Bolla, Raffaele

Giribaldi, Maurizio

Khan, Rafiullah

Repetto, Matteo

A network connected host is expected to generate/respond to applications and protocols specific messages. Billions of Euro of electricity is wasted to keep idle hosts powered up 24/7 just to maintain network presence. This short paper describes the design of our cooperative Network Connectivity Proxy (NCP) that can impersonate sleeping hosts and responds to packets on their behalf as they were connected and fully operational. Thus, NCP is in fact an efficient approach to reduce network energy waste

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Cooperative Proxying: An Approach to Reduce Network EnergyWasteBolla, R., Giribaldi, M., Khan, R., & Repetto, M. (2013). Cooperative Proxying: An Approach to Reduce NetworkEnergy Waste. IEEE INFOCOM 2013, Turin, Italy.Document Version:Peer reviewed versionQueen's University Belfast - Research Portal:Link to publication record in Queen's University Belfast Research PortalPublisher rights© 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or futuremedia, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale orredistribution to servers or lists, or reuse of any copyrighted component of this work in other works.General rightsCopyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or othercopyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associatedwith these rights.Take down policyThe Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made toensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in theResearch Portal that you believe breaches copyright or violates any law, please contact openaccess@qub.ac.uk.Download date:15. Feb. 2017Cooperative Proxying: An Approach to ReduceNetwork Energy WasteRaffaele Bolla∗ , Maurizio Giribaldi† , Rafiullah Khan∗ and Matteo Repetto‡∗ DITEN Dept. University of Genova (UNIGE), 16145 Genova, Italy, Email:{raffaele.bolla, rafiullah.khan}@unige.it† Infocom s.r.l, P.zza Alessi 2/7, 16128 Genova, Italy, Email: maurizio.giribaldi@infocomgenova.it‡ CNIT, Research Unit of University of Genova, 16145 Genova, Italy, Email: matteo.repetto@cnit.itAbstract—A network connected host is expected to gener-ate/respond to applications and protocols specific messages.Billions of Euro of electricity is wasted to keep idle hosts poweredup 24/7 just to maintain network presence. This short paperdescribes the design of our cooperative Network ConnectivityProxy (NCP) that can impersonate sleeping hosts and respondsto packets on their behalf as they were connected and fullyoperational. Thus, NCP is in fact an efficient approach to reducenetwork energy waste.Index Terms—Green networking, energy efficiency, networkconnectivity proxy, power measurement.I. INTRODUCTIONLow-power states are effective mechanisms for reducingnetwork energy waste by PCs but their use is hindered justbecause of the need to maintain network presence [1]. A low-power entity called "Network Connectivity Proxy" (NCP) canbe designed that impersonates the hosts during idle periodsand allows them to sleep [2]. It hides sleep state of coveredhosts and make them appear as fully operational and connected[3]. The NCP maintains host’s: (i) Link Layer Presence e.g.,responding to ARP requests, (ii) Network Layer Presence byimpersonating its IP addresses through gratuitous ARP andreplying to network presence and management packets e.g.,ICMP ping, DHCP etc, (iii) Application Layer Presence byresponding to routine application messages.Hosts should register their desired behaviors for differentapplications, protocols and packet types at the NCP beforeentering into sleeping state. The NCP then starts interceptingnetwork traffic addressed to sleeping hosts and takes appropri-ate actions [4]. It wakes up the hosts only when their resourcesare required e.g., a new TCP connection attempt. Moreover,the NCP could buffer packets to give enough time to the hoststo restore their full power state and to avoid packet loss. Thisshort paper briefly presents the NCP architecture and mainfunctionality of different components.II. DESIGN OF NETWORK CONNECTIVITY PROXYThe NCP service has three basic requirements: (i) Aware-ness of host’s power state, (ii) Ability to sniff and processpackets addressed to sleeping hosts and (iii) Knowledge aboutthe host’s registered rules. The generic reference architectureof the NCP is depicted in Fig. 1. The NCP provides a set ofrules that hosts can register. Rules specify actions for eachreceived packet e.g., direct respond, discard, buffer, wake up- Packet Sniffing- Packet Inspection (header & pattern matching)-Send reply packets- Wake-up host-- Send periodic packetsPacket FilteringPacket Processing- Registered Rules- Power StateHost 1- Registered Rules- Power StateHost 2- Registered Rules- Power StateHost NFigure 1. A generic NCP architecture.sleeping host etc. The NCP activates the rules once the hostswitches to a low power mode and deactivates them when itwakes-up. The packet filtering block is responsible to sniffand identify packets addressed to the sleeping hosts based onheader information (e.g., source and destination IP and portnumbers, protocol-specific flags and packet content patternmatching). The packet processing block performs specific ac-tions for each received packet based on the rules registered bysleeping host. The NCP design has three main requisites: rulesstructure, traffic diversion and packet classification engines.A. Rules StructureNCP rules can be classified into (i) Network connectivity:protocols that maintain host presence e.g, responding to ARPand ping requests, DHCP lease renewal etc, (ii) Packet man-agement: dealing with packets that require some response fromthe host, (iii) Heart-beating: sending periodic messages just torefresh some information e.g., keeping alive a TCP connection,keeping active a soft state, etc.Each rule is composed of four parts: host identification,power state, filter specification and an action. UniversallyUnique Identifier (UUID) is a better choice for host iden-tification instead of IP/MAC address as hosts may havemultiple NICs. The power state indicates when a rule shouldbe activated. The filter identifies the packets, based on theirheader and/or data fields, for which the rule applies. It consistsof a set of conditions which may be based on IP address, portnumber, network protocol, payload pattern etc. Finally, theaction specifies the NCP behavior when a packet matches thefilter specification.2Table ISUMMARY OF BASIC NCP RULES.ARPPingDHCPWoCWoPSRoPTypeNetwork Connectivity X X XPacket Management X X XHeat-beating XAction Wake-up the host X XSend predefined packet XBuild packet X X XBuild packet by templateNCP actions can be classified into four types: (i) Wake-up the host: when connection attempt at specific protocol andport is received (Wake on Connection (WoC)) or when receivedpacket matches specific pattern (Wake on Packet (WoP)). (ii)Send predefined packets: send a given reply when receivedpacket matches specific pattern (Send Reply on Packet (SRoP)).Hosts create the reply packets in advance and load themat NCP during rule registration. (iii) Building packets: theNCP creates reply packet on its own. (iv) Building packetsby templates: the NCP builds packets starting from templatessupplied by hosts. Table I shows the basic rules our NCPdesign provides so far.B. Traffic DiversionA basic prerequisite for NCP operation is the capabilityof getting traffic addressed to sleeping hosts. This obviouslyhappens if the NCP lays on the path between each of its clientdevices and all of their peers, but this is not always feasible andalso filtering could slow down packet forwarding operations ifthe traffic volume is high. Thus, traffic diversion mechanism isnecessary to redirect traffic addressed to sleeping hosts towardsthe NCP.Traffic diversion in local networks implies binding theNCP’s MAC address to the IP addresses of sleeping hosts.Thus, the NCP’s MAC replaces host’s MAC when the hosttransition into sleep state and host’s MAC is brought backwhen it wakes up. This job is accomplished by using "Gra-tuitous ARP", an unsolicited ARP message that holds the IPaddress and its associated MAC address. The gratuitous ARPenables the NCP to (i) answer ARP requests on behalf ofsleeping hosts providing its own MAC address, (ii) updateARP caches of local hosts when its clients enter or exit thelow-power mode to avoid sending packets to obsolete MACaddresses in caches.C. Packet Filtering/ClassificationPacket classification is the task of filtering and inspectingpackets in order to pick up those matching any of the currentlyregistered active rules. It turns out to be a critical task whenthe traffic load is high compared to the processing powerof the device hosting the NCP service. These issues can beovercome by: (i) limiting the traffic load (handle only trafficthat is addressed to sleeping hosts), (ii) using hardware basedpacket classification.Software classification engines e.g., Berkeley Packet Filters,RF_RING, Pcap libraries etc. are flexible, portable and cost-effective solutions under low traffic load. However, hardwareTable IIANNUAL SAVINGS WORLD-WIDE.World-wide SavingsTWh/year Billion Euro/yearAlways ON Sleep when idle Always ON Sleep when idleDesktop Computers 329.84 94.34 72.56 20.76Laptops 20.26 6.19 4.46 1.36packet classifiers e.g., TCAM based classifiers come withseveral benefits: performance improvement, scalability andadditional power savings. Packet classification is usually basedon simple logical structures (decision trees, finite state ma-chines) which are easy to realize in hardware. The CPU canthus run in low power modes until packets matching any ruleare found.III. EXPECTED ENERGY SAVINGSTable II forecasts the global energy savings if NCP wasfully deployed considering 815 million desktop PCs and 164million laptops connected to the Internet. It uses the defaultdata from Energy Star office equipment calculator that usesabout 6.5 hours/day as average PCs usage and 17.5 hours asidle period. Thus, the global energy savings will account toalmost 250 TWh annually. Similarly, considering 22 cent/kWhas the average electricity cost in Europe, the NCP has potentialto provide almost 55 Billion Euro savings annually.IV. CONCLUSIONSThe NCP is a quite useful approach that maintains thevirtual presence of network hosts and allows them to sleepduring idle periods. This short paper has addressed the genericNCP requirements, its basic functionalities and a referencearchitecture. It briefly presents our NCP design and focuseson three main components: rules structure, traffic diversionand packet classification engines. The NCP has potential toprovide about 60% network energy savings depending on thehosts time usage model.ACKNOWLEDGMENTSThis work was partially supported by the European Com-mission in the framework of the FP7 ECONET (low EnergyCOnsumption NETworks) project (contract no. INFSO-ICT-258454).REFERENCES[1] R. Khan, R. Bolla, M. Repetto, R. Bruschi, and M. Giribaldi, “SmartProxying for Reducing Network Energy Consumption,” in IEEE In-ternational Symposium on Performance Evaluation of Computer andTelecommunication Systems (SPECTS), July 2012.[2] K. Christensen, P. Gunaratne, B. Nordman, and A. George, “The NextFrontier for Communications Networks: Power Management,” in Com-puter Communications, Vol. 27, No. 18, pp. 1758-1770, Dec. 2004.[3] M. Jimeno, K. Christensen, and B. Nordman, “A Network ConnectionProxy to Enable Hosts to Sleep and Save Energy,” in IEEE InternationalConference on Performance, Computing and Communications Conference(IPCCC), Dec. 2008.[4] R. Khan, R. Bolla, and M. Repetto, “Design of UPnP based Coopera-tive Network Connectivity Proxy,” in The Second IFIP Conference onSustainable Internet and ICT for Sustainability (SustainIT 2012), Oct.2012.

Cooperative Proxying: An Approach to Reduce Network Energy Waste

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