In lase years with all of the attention paid to social networks (SN) and Web 2.0 tools these days, it is important to both explore their uses and evaluate their effectiveness in supporting communication, developing, and revolutions of countries, are rapidly evolving technology and play an important role in every daily life activities in societies. This technology includes wikis(Wikipedia, Seedwiki), blog, micro blogging (Twitter), YouTube, social book marking, podcasts, Second Life (virtual communities), and RSS.This paper will illustrate how Web 2.0 technology has been successfully used as a supplement for communicative practice in societies. Moreover, this paper explores the impact of communication SNs, Web 2.0 technologies, and the Internet in particular, has been widely credited as contributor to the democracy and freedom of countries. Some challenges of SNs and Web 2.0 have been overviewed. In addition to, the role of such technologies has been influenced by the Tunisian and Egyptian revolutions in 2011 which have been explained and highlighted in this work.

Despite of their energy efficiency, most of WSN's cluster-based routing protocols are vulnerable to security threats. Selective forwarding and black hole attacks are ranked among the most devastating attacks which they target this class of routing protocols. In this paper, a new centralized intrusion detection system is proposed to detect selective forwarding and black hole attacks in cluster-based wireless sensors networks. The main idea is the use of a centralized detection approach, where the base station decides on potential intrusions based on control packets sent from the cluster heads. The proposed intrusion detection technique is simple and energy efficient, it is thus suitable for sensor & Faouzi Hidoussi nodes with resource constrained. The simulation results confirm the expected performance of the proposed IDS in terms of security and energy efficiency.

This article investigates a novel mechanism of atomic broadcast in distributed systems. Various mechanisms are already given for moving sequencer based atomic broadcast like RMP [1], DTP [2] and Pin Wheel [3]. Since all these mechanisms are built on broadcast broadcast (BB) variant [4] of fixed sequencer atomic broadcast hence introduce a very large number of messages 141.Here we propose a novel mechanism that works on unicast broadcast (UB) invariant of fixed sequencer atomic broadcast in order to build moving sequencer atomic broadcast. The proposed mechanism relies on unicast broadcast hence it will introduce a very less number of messages in comparison to previous mechanisms [4]. Along with broadcast any process may get crash any time. Hence, system must be so efficient such that it can tolerate such crashes and maintains normal behavior so that reliability of system will be maintained. The proposed work will tolerate any crash failure of processes in system and reduce the load on sequencer (by providing an opportunity to each process to be a sequencer). We have used B 151 as formal technique for development of our model. B uses set theory as a modeling notation, refinements to represent system at different abstraction level. We have used Pro B [19] model checker and animator for constraint based checking, discover errors due to invariant violation and deadlocks, thereby, validating the specifications. We present an abstract model specifying atomic broadcast with a fixed sequencer and introducing moving sequencer in first refined version then introduction of crash tolerance in second refined version.

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Wireless sensor networks (WSN) have become one of the most attractive research areas in many scientific fields for the last years. WSN consists of several sensor nodes that collect data in inaccessible areas and send them to the base station (BS) or sink. At the same time sensor networks have some special characteristics compared to traditional networks, which make it hard to deal with such kind of networks. The architecture of protocol stack used by the base station and sensor nodes, integrates power and routing awareness (i.e., energy-aware routing), integrates data with networking protocols (i.e., data aggregation), communicates power efficiently through the wireless medium, and promotes cooperative efforts of sensor nodes (i.e., task management plane).

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Asterisk is a leading open source telephony software/system, easily implemented over intranet and internet. Asterisk empowers developers and integrators to create advanced communication solutions. An Asterisk system is a low cost type of a traditional PBX system. Any phone controlled by an Asterisk system can call a VoIP or analog phone controlled or managed by a traditional telephone system or by Asterisk telephone system. In this paper, the authors focus on the deployment and testing of various Open Source Asterisk Services in an enterprise level communication system. Selected services are listed in this paper that can be used to implement a telephone system with good Quality of Services (QoS) and good Quality of Experience (QoE) from the personal user to enterprise level users.