Secure Sharing of Tuple Spaces in Ad Hoc Settings

AbstractSecurity is emerging as a growing concern throughout the distributed computing community. Typical solutions entail specialized infrastructure support for authentication, encryption and access control. Mobile applications executing over ad hoc wireless networks present designers with a rather distinct set of security requirements. A totally open setting and limited resources call for lightweight and highly decentralized security solutions. In this paper we propose an approach that relies on extending an existing coordination middleware for mobility (Lime). The need to continue to offer a very simple model of coordination that assures rapid software development led to limiting extensions solely to password protected tuple spaces and per tuple access control. Password distribution and security are relegated to the application realm. Host level security is ensured by the middleware design and relies on standard support provided by the Java system. Secure interactions among agents across hosts are accomplished by careful exploitation of the interceptor pattern and the use of standard encryption. The paper explains the design strategy used to add security support in Lime and its implications for the development of mobile applications over ad hoc networks

Services Provision in Ad Hoc Networks

The client-server model continues to dominate distributed computing with increasingly more flexible variants being deployed. Many are centered on the notion of discovering services at run time and on allowing any system component to act as a service provider. The result is a growing reliance on the service registration and discovery mechanisms. This paper addresses the issue of facilitating such service provision capabilities in the presence of (logical and physical) mobility exhibited by applications executing over ad hoc networks. The solution being discussed entailes a new kind of service model, which we were able to build as an adaption layer on top of an existing coordination middleware, LIME (Linda in a Mobile Environment)

Tuple Space Coordination Across Space & Time

CAST is a coordination model designed to support interactions among agents executing on hosts that make up a mobile ad hoc network (MANET). From an application programmer’s point of view, CAST makes it possible for operations to be executed at arbitrary locations in space, at prescribed times which may be in the future, and on remote hosts even when no end-to-end connected route exists between the initiator and target(s) of the operation. To accomplish this, CAST assumes that each host moves in space in accordance with a motion profile which is accurate but which at any given time extends into the future for a limited duration. These motion profiles are freely exchanged among hosts in the network through a gossiping protocol. Knowledge about the motion profiles of the other hosts in the network allows for source routing of operation requests and replies over disconnected routes. In this paper, we present the CAST model and its formalization. We also discuss the feasibility of realizing this mode

Context Aware Service Oriented Computing in Mobile Ad Hoc Networks

These days we witness a major shift towards small, mobile devices, capable of wireless communication. Their communication capabilities enable them to form mobile ad hoc networks and share resources and capabilities. Service Oriented Computing (SOC) is a new emerging paradigm for distributed computing that has evolved from object-oriented and component-oriented computing to enable applications distributed within and across organizational boundaries. Services are autonomous computational elements that can be described, published, discovered, and orchestrated for the purpose of developing applications. The application of the SOC model to mobile devices provides a loosely coupled model for distributed processing in a resource-poor and highly dynamic environment. Cooperation in a mobile ad hoc environment depends on the fundamental capability of hosts to communicate with each other. Peer-to-peer interactions among hosts within communication range allow such interactions but limit the scope of interactions to a local region. Routing algorithms for mobile ad hoc networks extend the scope of interactions to cover all hosts transitively connected over multi-hop routes. Additional contextual information, e.g., knowledge about the movement of hosts in physical space, can help extend the boundaries of interactions beyond the limits of an island of connectivity. To help separate concerns specific to different layers, a coordination model between the routing layer and the SOC layer provides abstractions that mask the details characteristic to the network layer from the distributed computing semantics above. This thesis explores some of the opportunities and challenges raised by applying the SOC paradigm to mobile computing in ad hoc networks. It investigates the implications of disconnections on service advertising and discovery mechanisms. It addresses issues related to code migration in addition to physical host movement. It also investigates some of the security concerns in ad hoc networking service provision. It presents a novel routing algorithm for mobile ad hoc networks and a novel coordination model that addresses space and time explicitly

Accommodating Transient Connectivity in Ad Hoc and Mobile Settings

Much of the work on networking and communications is based on thepremise that components interact in one of two ways: either they are connected viaa stable wired or wireless network, or they make use of persistent storage repositoriesaccessible to the communicating parties. A new generation of networks raises seri-ous questions about the validity of these fundamental assumptions. In mobile ad hocwireless networks connections are transient and availability of persistent storage is rare.This paper is concerned with achieving communication among mobile devices that maynever find themselves in direct or indirect contact with each other at any point in time.A unique feature of our contribution is the idea of exploiting information associatedwith the motion and availability profiles of the devices making up the ad hoc network.This is the starting point for an investigation into a range of possible solutions whoseessential features are controlled by the manner in which motion profiles are acquiredand the extent to which such knowledge is available across an ad hoc networ

A Component Deployment Mechanism Supporting Service Oriented Computing in Ad Hoc Networks

Ad hoc networks are dynamic, open environments that exhibit decoupled computing due to frequent disconnections and transient interactions. Reliable deploy-ment of components in such demanding settings requires a different design approach for the mechanisms that perform these functions. Not only do the deployment mechanisms have to perform the traditional tasks of deploying, installing, integrating and activat-ing components, they must also be robust enough to handle the nuances of an ad hoc network. This paper proposes a mechanism for component deployment that is adapted for use in ad hoc networks, and, as such, can cope with the effects of disconnection and transient connectivity. We present the general architecture for the mechanism and follow it with a discussion of a Java-based implementation of the model

Knowledge-driven Interactions With Services Across Ad Hoc Networks

Service oriented computing, with its aim of unhindered in-teroperability, is an appropriate paradigm for ad hoc net-works, which are characterized by physical mobility of het-erogenous hosts and by the absence of standardized application level protocols. The decoupled nature of computing in ad hoc networks can result in disconnections at inoppor-tune times during the client-service interaction process. We introduce the notion of a priori selection of services to reduce the likelihood of disconnection during service usage. A client may specify the times when it requires certain ser-vices. A knowledge base of the physical motion profiles of various service providers is used to select instances of a ser-vice that are co-located with the client at the required time and least likely to disconnect. A system for constructing the knowledge base is presented in this paper, along with the implementation details and the algorithm used to deter-mine the service usage pattern

Automated Code Management for Service Oriented Computing in Ad Hoc Networks

Ad hoc networks are dynamic environments where fre-quent disconnections and transient interactions lead to de-coupled computing. Typically, participants in an ad hoc network are small mobile devices such as PDAs or cellu-lar phones that have a limited amount of resources avail-able locally, and must leverage the resources on other co-located devices to provide the user with a richer set of func-tionalities. Service-oriented computing (SOC), an emerging paradigm that seeks to establish a standard way of mak-ing resources and capabilities available for use by others in the form of services, is a useful model for engineering soft-ware that seeks to exploit capabilities on remote devices. This paper proposes an automatic code management sys-tem supporting SOC in ad hoc networks. The system is re-sponsible for ensuring that the binary code required to use a service on a remote machine is available on the local host only when required. To support this functionality, a local code base is maintained by discovering and installing code from remote hosts. Since the system is specifically designed for ad hoc networks, it incorporates additional features that help it withstand the inherent dynamism of the network. We present an architecture for our system supporting automatic code management and follow it with a discussion of a Java-based implementation

Context Aware Session Management for Services in Ad Hoc Networks

The increasing ubiquity of wireless mobile devices is promoting unprecedented levels of electronic collaboration among devices interoperating to achieve a common goal. Issues related to host interoperability are addressed partially by the service-oriented computing paradigm. However, certain technical concerns relating to reliable interactions among hosts in ad hoc networks have not yet received much attention. We introduce ”follow-me sessions”, where interaction occur between a client and a service, rather than a specific provider or server. We allow the client to switch service providers if needed. The redundancy offers scope for reliable communication in the presence of mobility induced disconnections. We exploit strategies involving the use of contextual information, strong process migration, context-sensitive binding, and location-agnostic communication protocols. We show how follow-me sessions mitigate issues related to proxy-based service-oriented architectures in ad hoc networks, making them more reliable

Service Oriented Computing Imperatives in Ad Hoc Wireless Settings

Service oriented computing is a new paradigm that is gaining popularity in dis-tributed computing environments due to its emphasis on highly specialized, modular and platform-agnostic code facilitating interoperability of systems. It borrows concepts from more mature paradigms such as object-oriented and component computing. This results in a progression from object-oriented computing to component computing and finally to service oriented computing, a new paradigm for designing and delivering software. Just as an object encapsulates state and behavior at a fine level of granularity, a service offers similar encapsulation at a larger scale. This evolution raises the level of abstraction at which systems are engineered, while preserving beneficial properties such as modularity, substitution and encapsulation. Every participant in a service oriented computing system is a provider or user of a service, or both. The service oriented computing paradigm is characterized by a minimalist philosophy, in that a user needs to carry only a small amount of code in its local storage, and exploits other services by discovering and using their capabilities to complete its assigned task. This chapter is the result of our experiences with designing and building service oriented computing frameworks for ad hoc wireless networks (Handorean & Roman, 2002). It examines the salient imperatives required to deliver a service oriented computing frame-work for ad hoc wireless networks. Ad hoc wireless networks are collections of hosts capable of wireless communication. Hosts within proximity of each other opportunistically form a network which changes due to host mobility. An ad hoc wireless network is a dynamic environment by necessity, which exhibits transient interactions, decoupled computing, physical mobility of hosts, and logical mobility of code. The network infrastructure is supported by the participating hosts themselves and there is no dependence on external, fixed resources. Ad hoc wireless environments are especially challenging to program when compared against other classes of fixed wireless environments because of the implications of mobility, i.e., frequent disconnections and inherent dynamism of the network on program execution. An important class of ad hoc mobile systems is based on small, portable devices, and this class of systems is the focus of this chapter. Such devices have limited storage capacity and battery power, which restricts the number of programs they can store and run locally. Service oriented computing offers a solution to this problem. By its very nature, service oriented computing is designed to facilitate sharing of capabilities while minimizing the amount of functionality a single host needs to maintain. Such a design is especially effective in ad hoc networks where storage space on individual hosts is at a premium, yet where the open environment allows a large number of hosts to contribute small functions resulting in a rich set of capabilities being available in the network as a whole. Service oriented computing has received much attention from researchers worldwide. However, most of this work has been focused on architectures and implementations for wired networks. Migrating service oriented computing to ad hoc networks is non-trivial and requires a systematic rethinking of core concepts. Many lessons have been learned from the work done in the wired setting, especially regarding description and matching of services. However, the more demanding environment of an ad hoc wireless network requires novel approaches to advertising, discovering and invoking services. We envision such ad hoc networks being used in a range of application domains, such as response coordination by firemen and police at disaster sites, or command and control of military units in a battlefield. Such scenarios demand reliability despite the dynamic nature of the underlying network. The motivation for this chapter is to understand the unique imperatives for a viable service oriented computing framework in ad hoc wireless settings, and to illustrate selected solution strategies. We begin by examining current technologies, algorithms and capabilities that have been implemented for use in wired networks as a baseline. We then extend these concepts to cater to the special challenges of service oriented computing in ad hoc networks and direct the reader’s attention to research issues in this area, presenting some of our own contributions in the process. The rest of the chapter is organized as follows. We describe existing service oriented computing architectures and the Semantic Web effort in the Background section. The section on Ad Hoc Wireless Network Perspective on Service Oriented Computing represents the main thrust of this chapter and discusses the elements of a service oriented computing framework, examining current technologies alongside our ideas on how these concepts may be applied to ad hoc networks. We cover potential areas of research in the Future Trends section. Finally, we summarize our findings in the Conclusion section