Ahmed E. Youssef

A Leader Replacement Protocol Based on Early Discovery of Battery Power Failure in MANETs

In cooperative Mobile Ad-hoc Networks (MANETs), copies of data are replicated on different mobile devices to increase resource accessibility and data availability. In order to preserve data consistency, a leader or authoritative control node is assigned to act as an organizer for the shared data copies. Since mobile devices have limited battery power, the leader may fail at any time. When the leader fails, another leader has to be elected to maintain data availability and consistency. Current leader election approaches in MANETs employ a notable wireless communication overhead to replace the leader. These wireless communications consume about 70% of total battery power. In this paper, we propose a novel approach to replace exhausted leader in MANETs based on the measurement of its remaining battery power early before it dies. More specifically, the proposed approach replaces the exhausted leader with a healthy one when its remaining battery power reaches a predefined threshold. Our approach has two contributions: 1) early precaution of leader power failure, 2) reducing power consumption used in leader replacement by reducing communication overhead.

Third line of defense strategy to fight against SMS-based malware in android smartphones

In this paper, we inspire from two analogies: the warfare kill zone and the airport check-in system, to design and deploy a new line in the defense-in-depth strategy, called the third line. This line is represented by a security framework, named the Intrusion Ambushing System and is designed to tackle the issue of SMS-based malware in the Android-based Smartphones. The framework exploits the security features offered by Android operating system to prevent the malicious SMS from going out of the phone and detect the corresponding SMS-based malware. We show that the proposed framework can ensure full security against SMS-based malware. In addition, an analytical study demonstrates that the framework offers optimal performance in terms of detection time and execution cost in comparison to intrusion detection systems based on static and dynamic analysis.

A Primary Shift Protocol for Improving Availability in Replication Systems

Backup Replication (PBR) is the most common technique to achieve availability in distributed systems. However, primary failure remains a crucial problem that threatens availability. When the primary fails, backup nodes in the system have to elect a new primary node in order to maintain adequate systems operation. During election, the system suffers from transaction loss, communication overhead due to messages exchange necessary to preserve data consistency, and a notable delay caused by the execution of Leader Election Algorithms (LEA). Primary failures can be unpredictable (i.e., unplanned), such as primary node crashes and network outages, or predictable (i.e., planned), such as primarys scheduled shutdown to perform routine maintenance or software upgrade. Traditionally, PBR employ LEA to recover from both unplanned and planned outages. In this paper, we propose a novel protocol, called Primary Shift Replication (PSR), to avoid election during planned outages. PSR shifts the primary role from the current primary to another scheduled node (without election) when a planned outage is about to occur. Number of messages and communication time required to shift the primary node to another node is much less than number of messages and time required to perform leader election; therefore, PSR improves systems availability. Moreover, PSR guarantees no transactions loss during the shift mode, hence, it preserves data consistency.

PRP: A primary replacement protocol based on early discovery of battery power failure in MANETs

In cooperative Mobile Ad-hoc Networks (MANETs), copies of data are replicated on different mobile devices to improve system’s availability. A primary or authoritative control node is assigned to act as a coordinator for the shared data copies, when this primary fails, another node has to be elected to replace the failed one. Since mobile devices have a limited battery power, the primary may fail at any time. Moreover, current primary election protocols in MANETs employ a notable wireless communication overhead which consumes a considerable amount of battery power. In this paper, we propose a novel protocol, called Primary Replacement Protocol (PRP), to replace an exhausted primary in MANETs based on the measurement of its remaining battery power early before it dies. More specifically, PRP replaces the exhausted primary with a healthy node when its remaining battery power reaches a predefined threshold. This replacement can be accomplished with much less communication overhead. Hence, our approach has two contributions: 1) reducing the chance of primary outage by early detection of potential power failure, 2) saving the power that is consumed in traditional primary election approaches due to communication overhead.

A multi-primary ownership partitioning protocol for highly scalable and available replication services

Primary Backup Replication (PBR) suffers from the bottleneck problem at the primary, single point of failure, poor scalability, and imbalanced utilization of computing resources. These shortcomings are mainly due to the exclusive role of the primary in accepting and executing clients requests. In this paper, we tackle this problem and propose a novel approach that distributes the primary role among several nodes, where each node owns a subset (partition) of replicated data objects. In our approach, when a client creates an object, the created object is propagated to all nodes; however, the node that executes objects creation call becomes the owner (the primary) of this object. As a result, several nodes own different disjoint subsets of replicated objects instead of having only a single primary node owning the whole object store. The expression “owning an object” means the exclusive right of the owner node to lock/unlock the object. Distribution of data ownership among several nodes achieves scalability and improves load balancing. Furthermore, under our approach a replication system can be administrated seamlessly in case of node failure and network partitioning. Our approach generalizes and subsumes the traditional PBR approach.