Stefan Schmid

Six in the city: introducing Real Tournament - a mobile IPv6 based context-aware multiplayer game

It is rapidly becoming clear that entertainment will be one of the killer applications of future wireless networks. More specifically mobile gaming is predicted to be worth

Component-based active network architecture

1.2 billion by the year 2006 to providers in the U.S. alone [20]. The driving force behind this is the introduction of powerful feature rich handsets and ubiquitous access to high performance wireless networks. However, mobile applications face issues that are subtly different from fixed network applications, including fluctuating connectivity, network QoS and host mobility issues. To investigate the requirements of future mobile applications we have deployed a wireless MAN consisting of GPRS and IEEE 802.11 hotspots based on Mobile IPv6 around the city of Lancaster and have built an augmented reality game designed to evaluate future mobile application requirements.In this paper we introduce Real Tournament, a prototype multi-player mobile game, which uses handheld computers augmented with an array of sensors to enable true mobile interaction in a real-world environment. We then evaluate current approaches to real-time interaction and follow by outlining our own architecture more suited to wireless environments and based on the peer-to-peer approach. The approach provides adaptation, shared state, and consistency mechanisms in order to provide support for scalable, low latency, soft real time mobile applications.

Network address hopping: a mechanism to enhance data protection for packet communications

We believe that the killer application of active networking will be the provision of services which are not known to either the hardware manufacturer or the vendor at the time of network deployment. This would enable the rapid deployment of new services by third parties, and an unprecedented level of customisation by network administrators and end users. This vision, however, requires a degree of flexibility not yet seen in any of the currently proposed active router architectures. The lack of flexibility found in current active router designs has inspired us to develop a novel component-based active router architecture enabling extensible network programmability based on a progressive service composition framework. This document presents this architecture, LARA++, discusses its rudimentary concepts, and illustrates by example how its component architecture can benefit network programmability.

An access control architecture for microcellular wireless IPv6 networks

This paper proposes a novel mechanism to enhance data protection in communications across untrusted networks. The approach is based on the principle of network address hopping, whereby a data stream is spread across multiple end-to-end connections. The aim is to obscure the data exchange between two peers by shuffling the communication pattern. The hopping pattern - a shared secret between the communication participants - defines the sequence for the address hopping and determines the data spreading. Besides a description of the basic operation of the network address hopping mechanism, the paper evaluates the level of protection it can offer for end-to-end communications. This theoretical analysis is accompanied by a quantitative evaluation of the processing overhead of our prototype implementation on commodity end hosts.

Flexible, Dynamic, and Scalable Service Composition for Active Routers

This document introduces a novel access control architecture for publicly accessible wireless overlay networks. The architecture is designed to address the problems of ubiquitous Internet service provisioning within the city of Lancaster. The proposed access control mechanism is based on the concepts of secure user authentication, packet marking, and network-level packet filtering. The novelty of the architecture lies in its use of microcellular layer three networks to acquire fine grained access control in a link independent manner. The paper describes the concepts behind the access control architecture and demonstrates to what extent it addresses the security, performance and extensibility concerns of public access packet switched wireless networks.

Network layer access control for context-aware IPv6 applications

This paper describes a novel model for the provision of service composites for active routers. The service composition framework enables flexible programmability of the routers data path through dynamically loadable software components, called active components. The composition model promotes transparent and dynamic creation of network-side services and allows independent users to partake in this process. A prototype implementation has revealed that the composition model using packet filters and a classification graph structure as a means to integrate active components into the forwarding path enables the dynamic alteration of the elements of a composite at run-time and permits scalability in the generation of such composites. Furthermore, it allows the flexible provision of a unique service profile for each packet passing through an active router. We show that the overhead of this composition model does not significantly affect the performance of the router.

QoS-based real-time audio streaming in IPv6 networks

As part of the Lancaster GUIDE II project, we have developed a novel wireless access point protocol designed to support the development of next generation mobile context-aware applications in our local environs. Once deployed, this architecture will allow ordinary citizens secure, accountable and convenient access to a set of tailored applications including location, multimedia and context based services, and the public Internet. Our architecture utilises packet marking and network level packet filtering techniques within a modified Mobile IPv6 protocol stack to perform access control over a range of wireless network technologies. In this paper, we describe the rationale for, and components of, our architecture and contrast our approach with other state-of-the-art systems. The paper also contains details of our current implementation work, including preliminary performance measurements.

A highly flexible service composition framework for real-life networks

Live audio streaming is an important component of Internet multimedia. The currently deployed Internet offers poor support for such streams due to the lack of QoS capabilities. However, IPv6, the new Internet Protocol has now included provision for QoS. The introduction of a flow label in the protocol header is intended to enable classification of packets according to their destination and service. Reservation protocols such as RSVP can make use of this stream identifier to reserve resources for particular streams in the routers along the transport path. This paper explores the effectiveness of resource reservation in IPv6 networks for live audio streaming. An important area for investigation is whether there is an efficiency gain due to the employment of low level flow labels. The paper summarizes the result of our extensive measurements and comparisons with currently deployed technologies. Specific attention is paid to the performance characteristics of real time applications, notably the delay, jitter and bandwidth. The results are based on a specially developed audio streaming application which enables RSVP over IPv6 using flow labels. Since the integration of RSVP in IPv6 is still work-in-progress, we had to modify the currently available RSVP implementation in order to access the IPv6 flow label. For audio data transport, we use the real-time transport protocol (RTP). The real-time transport control protocol, known as the feedback channel of RTP, forms with its receiver reports the basis of our benchmark tests.

Improving RSVP for better support of Internet multimedia communications

This article introduces a novel approach for service composition on active and programmable routers. The proposed composition framework enables flexible programmability of a routers data path through dynamically loadable software components, called active components. The composition framework promotes transparent, dynamic and incremental deployment of network-side functionality which renders active network technologies capable of fully replacing the existing routing infrastructure by supporting all the legacy network protocols and services, and the integration of novel ones. On the other hand, the composition framework provides the necessary structures and mechanisms to deal with services composed by independent users potentially unaware of each other. The latter is particularly important as network routers are regarded as shared resources. In order to evaluate the proposed service composition framework, we have developed an implementation for the LARA++ active router architecture [S. Schmid, A component-based active router architecture, Ph.D. Thesis, Lancaster University, UK, November 2002] and deployed several of these active routers in a real-world service network. The evaluation demonstrates the flexibility of the composition framework by enabling the alteration of service composites at run-time and provides scalability in the generation of such composites by users or administrators. This work also reports on lessons learned while deploying several active services in a production network. Besides a qualitative evaluation of the service composition framework and the LARA++ architecture, we provide a number of quantitative results, which show that the overhead of our composition model does not adversely affect the performance of the router, despite the increased flexibility achieved.

Mobile 4-in-6: a novel IPv4 / IPv6 transitioning mechanism for mobile hosts

We have observed the failure of RSVP to be widely accepted as the solution to resource reservation in the Internet. Because we are convinced of the need for resource reservation, in at least parts of the Internet, to support multimedia communications, we have set about trying to improve RSVP. By careful study of the protocol, we have identified areas for improvement, and propose REDO RSVP, a reduced overhead version that includes a fast establishment mechanism (FEM). We describe the rationale for REDO RSVP and present an analysis of its features and operations.