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Computers RSS FeedsResource Sharing Problem of Timing Variation-Aware Task Scheduling and Binding in MPSoC - This work addresses the new problem of timing variation-aware (TV) task scheduling and binding (TSB) for multiprocessor system-on-chip (MPSoC) architecture in the system-level design, where tasks have the full flexibilities of resource (i.e. processor) sharing to meet the design constraints. With the timing variation of processors’ clock speed, it has been observed that the consideration of the effect of resource sharing on the resulting performance yield computation is critically important for accurate design space exploration and evaluation in the system-level design. Nevertheless, unfortunately the previous statistical static timing analysis (SSTA) in the system level has never considered the resource sharing in the performance yield computation, or has overly simplified it by employing the gate-level SSTAs. In this work, we overcome this limitation of the previous work. Specifically, under the data of clock speed variation of each processor, we propose an effective techni...Feed Source: comjnl.oxfordjournals.org Implementing a Thermal-Aware Scheduler in Linux Kernel on a Multi-Core Processor -
As power dissipation causes thermal issues in cooling costs, lifetime and reliability, thermal management has become an important issue in today's OS and processor design. Early OS-level thermal management schemes were proposed and evaluated mainly with simulators or analytical models. In this paper, we implement a thermal-aware round-robin scheduling algorithm in the Linux kernel, and compare its performance with the ‘Heat-and-Run’ algorithm and the default Linux baseline scheduler on an Intel Core 2 Duo processor using representative benchmarks from SPEC2000, MiBench and NetBench. Our results indicate that the current Linux scheduler can easily be enhanced with thermal-awareness to show improved performance in terms of both the on-chip temperature condition and application throughput.
... Design of On-Chip Crossbar Network Topology Using Chained Edge Partitioning -
This paper proposes an efficient topology synthesis method for on-chip interconnection network based on crossbar switches. The efficiency of topology synthesis methods is often measured by two metrics—the quality of the synthesized topology and synthesis time. These two metrics are critically determined by the definition of the topology design space and the exploration method. Furthermore, an efficient representing method for the design space is required to tightly link the design space and the exploration method. Even though topology synthesis methods have actively been researched, most of the previous methods were not deep in thought for these factors. Unlike the previous methods, we propose a topology synthesis method with a careful consideration of these factors. Our method efficiently defines the design space by a technique called chained edge partitioning, in conjunction with a representing method for the points in the space, called enhanced restricted growth ... Distributed Hash Table-Based Interrogating-Call Session Control Function Network in the Internet Protocol Multimedia Subsystem for Efficient Query Services -
Internet protocol multimedia subsystem (IMS) is an overlaid infrastructure above the packet-switched domain of the universal mobile telecommunication system core network. IMS enables and enhances real-time multimedia mobile services. IMS signaling and media are separated in IMS. For media session negotiation, two basic procedures in IMS are (i) IMS registration procedure and (ii) IMS incoming call setup procedure. IMS signaling needs to traverse a set of call session control functions (CSCFs), which are proxy-CSCF, interrogating-CSCF (I-CSCF) and serving-CSCF (S-CSCF). However, we observe that I-CSCFs need to query the home subscriber server (HSS) to obtain the name of S-CSCF for each subscriber's request in both the basic procedures. It results in a certain load occuring in the HSS and a certain procedure delay also occurs. Therefore, we employ the distributed hash table (DHT) into IMS to form a DHT-based I-CSCF network. Each I-CSCF in the DHT-based I-CSCF network can share and re... Side-Channel Attack Using Meet-in-the-Middle Technique -
In this paper, we introduce a new side-channel attack using block cipher cryptanalysis named a meet-in-the-middle attack. Using our new side-channel technique we show that advanced encryption standard (AES) with reduced 10 masked rounds is broken, which is faster than the exhaustive key search attack. This implies that one has to mask the entire rounds of the 12-round 192-bit key AES to prevent our attacks. Our result is the first one to analyse AES with reduced 10 masked rounds, while the previous best known side-channel attack is on AES with reduced eight masked rounds.
... Multicast Key Management without Rekeying Processes -
Secure multicast provides efficient delivery which includes an identical data from a source to multiple receivers. A common solution is to apply a symmetric key that is used to encrypt the transmitted data. However, the heavy cost of the rekeying process is the main problem in large and dynamic multicast groups. The tree-based architecture is widely used to reduce the rekeying cost in terms of storage, transmission and computation. However, it usually requires extra overhead to keep key tree balance which is in order to achieve logarithmic rekeying cost. In this paper, we shall propose a new RSA-like multicast key management scheme to solve the rekeying problem. Our protocol applies a star-based architecture to eliminate the rekeying processes and provide the good performance when the membership changes in a multicast group. Furthermore, we also provide an extended multicast scheme, in which we combine public-key and symmetric-key cryptosystems to enhance the performance of multica... Robust Super-Peer-Based P2P File-Sharing Systems -
This paper presents an efficient approach for improving file availability in super-peer-based peer-to-peer (P2P) file-sharing systems. In the super-peer-based P2P file-sharing system, peers are organized into multiple groups. In each group, there is a special peer called super-peer to serve the regular peers within the same group. With this property, the proposed approach utilizes the super-peer to tolerate the departure (failure) of a regular peer in order to protect shared files. Unlike traditional replication-based approaches, the proposed approach keeps track of the file queries in the super-peer to support fault tolerance. The cost of tracking the file queries is much smaller than the cost of replicating the file contents in advance. Furthermore, the proposed approach uses a logical connection technique to consider the departure (failure) of the super-peer. Finally, simulation experiments are performed to quantify the performance and overhead of the proposed approach.
... A Bandwidth-Based Power-Aware Routing Protocol with Low Route Discovery Overhead in Mobile Ad hoc Networks -
In the design of power-aware on-demand routing protocols in mobile ad hoc networks, it must be taken into account that nodes may use a great amount of power to find the desired routing path during the path-discovery phase. In addition, in previous research on power-aware routing protocols, the path bandwidth was often not considered. In this paper, we tackle these issues by proposing a power-aware routing protocol with low route requests (LRR) to find a path with high path bandwidth. By making a low number of routing requests (RREQs), mobile nodes help to broadcast the routing request only when they first receive the routing requests. In addition, based on the receipt of the routing requests from the neighboring nodes, mobile nodes record the location information of its one-hop neighboring nodes. In the path-reply phase, mobile nodes in the found path use the collected location information of their neighbors and our proposed relay model to modify the found path so that the f... Sensornet Protocol Tuning Using Principled Engineering Methods -
Sensornet designers seek to maximize energy efficiency while maintaining acceptable Quality of Service. However, the interactions between multiple tunable protocol parameters and multiple performance metrics are generally complex and unknown, and combinatorial explosion renders impossible any exhaustive search approach. Most work published to date employs seemingly arbitrary choices of protocol parameters, derived by informal judgement and limited trial and error experiments. This lack of rigour may lead to sub-optimal parameter selection and sub-optimal network behaviour, and may mask the real performance differences of dissimilar protocols. We describe a reusable engineering method to address this multi-dimensional optimization problem, based on sound engineering principles widely recognized and applied beyond Computer Science. We provide a mechanism with which to de-risk deployment of sensornets tuned within training environments, and evaluate the robustness of these tunings to ... Protection Against Denial of Service Attacks: A Survey -
Denial of service (DoS) is a prevalent threat in today's networks because DoS attacks are easy to launch, while defending a network resource against them is disproportionately difficult. Despite the extensive research in recent years, DoS attacks continue to harm, as the attackers adapt to the newer protection mechanisms. For this reason, we start our survey with a historical timeline of DoS incidents, where we illustrate the variety of types, targets and motives for such attacks and how they evolved during the last two decades. We then provide an extensive literature review on the existing research on DoS protection with an emphasis on the research of the last years and the most demanding aspects of defence. These include traceback, detection, classification of incoming traffic, response in the presence of an attack and mathematical modelling of attack and defence mechanisms. Our discussion aims to identify the trends in DoS attacks, the weaknesses of protection approaches and the... Management of Server Farms for Performance and Profit -
We examine some of the problems associated with managing a server farm, that is, a collection of servers which are used to provide different types of services to paying customers. The users are charged for the services provided, but are also promised that certain Quality-of-Service (QoS) criteria will be met. Failure to satisfy those QoS undertakings incurs pre-specified penalties. In order to maximize the revenue obtained, the service provider must employ intelligent dynamic policies dealing with server allocation and job admission decisions. A number of such policies are surveyed.
... Energy-Efficient Cloud Computing -
Energy efficiency is increasingly important for future information and communication technologies (ICT), because the increased usage of ICT, together with increasing energy costs and the need to reduce green house gas emissions call for energy-efficient technologies that decrease the overall energy consumption of computation, storage and communications. Cloud computing has recently received considerable attention, as a promising approach for delivering ICT services by improving the utilization of data centre resources. In principle, cloud computing can be an inherently energy-efficient technology for ICT provided that its potential for significant energy savings that have so far focused on hardware aspects, can be fully explored with respect to system operation and networking aspects. Thus this paper, in the context of cloud computing, reviews the usage of methods and technologies currently used for energy-efficient operation of computer hardware and network infrastructure. After s... Adaptive Random Re-Routing for Differentiated QoS in Sensor Networks -
Sensor networks (SNs) consist of spatially distributed sensors which monitor an environment, and which are connected to some sinks or backbone system to which the sensor data is being forwarded. In many cases, the sensor nodes themselves can serve as intermediate nodes for data coming from other nodes, on the way to the sinks. Much of the traffic carried by SNs will originate from routine measurements or observations by sensors that monitor a particular situation, such as the temperature and humidity in a room or the infrared observation of the perimeter of a house, so that the volume of routine traffic resulting from such observations may be quite high. When important and unusual events occur, such as a sudden fire breaking out or the arrival of an intruder, it will be necessary to convey this new information very urgently through the network to a designated set of sink nodes where this information can be processed and dealt with. This paper addresses the important challenge by av... An ID-Based Mutual Authentication and Key Exchange Protocol for Low-Power Mobile Devices -
The identity (ID)-based public-key system using bilinear pairings defined on elliptic curves offers a flexible approach to simplify the certificate management. In 2006, the IEEE P1363.3 committee has defined the ID-based public-key system with bilinear pairings as one of public-key cryptography standards. In this, an authenticated key agreement (AKA) protocol is one important issue that provides mutual authentication and key exchange between two parties. Owing to the fast growth of mobile networks, the computational cost on the client side with low-power computing devices is a critical factor in designing an AKA protocol suited for mobile networks. In this paper, we present an efficient and secure ID-based mutual authentication and key exchange protocol using bilinear pairings. Performance analysis and experimental data are given to demonstrate that our proposed protocol is well suited for a client–server environment with low-power mobile devices. In comparison with the recen... Task Allocation and Optimization of Distributed Embedded Systems with Simulated Annealing and Geometric Programming -
We consider the task model of periodic tasks running on a network of processor nodes connected by a bus based on the time-triggered protocol, an industry-standard bus protocol designed for safety-critical automotive and avionics distributed embedded systems, and present an integrated optimization framework that jointly considers one or more of the following attributes: task-to-processor allocation, task priority assignment, task period assignment and bus access configuration. We adopt a hierarchical optimization framework, where each possible task allocation and priority assignment is treated as one top-level coarse-grained state, which may contain many lower-level fine-grained states defined by different task period assignments and bus access configurations. Simulated annealing is used to explore the top-level states, which calls a geometric programming solver as a subroutine to explore the lower-level states contained within a given top-level state. Performance evaluation shows t... New Benchmarks for Large-Scale Networks with Given Maximum Degree and Diameter -
Large-scale networks have become ubiquitous elements of our society. Modern social networks, supported by communication and travel technology, have grown in size and complexity to unprecedented scales. Computer networks, such as the Internet, have a fundamental impact on commerce, politics and culture. The study of networks is also central in biology, chemistry and other natural sciences. Unifying aspects of these networks are a small maximum degree and a small diameter, which are also shared by many network models, such as small-world networks. Graph theoretical methodologies can be instrumental in the challenging task of predicting, constructing and studying the properties of large-scale networks. This task is now necessitated by the vulnerability of large networks to phenomena such as cross-continental spread of disease and botnets (networks of malware). In this article, we produce the new largest known networks of maximum degree 17 ≤ ≤ 20 and diameter 2 ≤ D... Security Metrics Foundations for Computer Security -
Security has been among top priority in computer information systems for more than a decade. Despite the importance of this area, it is interesting to note that the area still lacks (completeness of) one of its basic elements of scientific arsenal, which is metric. This paper therefore presents the situation in this field by giving an analysis of existing metrics that could serve the above-mentioned purpose. Further, it presents a generic risk management model, and gives an analysis of possibilities for application of these existing metrics to the model. It also introduces new metric elements, where these are lacking. As a result, means are provided that enable evaluation of security in information technology systems in a tangible way. Such an approach is essential for every organization in business areas ranging from economical justifications for new security implementations to customized security services with appropriate service costs calculations, and even development of new bu... Engineering Policy-Based Ubiquitous Systems -
The advent of miniaturized sensors that can be carried on the body or embedded in the environment, together with ubiquitous ‘smartphones’ with various sensors means that ubiquitous computing systems already pervade our lives. However, for them to ‘disappear’ in the background, they need to be adaptive, autonomous and self-managing. We present an architectural model based on policy-based self-managed cells for engineering ubiquitous computing systems, and discuss issues of security and fault management. We indicate the need for learning adaptive behaviour from users and the importance of formal methods within the engineering design process.
... DNA Profiles Link Dope to Its Source - 09 Jul 03
Forensic scientists in the U.S. are applying DNA fingerprinting methods to the cannabis plant. They say the technique, which is being used to create a database of DNA profiles of different marijuana plants, will help them to trace the source of any sample.
'It links everybody together: the user, the distributor, the grower,' says the database's creator, Heather Miller Coyle of the Connecticut State Forensic Science Laboratory in Meriden. 'That's the real intent of it, to show it's not just one guy with a little bag of marijuana, but it's a group of people.'
A method for spotting the tiniest traces of marijuana, based on detecting DNA unique to cannabis chloroplasts, has already been developed in the UK (New Scientist print edition, 07 Aug 1999). B... Mathematics: Does the Proof Stack Up? - by George Szpiro
03 Jul 03
Just under five years ago, Thomas Hales made a startling claim. In an e-mail he sent to dozens of mathematicians, Hales declared that he had used a series of computers to prove an idea that has evaded certain confirmation for 400 years. The subject of his message was Kepler's conjecture, proposed by the German astronomer Johannes Kepler, which states that the densest arrangement of spheres is one in which they are stacked in a pyramid - much the same way as grocers arrange oranges.
Soon after Hales made his announcement, reports of the breakthrough appeared on the front pages of newspapers around the world. But today, Hales's proof remains in limbo. It has been submitted to the prestigious Annals of Mathematics, but... Scientists Discover Planetary System Similar to Our Own -
The image shows an impression by David A. Hardy of a possible scene from a moon orbiting the extra-solar planet in orbit around the star HD70642. Photo Credit: David A. Hardy.
... Hacker How-To Good Summer Reading - by Michelle Delio
27 Jun 03
Stealing the Network: How to Own the Boxby Ryan RussellSyngress, 330 pp., $49.95
Stealing The Network: How to Own the Box, a compendium of tales written by well-known hackers, is a perfect summer read. The stories are fictional. The technology and techniques described are very real.
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