps to lower
networking's greenhouse gas emissions including the carbon footprint, networking's greenhouse gas emissions including the carbon footprint,
which in turn includes technology that helps increase efficiency and which in turn includes technology that helps increase efficiency and
realize energy savings as well as facilitates managing networks realize energy savings as well as facilitates managing networks
toward a stronger use of renewables. toward a stronger use of renewables.
Arguably, networks can already be considered a "green" technology in Arguably, networks can already be considered a green technology in
that networks enable many applications that allow users and whole that networks enable many applications that allow users and whole
industries to save energy and thus become environmentally more industries to save energy and thus become environmentally more
sustainable in a significant way. For example, they allow (at least sustainable in a significant way. For example, they allow (at least
to an extent) to substitute travel with teleconferencing. They to an extent) to substitute travel with teleconferencing. They
enable many employees to work from home and telecommute, thus enable many employees to work from home and telecommute, thus
reducing the need for actual commuting. IoT applications that reducing the need for actual commuting. IoT applications that
facilitate automated monitoring and control from remote sites help facilitate automated monitoring and control from remote sites help
make agriculture more sustainable by minimizing the usage of water, make agriculture more sustainable by minimizing the usage of water,
fertilizer, and land area. Networked smart buildings allow for fertilizer, and land. Networked smart buildings allow for greater
greater energy optimization and sparser use of lighting and HVAC energy optimization and sparser use of lighting and HVAC (heating,
(heating, ventilation, air conditioning) than their non-networked, ventilation, air conditioning) than their non-networked, not-so-smart
not-so-smart counterparts. That said, calculating precise benefits counterparts. That said, calculating precise benefits in terms of
in terms of net sustainability contributions and savings is complex, net sustainability contributions and savings is complex, as a
as a holistic picture involves many effects including substitution holistic picture involves many effects including substitution effects
effects (perhaps saving on emissions caused by travel but incurring (perhaps saving on emissions caused by travel but incurring
additional costs associated with additional home office use) as well additional costs associated with additional home office use) as well
as behavioral changes (perhaps a higher number of meetings than if as behavioral changes (perhaps a higher number of meetings than if
travel were involved). travel were involved).
The IETF has recently initiated a reflection on the energy cost of The IETF has recently initiated a reflection on the energy cost of
hosting meetings three times a year (see [IETF-Net0]). It conducted hosting meetings three times a year (see [IETF-Net0]). It conducted
a study of the carbon emissions of a typical meeting and found out a study of the carbon emissions of a typical meeting and found out
that 99% of the emissions were due to air travel. In the same vein, that 99% of the emissions were due to air travel. In the same vein,
[Framework] compared an in-person with a virtual meeting and found a [Framework] compared an in-person with a virtual meeting and found a
reduction in energy of 66% for a virtual meeting. These findings reduction in energy of 66% for a virtual meeting. These findings
confirm that networking technology can reduce emissions when acting confirm that networking technology can reduce emissions when acting
as a virtual substitution for physical events. as a virtual substitution for physical events.
That said, networks themselves consume significant amounts of energy. That said, networks themselves consume significant amounts of energy.
Therefore, the networking industry has an important role to play in Therefore, the networking industry has an important role to play in
meeting sustainability goals and not just by enabling others to meeting sustainability goals, not just by enabling others to reduce
reduce their reliance on energy but by also reducing its own. Future their reliance on energy but also by reducing its own. Future
networking advances will increasingly need to focus on becoming more networking advances will increasingly need to focus on becoming more
energy efficient and reducing the carbon footprint, for reasons of energy efficient and reducing the carbon footprint, for reasons of
both corporate responsibility and economics. This shift has already both corporate responsibility and economics. This shift has already
begun, and sustainability is becoming an important concern for begun, and sustainability is becoming an important concern for
network providers. In some cases, such as in the context of network providers. In some cases, such as in the context of
networked data centers, the ability to procure enough energy becomes networked data centers, the ability to procure enough energy becomes
a bottleneck, prohibiting further growth, and greater sustainability a bottleneck, prohibiting further growth, and greater sustainability
thus becomes a business necessity. thus becomes a business necessity.
For example, in its annual report, Telefónica reports that in 2021, For example, in its annual report, Telefónica reports that in 2024,
its network's energy consumption per petabyte (PB) of data amounted its network's energy consumption per petabyte (PB) of data amounted
to 54 megawatt-hours (MWh) [Telefonica2021]. This rate has been to 38 megawatt-hours (MWh) [Telefonica2024]. This represents an
dramatically decreasing (by a factor of seven over six years), improvement of about 90% since the 2015 base year (400 MWh/PB),
although gains in efficiency are being offset by simultaneous growth achieved through steady year-on-year efficiency gains, although these
in data volume. The same report states that an important corporate are still partly offset by simultaneous growth in data volume. The
goal is continuing on that trajectory and aggressively reducing same report highlights an important corporate goal: continuing on
overall carbon emissions further. this trajectory and further reducing overall greenhouse gas
emissions.
1.2. Approaching the Problem 1.2. Approaching the Problem
An often-considered gain in networking sustainability can be made One way in which gains in network sustainability can be achieved
with regards to improving the efficiency with which networks utilize involves reducing the amount of energy needed to provide
power during their use phase, reducing the amount of energy that is communication services and improving the efficiency with which
required to provide communication services. However, for a holistic networks utilize power during their use phase. However, for a
approach, other aspects need to be considered as well. holistic approach, other aspects need to be considered as well.
The environmental footprint is not determined by energy consumption The environmental footprint is not determined by energy consumption
alone. The sustainability of power sources needs to be considered as alone. The sustainability of power sources needs to be considered as
well. A deployment that includes devices that are less energy well. A deployment that includes devices that are less energy
efficient but powered by a sustainable energy source can arguably be efficient but powered by a sustainable energy source can arguably be
considered "greener" than a deployment that includes highly efficient considered greener than a deployment that includes highly efficient
devices that are powered by diesel generators. In fact, in the same devices that are powered by diesel generators. In fact, in the same
Telefónica report mentioned earlier, extensive reliance on renewable Telefónica report mentioned earlier, extensive reliance on renewable
energy sources is emphasized. energy sources is emphasized.
Similarly, deployments can take other environmental factors into Similarly, deployments can take other environmental factors into
account that affect the carbon footprint. For example, deployments account that affect the carbon footprint. For example, deployments
where the need for cooling is reduced or where excessive heat where the need for cooling is reduced or where excessive heat
generated by equipment can be put to a productive use will be generated by equipment can be put to a productive use will be
considered greener than deployments where this is not the case. considered greener than deployments where this is not the case.
Examples include deployments in cooler natural surroundings (e.g., in Examples include deployments in cooler natural surroundings (e.g., in
colder climates) where that is an option. Likewise, manufacturing colder climates) where that is an option. Likewise, manufacturing
and recycling networking equipment are also part of the and recycling networking equipment are also part of the
sustainability equation, as the production itself consumes energy and sustainability equation, as the production itself consumes energy and
results in a carbon cost embedded as part of the device itself. results in a carbon cost embedded as part of the device itself.
Extending the lifetime of equipment may in many cases be preferable Extending the lifetime of equipment may in many cases be preferable
over replacing it earlier with equipment that is slightly more energy over replacing it earlier with equipment that is slightly more energy
efficient, but that requires the embedded carbon cost to be amortized efficient, but that requires the embedded carbon cost to be amortized
over a much shorter period of time. over a much shorter period of time.
Management has an outsized role to play in approaching those Network management has an outsized role to play in approaching those
problems. To reduce the amount of energy used, network providers problems. To reduce the amount of energy used, network providers
need to maximize ways in which they use scarce resources and need to maximize the use of scarce resources and eliminate the use of
eliminate the use of unneeded resources. They need to optimize the resources that are not strictly needed. They need to optimize the
way in which networks are deployed, which resources are placed where, way in which networks are deployed, which resources are placed where,
and how equipment lifecycles and upgrades are being managed -- all of and how equipment lifecycles and upgrades are being managed -- all of
which constitute classic operational problems. As best practices, which constitute classic operational problems. As best practices,
methods, and algorithms are developed, they need to be automated to methods, and algorithms are developed, they need to be automated to
the greatest extent possible, migrated over time into the network, the greatest extent possible, migrated over time into the network,
and performed on increasingly short timescales, transcending and performed on increasingly short timescales, transcending
management and control planes. management and control planes.
1.3. Structuring the Problem Space 1.3. Structuring the Problem Space
From a technical perspective, multiple vectors along which networks From a technical perspective, multiple vectors along which networks
can be made "greener" should be considered: can be made greener should be considered:
* Equipment level: * Equipment level:
Perhaps the most promising vector for improving networking Perhaps the most promising vector for improving networking
sustainability concerns the network equipment itself. At the most sustainability concerns the network equipment itself. At the most
fundamental level, networks (even softwarized ones) involve fundamental level, networks (even softwarized ones) involve
appliances, i.e., equipment that relies on electrical power to appliances, i.e., equipment that relies on electrical power to
perform its function. There are two distinct layers with perform its function. There are two distinct layers with
different opportunities for improvement: different opportunities for improvement:
- Hardware: Reducing embedded carbon during material extraction - Hardware: Reducing embedded carbon during material extraction
and manufacturing, improving energy efficiency, and reducing and manufacturing; improving energy efficiency and reducing
energy consumption during operations, and reuse, repurpose, and energy consumption during operations; and increasing reuse,
recycle motions. repurposing, and recycling.
- Software: Improving software energy efficiency, maximizing - Software: Improving software energy efficiency, maximizing
utilization of processing devices, and allowing for software to utilization of processing devices, and allowing for software to
interact with hardware to improve sustainability. interact with hardware to improve sustainability.
Beyond making network appliances merely more energy efficient, Beyond making network appliances merely more energy efficient,
there are other important ways in which equipment can help there are other important ways in which equipment can help
networks become greener. This includes aspects such as supporting networks become greener. This includes aspects such as supporting
port power-saving modes or down-speeding links to reduce power port power-saving modes or down-speeding links to reduce power
consumption for resources that are not fully utilized. To fully consumption for resources that are not fully utilized. To fully
tap into the potential of such features, it requires accompanying tap into the potential of such features requires accompanying
management functionality, for example, to determine when it is management functionality, for example to determine when it is
"safe" to down-speed a link or to enter a power-saving mode, and "safe" to down-speed a link or enter a power saving mode, and
to maximize the conditions when that action is appropriate. operate the network in such a way that conditions to do so are
maximized.
Most importantly, from a management perspective, improving Most importantly, from a management perspective, improving
sustainability at the equipment level involves providing sustainability at the equipment level involves providing
management instrumentation that allows for precise monitoring and management instrumentation that allows for precise monitoring and
managing power usage and doing so at different levels of managing power usage and doing so at different levels of
granularity, for example, accounting separately for the granularity, for example, accounting separately for the
contributions of CPU, memory, and different ports. This enables contributions of CPU, memory, and different ports. This enables
(for example) controller applications to optimize energy usage (for example) controller applications to optimize energy usage
across the network and to leverage control loops to assess the across the network and to leverage control loops to assess the
effectiveness (e.g., in terms of reducing power use) of the effectiveness (e.g., in terms of reducing power use) of the
measures that are taken. measures that are taken.
As a side note, the terms "device" and "equipment", as used in the As a side note, the terms "device" and "equipment", as used in the
context of this document, are used to refer to networking context of this document, are used to refer to networking
equipment. We are not taking into consideration end-user devices equipment. We are not taking into consideration end-user devices
and endpoints such as mobile phones or computing equipment. and endpoints such as mobile phones or computing equipment.
* Protocol level: * Protocol level:
Energy-efficiency and greenness are aspects that are rarely Energy-efficiency and "greenness" are aspects that are rarely
considered when designing network protocols. This suggests that considered when designing network protocols. This suggests that
there may be plenty of untapped potential. Some aspects involve there may be plenty of untapped potential. Some aspects involve
designing protocols in ways that reduce the need for redundant or designing protocols in ways that reduce the need for redundant or
wasteful transmission of data, allowing not only for better wasteful transmission of data, allowing not only for better
network utilization but for greater goodput per unit of energy network utilization but for greater goodput per unit of energy
being consumed. Techniques might include approaches that reduce being consumed. Techniques might include approaches that reduce
the "header tax" incurred by payloads as well as methods resulting the "header tax" incurred by payloads as well as methods resulting
in the reduction of wasteful retransmissions. Similarly, there in the reduction of wasteful retransmissions. Similarly, there
may be cases where chattiness of protocols may be preventing may be cases where chattiness of protocols may be preventing
equipment from going into sleep mode. Designing protocols that equipment from going into sleep mode. Designing protocols that
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Perhaps the greatest opportunities to realize power savings exist Perhaps the greatest opportunities to realize power savings exist
at the level of the network as whole. Many of these opportunities at the level of the network as whole. Many of these opportunities
are directly related to management functionality. For example, are directly related to management functionality. For example,
optimizing energy efficiency may involve directing traffic in such optimizing energy efficiency may involve directing traffic in such
a way that it allows the isolation of equipment that might not be a way that it allows the isolation of equipment that might not be
needed at certain moments so that it can be powered down or needed at certain moments so that it can be powered down or
brought into power-saving mode. By the same token, traffic should brought into power-saving mode. By the same token, traffic should
be directed in a way that requires bringing additional equipment be directed in a way that requires bringing additional equipment
online or out of power-saving mode in cases where alternative online or out of power-saving mode in cases where alternative
traffic paths are available for which the incremental energy cost traffic paths are available for which the incremental energy cost
would amount to zero. Likewise, some networking devices may be would amount to zero. Likewise, some networking devices may have
rated less "green" and more power-intensive than others or may be a lower sustainability rating, be less energy-efficient, or be
powered by less-sustainable energy sources. Their use might be powered less-sustainable energy sources than others. Their use
avoided except during periods of peak capacity demands. might be avoided except during periods of peak capacity demands.
Generally, incremental carbon emissions can be viewed as a cost Generally, incremental carbon emissions can be viewed as a cost
metric that networks should strive to minimize and consider as metric that networks should strive to minimize and consider as
part of routing and network path optimization. part of routing and network path optimization.
* Architecture level: * Architecture level:
The current network architecture supports a wide range of The current network architecture supports a wide range of
applications but does not consider energy efficiency as one of its applications but does not consider energy efficiency as one of its
design parameters. One can argue that the most energy efficient design parameters. One can argue that the most energy efficient
shift of the last two decades has been the deployment of Content shift of the last two decades has been the deployment of Content
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GPU: Graphical Processing Unit GPU: Graphical Processing Unit
HVAC: Heating, Ventilation, Air Conditioning HVAC: Heating, Ventilation, Air Conditioning
ICN: Information-Centric Network ICN: Information-Centric Network
IGP: Interior Gateway Protocol IGP: Interior Gateway Protocol
IoT: Internet of Things IoT: Internet of Things
IPU: Infrastructure Processing Unit
LEED: Leadership in Energy and Environmental Design (a green LEED: Leadership in Energy and Environmental Design (a green
building rating system) building rating system)
LEO: Low Earth Orbit LEO: Low Earth Orbit
LPM: Longest Prefix Match (a method to look up prefixes in a LPM: Longest Prefix Match (a method to look up prefixes in a
forwarding element) forwarding element)
MPLS: Multiprotocol Label Switching MPLS: Multiprotocol Label Switching
MTU: Maximum Transmission Unit (the largest packet size that can be MTU: Maximum Transmission Unit (the largest packet size that can be
transmitted over a network) transmitted over a network)
NIC: Network Interface Card NIC: Network Interface Card
QoE: Quality of Experience QoE: Quality of Experience
QoS: Quality of Service QoS: Quality of Service
QUIC: Quick UDP Internet Connections QUIC: the name of a UDP-based, stream-multiplexing, encrypted
transport protocol [RFC9000].
SDN: Software-Defined Networking SDN: Software-Defined Networking
TCP: Transport Control Protocol TCP: Transport Control Protocol
TE: Traffic Engineering TE: Traffic Engineering
TPU: Tensor Processing Unit TPU: Tensor Processing Unit
WAN: Wide Area Network WAN: Wide Area Network
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operational robustness). As data transmission needs tend to operational robustness). As data transmission needs tend to
fluctuate wildly and occur in bursts, any optimization schemes need fluctuate wildly and occur in bursts, any optimization schemes need
to be highly adaptable and allow control loops at very fast time to be highly adaptable and allow control loops at very fast time
scales. scales.
Similarly, for applications where this is possible, it may be Similarly, for applications where this is possible, it may be
desirable to replace continuous traffic at low data rates with desirable to replace continuous traffic at low data rates with
traffic that is sent in bursts at high data rates in order to traffic that is sent in bursts at high data rates in order to
potentially maximize the time during which resources can be idled. potentially maximize the time during which resources can be idled.
As a result, emphasis needs to be given to technology that allows, As a result, emphasis needs to be placed on technology that enables,
for example, (at the device level) very efficient and rapid for example, very efficient and rapid discovery, monitoring, and
discovery, monitoring, and control of networking resources so that control of networking resources. This allows devices to be
they can be dynamically taken offline or brought back in service dynamically taken offline or brought back online without extensive
without (at the network level) requiring an extensive convergence of network-level state convergence, route recalculation, or other
state across the network or a recalculation of routes and other complex optimizations at the network level. To facilitate such
optimization problems, and (at the network equipment level) support schemes, rapid power cycle and initialization schemes should be
rapid power cycle and initialization schemes. There may be some supported at the device level. There may be some lessons that can be
lessons that can be applied here from IoT, which has long had to applied here from IoT, which has long had to contend with power-
contend with power-constrained end devices that need to spend much of constrained end devices that need to spend much of their time in
their time in power-saving states to conserve battery. power-saving states to conserve battery.
4. Challenges and Opportunities - Equipment Level 4. Challenges and Opportunities - Equipment Level
We are categorizing challenges and opportunities to improve We are categorizing challenges and opportunities to improve
sustainability at the network equipment level along the following sustainability at the network equipment level along the following
lines: lines:
* Hardware and manufacturing: Related opportunities are arguably * Hardware and manufacturing: Related opportunities are arguably
among the most obvious and perhaps "largest". However, solutions among the most obvious and perhaps "largest". However, solutions
here lie largely outside the scope of networking researchers. here lie largely outside the scope of networking researchers.
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* Visibility and instrumentation: Instrumenting equipment to provide * Visibility and instrumentation: Instrumenting equipment to provide
visibility into how they consume energy is key to management visibility into how they consume energy is key to management
solutions and control loops to facilitate optimization schemes. solutions and control loops to facilitate optimization schemes.
4.1. Hardware and Manufacturing 4.1. Hardware and Manufacturing
Perhaps the most obvious opportunities to make networking technology Perhaps the most obvious opportunities to make networking technology
more energy efficient exist at the equipment level. After all, more energy efficient exist at the equipment level. After all,
networking involves physical equipment to receive and transmit data. networking involves physical equipment to receive and transmit data.
Making such equipment more power efficient, having it dissipate less Making such equipment more power efficient, having it dissipate less
heat to consume less energy and reduce the need for cooling, making heat to consume less energy and reduce the need for cooling, sourcing
it eco-friendly to deploy, sourcing sustainable materials, and sustainable materials, and facilitating the recycling of equipment at
facilitating the recycling of equipment at the end of its lifecycle the end of its lifecycle all contribute to making networks greener.
-- all contribute to making networks greener. Reducing the energy Reducing the energy usage of transmission technology, from wireless
usage of transmission technology, from wireless (antennas) to optical (antennas) to optical (lasers), is a strategy that is unique to
(lasers), is a strategy that is unique to networking. networking.
One critical aspect of the energy cost of networking is the cost to One critical aspect of the energy cost of networking is the cost to
manufacture and deploy the networking equipment. In addition, even manufacture and deploy the networking equipment. In addition, even
the development process itself comes with its own carbon footprint. the development process itself comes with its own carbon footprint.
This is outside of the scope of this document: we only consider the This is outside of the scope of this document: we only consider the
energy cost of running the network during the operational part of the energy cost of running the network during the operational part of the
equipment's lifecycle. However, a holistic approach would include equipment's lifecycle. However, a holistic approach would include
the embedded energy that is included in the networking equipment. As the embedded energy that is included in the networking equipment. As
part of this, aspects such as the impact of deploying new protocols part of this, aspects such as the impact of deploying new protocols
on the rate of obsolescence of existing equipment should be on the rate of obsolescence of existing equipment should be
considered. For instance, incremental approaches that do not require considered. For instance, incremental approaches that do not require
replacing equipment right away -- or even that extend the lifetime of replacing equipment right away -- or even that extend the lifetime of
deployed equipment -- would have a lower energy footprint. This is deployed equipment -- would have a lower carbon footprint. This is
one important benefit also of technologies such as Software-Defined one important benefit also of technologies such as Software-Defined
Networking and network function virtualization, as they may allow Networking and network function virtualization, as they may allow
support for new networking features through software updates without support for new networking features through software updates without
requiring hardware replacements. requiring hardware replacements.
[Emergy] describes an attempt to compute not only the energy of [Emergy] describes an attempt to compute not only the energy of
running a network but also the energy embedded into manufacturing the running a network but also the energy embedded into manufacturing the
equipment. This is denoted by "emergy", a portmanteau for embedded equipment. This is denoted by "emergy", a portmanteau for embedded
energy. Likewise, [Junkyard] describes an approach to recycling energy. Likewise, [Junkyard] describes an approach to recycling
equipment and a proof of concept using old mobile phones recycled equipment and a proof of concept using old mobile phones recycled
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* Virtualized energy and carbon metrics and assessment of their * Virtualized energy and carbon metrics and assessment of their
effectiveness in solutions that optimize carbon footprints in effectiveness in solutions that optimize carbon footprints in
virtualized environments (including SDN, network slicing, network virtualized environments (including SDN, network slicing, network
function virtualization, etc.). function virtualization, etc.).
* Certification and compliance assessment methods that ensure that * Certification and compliance assessment methods that ensure that
green instrumentation cannot be manipulated to give false and green instrumentation cannot be manipulated to give false and
misleading data. misleading data.
* Methods that account for equipment that powers an energy mix, to * Methods that allow for the energy mix of the power sources that
facilitate solutions that optimize carbon footprint and minimize are used to power equipment to be taken into account, in order to
pollution beyond mere energy efficiency [Hossain2019]. facilitate solutions that optimize the actual carbon footprint and
minimize pollution beyond mere energy efficiency [Hossain2019].
5. Challenges and Opportunities - Protocol Level 5. Challenges and Opportunities - Protocol Level
There are several opportunities to improve network sustainability at There are several opportunities to improve network sustainability at
the protocol level, which can be categorized as follows. The first the protocol level, which can be categorized as follows. The first
and arguably most impactful category concerns protocols that enable and arguably most impactful category concerns protocols that enable
carbon footprint optimization schemes at the network level and carbon footprint optimization schemes at the network level and
management towards those goals. Other categories concern protocols management towards those goals. Other categories concern protocols
designed to optimize data transmission rates under energy designed to optimize data transmission rates under energy
considerations, protocols designed to reduce the volume of data to be considerations, protocols designed to reduce the volume of data to be
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The following summarizes some challenges and opportunities in this The following summarizes some challenges and opportunities in this
space that can provide the basis for advances in greener networking: space that can provide the basis for advances in greener networking:
* Protocol advances to enable rapidly taking down, bringing back * Protocol advances to enable rapidly taking down, bringing back
online, and discovering availability and power-saving status of online, and discovering availability and power-saving status of
networking resources while minimizing the need for reconvergence networking resources while minimizing the need for reconvergence
and propagation of state. and propagation of state.
* An assessment of which protocols could be extended with energy- * An assessment of which protocols could be extended with energy-
and sustainability-related parameters in ways that would enable and sustainability-related parameters in ways that would enable
"greener" networking solutions, and an exploration of those greener networking solutions, and an exploration of those
solutions. solutions.
5.2. Protocol Optimization 5.2. Protocol Optimization
The second category involves designing protocols in such a way that The second category involves designing protocols in such a way that
the rate of transmission is chosen to maximize energy efficiency. the rate of transmission is chosen to maximize energy efficiency.
For example, Traffic Engineering (TE) can be manipulated to impact For example, Traffic Engineering (TE) can be manipulated to impact
the rate adaptation mechanism [Ren2018jordan]. By choosing where to the rate adaptation mechanism [Ren2018jordan]. By choosing where to
send the traffic, TE can artificially congest links so as to trigger send the traffic, TE can artificially congest links so as to trigger
rate adaptation and therefore reduce the total amount of traffic. rate adaptation and therefore reduce the total amount of traffic.
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Another example is to set up the proper rate of transmission to Another example is to set up the proper rate of transmission to
minimize the flow completion time (FCT) so as to enable opportunities minimize the flow completion time (FCT) so as to enable opportunities
to turn off links. In a wireless context, [TradeOff] studies how to turn off links. In a wireless context, [TradeOff] studies how
setting the proper initial value for the congestion window can reduce setting the proper initial value for the congestion window can reduce
the FCT and therefore allow the equipment to go faster into a low- the FCT and therefore allow the equipment to go faster into a low-
energy mode. By sending the data faster, the energy cost can be energy mode. By sending the data faster, the energy cost can be
significantly reduced. This is a simple proof of concept, but significantly reduced. This is a simple proof of concept, but
protocols that allow for turning links into a low-power mode by protocols that allow for turning links into a low-power mode by
transmitting the data over shorter periods could be designed for transmitting the data over shorter periods could be designed for
other types of networks beyond Wi-Fi access. This should be done other types of networks beyond Wi-Fi access. This should be done
carefully: in an extreme case, a high rate of transmission over a carefully: a sudden very high rate of transmission over a short
short period of time may create bursts that the network would need to period of time may create bursts that the network would need to
accommodate, with all attendant complications of bursty traffic. We accommodate, with all attendant complications of bursty traffic. We
conjecture there is a sweet spot between trying to complete flows conjecture there is a sweet spot between trying to complete flows
faster while controlling for burstiness in the network. It is faster while controlling for burstiness in the network. It is
probably advisable to attempt to send traffic paced yet in bulk probably advisable to attempt to send traffic paced yet in bulk
rather than spread out over multiple round trips. This is an area of rather than spread out over multiple round trips. This is an area of
worthwhile exploration. worthwhile exploration.
The following summarizes some challenges and opportunities in this The following summarizes some challenges and opportunities in this
space that can provide the basis for advances in greener networking: space that can provide the basis for advances in greener networking:
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5.3. Data Volume Reduction 5.3. Data Volume Reduction
The third category involves designing protocols in such a way that The third category involves designing protocols in such a way that
they reduce the volume of data that needs to be transmitted for any they reduce the volume of data that needs to be transmitted for any
given purpose. Loosely speaking, by reducing this volume, more given purpose. Loosely speaking, by reducing this volume, more
traffic can be served by the same amount of networking traffic can be served by the same amount of networking
infrastructure, hence reducing overall energy consumption. infrastructure, hence reducing overall energy consumption.
Possibilities here include protocols that avoid unnecessary Possibilities here include protocols that avoid unnecessary
retransmissions. At the application layer, protocols may also use retransmissions. At the application layer, protocols may also use
coding mechanisms that encode information close to the Shannon limit. coding mechanisms that encode information close to the Shannon limit
Currently, most of the traffic over the Internet consists of video [Shannon]. Currently, most of the traffic over the Internet consists
streaming, and video encoders are already quite efficient and keep of video streaming. Video encoders are already quite efficient and
improving all the time. This results in energy savings as one of keep improving all the time. This results in energy savings as one
many advantages, although of course the savings are offset by of many benefits, even if some of those savings may be partially
increasingly higher resolution. It is not clear that the extra work offset by increasingly higher resolution. It is not clear that the
to achieve higher compression ratios for the payloads results in a extra work to achieve higher compression ratios for the payloads
net energy gain: what is saved over the network may be offset by the results in a net energy gain: what is saved over the network may be
compression/decompression effort. Further research on this aspect is offset by the compression/decompression effort. Further research on
necessary. this aspect is necessary.
At the transport protocol layer, TCP and to some extent QUIC react to At the transport protocol layer, TCP and to some extent QUIC react to
congestion by dropping packets. This is an extremely energy congestion by dropping packets. This is an extremely energy
inefficient method to signal congestion because (a) the network has inefficient method to signal congestion because (a) the network has
to wait one RTT to be aware that the congestion has occurred, and (b) to wait one RTT to be aware that the congestion has occurred, and (b)
the effort to transmit the packet from the source up until it is the effort to transmit the packet from the source up until it is
dropped ends up being wasted. This calls for new transport protocols dropped ends up being wasted. This calls for new transport protocols
that react to congestion without dropping packets. ECN [RFC2481] is that react to congestion without dropping packets. ECN [RFC3168] is
a possible solution, however, it is not widely deployed. DCTCP a possible solution, however, it is not widely deployed. DCTCP
[Alizadeh2010DCTCP] is tuned for data centers; Low Latency, Low Loss, [Alizadeh2010DCTCP] is tuned for data centers; Low Latency, Low Loss,
and Scalable Throughput (L4S) is an attempt to port similar and Scalable Throughput (L4S) is an attempt to port similar
functionality to the Internet [RFC9330]. Qualitative Communication functionality to the Internet [RFC9330]. Qualitative Communication
[QUAL] [Westphal2021qualitative] allows the nodes to react to [QUAL] [Westphal2021qualitative] allows the nodes to react to
congestion by dropping only some of the data in the packet, thereby congestion by dropping only some of the data in the packet, thereby
only partially wasting the resource consumed by transmitted the only partially wasting the resource consumed by transmitted the
packet up to that point. Novel transport protocols for the WAN can packet up to that point. Novel transport protocols for the WAN can
ensure that no energy is wasted transmitting packets that will be ensure that no energy is wasted transmitting packets that will be
eventually dropped. eventually dropped.
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The following summarizes some challenges and opportunities in this The following summarizes some challenges and opportunities in this
space that can provide the basis for advances in greener networking: space that can provide the basis for advances in greener networking:
* Assessments of energy-related trade-offs regarding protocol design * Assessments of energy-related trade-offs regarding protocol design
space and trade-offs, such as maintaining state versus more space and trade-offs, such as maintaining state versus more
compact encodings, or extra computation for transcoding operations compact encodings, or extra computation for transcoding operations
versus larger data volume. versus larger data volume.
* Protocol advances for improving the ratio of goodput to throughput * Protocol advances for improving the ratio of goodput to throughput
and to reduce waste: reduction in header tax, in protocol and to reduce waste; this includes advances such as coding
verbosity, in need for retransmissions, improvements in coding, improvements, reductions in header tax, lower protocol verbosity,
etc. and reduced need for retransmissions.
* Protocols that allow for managing transmission patterns in ways * Protocols that allow for managing transmission patterns in ways
that facilitate periods of link inactivity, such as burstiness and that facilitate periods of link inactivity, such as burstiness and
chattiness. chattiness.
5.4. Network Addressing 5.4. Network Addressing
Network addressing is another way to shave off energy usage from Network addressing is another way to shave off energy usage from
networks. Address tables can get very large, resulting in large networks. Address tables can get very large, resulting in large
forwarding tables that require considerable amount of memory, in forwarding tables that require considerable amount of memory, in
addition to large amounts of state that needs to be maintained and addition to large amounts of state needing to be maintained and
synchronized. From an energy footprint perspective, both can be synchronized. Memory as well as the processing needed to maintain
considered wasteful and offer opportunities for improvement. At the and synchronize state both consume energy. Exploring ways to reduce
protocol level, rethinking how addresses are structured can allow for the amount of memory and synchronization of state that is required
flexible addressing schemes that can be exploited in network offers opportunities to reduce energy use. At the protocol level,
deployments that are less energy-intensive by design. This can be rethinking how addresses are structured can allow for flexible
complemented by supporting clever address allocation schemes that addressing schemes that can be exploited in network deployments that
minimize the number of required forwarding entries as part of are less energy-intensive by design. This can be complemented by
deployments. supporting clever address allocation schemes that minimize the number
of required forwarding entries as part of deployments.
Alternatively, the addressing could be designed to allow for more Alternatively, the addressing could be designed to allow for more
efficient processing than LPM. For instance, a geographic type of efficient processing than LPM. For instance, a geographic type of
addressing (where the next hop is computed as a simple distance addressing (where the next hop is computed as a simple distance
calculation based on the respective position of the current node, of calculation based on the respective position of the current node, of
its neighbors and of the destination) [Herzen2011PIE] could be its neighbors and of the destination) [Herzen2011PIE] could be
potentially more energy efficient. potentially more energy efficient.
The following summarizes some challenges and opportunities in this The following summarizes some challenges and opportunities in this
space that can provide the basis for advances in greener networking: space that can provide the basis for advances in greener networking:
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* Devise methods to improve addressing schemes, as well as address * Devise methods to improve addressing schemes, as well as address
assignment schemes, to minimize their footprint. assignment schemes, to minimize their footprint.
6. Challenges and Opportunities - Network Level 6. Challenges and Opportunities - Network Level
6.1. Network Optimization and Energy/Carbon/Pollution-Aware Networking 6.1. Network Optimization and Energy/Carbon/Pollution-Aware Networking
Networks have been optimized for many years under many criteria, for Networks have been optimized for many years under many criteria, for
example, to optimize (maximize) network utilization and to optimize example, to optimize (maximize) network utilization and to optimize
(minimize) cost. Hence, it is straightforward to add optimization (minimize) cost. Hence, it is straightforward to add optimization
for "greenness" (including energy efficiency, power consumption, for greenness (including energy efficiency, power consumption, carbon
carbon footprint) as important criteria. footprint) as important criteria.
This includes assessing the carbon footprints of paths and optimizing This includes assessing the carbon footprints of paths and optimizing
those paths so that overall footprint is minimized, then applying those paths so that overall footprint is minimized, then applying
techniques such as path-aware networking or segment routing [RFC8402] techniques such as path-aware networking or segment routing [RFC8402]
to steer traffic along those paths. (As mentioned earlier, other to steer traffic along those paths. (As mentioned earlier, other
proxy measures could be used for carbon footprint, such as energy- proxy measures could be used for carbon footprint, such as energy-
efficiency ratings of traversed equipment.) It also includes aspects efficiency ratings of traversed equipment.) It also includes aspects
such as considering the incremental carbon footprint in routing such as considering the incremental carbon footprint in routing
decisions. Optimizing cost has a long tradition in networking; many decisions. Optimizing cost has long been an area of focus in
of the existing mechanisms can be leveraged for greener networking networking; many of the existing mechanisms can be leveraged for
simply by introducing the carbon footprint as a cost factor. Low- greener networking simply by introducing the carbon footprint as a
hanging fruit includes adding carbon-related parameters as a cost cost factor. Low-hanging fruit includes adding carbon-related
parameter in control planes, whether distributed (e.g., IGP) or parameters as a cost parameter in control planes, whether distributed
conceptually centralized via SDN controllers. Likewise, there are (e.g., IGP) or conceptually centralized via SDN controllers.
opportunities in right-placing functionality in the network. An Likewise, there are opportunities to smartly place functionality in
example is placement of virtualized network functions in carbon- the network for optimal effectiveness. An example is placement of
optimized ways, i.e., cohosted on fewer servers in close proximity to virtualized network functions in carbon-optimized ways. For example,
each other in order to avoid unnecessary overhead in long-distance virtualized network functions can be cohosted on fewer servers to
achieve higher server utilization, which is more effective from an
energy and carbon perspective than larger numbers of servers with
lower utilization. Likewise, they can be placed in close proximity
to each other in order to avoid unnecessary overhead in long-distance
control traffic. control traffic.
Other opportunities concern adding carbon awareness to dynamic path Other opportunities concern adding carbon awareness to dynamic path
selection schemes. This is sometimes referred to as "energy-aware selection schemes. This is sometimes referred to as "energy-aware
networking" (or "pollution-aware networking" [Hossain2019] or networking" (or "pollution-aware networking" [Hossain2019] or
"carbon-aware networking", when parameters beyond simply energy "carbon-aware networking", when parameters beyond simply energy
consumption are taken into account). Again, considerable energy consumption are taken into account). Again, considerable energy
savings can potentially be realized by taking resources offline savings can potentially be realized by taking resources offline
(e.g., putting them into power-saving or hibernation mode) when they (e.g., putting them into power-saving or hibernation mode) when they
are not needed under current network demand and load conditions. are not needed under current network demand and load conditions.
Therefore, weaning such resources from traffic becomes an important Therefore, weaning resources from traffic is an important
consideration for energy-efficient traffic steering. This contrasts consideration for energy-efficient traffic steering. This approach
and indeed conflicts with existing schemes that typically aim to contrasts and indeed conflicts with existing schemes that typically
create redundancy and load-balance traffic across a network to aim to create redundancy and load-balance traffic across a network to
achieve even resource utilization. This usually occurs for important achieve even resource utilization across larger numbers of network
reasons, such as making networks more resilient, optimizing service resources as a means to increase network resilience, optimize service
levels, and increasing fairness. Thus, a big challenge is how levels, and ensure fairness. Thus, a big challenge is how resource-
resource-weaning schemes to realize energy savings can be weaning schemes to realize energy savings can be accommodated without
accommodated without cannibalizing other important goals, cannibalizing other important goals, counteracting other established
counteracting other established mechanisms, or destabilizing the mechanisms, or destabilizing the network.
network.
An opportunity may lie in making a distinction between "energy modes" An opportunity may lie in making a distinction between "energy modes"
of different domains. For instance, in a highly trafficked core, the of different domains. For instance, in a highly trafficked core, the
energy challenge is to transmit the traffic efficiently. The amount energy challenge is to transmit the traffic efficiently. The amount
of traffic is relatively fluid (due to multiplexing of multiple of traffic is relatively fluid (due to multiplexing of multiple
sessions) and the traffic is predictable. In this case, there is no sessions) and the traffic is predictable. In this case, there is no
need to optimize on a per-session basis or at a short timescale. In need to optimize on a per-session basis or at a short timescale. In
the access networks connecting to that core, though, there are the access networks connecting to that core, though, there are
opportunities for this fast convergence: traffic is much more bursty opportunities for this fast convergence: traffic is much more bursty
and less predictable, and the network should be able to be more and less predictable, and the network should be able to be more
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footprint will be required. These abstractions need to account for footprint will be required. These abstractions need to account for
not only the energy cost associated with packet forwarding across a not only the energy cost associated with packet forwarding across a
given path, but also the related cost for processing, for memory, and given path, but also the related cost for processing, for memory, and
for maintaining of state, to result in a holistic picture. for maintaining of state, to result in a holistic picture.
In many cases, optimization of carbon footprint has trade-offs that In many cases, optimization of carbon footprint has trade-offs that
involve not only packet forwarding but also aspects such as keeping involve not only packet forwarding but also aspects such as keeping
state, caching data, or running computations at the edge instead of state, caching data, or running computations at the edge instead of
elsewhere. (Note: There may be a differential in running a elsewhere. (Note: There may be a differential in running a
computation at an edge server vs. at a hyperscale DC. The latter is computation at an edge server vs. at a hyperscale DC. The latter is
often better optimized than the latter.) Likewise, other aspects of often better optimized than the former.) Likewise, other aspects of
carbon footprint beyond mere energy-intensity should be considered. carbon footprint beyond mere energy-intensity should be considered.
For instance, some network segments may be powered by more For instance, some network segments may be powered by more
sustainable energy sources than others, and some network equipment sustainable energy sources than others, and some network equipment
may be more environmentally friendly to build, deploy, and recycle, may be more environmentally friendly to build, deploy, and recycle,
all of which can be reflected in abstractions to consider. all of which can be reflected in abstractions to consider.
Assessing carbon footprint at the network level requires Assessing carbon footprint at the network level requires
instrumentation that associates that footprint not just with instrumentation that associates that footprint not just with
individual devices (as outlined in Section 4.2) but also with individual devices (as outlined in Section 4.2) but also with
concepts that are meaningful at the network level, i.e., to flows and concepts that are meaningful at the network level, i.e., to flows and
to paths. For example, it will be useful to provide visibility into to paths. For example, it will be useful to provide visibility into
the carbon intensity of a path: Can the carbon cost of traffic the carbon intensity of a path: Can the carbon cost of traffic
transmitted over the path be aggregated? Does the path include transmitted over the path be aggregated? Does the path include
outliers, i.e., segments with equipment with a particularly poor outliers, i.e., segments with equipment with a particularly large
carbon footprint? carbon footprint?
Similarly, how can the carbon cost of a flow be assessed? That might Similarly, how can the carbon cost of a flow be assessed? That might
serve many purposes beyond network optimization, e.g., introducing serve many purposes beyond network optimization, from the option to
green billing and charging schemes, and raising carbon awareness by introduce green billing and charging schemes that account for the
end users. amount of carbon-equivalent emissions that are attributed to the use
of communication services by particular users to the ability to raise
carbon awareness by end users.
The following summarizes some challenges and opportunities in this The following summarizes some challenges and opportunities in this
space that can provide the basis for advances in greener networking: space that can provide the basis for advances in greener networking:
* Devise methods to assess, estimate, and predict the carbon * Devise methods to assess, estimate, and predict the carbon
intensity of paths. intensity of paths.
* Devise methods to account for the carbon footprint of flows and * Devise methods to account for the carbon footprint of flows and
networking services. networking services.
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6.5. The Role of Topology 6.5. The Role of Topology
One of the most important network management constructs is that of One of the most important network management constructs is that of
the network topology. A network topology can usually be represented the network topology. A network topology can usually be represented
as a database or as a mathematical graph, with vertices or nodes, as a database or as a mathematical graph, with vertices or nodes,
edges or links, representing networking nodes, links connecting their edges or links, representing networking nodes, links connecting their
interfaces, and all their characteristics. Examples of these network interfaces, and all their characteristics. Examples of these network
topology representations include routing protocols' link-state topology representations include routing protocols' link-state
databases (LSDBs) and service function chaining graphs. databases (LSDBs) and service function chaining graphs.
To add carbon and energy awareness into networks, the energy As part of adding carbon and energy awareness into networks, it is
proportionality of topologies directly supports visibility into useful also for topology information to provide visibility into
energy consumption and improvements via automation. sustainability data. Such capabilities can help to assess
sustainability of the network overall and can enable automated
applications to improve it.
The following summarizes some challenges and opportunities in this The following summarizes some challenges and opportunities in this
space that can provide the basis for advances in greener networking: space that can provide the basis for advances in greener networking:
* Embedding carbon and energy awareness into the representation of * Embedding carbon and energy awareness into the representation of
topologies, whether considering IGP LSDBs and their topologies, whether considering IGP LSDBs and their
advertisements, BGP-LS (BGP Link-State), or metadata for the advertisements, BGP-LS (BGP Link-State), or metadata for the
rendering of service function paths in a service chain. rendering of service function paths in a service chain.
* Use of those carbon-aware attributes to optimize topology as a * Use of those carbon-aware attributes to optimize topology as a
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optimized data center at very large scale (but requiring transmission optimized data center at very large scale (but requiring transmission
of significant volumes of data across many nodes and long distances) of significant volumes of data across many nodes and long distances)
versus (b) at the edge where the energy may not be used as versus (b) at the edge where the energy may not be used as
efficiently (less multiplexing of resources and inherently lower efficiently (less multiplexing of resources and inherently lower
efficiency of smaller sites due to their smaller scale) but the efficiency of smaller sites due to their smaller scale) but the
amount of long-distance network traffic and energy required for the amount of long-distance network traffic and energy required for the
network is significantly reduced. Softwarization, containers, and network is significantly reduced. Softwarization, containers, and
microservices are direct enablers of such architectures. Their microservices are direct enablers of such architectures. Their
realization will be further aided by the deployment of programmable realization will be further aided by the deployment of programmable
network infrastructure, such as Infrastructure Processing Units network infrastructure, such as Infrastructure Processing Units
(IPUs) or SmartNICs that offload some computations from the CPU onto (IPUs) or Smart NICs that offload some computations from the CPU onto
the NIC. However, the power consumption characteristics of CPUs are the NIC. However, the power consumption characteristics of CPUs are
different from those of NPUs; this is another aspect to be considered different from those of NPUs; this is another aspect to be considered
in conjunction with virtualization. in conjunction with virtualization.
Other possibilities are taking economic aspects into consideration, Other possibilities are taking economic aspects into consideration,
such as providing incentives to users of networking services in order such as providing incentives to users of networking services in order
to minimize energy consumption and emission impact. In to minimize energy consumption and emission impact. In
[Wolf2014choicenet], an example is provided that could be expanded to [Wolf2014choicenet], an example is provided that could be expanded to
include energy incentives. include energy incentives.
skipping to change at line 1239 skipping to change at line 1254
reduce the energy cost at the network layer, for example, by reduce the energy cost at the network layer, for example, by
performing tasks that involve massive communications closer to the performing tasks that involve massive communications closer to the
user. To what extent these shifts result in a net reduction of user. To what extent these shifts result in a net reduction of
carbon footprint is an important question that requires further carbon footprint is an important question that requires further
analysis on a case-by-case basis. analysis on a case-by-case basis.
The following summarizes some challenges and opportunities in this The following summarizes some challenges and opportunities in this
space that can provide the basis for advances in greener networking: space that can provide the basis for advances in greener networking:
* Investigate organization of networking architecture for important * Investigate organization of networking architecture for important
classes of applications (e.g., content delivery, right-placing of classes of applications (e.g., content delivery, most suitable
computational intelligence, industrial operations and control, placement of computational intelligence and network functionality
massively distributed ML and AI) to optimize green footprint and within the network design, industrial operations and control,
holistic approaches to trade-offs of carbon footprint with massively distributed ML and AI) to optimize overall
forwarding, storage, and computation. sustainability and holistic approaches to trade off carbon
footprint between forwarding, storage, and computation.
* Models to assess and compare alternatives in providing networked * Models to assess and compare alternatives in providing networked
services, e.g., evaluate carbon impact relative to where to services, e.g., evaluate carbon impact relative to where to
perform computation, what information to cache, and what perform computation, what information to cache, and what
communication exchanges to conduct. communication exchanges to conduct.
8. Conclusions 8. Conclusions
How to make networks "greener" and reduce their carbon footprint is How to make networks greener and reduce their carbon footprint is an
an important problem for the networking industry to address, both for important problem for the networking industry to address, both for
societal and for economic reasons. This document has highlighted a societal and for economic reasons. This document has highlighted a
number of the technical challenges and opportunities in that regard. number of the technical challenges and opportunities in that regard.
Of those, perhaps the key challenge to address right away is the Of those, perhaps the key challenge to address right away is the
ability to expose at a fine granularity the energy impact of any ability to expose at a fine granularity the energy impact of any
networking actions. Providing visibility into this will enable many networking actions. Providing visibility into this will enable many
approaches to come towards a solution. It will be key to approaches to come towards a solution. It will be key to
implementing optimization via control loops that can assess the implementing optimization via control loops that can assess the
energy impact of a decision taken. It will also help to answer energy impact of a decision taken. It will also help to answer
questions such as: questions such as (but not limited to) the following:
* Is caching (with the associated storage) better than * Is caching (with the associated storage) better than
retransmitting from a different server (with the associated retransmitting from a different server (with the associated
networking cost)? networking cost)?
* Is compression more energy efficient once factoring in the * Is compression more energy efficient once factoring in the
computation cost of compression vs. transmitting uncompressed computation cost of compression vs. transmitting uncompressed
data? data? Which compression scheme is more energy efficient?
* Which compression scheme is more energy efficient?
* Is energy saving of computing at an efficient hyperscale DC * Is energy saving of computing at an efficient hyperscale DC
compensated by the networking cost to reach that DC? compensated by the networking cost to reach that DC?
* Is the overhead of gathering and transmitting fine-grained energy * Is the overhead of gathering and transmitting fine-grained energy
telemetry data offset by the total energy gain resulting from the telemetry data offset by the total energy gain resulting from the
better decisions that this data enables? better decisions that this data enables?
* Is transmitting data to a Low Earth Orbit (LEO) satellite * Is the energy cost needed to transmit data to a Low Earth Orbit
constellation compensated by the fact that once in the (LEO) satellite constellation offset by the fact that the
constellation, the networking is fueled by solar energy? constellation and any networking within it are powered by solar
energy?
* Is the energy cost of sending rockets to place routers in LEO * Is the energy cost of sending rockets to place routers in LEO
amortized over time? amortized over time?
Determining where the sweet spots are and optimizing networks along Determining where the sweet spots are and optimizing networks along
those lines will be a key towards making networks "greener". We those lines will be a key towards making networks greener. We expect
expect to see significant advances across these areas and believe to see significant advances across these areas and believe that
that researchers, developers, and operators of networking technology researchers, developers, and operators of networking technology have
have an important role to play in this. an important role to play in this.
9. IANA Considerations 9. IANA Considerations
This document has no IANA actions. This document has no IANA actions.
10. Security Considerations 10. Security Considerations
Security considerations may appear to be orthogonal to green Security considerations may appear to be orthogonal to green
networking considerations. However, there are a number of important networking considerations. However, there are a number of important
caveats. caveats.
skipping to change at line 1427 skipping to change at line 1443
easy as PIE: A practical isometric embedding protocol", easy as PIE: A practical isometric embedding protocol",
19th IEEE International Conference on Network Protocols 19th IEEE International Conference on Network Protocols
(ICNP), pp. 49-58, DOI 10.1109/ICNP.2011.6089081, 2011, (ICNP), pp. 49-58, DOI 10.1109/ICNP.2011.6089081, 2011,
<https://doi.org/10.1109/ICNP.2011.6089081>. <https://doi.org/10.1109/ICNP.2011.6089081>.
[Hossain2019] [Hossain2019]
Hossain, M., Georges, J., Rondeau, E., and T. Divoux, Hossain, M., Georges, J., Rondeau, E., and T. Divoux,
"Energy, Carbon and Renewable Energy: Candidate Metrics "Energy, Carbon and Renewable Energy: Candidate Metrics
for Green-Aware Routing?", Sensors, vol. 19, no. 3, for Green-Aware Routing?", Sensors, vol. 19, no. 3,
DOI 10.3390/s19132901, June 2019, DOI 10.3390/s19132901, June 2019,
<https://doi.org/10.3390/s19132901>. <https://hal.science/hal-02169758/>.
[IETF-Net0] [IETF-Net0]
Daley, J., "Towards a net zero IETF", IETF News, 6 May Daley, J., "Towards a net zero IETF", IETF News, 6 May
2022, 2022,
<https://www.ietf.org/blog/towards-a-net-zero-ietf/>. <https://www.ietf.org/blog/towards-a-net-zero-ietf/>.
[Islam2012evaluating] [Islam2012evaluating]
Islam, S. U. and J. Pierson, "Evaluating Energy Islam, S. U. and J. Pierson, "Evaluating Energy
Consumption in CDN Servers", Proceedings of the Second Consumption in CDN Servers", Proceedings of the Second
International Conference on ICT as Key Technology against International Conference on ICT as Key Technology against
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[Ren2018jordan] [Ren2018jordan]
Ren, J., Lu, K., Westphal, C., Wang, J., Wang, J., Song, Ren, J., Lu, K., Westphal, C., Wang, J., Wang, J., Song,
T., Liu, S., and J. Wang, "JORDAN: A Novel Traffic T., Liu, S., and J. Wang, "JORDAN: A Novel Traffic
Engineering Algorithm for Dynamic Adaptive Streaming over Engineering Algorithm for Dynamic Adaptive Streaming over
HTTP", 2018 International Conference on Computing, HTTP", 2018 International Conference on Computing,
Networking and Communications (ICNC), pp. 581-587, Networking and Communications (ICNC), pp. 581-587,
DOI 10.1109/ICCNC.2018.8390337, 2018, DOI 10.1109/ICCNC.2018.8390337, 2018,
<https://doi.org/10.1109/ICCNC.2018.8390337>. <https://doi.org/10.1109/ICCNC.2018.8390337>.
[RFC2481] Ramakrishnan, K. and S. Floyd, "A Proposal to add Explicit
Congestion Notification (ECN) to IP", RFC 2481,
DOI 10.17487/RFC2481, January 1999,
<https://www.rfc-editor.org/info/rfc2481>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001, DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>. <https://www.rfc-editor.org/info/rfc3031>.
[RFC3095] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H., [RFC3095] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
Hannu, H., Jonsson, L., Hakenberg, R., Koren, T., Le, K., Hannu, H., Jonsson, L., Hakenberg, R., Koren, T., Le, K.,
Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K.,
Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header
Compression (ROHC): Framework and four profiles: RTP, UDP, Compression (ROHC): Framework and four profiles: RTP, UDP,
ESP, and uncompressed", RFC 3095, DOI 10.17487/RFC3095, ESP, and uncompressed", RFC 3095, DOI 10.17487/RFC3095,
July 2001, <https://www.rfc-editor.org/info/rfc3095>. July 2001, <https://www.rfc-editor.org/info/rfc3095>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<https://www.rfc-editor.org/info/rfc3168>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016, RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>. <https://www.rfc-editor.org/info/rfc7950>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>. July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
[RFC9330] Briscoe, B., Ed., De Schepper, K., Bagnulo, M., and G. [RFC9330] Briscoe, B., Ed., De Schepper, K., Bagnulo, M., and G.
White, "Low Latency, Low Loss, and Scalable Throughput White, "Low Latency, Low Loss, and Scalable Throughput
(L4S) Internet Service: Architecture", RFC 9330, (L4S) Internet Service: Architecture", RFC 9330,
DOI 10.17487/RFC9330, January 2023, DOI 10.17487/RFC9330, January 2023,
<https://www.rfc-editor.org/info/rfc9330>. <https://www.rfc-editor.org/info/rfc9330>.
[Shannon] Shannon, C. E., "A Mathematical Theory of Communication",
The Bell System Technical Journal, vol. 27, no. 3, pp.
379-423, DOI 10.1002/j.1538-7305.1948.tb01338.x, July
1948,
<https://doi.org/10.1002/j.1538-7305.1948.tb01338.x>.
[SideChannel] [SideChannel]
Randolph, M. and W. Diehl, "Power Side-Channel Attack Randolph, M. and W. Diehl, "Power Side-Channel Attack
Analysis: A Review of 20 Years of Study for the Layman", Analysis: A Review of 20 Years of Study for the Layman",
Cryptography, vol. 4, no. 2, Cryptography, vol. 4, no. 2,
DOI 10.3390/cryptography4020015, 2020, DOI 10.3390/cryptography4020015, 2020,
<https://doi.org/10.3390/cryptography4020015>. <https://doi.org/10.3390/cryptography4020015>.
[TCC] Rahimi, P., Singh, A. K., and X. Wang, "Selective Noise [TCC] Rahimi, P., Singh, A. K., and X. Wang, "Selective Noise
Based Power-Efficient and Effective Countermeasure Against Based Power-Efficient and Effective Countermeasure Against
Thermal Covert Channel Attacks in Multi-Core Systems", Thermal Covert Channel Attacks in Multi-Core Systems",
Journal on Low Power Electronics and Applications, vol. Journal on Low Power Electronics and Applications, vol.
12, no. 2, DOI 10.3390/jlpea12020025, 2022, 12, no. 2, DOI 10.3390/jlpea12020025, 2022,
<https://doi.org/10.3390/jlpea12020025>. <https://doi.org/10.3390/jlpea12020025>.
[Telefonica2021] [Telefonica2024]
Telefonica, "Telefonica Consolidated Annual Report 2021", Telefonica, "Telefonica Consolidated Annual Report 2024",
2021. 2025, <https://www.telefonica.com/en/wp-
content/uploads/sites/5/2025/02/Consolidated-Annual-
Accounts-2024.pdf>.
[TradeOff] Welzl, M., "Not a Trade-Off: On the Wi-Fi Energy [TradeOff] Welzl, M., "Not a Trade-Off: On the Wi-Fi Energy
Efficiency of Effective Internet Congestion Control", 2022 Efficiency of Effective Internet Congestion Control", 2022
17th Wireless On-Demand Network Systems and Services 17th Wireless On-Demand Network Systems and Services
Conference (WONS), pp. 1-4, Conference (WONS), pp. 1-4,
DOI 10.23919/WONS54113.2022.9764413, 2022, DOI 10.23919/WONS54113.2022.9764413, 2022,
<https://doi.org/10.23919/WONS54113.2022.9764413>. <https://doi.org/10.23919/WONS54113.2022.9764413>.
[TVR_REQS] King, D., Contreras, L. M., Sipos, B., and L. Zhang, "TVR [TVR_REQS] King, D., Contreras, L. M., Sipos, B., and L. Zhang, "TVR
(Time-Variant Routing) Requirements", Work in Progress, (Time-Variant Routing) Requirements", Work in Progress,
skipping to change at line 1566 skipping to change at line 1595
"Qualitative Communications for Augmented Reality and "Qualitative Communications for Augmented Reality and
Virtual Reality", 22nd IEEE International Conference on Virtual Reality", 22nd IEEE International Conference on
High Performance Switching and Routing (HPSR), pp. 1-6, High Performance Switching and Routing (HPSR), pp. 1-6,
DOI 10.1109/HPSR52026.2021.9481793, 2021, DOI 10.1109/HPSR52026.2021.9481793, 2021,
<https://doi.org/10.1109/HPSR52026.2021.9481793>. <https://doi.org/10.1109/HPSR52026.2021.9481793>.
[Wolf2014choicenet] [Wolf2014choicenet]
Tilman, W., Griffioen, J., Calvert, L., Dutta, R., Tilman, W., Griffioen, J., Calvert, L., Dutta, R.,
Rouskas, G., Baldin, I., and A. Nagurney, "ChoiceNet: Rouskas, G., Baldin, I., and A. Nagurney, "ChoiceNet:
Toward an Economy Plane for the Internet", ACM SIGCOMM Toward an Economy Plane for the Internet", ACM SIGCOMM
Computer Communciations Review, vol. 44, no. 3, pp. 58-65, Computer Communications Review, vol. 44, no. 3, pp. 58-65,
DOI 10.1145/2656877.2656886, July 2014, DOI 10.1145/2656877.2656886, July 2014,
<https://doi.org/10.1145/2656877.2656886>. <https://doi.org/10.1145/2656877.2656886>.
Acknowledgments Acknowledgments
The authors thank Dave Oran for providing the information regarding The authors thank Dave Oran for providing the information regarding
covert channels using energy measurements and Mike King for an covert channels using energy measurements and Mike King for an
exceptionally thorough review and useful comments. exceptionally thorough review and useful comments.
Contributors Contributors
Michael Welzl Michael Welzl
University of Oslo University of Oslo
Email: michawe@ifi.uio.no Email: michawe@ifi.uio.no
Authors' Addresses Authors' Addresses
Alexander Clemm (editor) Alexander Clemm (editor)
Independent Sympotech
Los Gatos, CA Los Gatos, CA
United States of America United States of America
Email: ludwig@clemm.org Email: ludwig@clemm.org
Carlos Pignataro (editor) Carlos Pignataro (editor)
North Carolina State University North Carolina State University & Blue Fern Consulting
United States of America United States of America
Email: cpignata@gmail.com, cmpignat@ncsu.edu Email: cmpignat@ncsu.edu, carlos@bluefern.consulting
Cedric Westphal Cedric Westphal
Email: westphal@ieee.org Department of Computer Science and Engineering
University of California, Santa Cruz
Email: cedric@ucsc.edu
Laurent Ciavaglia Laurent Ciavaglia
Nokia Nokia
Email: laurent.ciavaglia@nokia.com Email: laurent.ciavaglia@nokia.com
Jeff Tantsura Jeff Tantsura
Nvidia Nvidia
Email: jefftant.ietf@gmail.com Email: jefftant.ietf@gmail.com
Marie-Paule Odini Marie-Paule Odini
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