Ian Wakeman

Scalable feedback control for multicast video distribution in the Internet

We describe a mechanism for scalable control of multicast continuous media streams. The mechanism uses a novel probing mechanism to solicit feedback information in a scalable manner and to estimate the number of receivers. In addition, it separates the congestion signal from the congestion control algorithm, so as to cope with heterogeneous networks. This mechanism has been implemented in the IVS video conference system using options within RTP to elicit information about the quality of the video delivered to the receivers. The H.261 coder of IVS then uses this information to adjust its output rate, the goal being to maximize the perceptual quality of the image received at the destinations while minimizing the bandwidth used by the video transmission. We find that our prototype control mechanism is well suited to the Internet environment. Furthermore, it prevents video sources from creating congestion in the Internet. Experiments are underway to investigate how the scalable proving mechanism can be used to facilitate multicast video distribution to large number of participants.

The state of peer-to-peer simulators and simulations

In this paper, we discuss the current situation with respect to simulation usage in P2P research, testing the available P2P simulators against a proposed set of requirements, and surveying over 280 papers to discover what simulators are already being used. We found that no simulator currently meets all our requirements, and that simulation results are generally reported in the literature in a fashion that precludes any reproduction of results. We hope that this paper will give rise to further discussion and knowledge sharing among those of the P2P and network simulation research communities, so that a simulator that meets the needs of rigorous P2P research can be developed

The conference control channel protocol (CCCP): a scalable base for building conference control applications

This paper presents the Conference Control Channel Protocol (CCCP), a new scheme intended for controlling conferences ranging from small, tightly coupled meetings, to extremely large loosely coupled seminars. We describe the requirements of such a scheme, and present a framework for building systems that connect together new and existing applications.

Packetized Video—Options for Interaction between the User, the Network and the Codec

In this paper we analyse the requirements that the user and a pocket network have of compressed video. From these, we produce a synthesis of the characteristics of an ideal video compression coding. Using this dialectic, we then examine the currently available compression schemes and determine which is closest to the ideal

Towards a design methodology for adaptive applications

We describe an abstract architecture of adaptive applications, and indicate where we believe crucial design decisions must be made. We illustrate the use of the abstract model in the design and implementation ofan image proxy, and describe the studies required in determining the appropriate design points. In particular, even though adaptation to resource constraints is generally considered a systems probleu the adaptation is visible to the user in changes in utility, and so the user must be involved in designing the application. Finally, we discuss the politics that creep in when dwigners change the semantics of applications.

Scooby: middleware for service composition in pervasive computing

In this paper we argue for middleware languages that aid in service composition. We outline where such languages could be useful through the description of our current architecture, and describe what we believe are the key requirements of such a language. We outline the current state of our implementation, and conclude by describing what requirements are placed on service providers by such composition middleware.

A survey of adaptive applications in mobile computing

Mobile computing is gaining wide acceptance due to the rapid enhancement in wireless communications technologies. This has led to an increase in the demand for mobile information access. However, most mobile computing environments are very limited in resources, hence introducing new requirements and challenges for the software developer and engineer. To address these challenges applications have to be adaptive. We describe mobile computing and its constraints. We describe adaptation spaces as a common framework for understanding the state-of-the-art in adaptive applications. A number of projects are reviewed and discussed. Then, a new rising paradigm in building adaptive applications is introduced based on a component-based architecture. We believe this new approach will provide a more flexible environment for building mobile applications.

Is layering, harmful? (remote procedure call)

Remote procedure call (RPC) mechanisms over the US Department of Defense transmission control protocol. (TCP) can produce behavior analogous to the silly window syndrome because of a mismatched interface between the socket and the TCP modules. The detection and diagnosis of the problem are addressed. Some pointers to a design approach that could avoid the problems of mismatched communication layers are provided.<<ETX>>

The state of peer-to-peer network simulators

Networking research often relies on simulation in order to test and evaluate new ideas. An important requirement of this process is that results must be reproducible so that other researchers can replicate, validate, and extend existing work. We look at the landscape of simulators for research in peer-to-peer (P2P) networks by conducting a survey of a combined total of over 280 papers from before and after 2007 (the year of the last survey in this area), and comment on the large quantity of research using bespoke, closed-source simulators. We propose a set of criteria that P2P simulators should meet, and poll the P2P research community for their agreement. We aim to drive the community towards performing their experiments on simulators that allow for others to validate their results.

SafetyNet: a language-based approach to programmable networks

It appears that some degree of programmability is inevitable within the network, whether it be through active networks, active services, or programmable middleware. We argue that programming network elements with languages designed for use within a single machine is inappropriate, since the only defense for the shared resource of the network is through the use of sandboxes, which are prone to performance problems and are difficult to implement correctly. Instead, we believe that new languages should be designed for programmable networks, using type systems that ensure safe programs, and encourage correct programs. We have designed and provided the full semantics for such a language, SafetyNet. Building upon this, we have implemented a compiler, run time environment and a simulation environment for our language. In this paper we describe the major features of the language that protect the network: abstracted locations; located objects; volatile routing; thread and class loading; and enforced resource counting. We show how these features are used in a number of small case studies, and in implementing optimised communication libraries. We describe the implications of the language design for the implementation of the run time support environment. The ease with which these demonstrations have been built and debugged shows the potential for enforcing network programming models with well-typed languages.