Shantanu Sharma

Self-stabilizing end-to-end communication in (bounded capacity, omitting, duplicating and non-FIFO) dynamic networks

End-to-end communication over the network layer (or data link in overlay networks) is one of the most important communication tasks in every communication network, including legacy communication networks as well as mobile ad hoc networks, peer-to-peer networks and mash networks. We study end-to-end algorithms that exchange packets to deliver (high level) messages in FIFO order without omissions or duplications. We present a self-stabilizing end-to-end algorithm that can be applied to networks of bounded capacity that omit, duplicate and reorder packets. The algorithm is network topology independent, and hence suitable for always changing dynamic networks with any churn rate.

Security and privacy aspects in MapReduce on clouds: A survey

MapReduce is a programming system for distributed processing large-scale data in an efficient and fault tolerant manner on a private, public, or hybrid cloud. MapReduce is extensively used daily around the world as an efficient distributed computation tool for a large class of problems, e.g., search, clustering, log analysis, different types of join operations, matrix multiplication, pattern matching, and analysis of social networks. Security and privacy of data and MapReduce computations are essential concerns when a MapReduce computation is executed in public or hybrid clouds. In order to execute a MapReduce job in public and hybrid clouds, authentication of mappers-reducers, confidentiality of data-computations, integrity of data-computations, and correctness-freshness of the outputs are required. Satisfying these requirements shield the operation from several types of attacks on data and MapReduce computations. In this paper, we investigate and discuss security and privacy challenges and requirements, considering a variety of adversarial capabilities, and characteristics in the scope of MapReduce. We also provide a review of existing security and privacy protocols for MapReduce and discuss their overhead issues.

Elite Leader Finding Algorithm for MANETs

The mobile ad hoc network (MANET) is a hostile environment to design and implement computing algorithms. In MANETs, the coordinator election is the opening step to execute any service. Thus, the leader election is, de facto, prerequisite to various applications e.g., agreement, inter node communication, data exchange, serve the incoming request, key distribution, group communication, grant privileges, etc. The message propagation is costly affair as compared to computation. The MANET being bandwidth and power scarce, the development of message efficient protocols has been a preferred problem of research. Hence, in the contemporary literature, several protocols exist for leader election which focuses on reducing the number of algorithmic messages. The present article proposes a message efficient and failure resilient technique that improves leader availability. The proposed technique elects a vice-coordinator and a group of elite nodes as cabinet that avoids frequent leader election in the event of leader crash. Unlike, most of the contemporary leader election protocols, it avoids the broadcast of messages, to a large extent, and uses multicast and eventually unicast in leader election. The illustration also includes the simulated results and efficiency analysis of the proposed technique.

On detecting termination in cognitive radio networks

The cognitive radio network is an emerging wireless communication and computing paradigm where the network is not equipped with control infrastructure. The cognitive radios are allowed to execute the processes over the multiple heterogeneous channels without perturbing the licensed users of respective channels. The termination detection is a fundamental and non-trivial problem in the distributed computing systems. In this article, we present a termination detection protocol for heterogeneous multihop cognitive radio network. The proposed protocol applies the credit distribution and recovery approach. We present the two types of termination detection, i.e., strong and weak termination. Also, we give the correctness proof of the protocol.

Message efficient leader finding algorithm for mobile ad hoc networks

MANET is very hostile environment to design and implement computing algorithms. One of the major concerns in MANETs is to elect a coordinator in order to manage many mobile computing applications. In the contemporary literature, many protocols exist for leader election. However, most of them use message broadcast technique. The present article proposes a technique that avoids the broadcast of messages and uses multicast and unicast for leader election. The correctness proof and efficiency analysis of the proposed technique has also been included.

Assignment Problems of Different-Sized Inputs in MapReduce

A MapReduce algorithm can be described by a mapping schema, which assigns inputs to a set of reducers, such that for each required output there exists a reducer that receives all the inputs participating in the computation of this output. Reducers have a capacity that limits the sets of inputs they can be assigned. However, individual inputs may vary in terms of size. We consider, for the first time, mapping schemas where input sizes are part of the considerations and restrictions. One of the significant parameters to optimize in any MapReduce job is communication cost between the map and reduce phases. The communication cost can be optimized by minimizing the number of copies of inputs sent to the reducers. The communication cost is closely related to the number of reducers of constrained capacity that are used to accommodate appropriately the inputs, so that the requirement of how the inputs must meet in a reducer is satisfied. In this work, we consider a family of problems where it is required that each input meets with each other input in at least one reducer. We also consider a slightly different family of problems in which each input of a list, X, is required to meet each input of another list, Y, in at least one reducer. We prove that finding an optimal mapping schema for these families of problems is NP-hard, and present a bin-packing-based approximation algorithm for finding a near optimal mapping schema.

Private and Secure Secret Shared MapReduce (Extended Abstract)

Data outsourcing allows data owners to keep their data in public clouds, which do not ensure the privacy of data and computations. One fundamental and useful framework for processing data in a distributed fashion is MapReduce. In this paper, we investigate and present techniques for executing MapReduce computations in the public cloud while preserving privacy. Specifically, we propose a technique to outsource a database using Shamir secret-sharing scheme to public clouds, and then, provide privacy-preserving algorithms for performing search and fetch, equijoin, and range queries using MapReduce. Consequently, in our proposed algorithms, the public cloud cannot learn the database or computations. All the proposed algorithms eliminate the role of the database owner, which only creates and distributes secret-shares once, and minimize the role of the user, which only needs to perform a simple operation for result reconstructing. We evaluate the efficiency by (i) the number of communication rounds (between a user and a cloud), (ii) the total amount of bit flow (between a user and a cloud), and (iii) the computational load at the user-side and the cloud-side.

A Survey on Geographically Distributed Big-Data Processing using MapReduce

Hadoop and Spark are widely used distributed processing frameworks for large-scale data processing in an efficient and fault-tolerant manner on private or public clouds. These big-data processing systems are extensively used by many industries, e.g., Google, Facebook, and Amazon, for solving a large class of problems, e.g., search, clustering, log analysis, different types of join operations, matrix multiplication, pattern matching, and social network analysis. However, all these popular systems have a major drawback in terms of locally distributed computations, which prevent them in implementing geographically distributed data processing. The increasing amount of geographically distributed massive data is pushing industries and academia to rethink the current big-data processing systems. The novel frameworks, which will be beyond state-of-the-art architectures and technologies involved in the current system, are expected to process geographically distributed data at their locations without moving entire raw datasets to a single location. In this paper, we investigate and discuss challenges and requirements in designing geographically distributed data processing frameworks and protocols. We classify and study batch processing (MapReduce-based systems), stream processing (Spark-based systems), and SQL-style processing geo-distributed frameworks, models, and algorithms with their overhead issues.

On Detecting Termination in Cognitive Radio Networks

The cognitive radio network is an emerging wireless communication and computing paradigm where the network is not equipped with control infrastructure. The cognitive radios are allowed to execute the processes over the multiple heterogeneous channels without perturbing the licensed users of respective channels. The termination detection is a fundamental and non-trivial problem in the distributed computing systems. In this article, we present a termination detection protocol for heterogeneous multihop cognitive radio network. The proposed protocol applies the credit distribution and recovery approach. We present the two types of termination detection, i.e., strong and weak termination. Also, we give the correctness proof of the protocol.

Democratic Leader Finding Algorithm for Large Mobile Ad Hoc Networks

In order to monitor ad hoc applications, it is necessary for MANET to possess a coordinator. Hence, a large number of protocols have been proposed for coordinator election in MANETs. Although, most of the protocols focus on reducing the number of control messages, there have been very little attention on ensuring the high availability of leader in the event of various types of failures, e.g., leader crash and unreachability of leader, especially in the scenario like rescue and warfare, where absence of leader, even for a short duration, may lead to havoc. The motivation for the present article is to address this issue, especially for large MANETs where it is impossible for most applications to run in the absence of coordinator. The proposed protocol is inspired by prevailing parliamentary polity, followed in most of the democratic countries, which always ensures the existence of an executive in order to coordinate and monitor various activities in addition to taking decisions regarding affairs of the state.