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Energy Consumption Anatomy of 802.11 Devices and its Implication on Modeling and Design
Get PDFA thorough understanding of the power consumption behavior
of real world wireless devices is of paramount importance
to ground energy-efficient protocols and optimizations on realistic and accurate energy models. This paper provides an
in-depth experimental investigation of the per-frame energy
consumption components in 802.11 Wireless LAN devices.To the best of our knowledge, our measurements are the first to unveil that a substantial fraction of energy consumption, hereafter descriptively named cross-factor, may be ascribed to each individual frame while it crosses the protocol/implementation stack (OS, driver, NIC). Our findings, summarized in a convenient new energy consumption model, contrast traditional models which either neglect or amortize such energy cost component in a fixed baseline cost, and raise the alert that, in some cases, conclusions drawn using traditional energy models may be fallacious.TRUEpu
Failure Detectors in Homonymous Distributed Systems (with an Application to Consensus)
Get PDFAlso in: XX Jornadas de Concurrencia y Sistemas Distribuidos, JCSD 2012, 13-15 June 2012, Pamplona, Spain.This paper is on homonymous distributed systems where processes are prone to crash failures and have no initial knowledge of the system membership (“homonymous” means that several processes may have the same identifier). New classes of failure detectors suited to these systems are first defined. Among them, the classes HΩ and HΣ are introduced that are the homonymous counterparts of the classes Ω and Σ, respectively. (Recall that the pair hΩ,Σi defines the weakest failure detector to solve consensus.) Then, the paper shows how HΩ and HΣ can be implemented in homonymous systems without membership knowledge (under different synchrony requirements). Finally, two algorithms are presented that use these failure detectors to solve consensus in homonymous asynchronous systems where there is no initial knowledge of the membership. One algorithm solves consensus with hHΩ, HΣi, while the other uses only HΩ, but needs a majority of correct processes.
Observe that the systems with unique identifiers and anonymous systems are extreme cases of homonymous systems
from which follows that all these results also apply to these systems. Interestingly, the new failure detector class HΩ can be implemented with partial synchrony, while the analogous class AΩ defined for anonymous systems can not be implemented(even in synchronous systems). Hence, the paper provides us with the first proof showing that consensus can be solved in anonymous systems with only partial synchrony (and a majority of correct processes).TRUEpu
Ghost Domain Names: Revoked Yet Still Resolvable
Get PDFAttackers often use domain names for various malicious
purposes such as phishing, botnet command and control, and malware propagation. An obvious strategy for preventing these activities is deleting the malicious domain from the upper level DNS servers. In this paper, we show that this is insufficient. We demonstrate a vulnerability affecting the large majority of popular DNS implementations which allows a malicious domain name to stay resolvable long after it has been removed from the upper level servers. Our experiments with 19,045 open DNS servers show that even one week after a domain name has been revoked and its TTL expired, more than 70% of the servers will still resolve it. Finally, we discuss several strategies to prevent this attack.TRUEpu
Loop-free convergence using oFIB
Get PDFOFIB: With link-state protocols, such as IS-IS and OSPF, each time the network topology changes, some routers need to modify their forwarding information base (FIB) to take into account the new topology. Each topology change causes a convergence phase. During this phase, routers may transiently have inconsistent FIBs, which may lead to packet loops and losses, even if the reachability of the destinations is not compromised after the topology change. Packet losses and transient loops can also occur in the case of a link down event implied by a maintenance operation, even if this operation is predictable and not urgent.
The goal of this work is to define a mechanism that sequences the router FIB updates to maintain consistency throughout the network. By correctly setting the FIB change order no looping or packet loss can occur. This mechanism may be applied to the case of managed link-state changes, i.e. link metric change, manual link down/up, manual router down/up, and managed state changes of a set of links attached to one router.This document describes a mechanism for use in conjunction with link state routing protocols which prevents the transient loops which would otherwise occur during topology changes. It does this by correctly sequencing the forwarding information base (FIB) updates on the routers.
This mechanism can be used in the case of non-urgent link or node shutdowns and restarts or link metric changes. It can also be used in conjunction with a fast re-route mechanism which converts a sudden link or node failure into a non-urgent topology change. This is possible where a complete repair path is provided for all affected destinations.
After a non-urgent topology change, each router computes a rank that defines the time at which it can safely update its FIB. A method for accelerating this loop-free convergence process by the use of completion messages is also described.
The technology described in this document has been subject to extensive simulation using real network topologies and costs, and pathological convergence behaviour.Internet Engineering Task Force (IEFT)pu
TREND: Toward Real Energy-efficient Network Design
Get PDFThis paper briefly describes the objectives of the
TREND (Toward Real Energy-efficient Network Design)
Network of Excellence of the European Commission 7th
Framework Programme, and outlines some of the main results
obtained so far within the project, looking at wireless access networks, core networks, and content distribution issues.TRUEpu
Virtual lifeline: Multimodal sensor data fusion for robust navigation in unknown environments
Get PDFWe present a novel, multimodal indoor navigation technique that combines pedestrian dead reckoning (PDR) with relative position information from wireless sensor nodes. It is motivated by emergency response scenarios where no fixed or pre-deployed global positioning infrastructure is available and where typical motion patterns defeat standard
PDR systems. We use RF and ultrasound beacons to periodically re-align the PDR system and reduce the impact of incremental error accumulation. Unlike previous work on
multimodal positioning, we allow the beacons to be dynamically deployed (dropped by the user) at previously unknown locations. A key contribution of this paper is to show that despite the fact that the beacon locations are not known (in terms of absolute coordinates), they significantly improve the performance of the system. This effect is especially relevant when a user re-traces (parts of) the path he or she had previously traveled or lingers and moves around in an irregular pattern at single locations for extended periods of time. Both situations are common and relevant for emergency response scenarios. We describe the system architecture, the fusion algorithms and provide an in depth evaluation in a large scale, realistic experiment.TRUEpu
Complexity aided design - The FuturICT technological innovation paradigm
Get PDFIn the next century, planet earth will don an electronic skin. It will use the Internet as a scaffold to support and transmit its sensations. This skin is already being stitched together. It consists of millions of embedded electronic measuring devices: thermostats, pressure gauges, pollution detectors, cameras, microphones, glucose sensors, EKGs, electroencephalographs. These will probe and monitor cities and endangered species, the atmosphere, our ships, highways and fleets of trucks, our conversations, our bodies–even our dreams ....What will the earth’s new skin permit us to feel? How will we use its surges of sensation? For several years–maybe for a decade–there will be no central nervous system to manage this vast signaling network. Certainly there will be no central intelligence...some qualities of self-awareness will emerge once the Net is sensually enhanced. Sensuality is only one force pushing the Net toward intelligence”.
These statements are quoted by an interview by Cherry Murray, Dean of the Harvard School of Engineering and Applied Sciences and Professor of Physics. It is interesting to outline the timeliness and highly predicting power of these statements. In particular, we would like to point to the relevance of the question “What will the earth’s new skin permit us to feel?” to the work we are going to discuss in this paper. There are many additional compelling questions, as for example: “How can the electronic earth’s skin be made more resilient?”; “How can the earth’s electronic skin be improved to better satisfy the need of our society?”;“What can the science of complex systems contribute to this endeavour?”TRUEpu
Balancing energy efficiency and throughput fairness in IEEE 802.11 WLANs
Get PDFThe proliferation of wireless networks based on IEEE 802.11 has resulted in a heterogenous set of devices using a variety of applications to compete for the desired service
performance. Most notably, the class of highly mobile and energy constrained devices is showing high growth rates. Yet, fairness of resource allocation is still only considered in terms of achievable throughput and without considering energy efficiency. In this paper we first show that performing an energy efficient and fair resource allocation in current IEEE 802.11 WLANs is challenging, given the diversity of power consumption figures among mobile devices. We then propose a criterion to objectively balance between the most energy-efficient configuration (where all resources are given to one station) and the
throughput-fair allocation (where the power consumption is not considered). We derive a closed-form expression for the optimal configuration of 802.11 with respect to this criterion. Our analysis is validated through simulations, showing that our approach betters the prevalent allocation schemes discussed in literature in terms of energy efficiency, while maintaining the notion of fairness among devices. Experimental results obtained in a real world
testbed confirm the main results derived from our analysis and simulations.TRUEpu