Stevens Le Blond
Word count: 1600/PIN: 10405 For a Sustainable Internet 1
Stevens Le Blond
Introduction
In 2008, the Internet accounted 1.5 billion users world-wide and the U.S. e-commerce reached $204 billion. In addition, since the creation of the World Wide Web in 1990, the number of Internet users has increased exponentially each year and one human being on two should be connected by 2030 [2]. Today, the Internet is even considered as an application of the human right to education, as illustrated by the recent rejection of the 3-strikes law by the European parliament [5]. However, the Internet is still an infant and a very energy-hungry one. The Internet comprises routing devices, e.g., routers, that are hosted by Internet Service Providers and shared to allow communication across user computing devices, e.g., desktops. Imagine the past 3,000 years as a 60-minutes clock and the Internet becomes 30-seconds old, with the same potential for change than a newborn. In 2000, the electricity needed by the Internet routing devices alone was estimated to 144 TWh per year; this amount of energy is equivalent to the one produced by 9 nuclear power plants, and costs $6 billion [6]. The main problem with current routing devices is that they are powered 24/7 and do not support various energy saving states when idle, unlike other devices like monitors. In fact, idling routing devices consume as much as 80% of their energetic capacity [7]. This is an undesirable property for an infrastructure that spans the planet and also targets countries where energy is scarce. This situation has come to the attention of Cisco, the world-leading manufacturer of routing devices, that attributed its first I-Prize of $250, 000 to the “smart grid” idea in year 2008 [3]. The idea is to let the routing devices request the power that they need from a power grid instead of passively consuming it. Cisco declared that the idea had the potential for $1 billion in revenue over 5 − 7 years. With a giant like Cisco supporting the smart grid idea, routing devices should soon con1
Stevens Le Blond
sume an amount of energy that is proportional to their load [1], as Google also makes the case for other computing devices [8]. The principle for the devices to consume an amount of energy that is proportional to their load is called energyproportional computing. In this essay, we project ourselves in a near future where routing devices respect the principle of energy-proportional computing and we seek to offload routers to save energy. We argue that data-centric networking [9], i.e., structuring the communication around data, can save energy by preferring close-by data over far-away data, hence reducing the number of intermediate routing devices involved in the transfer. Data-centric networking is a recent trend in networking research which says that our utilization of the network today greatly differs from its original design. Indeed, whereas the first computer networks allowed multiple users to share expensive physical resources such as processing power or a printer, what we really care about today is to move data around. Peer-to-Peer (P2P) filesharing systems, e.g., eMule or BitTorrent, are popular examples of data-centric networking; instead of transferring data from a predetermined computing device (server), data can be transferred from any peer that hosts it. Hence, it is possible to offload routing devices by transferring data among close-by peers, i.e., few routing devices apart, instead of between computing devices and servers that are far away, i.e., many routing devices apart, from each others. As P2P traffic represents more than 50% of the total traffic of the Internet in year 2009 [4], we believe that data-centric networking has a great potential to appease the energy hunger of the Internet. The problem though, is that current P2P applications do not differentiate between close-by and far-away peers when transferring data hence, they do not exploit the energy-saving properties of data-centric networking. Our main contributions are the following. 1) We describe how BitTorrent could favor transfers among close-by peers, instead of far-away ones, to offload routing devices and save energy. 2) We propose a simple metric to evaluate the potential of an energy-aware BitTorrent to save energy and show that it could save a significant fraction of Internet traffic, i.e., 4.7 petabytes (1015 ). 2
Global Initiatives Symposium in Taiwan 2009
3) We discuss the impact that energy savings could have on the Internet ecosystem and the new business opportunities it could trigger
2
Making BitTorrent Energy-aware
As of April 1st 2009, the Internet is composed of 22, 319 registered administrative domains with, in each one, some routing devices that forward data among neighbor domains. For historical reasons, most administrative domains, or Autonomous Systems (ASes), belong to a national telecom operator and lies within the same country or geographical area. Hence, the data that stays within an AS crosses fewer routing devices than the data that traverses multiple ASes. In the following, we consider an AS as a logical unit in which data transfers cost little energy. Today, P2P filesharing applications that generate the majority of Internet traffic are AS-agnostic. In BitTorrent, for instance, peers randomly transfer data among each others, i.e., do not prefer peers in the same AS, resulting in orders of magnitude more inter-AS traffic than with an AS-aware BitTorrent [10]. As we have defined an AS as a unit in which traffic costs little energy, reducing inter-AS traffic is qualitatively equivalent to reducing energy consumption. Hereafter, we use the inter-AS traffic as a indication of the amount of energy that is saved. Making BitTorrent AS-aware, i.e., energy-aware, merely requires a few changes to the BitTorrent software. Namely, it requires the peers to know their AS Number (ASN), a public information, and to transfer data with those peers that have the same ASN. Although this mechanism is straightforward, the benefit is not clear as it would require many peers per AS transferring the same data to save energy; this is an open research question. In the next section, we shade an optimistic light on this question.
3
Towards A More Sustainable Internet
Before transferring a datum using BitTorrent, a user must first download a “torrent” file that contains the hostname of a server (tracker) which knows all the peers currently transferring that datum. Hence, to determine the distribution of 3
Find the Next Wave to Ride On - New Business Strategies in the Changing World
Stevens Le Blond
peers per AS for a large number of data, we download 790, 717 torrent files from Mininova.org, the world’s largest torrent files repository. Then, we repeatedly contact the trackers to learn about all the peers transferring these data. In total, we identify 214, 443 active data, i.e., generating traffic, and we learn the distribution of peers per AS for 6, 113, 224 peers. To determine the energy savings of AS-aware BitTorrent, we experiment with a real BitTorrent software on a computational Grid with 1, 604 computing nodes. To do so, we map peers to virtual ASes to respect the distributions of peers per AS that we observed for 12 reference data, and monitor the inter-AS traffic with ASagnostic and AS-aware BitTorrent. We observe that the inter-AS traffic mainly depends on the number of peers per AS for a given datum and derive a analytical model to compute the inter-AS traffic for the 214, 443 active data. We find that AS-agnostic BitTorrent generates 11.6 petabytes of inter-AS traffic as compared to 6.9 petabytes with AS-aware BitTorrent. That is 40% savings of inter-AS traffic.
4
A Glance At New Business Opportunities
The Internet has three main actors: the Internet Service Providers (ISPs), the content provider, and the end-users. As more and more end-users are adopting P2P applications, the costs are rapidly shifting from the content providers to the ISPs. Indeed, as end-users transfer data from each others’ ISPs rather than from content providers, the ISPs’ bandwidth utilization has dramatically increased over the past few years. This situation is undesirable for them as they are billed according the 95-th percentile of the bandwidth utilization on their inter-AS links [11]. A sustainable Internet would be desirable for both content providers and ISPs. The situation would virtually remain unchanged for the content providers however, a sustainable Internet would lower ISPs’ bills by reducing their inter-AS traffic and the operational costs of their routing devices. Maybe the end-users are those who would benefit the most from a sustainable Internet. It would allow them to distribute their own data instead of relying on popular content providers such as Google, MySpace, or FaceBook. Hence, users would finally get the reward for data they have created. 4
Global Initiatives Symposium in Taiwan 2009
References [1] Private communication with David Tsiang, Cisco [2] AMD. http://www.50x15.com/en-us/internet usage.aspx [3] Cisco. http://www.cisco.com/web/solutions/iprize/index.html [4] Ipoque. http://www.ipoque.com/resources/internet-studies/internet-study2008 2009 [5] TorrentFreak. EU rejects “3 strikes” for file-sharers. http://torrentfreak.com/eu-rejects-3-strikes-for-file-sharers-090327/. [6] M. Gupta and S. Singh. Greening the internet. In SIGCOMM, August 25-29 2003. Karlsruhe, Germany. [7] J. Chabareck, J. Sommers, P. Barford, C. Estan, D. Tsiang, and S. Wright. Power awareness in network design and routing. In INFOCOM, April 15-17 2008. Phoenix, AZ, USA. [8] L.A. Barroso and H. H¨olze. The case for energy-proportional computing. Computer, 40(12):33–37, 2007. [9]
A Data-Oriented (and Beyond) Network Architecture T. Koponen, M. Chawla, B.-G. Chun, A. Ermolinskiy, K. H. Kim, S. Shenker, and I. Stoica. In SIGCOMM, August 27-31 2007. Tokyo, Japan.
[10] S. Le Blond, A. Legout, W. Dabbous. Pushing BitTorrent Locality to the Limit. Technical Report, INRIA, Sophia Antipolis, December 2008. [11] A. Odlyzko. Internet Pricing and the history of communications Computer Networks, 36:493-517, 2000.
5
Find the Next Wave to Ride On - New Business Strategies in the Changing World
Stevens Le Blond
Global Initiatives Symposium in Taiwan 2009