Trude Hafsøe

Using web services to realize service oriented architecture in military communication networks

The principles of network enabled capability highlight the need for seamless information exchange. The service oriented architectural paradigm has been recognized as one of the key enablers to achieve this. At the same time, Web services have become the de facto standard for implementing service oriented architecture. However, these technologies have been developed for environments with abundant data rates, environments which are very different from military tactical networks. In this article, we present possible solutions and remaining challenges on the way toward also realizing service oriented architecture on the tactical level. Our goal is to make it possible to take advantage of the benefits promised by this architectural paradigm at all military levels, ranging from strategic to tactical networks.

Robust web services in heterogeneous military networks

NATO Network Enabled Capability is first and foremost about achieving better interaction between the different actors involved in military operations. This implies more efficient exchange of information. Consequently, the NATO information infrastructure will consist of a federation of systems, including a plethora of different information and communication systems, as well as a mix of new and legacy systems. NATO recommends a service-oriented architecture approach based on Web services to enable such a federation. In this article we explain how the communication protocols normally used in Web services are unsuited for disadvantaged and heterogeneous networks. We then present our prototype proxy, which enables the use of standard unmodified Web services across all network types, including tactical networks with low data rates and frequent disruptions. It is designed to work with existing security mechanisms, and also offers further optimizations in the form of optional plug-ins.

Web services discovery across heterogeneous military networks

NATO has identified Web services standards as a key enabler for interoperability between the different military systems used by various NATO nations. Compared to many civilian systems, military networks vary greatly in terms of computing resources, network bandwidth, mobility and stability, and distributed applications use several different networks concurrently or interact across them. In such dynamic and heterogeneous environments, runtime service discovery is a necessity. According to the W3C, discovery is the act of locating a machine-processable description of a Web service-related resource that may have been previously unknown and that meets certain functional criteria. In this article we present our approach to service discovery, where we combine Web services standards and proprietary solutions using our prototype interoperability gateway. This approach has been experimentally evaluated in a military experiment featuring both mobile ad hoc networks and fixed infrastructure networks, and the results show that transparent discovery between proprietary solutions and Web services discovery standards can be achieved.

Workload Characterization for News-on-Demand Streaming Services

This paper focuses on design issues for multimedia distribution architectures and the impact workload characteristics have on architecture design. Our contribution is an analysis of server load and user behavior in a news-on-demand environment, with focus on access patterns, popularity modeling, and the formation of traffic peaks. Finally, we evaluate an existing synthetic workload generator, MediSyn, and suggest some enhancements which will improve its suitability for news-on-demand workload modeling.

Efficient Web Services in Mobile Networks

Efficient solutions for Web services on mobile devices would allow truly global, platform independent, and interoperable information access, anywhere and at any time. While Web services are continuously gaining ground, they are commonly reserved for use on personal computers and high-capacity servers. However, mobile devices are gradually becoming more advanced in terms of processing resources and wireless communication capabilities, making it feasible to use Web services on such devices as well. Some of the challenges related to mobile Web services are limited bandwidth, high communication latency and high communication cost. In this paper, we focus on techniques for reducing XML overhead as a solution to overcome these challenges. Compression is a well known technique for reducing bandwidth consumption. Our contribution is an evaluation of compression techniques for use with Web services in mobile networks. In addition to performing simulations, we have verified our results using real GPRS and UMTS network connections.

Delay and disruption tolerant Web services for heterogeneous networks

Web services technology is considered a key enabler for NEC. However, existing Web service protocols are designed for use over the Internet, and cannot necessarily be directly applied in military tactical networks where bandwidths are low and communication disruptions are frequent. In this paper we present a novel prototype proxy solution which adds both delay and disruption tolerance to SOAP. The ¿Delay and disruption tolerant SOAP Proxy¿ solution can bridge heterogeneous networks and offers store-and-forward capabilities, delay tolerant network capabilities and swappable transport protocols while retaining backward compatibility with COTS Web service clients and servers. The proxy solution does not rely upon parsing or inspecting the SOAP messages, which allows for end-to-end security through encryption.

Enabling Publish/Subscribe with COTS Web Services across Heterogeneous Networks

In scenarios such as search-and-rescue operations, it may be required to transmit information across multiple, heterogeneous networks, often experiencing unreliable connections and limited bandwidths. Under such conditions, Publish/subscribe-based communication, combined with store-and-forward capabilities in the network nodes, greatly improves the ability to transmit information. At the same time, it is desirable to use commercial, standards-based software as much as possible, in order to reduce both cost and development time, and to ease the interconnection of systems from different organizations. In this paper, we present our prototype middleware solution called the Delay and Disruption Tolerant SOAP Proxy (DSProxy) which adds Publish/Subscribe functionality to standard, unmodified Web services. Together with its ability to make Web services delay and disruption tolerant, the DSProxy enables SOA based on Web services in scenarios as described above. The DSProxy has been tested in field trials, with promising results.

A protocol for robust and efficient service discovery in large, highly mobile radio networks

Existing service discovery mechanisms for ad hoc networks are often designed with one specific network type in mind. Solutions capable of handling highly mobile nodes usually have high bandwidth requirements, particularly as the number of nodes increases. The bandwidth requirement can be reduced by locally caching state information, but this increases the risk of nodes having outdated state information when mobility is high. Some solutions avoid these two issues by tightly coupling service discovery with the routing mechanism itself. However, this requires that nodes are homogeneous on the network layer. We propose a solution that leverages the special properties inherent in broadcast-based radio networks. In such networks, every node within transmission range will hear a transmission, be it unicast or broadcast. Each node therefore aggregates relevant service information and broadcasts it at regular intervals. Unnecessary transmissions are suppressed by efficiently synchronizing local state information. In this paper, we describe the Mist-protocol, a robust and efficient adaptive service discovery protocol, that supports large, highly mobile networks consisting of heterogeneous nodes. We test the protocol in large scale simulations in both static and mobile environments. Finally, we show that it is feasible to actually implement the design by providing a proof-of-concept prototype, which has been evaluated in a small scale experiment.

Analysis of Server Workload and Client Interactions in a News-on-Demand Streaming System

This paper investigates several aspects of streaming in news-on-demand services on the Internet by analyzing log files of a news service from Norways largest online newspaper. We investigate both short and long term effects of client usage of the service. By comparing our results with earlier work, we found that variations in server load depend strongly on local culture. Furthermore, we found that there are slight variations between client usage of the audio and video material

Pervasive service discovery across heterogeneous tactical networks

The Service Oriented Architecture concept is vital in order to interconnect different systems and to achieve a functional Network Centric Warfare (NCW). In order to realize an architecture based on loosely coupled services, a well-designed and efficient means of discovering the available services in the network is crucial. The service discovery mechanism used in any network must take the capabilities and limitations of the network into account. Due to the large variation in network capabilities on different operational levels, one single service discovery mechanism can not be chosen. Thus, there is a need for a toolkit consisting of different service discovery mechanisms so that each network can use the mechanism that is most suited for that particular network. In NCW, information exchange, and thus service discovery, must be available across network boundaries. This means that the different service discovery mechanisms must be able to interact with each other without the need for manual configuration. In this paper we present our novel prototype solution integrating WS-Discovery, a Web Services discovery mechanism, with Mercury, our proposed cross-layer service discovery solution tailored for use in MANETs. By using an interoperability gateway, service discovery is feasible across network boundaries, connecting mobile soldier systems and deployed tactical systems.