45075264
Multi-path GEM for Routing in Wireless Sensor Networks
Wireless sensor networks are expected to be used in many different applications such as disaster relief and environmental control. Efficient routing protocols need to be thoroughly studied before wireless sensor networks are widely deployed. GEM is an ingenious routing algorithm that is based on the idea of graph embedding. Using a well designed virtual coordinate system, GEM provides a remarkably simple route selection mechanism. However, GEM does not survive edge failures well. In this paper, we propose R-GEM and S-GEM that use the idea of GEM and improve its reliability performance significantly. Both of them outperform GEM in all of the experimental scenarios. Specifically, in the case that 2% of all edges in the network fail to transfer packets, when only disjoint pairs are taken into consideration, GEM leads to a path error rate of 10% while R-GEM and S-GEM only result in a path error rate of 2%.
14387828
Escape analysis for synchronization removal
In this paper we introduce our escape analysis framework for Java, which is a kind of flow-insensitive, inter-procedural, and context-sensitive data flow analysis. And we present an efficient static intra-procedural algorithm for inferring the set of types that can occur at runtime for each object. With intra-procedural type information, virtual method resolution, callee-stub inline, exception analysis, and thread allocation site analysis are implemented. Virtual method resolution and callee-stub inline effectively reduce the call graph and SCC (strongly connected components). In exception analysis, we present a more precise analysis algorithm, especially in the inter-procedural exception in SCC.Our escape analysis can be applied to the whole Java program and Java libraries to identify unnecessary synchronization in Java and remove them. We have developed an implementation on Intel's Open Runtime Platform. For our benchmarks, 7.3% to 99% (with an average of 54%) of synchronization operations are eliminated.
9419059
TLDFS: A Distributed File System based on the Layered Structure
This paper presents a novel distributed file system TLDFS, which consists of two layers. One is the block device layer, which makes the distributed file system manage the consistency of data easily by choosing an appropriate granularity of lock. We implement the distributed interfaces and the new data organization at the block level, which is different from most distributed file systems. The other is the file system layer that consists of three parts: interconnecting module, locking module and distributed file system module. Our prototype system proves the feasibility of the two-layered structure and the experiments show several advantages of TLDFS.
41699961
Automated Detection of Code Vulnerabilities Based on Program Analysis and Model Checking
Ensuring the correctness and reliability of software systems is one of the main problems in software development. Model checking, a static analysis method, is preponderant in improving the precision of vulnerabilities detection. However, when applied to buffer overflow and other bugs, it is hard to automatically construct the model for detecting the vulnerabilities. To address this problem we propose an approach that combines constraint based analysis and model checking together. We trace the memory size of buffer-related variables and instrument the code with corresponding constraint assertions before the potential vulnerable points by constraint based analysis. Then the problem of detecting vulnerabilities is converted into the problem of detecting vulnerabilities to verifying the reach ability of these assertions by model checking. In order to reduce the cost of model checking, program slicing is introduced to reduce the code size. CodeAuditor is a prototype implementation of our approach. With CodeAuditor, several yet unreported vulnerabilities are discovered in several open source software, and the performance is shown to be improved significantly with the help of program slicing.
14688887
Data Compression Algorithm Based on Hierarchical Cluster Model for Sensor Networks
A new distributed algorithm of data compression based on hierarchical cluster model for sensor networks is proposed, in which, the whole sensor network is mapped into a kind of hierarchical clusters model firstly, and then different wavelet transform models are used to commit data compression in inner and super clusters respectively. Theoretical analyses and simulation results show that, the above new methods have good performance of approximation, and can compress data and reduce the amount of data efficiently.
60472167
A RM-Based Static Deployment System for Cluster
In this paper, a Reliable-Multicast (RM) based static deployment system for cluster is designed which can be functionally divided into three parts: image capture, image transference, and node configuration. Image capture takes the snapshot of the operating system in the source node. Image transference distributes the captured image to target nodes. Node configuration mainly finishes the configuration of some identified information to target nodes. Applying the technology of Image-Based Installation [1] and an idea of separating the operating system image from service software, this system solves the tedious problems involved when the large-scale cluster is divided into a number of functional pools; using the network transmit model of RM, this system reduces the cost of network bandwidth and significantly improves the efficiency in deployment; combining WOL [2] and PXE [3], the system provides the function of single control point and lightens the workload of the system administrator. So this system can solve the problems of current cluster deployment mechanisms, such as inefficiency, imperfection of automated node configuration, and only supporting the Linux-based operating system deployment, etc. The deployment system consists of the deployment server, image servers, and target nodes. The deployment server is the core of the entire deployment system, which provides DHCP and TFTP service to ensure that the deployment control program can finish the deployment of target nodes after the cluster nodes start up from the NIC. Image servers mainly store the images and applications which can be accessed by the deployment server or target nodes by the NFS service. Target nodes are the nodes which need to be deployed in the cluster. Before the deployment process, the image of the source node and the service environment of the deployment server and image server should be prepared. During the deployment, the target node communicates with the deployment server by using PXE and WOL, and then the deployment server deploys the corresponding image and application service to the target nodes through the RM method. Finally, the target nodes finish their configurations. In the same experimental environment, some experiments respectively for this system, clonesys, and a deployment system identified by X have been built. As proved in experiments, this system can build a cluster more quickly and efficiently.
8793822
An efficient clustering algorithm for large-scale topical web pages
The clustering of topic-related web pages has been recognized as a foundational work in exploiting large sets of web pages such as the cases in search engines and web archive systems, which collect and preserve billions of web pages. However, this task faces great challenges both in efficiency and accuracy. In this paper we present a novel clustering algorithm for large scale topical web pages which achieves high efficiency together with considerately high accuracy. In our algorithm, a two-phase divide and conquer framework is developed to solve the efficiency problem, in which both link analysis and content analysis are utilized in mining the topical similarity between pages to achieve a high accuracy. A comprehensive experiment was conducted to evaluate our method in terms of its effectiveness, efficiency, and quality of result.
6110501
A backoff copying scheme for contention resolution in wireless sensor networks
This paper aims at improving the throughput and fairness of the wireless sensor networks (WSN). Due to the disproportionate larger number of packets accumulated in the sensors that are closer to the base station, it's necessary to have a better contention resolution scheme to improve the throughput and fairness in WSN. In this paper, we propose a new mechanism named BCCR (Backoff Copying for Contention Resolution), which is targeted to a system-wide proportional fairness in WSN. The new method is designed particularly for a many-to-one data collection tree structure, employing a mechanism that translates a fairness model into contention resolution. In BCCR, the size of the backoff window is dynamically adjusted to the channel allocation rate of the flow sent by the sensors. And the backoff algorithm does not focus on each node, but focus on each region which is divided according to the traffic flow contention. In every contention region, sensor nodes will share the same backoff window by a copying scheme. With extensive simulations and testbed experiments, we show that BCCR can achieve the expected fairness and throughput increase over the traditional CSMA, especially when the network is congested.
11702603
Active network supports for mobile IP
The basic mobile IP protocol is difficult to implement on the traditional IP network and not flexible and efficient under certain conditions. For example, firewalls or boundary routers may drop packets sent by mobile nodes for security reasons. Traditional networking devices such as routers cannot dynamically load and unload extended services to achieve different qualities of services. In this paper, a new scheme of using the active network to support the mobile IP is presented. The Softnet, a prototype of active networks based on mobile agents, is introduced. The active network is characterized by the programmability of its intermediate nodes and therefore presents dynamic and flexible behaviors. Special services can be dynamically deployed onto the active nodes in the Softnet. This property is definitely required in implementing the mobile IP protocols. The Softnet supports not only the basic mobile IP protocol but also other extended mobile IP protocols. Virtual networks for mobile IP services are dynamically formed by mobile agents in the Softnet to provide different qualities of services.