R. K. Ghosh

Cooperative black and gray hole attacks in mobile ad hoc networks

In this paper, we propose a complete protocol to detect a chain of cooperating malicious nodes in an ad hoc network that disrupts transmission of data by feeding wrong routing information. Our technique is based on sending data in equal but small sized blocks instead of sending whole of data in one continuous stream. The flow of traffic is monitored independently at the neighborhoods of both source and destination. The results of monitoring are gathered by a backbone network of trusted nodes. With assumption that a neighborhood of any node in the ad hoc network has more trusted nodes than malicious nodes, our protocol can not only detect but also remove a chain of cooperating malicious nodes (gray/black hole) by ensuring an end-to-end checking between the transmission of two blocks of data. The protocol takes O(mdBN) time for detection and removal of gray/black holes chain which betters an earlier O(n2) time bound [4] for detecting a single black hole in the network. Here, m is the number of malicious nodes in the network, dBN is the diameter of a backbone network formed out of the flat ad hoc network, and n is the total number of nodes in the ad hoc network.

Cluster based routing using a k-tree core backbone for mobile ad hoc networks

The problem of routing in Mobile Ad hoc Networks is non-trivial because of the dynamic nature of the network topology. In addition to computing shortest paths, as in wire-line networks, any routing scheme must consider that the topology of the network can vary while the packet is being routed.Cluster based schemes have been proposed which segregate the network into manageable sets for maintaining routing information. In this paper we propose a novel method of constructing the clusters and a backbone based on the concept of a k-tree core. We also propose an hierarchical routing scheme using this cluster information and evaluate its performance through extensive simulations.

Dense cluster gateway based routing protocol for multi-hop mobile ad hoc networks

In a multi-hop mobile ad hoc network dynamic clusterization of nodes can be quite effective for better management of routing problems. In a cluster based protocol inter cluster data transfer takes place through the cluster gateways. Therefore, it is important to maintain information about the gateways as a part of the routing tables in order that the inter cluster routing proceeds smoothly even as the nodes move about. In this paper we propose a randomized approach for inter cluster routing over dense cluster gateways (DCG). A group of large number of gateway edges between two adjacent clusters offering inter cluster connectivity between the two is referred to as a DCG. The minimum number of gateway edges that define a DCG is dependent on the characteristics of particular ad hoc network. A DCG is expected to offer robust inter cluster connectivity as it typically has a large number of gateway edges. Our protocol is an improvement over the cluster based routing using k-tree core backbone proposed in [Information Processing Letters 88 (2003) 187-194]. It distributes the routing load on the cluster gateways without adding the extra overhead of maintaining information about dense cluster gateways. We also propose a heuristic which reduces the load on the cluster-heads. The heuristic elects some nodes to act as sub-cluster-heads which share a part of the workload of the respective cluster-heads. The protocol has been implemented on ns-2 simulator. An analysis of the result of the experiments has been presented.

Distributed algorithms for finding and maintaining a k -tree core in a dynamic network

A k-core Ck of a tree T is subtree with exactly k leaves for k ≤ nl, where nl the number of leaves in T, and minimizes the sum of the distances of all nodes from Ck. In this paper first we propose a distributed algorithm for constructing a rooted spanning tree of a dynamic graph such that root of the tree is located near the center of the graph. Then we provide a distributed algorithm for finding k-core of that spanning tree. The spanning tree is constructed in two stages. In the first stage, a forest of trees is generated. In the next stage these trees are connected to form a single rooted tree. An interesting aspect of the first stage of proposed spanning algorithm is that it implicitly constructs the (convex) hull of those nodes which are not already included in the spanning forest. The process is repeated till all non root nodes of the graph have chosen a unique parent. We implemented the algorithms for finding spanning tree and its k-core. A core can be quite useful for routing messages in a dynamic network consisting of a set of mobile devices.

Causal ordering in event notification service systems for mobile users

Advances in wireless network technology and the increasing use of number of handheld mobile devices make many services and applications necessary to be offered to mobile users. An event notification service (ENS) system is an extremely useful communication service for those applications. Therefore, it becomes necessary to extend ENS system to a mobile environment. A distributed ENS system is an asynchronous system consisting of several subsystems, namely, producer clients, consumer clients and servers without common memory and global clock. The subsystems communicate each other by sending messages with unpredictable transmission delays causing unordered propagation of messages. We describe a model of ENS system for mobile environment. Then we present a causal ordering algorithm of ENS systems for mobile environment.

Efficient target tracking through binary-detection in sparsely deployed WSN

The problem of tracking moving objects with help of wireless sensor network (WSN) has been studied in past. Most of the solutions rely on the use of specialized and expensive sensors, and on dense deployment of sensors. These techniques are infeasible for applications in low budget domains. In this paper, we propose two novel techniques to track targets using binary sensing that does not need overlapping sensing regions. These techniques can track a target, and estimate the distance it has traversed on the basis of the time that target spends in the vicinity of sensors. In the first technique, the path traced by a moving target is approximated by tangent estimations to three circles, each representing range of a sensor. It allows us to convert the original problem into a semi definite program. The other tracking scheme identifies a band of small width where the target is guaranteed to lie. The band is first approximated using the distance travelled after coming out of vicinity of one sensor and before entering the vicinity of second sensor. This band is then reduced using the distance travelled inside the vicinity of the sensors. We simulated the two methods in NS2 and evaluate both the methods.

Holistic Performance Monitoring of Hybrid Clouds: Complexities and Future Directions

Effective monitoring solutions are critical to the smooth running of enterprise systems. However, real-world constraints present several challenges in designing such solutions. With the increasing scale and complexity of todays enterprise IT systems and their increasing use for business-critical applications, traditional approaches to monitoring must be reconsidered. This article stresses the need for a paradigm-shift from manual intuition-led approaches to an automated analytics-driven approach to monitor the IT systems. The authors propose that analytics-led solutions can provide powerful levers to design monitoring and event management solutions for next-generation enterprise IT systems.

Adaptive Monitoring: Application of Probing to Adapt Passive Monitoring

Availability of good quality monitoring data is a vital need for management of today’s data centers. However, effective use of monitoring tools demands an understanding of the monitoring requirements that system administrators most often lack. Instead of a well-defined process of defining a monitoring strategy, system administrators adopt a manual and intuition-based approach. In this paper, we propose to replace the ad-hoc, manual, intuition-based approach with a more systematic, automated, and analytics-based approach for system monitoring. We propose an adaptive monitoring framework where end-to-end probing-based solutions are used to adapt the at-a-point monitoring tools. We present a systematic framework to use probes for adjusting monitoring levels. We present algorithms to select and analyze probes and to dynamically adapt the monitoring policies based on probe analysis. We demonstrate the effectiveness of the proposed solution using real-world examples as well as simulations.

Algorithms for validating E-tickets in mobile computing environment

E-tickets issued online can be used by different vendors to provide services such as discount coupons for E-shopping, or an entrance for a football game. One major issue associated with E-tickets is the problem of validation, which becomes more severe in a mobile environment due to mobility of a mobile host (MH) and frequent failure/disconnection of validation servers known as mobile support stations (MSSs). Some additional problems include the identification of duplicate submissions of an E-ticket by a MH. Thus, this paper proposes two protocols using the Flat and Hierarchical schemes for E-ticket processing and validation in a mobile environment that guarantee at least and at most once property (each E-ticket is validated at least and at most once). The protocols have been validated and compared through complexity analysis and experiments.

Algorithmic Aspects of Sensor Localization

Identifying locations of nodes in wireless sensor networks (WSNs) is critical to both network operations and most application level tasks. Sensor nodes equipped with geographical positioning system (GPS) devices are aware of their locations at a precision level of few meters. However, installing GPS devices on a large number of sensor nodes not only is expensive but also affects the form factor of these nodes. Moreover, GPS-based localization is not applicable in the indoor environments such as buildings. There exists an extensive body of research literature that aims at obtaining absolute locations as well as relative spatial locations of nodes in a WSN without requiring specialized hardware at large scale. The typical approach consists of employing only a limited number of anchor nodes that are aware of their own locations, and then trying to infer locations of non-anchor nodes using graph-theoretic, geometric, statistical, optimization, and machine learning techniques. Thus, the literature represents a very rich ensemble of algorithmic techniques applicable to low power, highly distributed nodes with resource-optimal computations. In this chapter we take a close look at the algorithmic aspects of various important localization techniques for WSNs.