Internet DRAFT - draft-zhang-panet-problem-statement
draft-zhang-panet-problem-statement
Internet Engineering Task Force B. Zhang
Internet-Draft J. Shi
Intended status: Informational Univ. of Arizona
Expires: April 18, 2014 J. Dong
M. Zhang
Huawei
M. Boucadair
France Telecom
October 15, 2013
Power-Aware Networks (PANET): Problem Statement
draft-zhang-panet-problem-statement-03
Abstract
Energy consumption of network infrastructures is growing fast due to
exponential growth of data traffic and the deployment of increasingly
powerful equipment. There are emerging needs for power-aware routing
and traffic engineering, which adapt routing paths to traffic load in
order to reduce energy consumption network-wide. This document
outlines the design space and problem areas for potential IETF work.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Motivation and Problem Scope . . . . . . . . . . . . . . . . . 3
3. Potential Solution Approaches . . . . . . . . . . . . . . . . 4
4. Problem Areas for IETF . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Informative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
Driven by exponential growth of Internet traffic, networks worldwide
are expanding their infrastructures at a fast pace by deploying more
high-capacity, power-hungry routers, which also leads to increasing
energy consumption. For example, in the US, the energy bill for
powering the wired network reaches up to 2.4 billion dollars per year
[Doverspike10]. Telecom Italia, the largest ISP in Italy, is now the
second largest consumer of electricity after the National Railway
system [Pileri07]. As one of the biggest energy consumers in the
United Kingdom, British Telecom consumed about 0.7% of the entire
nation's electricity in 2007 [Bolla11]. In Japan, predictions say
that routers will consume 9% of the total electricity by 2015
[Nakamura07]. Besides operational costs and environmental impacts,
the ever-increasing energy consumption has become a limiting factor
to long-term growth of network infrastructure due to challenges in
power delivery and heat removal for both router components and
hosting facilities [Gupta03] [Epps06].
Traditionally energy efficiency is improved at the device level or
the link level. For example, energy management techniques can be
applied to adjust router CPU's power status or CPU frequency in
response to different CPU workload; Links can be put to sleep mode
when it has been idle for a while. More recently, there have been a
number of research work that look beyond a single router or linecard
for network-wide solutions towards energy proportionality.
The purpose of this document is to discuss the problem scope, outline
potential approaches, and problem areas for IETF work on power-aware
networks.
2. Motivation and Problem Scope
Today's ISP networks have redundant routers and links, over-
provisioned link capacity, and load-balancing traffic engineering. As
a result, routers and links operate at full capacity all the time
with low average usage, typically less than 40% of link utilization.
This practice makes networks resilient to traffic spikes and
component failures, but also makes networks far from energy-
efficient.
Power-aware routing and traffic engineering have been proposed to
improve network's energy efficiency, for example, by aggregating
traffic onto a subset of links and putting other links with no
traffic into sleep. Data from various sources (e.g., [Heddeghem12]
[Chabarek08]) have shown that line cards are a significant source of
router's power consumption, accounting for 40% - 70% of total power
consumption. Most of the energy is consumed even in standby state,
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and forwarding packets at full speed only increases the energy
consumption by a small percentage. This implies that being able to
put links into sleep mode can potentially save a lot of energy. In
face, this has been demonstrated in several research works such as
[GreenTE] [Nedevschi08] [Chabarek08].
Designing practical protocols, however, has been challenging, because
making routing protocols power-aware brings significant changes to
the routing system and the entire network, thus it involves hardware
support, protocol design, network monitoring, and operational
practices. These issues often depend on the specific network
environments under discussion. In order to focus on protocol-related
issues, we suggest that as the first step we limit the scope of the
discussion to intra-domain routing within one administrative domain,
to avoid inter-domain policy issues. This includes transit networks
as well as edge networks. We leave data center networks out of this
draft since that usually requires concerted efforts beyond network
protocols.
3. Potential Solution Approaches
The high-level idea of power-aware networks is to adjust routing
paths based on traffic level. When traffic level is high, use more
links to carry the traffic; when traffic level is low, merge traffic
onto a subset of all links so that other links can be put to sleep or
reduce rate in order to save power. This needs to be done without
significantly impacting network QoS, network resiliency, and
interoperation with other protocols.
In the last few years a number of power-aware network designs have
emerged. Instead of listing them individually, here we categorize
the solutions along three different dimensions.
Link Sleep vs. Rate Adaptation
Sleeping and rate adaptation are two major ways to save energy in
computer systems. Many hardware, including line cards and chassises,
consumes a significant amount of power when they stand by without
doing any actual work. When put into sleep mode, they will consume
only a little power. Thus putting an idle component to sleep is a
common way to save energy. If there is a need to use this component,
it can be waken up and become usable after a transition time. The
longer a component is in sleep mode, the more power saved. A power-
aware protocol adjusts routing paths to increase the sleep time for
certain links in the network.
A network interface often supports multiple data rates. Operating at
a lower data rate usually consumes less energy, though the actual
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rate-power curve varies from device to device. Rate-adaptation-based
approaches operate interfaces at lower data rates when the traffic
demand is low and increase the data rate when traffic demand is high.
Thus the routers can save power during low utilization period.
These two approaches are also related in the case of "bundled links"
[Fisher10]. A bundled link is a virtual link comprised of multiple
physical links. A sleep-based approach can put some physical links
into sleep to save power, which is same as conducting rate adaptation
on the virtual link with adjustment unit of a physical link.
Configured vs. Adaptive
The key in power-aware routing and traffic engineering is to adjust
routing paths in response to traffic changes, so that the power state
of routers (or router components) will also change accordingly to
achieve energy saving. Different approaches differ at the
granularity of the adjustment.
Some approaches take the long-term traffic average as input, and
output a routing configuration that is applied to the network
regardless of short-term traffic variation. This is mostly useful
when network traffic exhibits a stable, clear pattern, e.g., diurnal
pattern where traffic is high during work hours and low during off
hours. It can only exploit the target traffic pattern; it cannot
react dynamically to short-term traffic changes to either save energy
(by putting links to sleep) or avoid congestion (by waking links up),
but the design and implementation should be simple.
Another type of approach is to adapt to traffic changes dynamically
on much smaller time granularity. This approach may be able to save
more energy and have better performance because it is more
responsive, but the design and implementation usually are more
complicated. This approach needs to continuously collect traffic
data in order to adjust routing dynamically. The adjustment may be
done periodically or whenever significant traffic changes are
observed.
Distributed vs. Centralized
In distributed solutions, routers make power-aware adjustment
decisions, such as link sleep/wake-up and rate increase/decrease,
locally without a central controller. These routers need to exchange
information in order to achieve consistent network states.
Distributed approach fits the Internet operation model well but its
design is the most challenging. Traditional routing does not respond
to traffic variation while power-aware routing does, and it needs to
do so without causing loops or congestions.
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In centralized solutions, a controller computes the routing paths
considering the network topology and traffic demand, and informs
routers how to adjust their routing paths. A centralized server
usually has more complete information, more computation power, and
more memory and storage than routers, thus it may make better
decisions than distributed approach. The server locates in the
network NOC and can be backed up by server replicas. Nevertheless,
this approach requires high reliability of the server.
Both distributed and centralized solutions may find their places in
ISP networks. For example, centralized solution can be integrated
into the Path Computation Element (PCE) framework [PCE-WG]. There
can also be hybrid designs, e.g., using a centralized solution based
on long-term traffic pattern, and distributed mechanisms to handle
short-term traffic variations.
4. Problem Areas for IETF
Power-aware networks have great potentials to improve network energy
efficiency while maintaining network services at desired levels. Its
effectiveness, however, depends on various supports from hardware and
software, especially protocol designs that address operational
issues. In this section we list a few problem areas that will
benefit from additional input from the IETF community, or have the
potential to become work items in related IETF working groups.
Motivation and Problem Scope
o What are the motivations for Power-Aware Networking (PANET)?
o To what extent power consumption is a key factor for Internet
scaling?
o To what extent power-aware system at router level and link level
are not sufficient to reduce the overall energy consumption of
networks?
Technical Development
o What are the technical requirements for an efficient PANET
solution?
o What are the technical tracks to reduce the overall power
consumption at the level of an IP network?
o How protocols can be designed to be power-aware and still maintain
enough network resiliency?
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o What are the technical challenges for deploying efficient PANET
solutions?
o How routing protocols (e.g., OSPF) can be extended to disseminate
power-related information?
o How PCE architecture can be used to compute power-aware paths?
o How PANET can be deployed in centralized or in distributed model?
Operation Practice
o What will be the impacts of PANET to network operations?
o What will be the guidelines for deploying PANET systems?
5. Security Considerations
This draft is a discussion on the Internet's necessity to follow an
evolutionary path towards the future. There is no direct impact on
the Internet security.
6. Informative References
[Bolla11] Bolla, R. and et al. , "Energy Efficiency in the Future
Internet: A Survey of Existing Approaches and Trends in Energy-
Aware Fixed Network Infrastructures", IEEE Communications Surveys
and Tutorials, 2011.
[Chabarek08] Chabarek, J. and et al. , "Power Awareness in Network
Design and Routing", IEEE INFOCOM 2008.
[Doverspike10] Doverspike, R., Ramakrishnan, K., and C. Chas,
"Structural overview of ISP networks", Guide to Reliable Internet
Services and Applications, Springer, 2010.
[EMAN-WG] "IETF Energy Management Working Group", 2012,
<https://datatracker.ietf.org/wg/eman/>.
[Epps06] Epps, G. and et al. , "System Power Challenges", 2006,
<http://www.slidefinder.net/c/cisco routing research/ seminar
august 29/1562106>.
[Fisher10] Fisher, W. and et al. , "Greening Backbone Networks:
Reducing Energy Consumption by Shutting Off Cables in Bundled
Links", Green Networking 2010.
[GreenTE] Zhang, M. and et al. , "GreenTE: Power-Aware Traffic
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Engineering", ICNP 2010.
[Gupta03] Gupta, M. and S. Singh, "Greening the Internet", ACM
SIGCOMM 2003.
[Heddeghem12] Van Heddeghem, W. and F. Idzikowski, "Equipment power
consumption in optical multilayer networks - source data", IBCN
Technical Report 2012.
[Nakamura07] Nakamura, M., "Advanced photonic technologies for the
information era", Nature Photonics Technology conference, 2007.
[Nedevschi08] Nedevschi, S. and et al. , "Reducing Network Energy
Consumption via Sleeping and Rate- Adaptation", USENIX NSDI 2008.
[PCE-WG] "IETF Path Computation Element Working Group", 2012,
<https://datatracker.ietf.org/wg/pce/>.
[Pileri07] Pileri, S., "Energy and communication: engine of the human
progress", 2007.
[TM] Roughan, M., Thorup, M., and Y. Zhang, "Traffic Engineering with
Estimated Traffic Matrices", IMC 2003.
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Authors' Addresses
Beichuan Zhang
Univ. of Arizona
Email: bzhang@cs.arizona.edu
Junxiao Shi
Univ. of Arizona
Email: shijunxiao@cs.arizona.edu
Jie Dong
Huawei
Email: jie.dong@huawei.com
Mingui Zhang
Huawei
Email: zhangmingui@huawei.com
Mohamed Boucadair
France Telecom
Email: mohamed.boucadair@orange.com
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