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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (October 15, 2013) is 3133 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'EMAN-WG' is defined on line 295, but no explicit reference was found in the text == Unused Reference: 'TM' is defined on line 326, but no explicit reference was found in the text Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force B. Zhang 3 Internet-Draft J. Shi 4 Intended status: Informational Univ. of Arizona 5 Expires: April 18, 2014 J. Dong 6 M. Zhang 7 Huawei 8 M. Boucadair 9 France Telecom 10 October 15, 2013 12 Power-Aware Networks (PANET): Problem Statement 13 draft-zhang-panet-problem-statement-03 15 Abstract 17 Energy consumption of network infrastructures is growing fast due to 18 exponential growth of data traffic and the deployment of increasingly 19 powerful equipment. There are emerging needs for power-aware routing 20 and traffic engineering, which adapt routing paths to traffic load in 21 order to reduce energy consumption network-wide. This document 22 outlines the design space and problem areas for potential IETF work. 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on August 29, 2013. 41 Copyright Notice 43 Copyright (c) 2013 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Motivation and Problem Scope . . . . . . . . . . . . . . . . . 3 60 3. Potential Solution Approaches . . . . . . . . . . . . . . . . 4 61 4. Problem Areas for IETF . . . . . . . . . . . . . . . . . . . . 6 62 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 63 6. Informative References . . . . . . . . . . . . . . . . . . . . 7 64 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 66 1. Introduction 68 Driven by exponential growth of Internet traffic, networks worldwide 69 are expanding their infrastructures at a fast pace by deploying more 70 high-capacity, power-hungry routers, which also leads to increasing 71 energy consumption. For example, in the US, the energy bill for 72 powering the wired network reaches up to 2.4 billion dollars per year 73 [Doverspike10]. Telecom Italia, the largest ISP in Italy, is now the 74 second largest consumer of electricity after the National Railway 75 system [Pileri07]. As one of the biggest energy consumers in the 76 United Kingdom, British Telecom consumed about 0.7% of the entire 77 nation's electricity in 2007 [Bolla11]. In Japan, predictions say 78 that routers will consume 9% of the total electricity by 2015 79 [Nakamura07]. Besides operational costs and environmental impacts, 80 the ever-increasing energy consumption has become a limiting factor 81 to long-term growth of network infrastructure due to challenges in 82 power delivery and heat removal for both router components and 83 hosting facilities [Gupta03] [Epps06]. 85 Traditionally energy efficiency is improved at the device level or 86 the link level. For example, energy management techniques can be 87 applied to adjust router CPU's power status or CPU frequency in 88 response to different CPU workload; Links can be put to sleep mode 89 when it has been idle for a while. More recently, there have been a 90 number of research work that look beyond a single router or linecard 91 for network-wide solutions towards energy proportionality. 93 The purpose of this document is to discuss the problem scope, outline 94 potential approaches, and problem areas for IETF work on power-aware 95 networks. 97 2. Motivation and Problem Scope 99 Today's ISP networks have redundant routers and links, over- 100 provisioned link capacity, and load-balancing traffic engineering. As 101 a result, routers and links operate at full capacity all the time 102 with low average usage, typically less than 40% of link utilization. 103 This practice makes networks resilient to traffic spikes and 104 component failures, but also makes networks far from energy- 105 efficient. 107 Power-aware routing and traffic engineering have been proposed to 108 improve network's energy efficiency, for example, by aggregating 109 traffic onto a subset of links and putting other links with no 110 traffic into sleep. Data from various sources (e.g., [Heddeghem12] 111 [Chabarek08]) have shown that line cards are a significant source of 112 router's power consumption, accounting for 40% - 70% of total power 113 consumption. Most of the energy is consumed even in standby state, 114 and forwarding packets at full speed only increases the energy 115 consumption by a small percentage. This implies that being able to 116 put links into sleep mode can potentially save a lot of energy. In 117 face, this has been demonstrated in several research works such as 118 [GreenTE] [Nedevschi08] [Chabarek08]. 120 Designing practical protocols, however, has been challenging, because 121 making routing protocols power-aware brings significant changes to 122 the routing system and the entire network, thus it involves hardware 123 support, protocol design, network monitoring, and operational 124 practices. These issues often depend on the specific network 125 environments under discussion. In order to focus on protocol-related 126 issues, we suggest that as the first step we limit the scope of the 127 discussion to intra-domain routing within one administrative domain, 128 to avoid inter-domain policy issues. This includes transit networks 129 as well as edge networks. We leave data center networks out of this 130 draft since that usually requires concerted efforts beyond network 131 protocols. 133 3. Potential Solution Approaches 135 The high-level idea of power-aware networks is to adjust routing 136 paths based on traffic level. When traffic level is high, use more 137 links to carry the traffic; when traffic level is low, merge traffic 138 onto a subset of all links so that other links can be put to sleep or 139 reduce rate in order to save power. This needs to be done without 140 significantly impacting network QoS, network resiliency, and 141 interoperation with other protocols. 143 In the last few years a number of power-aware network designs have 144 emerged. Instead of listing them individually, here we categorize 145 the solutions along three different dimensions. 147 Link Sleep vs. Rate Adaptation 149 Sleeping and rate adaptation are two major ways to save energy in 150 computer systems. Many hardware, including line cards and chassises, 151 consumes a significant amount of power when they stand by without 152 doing any actual work. When put into sleep mode, they will consume 153 only a little power. Thus putting an idle component to sleep is a 154 common way to save energy. If there is a need to use this component, 155 it can be waken up and become usable after a transition time. The 156 longer a component is in sleep mode, the more power saved. A power- 157 aware protocol adjusts routing paths to increase the sleep time for 158 certain links in the network. 160 A network interface often supports multiple data rates. Operating at 161 a lower data rate usually consumes less energy, though the actual 162 rate-power curve varies from device to device. Rate-adaptation-based 163 approaches operate interfaces at lower data rates when the traffic 164 demand is low and increase the data rate when traffic demand is high. 165 Thus the routers can save power during low utilization period. 167 These two approaches are also related in the case of "bundled links" 168 [Fisher10]. A bundled link is a virtual link comprised of multiple 169 physical links. A sleep-based approach can put some physical links 170 into sleep to save power, which is same as conducting rate adaptation 171 on the virtual link with adjustment unit of a physical link. 173 Configured vs. Adaptive 175 The key in power-aware routing and traffic engineering is to adjust 176 routing paths in response to traffic changes, so that the power state 177 of routers (or router components) will also change accordingly to 178 achieve energy saving. Different approaches differ at the 179 granularity of the adjustment. 181 Some approaches take the long-term traffic average as input, and 182 output a routing configuration that is applied to the network 183 regardless of short-term traffic variation. This is mostly useful 184 when network traffic exhibits a stable, clear pattern, e.g., diurnal 185 pattern where traffic is high during work hours and low during off 186 hours. It can only exploit the target traffic pattern; it cannot 187 react dynamically to short-term traffic changes to either save energy 188 (by putting links to sleep) or avoid congestion (by waking links up), 189 but the design and implementation should be simple. 191 Another type of approach is to adapt to traffic changes dynamically 192 on much smaller time granularity. This approach may be able to save 193 more energy and have better performance because it is more 194 responsive, but the design and implementation usually are more 195 complicated. This approach needs to continuously collect traffic 196 data in order to adjust routing dynamically. The adjustment may be 197 done periodically or whenever significant traffic changes are 198 observed. 200 Distributed vs. Centralized 202 In distributed solutions, routers make power-aware adjustment 203 decisions, such as link sleep/wake-up and rate increase/decrease, 204 locally without a central controller. These routers need to exchange 205 information in order to achieve consistent network states. 206 Distributed approach fits the Internet operation model well but its 207 design is the most challenging. Traditional routing does not respond 208 to traffic variation while power-aware routing does, and it needs to 209 do so without causing loops or congestions. 211 In centralized solutions, a controller computes the routing paths 212 considering the network topology and traffic demand, and informs 213 routers how to adjust their routing paths. A centralized server 214 usually has more complete information, more computation power, and 215 more memory and storage than routers, thus it may make better 216 decisions than distributed approach. The server locates in the 217 network NOC and can be backed up by server replicas. Nevertheless, 218 this approach requires high reliability of the server. 220 Both distributed and centralized solutions may find their places in 221 ISP networks. For example, centralized solution can be integrated 222 into the Path Computation Element (PCE) framework [PCE-WG]. There 223 can also be hybrid designs, e.g., using a centralized solution based 224 on long-term traffic pattern, and distributed mechanisms to handle 225 short-term traffic variations. 227 4. Problem Areas for IETF 229 Power-aware networks have great potentials to improve network energy 230 efficiency while maintaining network services at desired levels. Its 231 effectiveness, however, depends on various supports from hardware and 232 software, especially protocol designs that address operational 233 issues. In this section we list a few problem areas that will 234 benefit from additional input from the IETF community, or have the 235 potential to become work items in related IETF working groups. 237 Motivation and Problem Scope 239 o What are the motivations for Power-Aware Networking (PANET)? 241 o To what extent power consumption is a key factor for Internet 242 scaling? 244 o To what extent power-aware system at router level and link level 245 are not sufficient to reduce the overall energy consumption of 246 networks? 248 Technical Development 250 o What are the technical requirements for an efficient PANET 251 solution? 253 o What are the technical tracks to reduce the overall power 254 consumption at the level of an IP network? 256 o How protocols can be designed to be power-aware and still maintain 257 enough network resiliency? 259 o What are the technical challenges for deploying efficient PANET 260 solutions? 262 o How routing protocols (e.g., OSPF) can be extended to disseminate 263 power-related information? 265 o How PCE architecture can be used to compute power-aware paths? 267 o How PANET can be deployed in centralized or in distributed model? 269 Operation Practice 271 o What will be the impacts of PANET to network operations? 273 o What will be the guidelines for deploying PANET systems? 275 5. Security Considerations 277 This draft is a discussion on the Internet's necessity to follow an 278 evolutionary path towards the future. There is no direct impact on 279 the Internet security. 281 6. Informative References 283 [Bolla11] Bolla, R. and et al. , "Energy Efficiency in the Future 284 Internet: A Survey of Existing Approaches and Trends in Energy- 285 Aware Fixed Network Infrastructures", IEEE Communications Surveys 286 and Tutorials, 2011. 288 [Chabarek08] Chabarek, J. and et al. , "Power Awareness in Network 289 Design and Routing", IEEE INFOCOM 2008. 291 [Doverspike10] Doverspike, R., Ramakrishnan, K., and C. Chas, 292 "Structural overview of ISP networks", Guide to Reliable Internet 293 Services and Applications, Springer, 2010. 295 [EMAN-WG] "IETF Energy Management Working Group", 2012, 296 . 298 [Epps06] Epps, G. and et al. , "System Power Challenges", 2006, 299 . 302 [Fisher10] Fisher, W. and et al. , "Greening Backbone Networks: 303 Reducing Energy Consumption by Shutting Off Cables in Bundled 304 Links", Green Networking 2010. 306 [GreenTE] Zhang, M. and et al. , "GreenTE: Power-Aware Traffic 307 Engineering", ICNP 2010. 309 [Gupta03] Gupta, M. and S. Singh, "Greening the Internet", ACM 310 SIGCOMM 2003. 312 [Heddeghem12] Van Heddeghem, W. and F. Idzikowski, "Equipment power 313 consumption in optical multilayer networks - source data", IBCN 314 Technical Report 2012. 315 [Nakamura07] Nakamura, M., "Advanced photonic technologies for the 316 information era", Nature Photonics Technology conference, 2007. 318 [Nedevschi08] Nedevschi, S. and et al. , "Reducing Network Energy 319 Consumption via Sleeping and Rate- Adaptation", USENIX NSDI 2008. 320 [PCE-WG] "IETF Path Computation Element Working Group", 2012, 321 . 323 [Pileri07] Pileri, S., "Energy and communication: engine of the human 324 progress", 2007. 326 [TM] Roughan, M., Thorup, M., and Y. Zhang, "Traffic Engineering with 327 Estimated Traffic Matrices", IMC 2003. 329 Authors' Addresses 331 Beichuan Zhang 332 Univ. of Arizona 334 Email: bzhang@cs.arizona.edu 336 Junxiao Shi 337 Univ. of Arizona 339 Email: shijunxiao@cs.arizona.edu 341 Jie Dong 342 Huawei 344 Email: jie.dong@huawei.com 346 Mingui Zhang 347 Huawei 349 Email: zhangmingui@huawei.com 351 Mohamed Boucadair 352 France Telecom 354 Email: mohamed.boucadair@orange.com