Network Working Group R. Winter
Internet-Draft HSA
Intended status: Informational S. Jeong
Expires: April 23, 2013 ETRI
JH. Choi
Samsung AIT
October 22, 2012
Towards an Energy-Efficient Internet
draft-winter-energy-efficient-internet-01.txt
Abstract
Climate change and cost drives all sectors of industry and society as
a whole towards more energy-efficient technology, products and life
styles. The collection of Internet infrastructure and the attached
devices are a large user of electrical energy and therefore of course
are no exception regarding this trend. This memo attempts to
identify obstacles and more importantly technology options for an
energy-efficient Internet with a focus on the protocols that are the
product of the IETF.
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 http://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 April 23, 2013.
Copyright Notice
Copyright (c) 2012 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 (http://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
3. State of Affairs . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. The Current Network Energy Use . . . . . . . . . . . . . . 3
3.2. IETF/IRTF Work on Energy-Efficiency . . . . . . . . . . . 4
3.3. Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Potential Obstacles for Realizing an Energy-Efficient Internet 5
4.1. Problems Caused by Sleep Modes . . . . . . . . . . . . . . 5
4.2. The Lack of Efficiency Metrics and Evaluation Methodologies 6
4.3. Problems due to Common Network Operation Practices . . . . 7
5. Potential IETF/IRTF Work Items . . . . . . . . . . . . . . . . 7
5.1. Load-adaptive Resource Management . . . . . . . . . . . . 7
5.2. Energy-efficient Protocol Design . . . . . . . . . . . . . 8
5.3. Energy-efficiency Metrics and Standard Benchmarking
Methodologies . . . . . . . . . . . . . . . . . . . . . . 9
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . . 10
Appendix A. Other energy-related IETF documents . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
Regarding energy efficiency, many people regard the role of the
Internet to be an enabler for it in sectors other than
communications, e.g. the potential for dematerialization (e.g.
replacing letters with Email or DVDs with video streaming), the
potential to reduce travel (e.g. by allowing employees to work from
home rather to commute to work or by replacing physcial meetings with
video conferencing) just to name two areas.
More recently, the energy use of the Internet itself, and more
generally Information and Communication Technology (ICT), has
attracted quite some attention which has lead to technologies such as
Energy Efficient Ethernet [EEE] or the ProxZZZy Standard [PROXZZZY]
and a large body of scientific publications.
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The question is how can the IETF/IRTF help with existing and/or
future protocol standards to support, exploit or enhance these
developments that happen outside of the IETF. Even without these
external technologies, can IETF protocols with or without
modifications help to lower the energy use of the global Internet?
This memo is intended to identify existing obstacles and potential
places in the IETF protocol landscape where there is potential to
achieve this goal: lowering the energy use of the Internet as a whole
from end host to core router.
2. Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. State of Affairs
Energy-efficiency certainly is important. But is the Internet
infrastructure a good place to look at and what is already out there
that addresses energy-efficient communication?
3.1. The Current Network Energy Use
For a long time now, the Information Communications Technology (ICT)
sector as a whole has experienced a rapid growth. With this growth
however comes a steep increase in power demand. According to an
ITU-T report [ITU] from 2008, wired and wireless networks consume a
significant fraction of the overall electrical power. Consequently,
the fraction of green-house gas emissions that can be attributed to
the ICT sector is significant and is currently estimated to be 2% of
the overall man-made emissions.
A report issued by the European Commission in 2008 [EC] is slightly
more detailed regarding the energy use of ICT and makes forecasts
regarding the development of the sector's energy use till 2020. In a
scenario the report calls "business as usual" (BAU), the electricity
consumption of ICT is predicted to double based on data from 2005.
That equals over 10% of the total electricity consumption in the 25
EU member states under observation. It is this energy trend that is
alarming. It has to be noted however that consumer devices are part
of this calculation but even when these devices are removed from this
calaculation, the trend remains the same and over 50% of the energy
budget remains. Another large, and increasingly important consumer
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in this whole mix of technologies are data centers.
3.2. IETF/IRTF Work on Energy-Efficiency
It would be wrong to say that energy-efficiency has not yet been
considered within the IETF/IRTF. E.g. during the 81st IETF meeting
the very first IRTF Applied Networking Research Prize was awarded to
work on energy-efficient traffic engineering [ANRP]. In addition the
IETF EMAN working group is actively working on standards to measure
and control energy-related aspects of powered entities. Also, a
growing number of internet drafts are being submitted that address
energy issues and energy-efficiency such as [I-D.chakrabarti-
nordmark-energy-aware-nd], [I-D.manral-bmwg-power-usage] and [I-D
.okamoto-ccamp-midori-gmpls-extension-reqs] to name just a few.
Finally, there are a number of other activities that face similar
problems such as the Internet of Things [RFC6574] which likely would
benefit from general energy-efficiency methods that are applicable in
a wider context.
3.3. Taxonomy
The following represents a classification based on the one found in
[GREENR] and lists examples for each category.
o Adaptive layer-2 technology: Most current types of network
equipment show a constant power consumption profile largely
irrespective of their actual utilization. The computing world on
the other hand has long embraced methods to approximate energy-
proportional computing. In the networking world we see first
steps into energy-proportional communications. Adaptive link rate
technology is such a step where the energy use changes with link
utilization. Also, IEEE Energy Efficient Ethernet is a step into
this direction. The respective Task Force has devoted
considerable efforts in this area and has published IEEE Std
802.3az-2010 (Amendment to IEEE 802.3-2008) [EEE]. The amendment
describes modifications to existing physical layer specifications
in order to make Ethernet more energy efficient. The amendment
covers various technologies such as 10BASE-T or 100BASE-TX. It
also proposes a new Low Power Idle (LPI) mode and related
mechanisms and protocols in order to energy efficiently manage
Ethernet links.
o Network interface proxy technology: Proxying describes
technologies that maintain network connectivity for other devices
so that these can go into low power sleep modes. This mainly
targets the reduction of unnecessary energy waste through edge
devices. ECMA has published a proxying document [PROXZZZY]. This
specification describes an overall architecture for network
proxying and provides capabilities that a proxy may expose to a
host. Also, information that must be exchanged between a host and
a proxy, and required and optional behavior of a proxy during its
operation are described.
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o Energy-aware infrastructure: in order to achieve a further
reduction in energy use, coordination and manangement of larger
parts of the network appears to be a promising idea. Energy-aware
infrastructure describes a class of techniques to this end.
Energy-aware routing is one example that falls into this category.
Energy-aware routing makes use of the fact that traffic follows
certain patterns. Based on this knowledge, in times where network
traffic is low, a number of routers can be put to sleep while the
network as a whole still preserves connectivity and an adequate
service level. Requirements for an energy-aware control plane are
outlined in [I-D.retana-rtgwg-eacp].
4. Potential Obstacles for Realizing an Energy-Efficient Internet
The following is a short list of problems that need to be addressed
in order to introduce techniques that make the Internet more energy-
efficient.
4.1. Problems Caused by Sleep Modes
A sleep mode is a kind of "deep" idle state which results in
significant power savings but also requires a significant amount of
time in order to wake the sleeping node up. When not in use, network
nodes could go to sleep in order to save power. Sleep mode operation
is a common practice e.g. in cellular networks where mobile
terminals spend most of their time in a sleep mode to conserve
energy. Many Internet protocols however could break if sleep modes
would be introduced because they operate based on the assumption that
the participating nodes are always-on [RFC4861] [RFC4862].
Current networking services and applications are commonly designed to
be fully available at all times with minimal response times. If
network nodes are allowed to go into a sleep mode, they effectively
lose network connectivity and their applications and services stop
working. When these nodes wake up again, they have to re-initialize
their applications and services potentially resulting in a non-
negligible amount of signalling overhead [EEFI].
Several IETF protocols require a node to keep constant network
presence and process periodic or event-driven messages in order to
maintain a persistent configuration or state. For example, if an
IPv6 node goes to sleep, it cannot perform Duplicate Address
Detection (DAD) to defend its configured addresses. In that case
some other node may usurp its addresses [RFC4862]. Upon waking up,
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the node needs to go through a costly re-attachment procedure
resulting in even larger delays until network connectivity is
restored.
Even when a node is idle with no running applications, background
traffic is received that needs to be processed which inhibits the
node from sleeping. The good news is that common message exchanges
during otherwise idle periods such as ARP processing or DAD, can
either simply be dropped or be dealt with using minimal computational
resources through a 3rd party - a Network Connectivity Proxy (NCP)
[Wasserman] [SCE] [NCP].
The issues described above can also be addressed by designing sleep-
compatible protocols or by extending existing protocols (where
possible) to include the ability to distinguish sleep form failure.
4.2. The Lack of Efficiency Metrics and Evaluation Methodologies
The mechanism side of energy-efficient protocol design is only one
aspect that will lead to a greener Internet. Another aspect is the
evaluation of and the comparision between different possible
approaches. Currently, there is a lack of standard energy-efficiency
metrics that are applicable to Internet protocols.
There are a number of metrics and some of these actually attempt to
quantify energy use with a direct reference to networking (e.g. [I-D
.manral-bmwg-power-usage]). Right now however, it is challenging at
best to perform an objective and useful comparision of mechanisms
that attempt to increase the energy-efficiency of a protocol.
Energy-efficiency is a metric that should be evaluated in a holistic
way, taking into account consideration across various aspects of the
network. The central problem is that there is a looming danger that
savings in one part of the network can be the cause for an increased
use in another.
In addition, the use cases can vary drastically which might call for
a range of metrics each suitable for a different scenario. For
example, the energy-efficiency of data centers is commonly evaluated
using the Power Usage Effectiveness (PUE) but there are many other
metrics such as the IT Equipment Energy Efficiency (ITEE), IT
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Equipment Utilization (ITEU), and so on [GGrid]. While many of these
metrics have a significant value in isolation , a holistic
methodology for measuring the energy-efficiency spanning multiple
such metrics would be beneficial.
The first big step, which to some degree is already been taken, is to
assess current power consumption patterns and to come to an
understanding how the power consumption is distributed in the
network, in devices, in device components and how the utilization of
the network impacts these patterns [PowerTrend] [GTC].
4.3. Problems due to Common Network Operation Practices
Many of the networks that constitute the Internet are over-
provisioned and offer a large degree of redundancy, which, while
contributing to the overall quality of the Internet service, results
in low energy-efficiency.
A lot of people feel that the QoS support of the Internet
architecture itself is inadequate and see over-provisioning a the
only sensible means to achieve it. And indeed, it is a common
practice. Usually network traffic shows significant temporal
fluctuations and, during low traffic periods, an over-provisioned
network uses unnessecarily large quantaties of energy.
Experimental measurements have showen that the energy consumption of
some devices and components (such as Ethernet links) depend mainly on
their capacity, not on actual utilization. Most devices keep drawing
a certain amount of power even in the absence of traffic, i.e.
without providing a meaningful service.
Moreover, for resiliency and fault-tolerance purposes, certain
equipment is put into the infrastructure solely for backup purposes.
Such redundancy also decreases the effective network energy-
efficiency further [GREENR] [GTC] [EARTH].
The above certainly is important and vital in many cases. Often
strong requirement make the above necessary (e.g. switch-over times
in the range of 50ms). It is not just a technical issue that needs to
be solved here but also an issue of operation principles. Putting
nodes into sleep operation or incorprating energy-efficiency
considerations into network operations will be challenging for the
reasons stated above and there will be reluctance to allow energy-
efficiency mechanisms to profoundly change the way networks are
operated today.
5. Potential IETF/IRTF Work Items
The following is an (incomplete) list of potential work items where
the IETF/IRTF might start to pave a path for energy-efficient
protocol desgin and network operations.
5.1. Load-adaptive Resource Management
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In common networks that are provisioned for peak traffic load, a
substantial amount of energy can be saved by dynamically allocating
resources according to actual traffic.
Conceptually, network resources may be shut down when there is no
traffic or scaled down when there is little traffic to improve the
overall energy-efficiency [GreenInternet]. Network equipment, such
as base stations, may be turned off when there is no user within
coverage or link capacity may be reduced when traffic demand is low.
This type of approach potentially has a broad applicability to
various areas not just wireless network, but also core routers/
switches, optical transmission equipment and office networks. Simply
turning equipment off clearly would result in service degradation,
instability and in the worst case loss of connectivity. The overall
optimization goal therefore is to minimize the network power
consumption while maintain network performance resulting in a non-
trivial contraint optimization problem [ANRP] [OptMgmt].
In this area, the IETF/IRTF could work on algorithms to solve the
above described optimization problem and on protocol support for it.
Measuring and monitoring is already being worked on in the EMAN
working group. The control side, i.e. acting on the measurements
and configuring the network accordingly is still very much an open
question. While the EMAN MIBs allow control, the whole "how" is not
addressed right now. Also a set of best current practices can be
developed.
5.2. Energy-efficient Protocol Design
Energy-efficiency is one of these topics that need to be a design
goal or otherwise it will be difficult to retrofit it into a protocol
specification. The question is what are the factors that need to be
considered. It might well be that there are certain design patterns
and options that can be distilled that are vital and a protocol
specification can be checked against these. Such a list could be the
product of the IETF/IRTF. The security aspects of the IETF underwent
a similar evolution and security considerations are now a mandatory
part of every new protocol specification. This is not to say the
there should be an Energy-Efficiency Considerations section in each
new Internet draft, but there are a lot of lessons learned from this
example. There are a number of important security principles such as
crypto-agility and it would be beneficial if something similar could
be established for energy-effciency. A trivial example would be to
require that nodes can re-negotiate timeouts (in protocols that make
use of timeouts) so that a node might be able to go into sleep mode
or to attempt to synchronize periodic messages across a number of
protocols so that these messages all fall into a certain timeframe
and inbetween the node can sleep.
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In addition, it IETF/IRTF could pick a number of existing protocols
and attempt to extend them so as to make them more energy-efficient,
or more likely allow the underlying technology to be more energy-
efficient without breaking communication. In some cases, entirely
new protocols may be needed to support the sleep mode of nodes.
Also, the IETF/IRTF can start to develop proxying solutions as
discussed before. Before going into sleep, a node delegates its
functionalites to such a proxy, which will then respond to routine
network traffic on behalf of the sleeping node and it will wake the
node up when it is needed. Proxys could handle traffic for network
connectivity-related operations such as (ARP, ICMP, DHCP) and also
proxy functions that are application specific could be developed
(P2P). . The IETF/IRTF would need to define the protocols and
procedures for proxy operation such as discovery, selection,
delegation and wake-up [SCE] [NCP].
5.3. Energy-efficiency Metrics and Standard Benchmarking Methodologies
Energy-efficient research and development needs standard performance
metrics in order to evaluate and quantatively compare the
effectiveness of energy-efficient solutions.
Energy-efficiency of a network and the devices therein can be
assessed using measures of energy per sent data unit (e.g. in the
unit of joule/bit) or power per date rate (watt/bps). In principle,
these measures indicate how much energy is needed to send a bit.
Many approaches to network energy-efficiency are limited to the power
consumption of a single device (router, switch or base station).
This scope is comparably easy to specify and measure, but fails to
capture performance aspects such as daily traffic fluctuation or
network under-utilization [GTC].
There are various options to approach this problem. Energy-
efficiency metrics could be extracted e.g. from reference scenarios
such as network topologies and traffic profiles (similar to what the
automobile industry does).
6. Conclusion
Energy-efficiency cerainly is a buzz word right now but beyond the
hype it indeed becomes an important economical and societal aspect.
This document is an attempt to discern a number of work items in this
space for the IETF/IRTF to consider. While the IETF/IRTF is clearly
not able to work on all of the above, some of the mentioned
mechanisms are clearly more far reaching than others and some of the
topics are surely outside of what the IETF/IRTF usually works on,
there are a number of things that the IETF/IRTF can and should take
on as work items to investigate.
We present these ideas for discussion in the community and hope to
extract a number of realistic action items to work on in the near
future.
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7. Security Considerations
The draft covers a range of potential work items and research
activities, each with its own security considerations. These will be
addressed once their actual form and nature become more concrete.
8. IANA Considerations
This document does not require any action from IANA.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[ANRP] Zhang, M., Yi, C., Liu, B. and B. Zhang, "GreenTE: Power-
Aware Traffic Engineering", Proc. IEEE International
Conference on Network Protocols (ICNP) , October 2010.
[EARTH] "Energy-aware radio network technologies", https://www
.ict-earth.eu , .
[EC] "Impacts of Information and Communication Technologies on
Energy Efficiency", September 2008.
[EECDA] Guan, K., Atkinson, G., Kilper, D. and E. Gulsen, "On the
Energy Efficiency of Content Delivery Architectures",
GreenComm4 , 2011.
[EEE] "802.3az-2010", IEEE std , 2010.
[EEFI] Bolla, R., Bruschi, R., Davoli, F. and F. Cucchietti,
"Energy effciency in the future internet: A survey of
existing approaches and trends in energy-aware fixed
network infrastructures", IEEE Communications Surveys
Tutorials , 2010.
[GGrid] Belady, C., "Green Grid Data Center Power Efficiency
Metrics: PUE and DCiE", http://www.thegreengrid.org ,
2008.
[GREENR] Bianzino, A.P., Chaudet, C., Rossi, D. and J.-L. Rougier,
"A survey of green networking research", IEEE
Communications Surveys Tutorials , 2012.
[GTC] "Green Touch Consortium", http://greentouch.org , .
[GreenInternet]
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Gupta, M. and S. Singh, "Greening the Internet", ACM
SIGCOMM , 2003.
[I-D.chakrabarti-nordmark-energy-aware-nd]
Chakrabarti, S., Nordmark, E. and M. Wasserman, "Energy
Aware IPv6 Neighbor Discovery Optimizations", Internet-
Draft draft-chakrabarti-nordmark-energy-aware-nd-02, March
2012.
[I-D.manral-bmwg-power-usage]
Manral, V., "Benchmarking Power usage of networking
devices", Internet-Draft draft-manral-bmwg-power-usage-02,
January 2011.
[I-D.okamoto-ccamp-midori-gmpls-extension-reqs]
Okamoto, S., "Requirements of GMPLS Extensions for Energy
Efficient Traffic Engineering", Internet-Draft draft-
okamoto-ccamp-midori-gmpls-extension-reqs-01, February
2012.
[I-D.retana-rtgwg-eacp]
Retana, A., White, R. and M. Paul, "A Framework and
Requirements for Energy Aware Control Planes", Internet-
Draft draft-retana-rtgwg-eacp-00, July 2012.
[ITU] "Resolution 73 - Information and communication
technologies and climate change", October 2008.
[NCP] Jimeno, M., Christensen, K. and B. Nordman, "A Network
Connection Proxy to Enable Hosts to Sleep and Save
Energy", Proc. IEEE Internat. Performance Computing and
Communications Conf , 2008.
[OptMgmt] Lorincz, J., Capone, A. and D. Begusic, "Optimized network
management for energy savings of wireless access
networks", Computer Networks , 2011.
[PROXZZZY]
"ProxZZZy for sleeping hosts", ECMA International
ECMA-393, February 2010.
[PowerTrend]
Kilper, D., Atkinson, G., Korotky, S. K., Goyal, S.,
Vetter, P., Suvakovic, D. and O. Blume, "Power Trends in
Communication Networks", IEEE J on Selected Topics in
Quantum Electronics , 2011.
[RFC4861] Narten, T., Nordmark, E., Simpson, W. and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4862] Thomson, S., Narten, T. and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
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[RFC6574] Tschofenig, H. and J. Arkko, "Report from the Smart Object
Workshop", RFC 6574, April 2012.
[SCE] Allman, M., Christensen, K., Nordman, B. and V. Paxson,
"Enabling an Energy-Efficient Future Internet Through
Selectively Connected End Systems", ACM SIGCOMM HotNets
Workshop , 2007.
[Wasserman]
Wasserman, M., "It's Not Easy Being 'Green'", IAB
Interconnecting Smart Objects with the Internet Workshop ,
2011.
Appendix A. Other energy-related IETF documents
Below is a list of other relevant documents the authors are aware of
(in no particlar order).
M. Zhang, J. Dong, B. Zhang, "Use Cases for Power-Aware Networks",
draft-zhang-panet-use-cases (work in progress)
B. Nordman, K. Christensen, "Nanogrids", draft-nordman-nanogrids-00
(work in progress)
T. Suzuki, T. Tarui, "Requirements for an Energy-Efficient Network
System", draft-suzuki-eens-requirements (work in progress)
Z. Cao, "Synchronization Layer: an Implementation Method for Energy
Efficient Sensor Stack", draft-cao-lwig-syn-layer (work in progress)
A. Junior, R. Sofia, "Energy-awareness metrics global applicability
guideline", draft-ajunior-energy-awareness-00 (work in progress)
B. Zhang, J. Shi, M. Zhang, J. Dong, "Power-aware Routing and Traffic
Engineering: Requirements, Approaches, and Issues", draft-zhang-
greennet (work in progress)
T. Suganuma, N. Nakamura, S. Izumi, H. Tsunoda, M. Matsuda, K. Ohta,
"Green Usage Monitoring Information Base", draft-suganuma-greenmib
(work in progress)
S. Raman, B. V. Venkataswami, G. Raina, V. Srini, "Power Based
Topologies and TE-Shortest Power Paths in OSPF", draft-mjsraman-
rtgwg-ospf-power-topo-01 (work in progress)
S. Raman, B. V. Venkataswami, G. Raina, V. Srini, "Building power
optimal Multicast Trees", draft-mjsraman-rtgwg-pim-power-02 (work in
progress)
S. Raman, B. V. Venkataswami, G. Raina, "Reducing Power Consumption
using BGP", draft-mjsraman-rtgwg-inter-as-psp-03 (work in progress)
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S. Raman, B. V. Venkataswami, G. Raina, "Building power shortest
inter-Area TE LSPs using pre-computed paths", draft-mjsraman-rtgwg-
intra-as-psp-te-leak-02 (work in progress)
S. Raman, B. V. Venkataswami, G. Raina, V. Srini, "Reducing Power
Consumption using BGP path selection", draft-mjsraman-rtgwg-bgp-
power-path-02 (work in progress)
Authors' Addresses
Rolf Winter
University of Applied Sciences Augsburg
An der Hochschule 1
Augsburg 86161
Germany
Email: rolf.winter@hs-augsburg.de
Sangjin Jeong
ETRI
138 Gajeongno, Yuseong
Daejeon 305-700
Korea
Phone: +82 42 860 1877
Email: sjjeong@etri.re.kr
JinHyeock Choi
Samsung AIT
FIL SAIT GiHeung
Yongin 446-712
Korea
Phone: +82 31 280 9589
Email: jinchoe@samsung.com
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