DDoS attacks aim to deny legitimate users of the services. In this paper, we introduce novel dual - level attack detection (D-LAD) scheme for defending against the DDoS attacks. At higher and coarse level, the macroscopic level detectors (MaLAD) attempt to detect congestion inducing attacks which cause apparent slowdown in network functionality. The large volumes attacks are detected early at border routers in transit network before they converge at the victim. At lower and fine level, the microscopic level detectors (MiLAD) detect sophisticated attacks that cause network performance to degrade gracefully and stealth attacks that remain undetected in transit domain and do not impact the victim. These attacks have dramatic impact on victim and are detected at border routers in stub domain near the victim. We employ the concepts of varying threshold and change point detection on entropy to enhance the detection rate. Honeypots help achieve high filtering accuracy. Results demonstrate that in addition to being competitive than other techniques with respect to detection rate and false alarm rate, our scheme is very effective and works well in the presence of different DDoS attacks. The proposed technique provides the quite demanded solution to the DDoS problem.

In most of Wireless Sensor Networks (WSNs) deployments, application requirements at sink and nature of event decide sensing frequency. Very high sensing frequency at sensor node (SNs) may result in generation of useless redundant data and too low sensing frequency may miss useful data about the event. Also, spurious data may be injected into network due to some temporary abnormal conditions near some active SNs. Therefore, in this paper we propose a data reporting scheme where prior to dissemination SN checks accumulated data against a filtering criteria. Further, sensing a slowly changing event with very high frequency results in lot of energy waste as it may generate redundant data. Whereas, sensing rapidly changing event with low frequency may cause loss of useful information. Since, the rate of change in the behavior of an event may be unpredictable, therefore along with data filtering we also propose an approach in which a cluster head node (CHN) dynamically sets sensing frequency in its cluster SNs by analyzing the flow of data reports received from these SNs. Simulation results show significant energy savings when this scheme is applied to various data dissemination approaches as opposed to scenarios when no data filtering is used and sensing frequency is fixed.

The inherent vulnerabilities in TCT/IP architecture give dearth of opportunities to DDoS attackers. The array of schemes proposed for detection of these attacks in real time is either targeted towards low rate attacks or high bandwidth attacks. Tresence of low rate attacks leads to graceful degradation of QoS in the network thus making them further undetectable. In this paper, we propose a scheme that uses three lines of defense. The first line of defense is towards detecting the presence of low rate as well as high bandwidth attacks based on entropy variations in small time windows. The second line of defense identifies and tags attack flows in real time. The last line of defense is redirecting the attack flows to honeypot server that responds in contained manner to the attack flows, thus providing deterrence and maintaining QoS at ISP level. We validate the effectiveness of the approach with simulation in ns-2 on a Linux platform.

Abstract Sparse connectivity, limited energy, and restricted memory of Mobile Hosts (MHs) are the main characteristics of today's Mobile Ad hoc NETwork (MANET). Present wireless technology is now enabling MHs not only to have multi‐hop communication among themselves, but also to have direct connection with an Access Point (AP) also. The emergence of such heterogeneous technologies brings cooperative caching to reality wherein MHs can access data items from caches at MHs in their neighborhood and can drastically minimize query latency. This key technique reduces the number of uplink channel requests, alleviates server load, and increases data availability. In this paper, we assume a heterogonous mobile environment where combination of ad hoc communication and infrastructured APs can be used to better manage the data needs of MHs through cooperative caching. We call such an environment as Cooperation‐based Access Point MANET (CAPMANET). We present a Hop‐Oriented Cooperative Caching (HOCC) scheme for CAPMANET which helps in reducing the communication overhead and the query latency. HOCC employs a hybrid Pull with Push (PwP) mechanism to maintain data consistency. Simulation results demonstrate that HOCC outperforms the pure push and pure pull‐based strategies by taking advantages of underlying characteristics and avoiding associated weaknesses. Copyright © 2007 John Wiley & Sons, Ltd.

Similarity search in time series data is an area of active interest in the data mining community. In this paper we introduce a simple and novel approach for performing similarity search over time series data using moments. This technique is based on the observation that similar time sequences will have their centroids close to each other. The proposed technique is capable of handling variable length queries and works irrespective of global scaling and shrinking of time series data. It can also handle vertical shifts.

A checkpoint algorithm for a mobile distributed computing system (MDCS) needs to handle many new issues like: mobility, low bandwidth of wireless channels, lack of stable storage on mobile nodes, disconnections, limited battery power and high failure rate of mobile nodes. These issues make traditional checkpointing techniques unsuitable for mobile distributed systems. Coordinated checkpointing may be useful to checkpoint MDCS if it is nonblocking and require minimum number of processes to checkpoint. Cao and Singhal [G. Cao et al., (2001)] achieved both by introducing the concept of mutable checkpoints. Many of these mutable checkpoints may be useless. We propose a nonblocking minimum process coordinated checkpointing protocol that not only minimizes useless checkpoints but also minimizes overall bandwidth required over wireless channels.

Distributed Message-Task System (DMTS) is designed and implemented on GURU Distributed Database Management System (GURU DDBMS). It incorporates the advantages of Message Based Communication System (MBCS) and Distributed Shared Memory System (DSMS). The message carrying ordinary data is scheduled by the scheduler for the translation in the local DBMS environment, and later passed to the supervisor of the object as a simple message. The other kind of messages having the control instructions are first scheduled for the translation of the data conversions and later are rescheduled for the instruction translation in the local DBMS environment. The intelligent translator and mapper handle the objects and provide the exact meaning of the data and control instructions. Finally synchronously and asynchronously exited task scheduling policies and concurrency control procedures are suggested.

A new class of irregular fault-tolerant multistage interconnection networks named quad tree (QT) networks is proposed and analyzed. The network can achieve significant tolerance to faults and good performance with relatively low costs and a simple control scheme. The construction procedure of the QT network is described. Algorithms for allocation of path length and routing along with the routing procedure are proposed. The fault-tolerance aspect is described, and the cost-effectiveness of the QT network is discussed.>

An attempt has been made to analyze the characteristics of a new class of irregular fault-tolerant multistage interconnection network known as the fault-tolerant double tree (FDOT) network. FDOTs can provide full access capability in the presence of multiple faults. It supports on-line repairability and is more cost-effective than other fault-tolerant multistage interconnection networks with similar fault-tolerant capability. Further, it provides better permutation capability than a DOT network of the same size, in the presence of any single fault. The number of favorite memory modules to which a processor can communicate with the shortest delay is increased compared to a DOT network of similar size. The general algorithm for computing the path lengths between a source-destination pair has been proposed. A simple distributed routing control algorithm has also been developed for setting a path.>