The STRESS Method for Boundary-point Performance Analysis of End-to-end Multicast Timer-Suppression Mechanisms

Evaluation of Internet protocols usually uses random scenarios or scenarios based on designers' intuition. Such approach may be useful for average-case analysis but does not cover boundary-point (worst or best-case) scenarios. To synthesize boundary-point scenarios a more systematic approach is needed.In this paper, we present a method for automatic synthesis of worst and best case scenarios for protocol boundary-point evaluation. Our method uses a fault-oriented test generation (FOTG) algorithm for searching the protocol and system state space to synthesize these scenarios. The algorithm is based on a global finite state machine (FSM) model. We extend the algorithm with timing semantics to handle end-to-end delays and address performance criteria. We introduce the notion of a virtual LAN to represent delays of the underlying multicast distribution tree. The algorithms used in our method utilize implicit backward search using branch and bound techniques and start from given target events. This aims to reduce the search complexity drastically. As a case study, we use our method to evaluate variants of the timer suppression mechanism, used in various multicast protocols, with respect to two performance criteria: overhead of response messages and response time. Simulation results for reliable multicast protocols show that our method provides a scalable way for synthesizing worst-case scenarios automatically. Results obtained using stress scenarios differ dramatically from those obtained through average-case analyses. We hope for our method to serve as a model for applying systematic scenario generation to other multicast protocols.Comment: 24 pages, 10 figures, IEEE/ACM Transactions on Networking (ToN) [To appear

A Review of the Energy Efficient and Secure Multicast Routing Protocols for Mobile Ad hoc Networks

This paper presents a thorough survey of recent work addressing energy efficient multicast routing protocols and secure multicast routing protocols in Mobile Ad hoc Networks (MANETs). There are so many issues and solutions which witness the need of energy management and security in ad hoc wireless networks. The objective of a multicast routing protocol for MANETs is to support the propagation of data from a sender to all the receivers of a multicast group while trying to use the available bandwidth efficiently in the presence of frequent topology changes. Multicasting can improve the efficiency of the wireless link when sending multiple copies of messages by exploiting the inherent broadcast property of wireless transmission. Secure multicast routing plays a significant role in MANETs. However, offering energy efficient and secure multicast routing is a difficult and challenging task. In recent years, various multicast routing protocols have been proposed for MANETs. These protocols have distinguishing features and use different mechanismsComment: 15 page

Towards formal models and languages for verifiable Multi-Robot Systems

Incorrect operations of a Multi-Robot System (MRS) may not only lead to unsatisfactory results, but can also cause economic losses and threats to safety. These threats may not always be apparent, since they may arise as unforeseen consequences of the interactions between elements of the system. This call for tools and techniques that can help in providing guarantees about MRSs behaviour. We think that, whenever possible, these guarantees should be backed up by formal proofs to complement traditional approaches based on testing and simulation. We believe that tailored linguistic support to specify MRSs is a major step towards this goal. In particular, reducing the gap between typical features of an MRS and the level of abstraction of the linguistic primitives would simplify both the specification of these systems and the verification of their properties. In this work, we review different agent-oriented languages and their features; we then consider a selection of case studies of interest and implement them useing the surveyed languages. We also evaluate and compare effectiveness of the proposed solution, considering, in particular, easiness of expressing non-trivial behaviour.Comment: Changed formattin

Spatiotemporal Multicast and Partitionable Group Membership Service

The recent advent of wireless mobile ad hoc networks and sensor networks creates many opportunities and challenges. This thesis explores some of them. In light of new application requirements in such environments, it proposes a new multicast paradigm called spatiotemporal multicast for supporting ad hoc network applications which require both spatial and temporal coordination. With a focus on a special case of spatiotemporal multicast, called mobicast, this work proposes several novel protocols and analyzes their performances. This dissertation also investigates implications of mobility on the classical group membership problem in distributed computing, proposes a new specification for a partitionable group membership service catering to applications on wireless mobile ad hoc networks, and provides a mobility-aware algorithm and middleware for this service. The results of this work bring new insights into the design and analysis of spatiotemporal communication protocols and fault-tolerant computing in wireless mobile ad hoc networks

Security and Privacy Issues in Wireless Mesh Networks: A Survey

This book chapter identifies various security threats in wireless mesh network (WMN). Keeping in mind the critical requirement of security and user privacy in WMNs, this chapter provides a comprehensive overview of various possible attacks on different layers of the communication protocol stack for WMNs and their corresponding defense mechanisms. First, it identifies the security vulnerabilities in the physical, link, network, transport, application layers. Furthermore, various possible attacks on the key management protocols, user authentication and access control protocols, and user privacy preservation protocols are presented. After enumerating various possible attacks, the chapter provides a detailed discussion on various existing security mechanisms and protocols to defend against and wherever possible prevent the possible attacks. Comparative analyses are also presented on the security schemes with regards to the cryptographic schemes used, key management strategies deployed, use of any trusted third party, computation and communication overhead involved etc. The chapter then presents a brief discussion on various trust management approaches for WMNs since trust and reputation-based schemes are increasingly becoming popular for enforcing security in wireless networks. A number of open problems in security and privacy issues for WMNs are subsequently discussed before the chapter is finally concluded.Comment: 62 pages, 12 figures, 6 tables. This chapter is an extension of the author's previous submission in arXiv submission: arXiv:1102.1226. There are some text overlaps with the previous submissio

Design, Implementation, and Verification of the Reliable Multicast Protocol

This document describes the Reliable Multicast Protocol (RMP) design, first implementation, and formal verification. RMP provides a totally ordered, reliable, atomic multicast service on top of an unreliable multicast datagram service. RMP is fully and symmetrically distributed so that no site bears an undue portion of the communications load. RMP provides a wide range of guarantees, from unreliable delivery to totally ordered delivery, to K-resilient, majority resilient, and totally resilient atomic delivery. These guarantees are selectable on a per message basis. RMP provides many communication options, including virtual synchrony, a publisher/subscriber model of message delivery, a client/server model of delivery, mutually exclusive handlers for messages, and mutually exclusive locks. It has been commonly believed that total ordering of messages can only be achieved at great performance expense. RMP discounts this. The first implementation of RMP has been shown to provide high throughput performance on Local Area Networks (LAN). For two or more destinations a single LAN, RMP provides higher throughput than any other protocol that does not use multicast or broadcast technology. The design, implementation, and verification activities of RMP have occurred concurrently. This has allowed the verification to maintain a high fidelity between design model, implementation model, and the verification model. The restrictions of implementation have influenced the design earlier than in normal sequential approaches. The protocol as a whole has matured smoother by the inclusion of several different perspectives into the product development

A wireless multicast delivery architecture for mobile terminals

Content delivery over the Internet to a large number of mobile users offers interesting business opportunities for content providers, intermediaries, and access network operators. A user could receive, for example, music or a digital newspaper directly to a mobile device over wireless networks. Currently, content delivery over the Internet is held back by a number of reasons. Existing network technologies, such as GPRS, have a very limited capacity to transfer large files, such as those required for good-quality pictures in a newspaper. Another problem is security. Content received over the Internet is very vulnerable to being forged. A user who cannot be certain about the source and consistency of the received stock quotes is unlikely to pay for the information. Furthermore, content providers are unwilling to distribute their valuable information over the Internet due to their fear of copyright infringements. Traditionally, content has been considered consumed as soon as it has been downloaded. Content providers have been keen on preventing their content from being transferred over peer-to-peer networks because they consider the delivery itself to be a copyright infringement. In this dissertation, content delivery is separated from content consumption by encrypting the content before delivery. When the users wishes to consume the content, a license which includes the decryption key is provided. The architecture allows content to be delivered to users' devices even before the user commits to consume the content. The user can choose to receive content whenever downloading it is the most convenient and affordable. Thus, the content providers are able to maintain control over the use of their information even after the data has been transferred to the users' terminals. In addition, content received by users can be strongly source authenticated. The architecture allows secure, efficient and reliable delivery of content to a large group of receivers. The architecture does not commit itself to any specific delivery technique, and the content can be delivered using any delivery technique including multicast, broadcast, unicast, and peer-to-peer. This dissertation focuses mostly on multicast as the delivery technique. The efficiency of the multicast delivery over unreliable heterogenous wireless access networks is thoroughly analyzed. Mobile terminals can seamlessly switch between access points and access technologies while continuing to receive data reliably from the network. The multicast delivery uses adaptive error correction and retransmissions to deliver the content as efficiently as possible to a very large number of receivers. The simulations show, that the vast majority of receivers are able to receive the content reliably with a small delay even when the radio network suffers from high packet loss probability. Although the architecture is designed to deliver content to mobile terminals, it is also suitable for delivering content to terminals with fixed Internet connectivity.Digitaalisen sisällön siirtäminen liikkuville käyttäjille Internetin yli tarjoaa uusia liiketoimintamahdollisuuksia niin sisällöntuottajille, välittäjille kuin verkko-operaattoreille. Teknikkaa voidaan käyttää esimerkiksi musiikin tai sähköisten lehtien välittämiseen käyttäjille langattoman verkon kautta. Sisällön välittämistä Internetin kautta hankaloittaa yhä usea seikka. Nykyisin laajassa käytössä olevat verkkotekniikat, kuten GPRS, ovat liian hitaita siirtämään hyvin suuria tiedostoja suurelle määrällä vastaanottajia. Lisäksi väärennetyn tiedon välittäminen Internetin kautta on erittäin helppoa. Sisältö, jonka aitoudesta ja alkuperästä ei ole varmuutta, on usein arvotonta käyttäjälle. Sisällöntuottajat puolestaan ovat haluttomia käyttämään sisältönsä levittämiseen Internetiä mikäli digitaalisesti levitettävän sisällön kopioiminen ja oikeudeton kuluttaminen on liian helppoa. Perinteisesti sisältö ajatellaankin kulutetuksi jo sillä hetkellä, kun se on siirretty käyttäjän laitteeseen. Sen vuoksi sisällön tuottajat ovatkin käyttäneet paljon resursejaan estääkseen sisältönsä välittämisen vertaisverkoissa, koska jo pelkkää sisällön siirtämistä pidetään tekijänoikeusrikkomuksena. Tässä työssä erotetaan sisällön siirtäminen sisällön kuluttamisesta suojaamalla sisältö salauksella ennen sen siirtämistä käyttäjille ja sallimalla vapaa salatun sisällön jakelu. Arkkitehtuuri mahdollistaa sisällön siirtämisen käyttäjien laitteille silloin kun sisällön siirtäminen on edullisinta ja tehokkainta. Vasta käyttäjän halutessa kuluttaa aiemmin lataamaansa sisältöä, tarkistetaan oikeis sisällön käyttöön. Arkkitehtuuri mahdollistaa myös ladatun sisällön alkuperän ja eheyden vahvan tarkistamisen. Arkkitehtuuri mahdollistaa turvallisen, tehokkaan ja luotettavan sisällön siirtämisen suurelle määrälle vastaanottajia. Arkkitehtuuri ei pakota sisällön jakelua käyttämään mitään tiettyä siirtomenetelmää vaan sisältö voidaan siirtää käyttäen esimerkiksi ryhmälähetystä (multicast), joukkolähetystä (broadcast), täsmälähetystä (unicast) tai vertaisverkkoja (peer-to-peer). Tässä työssä on keskitytty analysoimaan ryhmälähetyksen soveltuvuutta tiedon siirtomenetelmänä. Ryhmälähetysmenetelmän tehokkuutta on analysoitu siirrettäessä sisältöä heterogeenisen langattoman liityntäverkon yli. Liikkuvat päätelaitteet voivat siirtyä saumattomasti liityntäverkosta toiseen samalla kun ne vastaanottavat sisältöä. Ryhmälähetys hyödyntää adaptiivista virheenkorjausta ja uudelleenlähetyksiä siirtääkseen sisällönmahdollisimman tehokkaasti suurelle joukolle vastaanottajia. Simulaatiot osoittavat, että erittäin suuri osa vastaanottajista saa sisällön luotettavasti ja pienellä viiveellä vaikka liityntäverkossa pakettien virhetodennäköisyys olisi suuri. Arkkitehtuuri on suunniteltu siirtämään sisältöä liikkuville laitteille, mutta sitä voidaan käyttää yhtä hyvin myös kiinteään verkkoon liitettyjen laitteiden kanssa.reviewe

A Multi-User, Single-Authentication Protocol for Smart Grid Architectures

open access articleIn a smart grid system, the utility server collects data from various smart grid devices. These data play an important role in the energy distribution and balancing between the energy providers and energy consumers. However, these data are prone to tampering attacks by an attacker, while traversing from the smart grid devices to the utility servers, which may result in energy disruption or imbalance. Thus, an authentication is mandatory to efficiently authenticate the devices and the utility servers and avoid tampering attacks. To this end, a group authentication algorithm is proposed for preserving demand–response security in a smart grid. The proposed mechanism also provides a fine-grained access control feature where the utility server can only access a limited number of smart grid devices. The initial authentication between the utility server and smart grid device in a group involves a single public key operation, while the subsequent authentications with the same device or other devices in the same group do not need a public key operation. This reduces the overall computation and communication overheads and takes less time to successfully establish a secret session key, which is used to exchange sensitive information over an unsecured wireless channel. The resilience of the proposed algorithm is tested against various attacks using formal and informal security analysis