Showing papers by "Jon Crowcroft published in 1996"

Quality-of-service routing for supporting multimedia applications

Abstract: Several new architectures have been developed for supporting multimedia applications such as digital video and audio. However, quality-of-service (QoS) routing is an important element that is still missing from these architectures. In this paper, we consider a number of issues in QoS routing. We first examine the basic problem of QoS routing, namely, finding a path that satisfies multiple constraints, and its implications on routing metric selection, and then present three path computation algorithms for source routing and for hop-by-hop routing.

Prefetching in World Wide Web

Abstract: This paper considers the use of prefetching in WWW for reducing the perceived latency. We first look at a number of basic issues and tradeoffs in prefetching. Our analysis shows that, unless the traffic is very light or the prefetching efficiency is very high, statistical prefetching may not necessarily reduce perceived delay. We then present an implementation of deterministic prefetching in a hotlist manager.

A hybrid BTC/ADCT video codec simulation bench

Abstract: We compare the performance of video compression algorithms in terms of compression ratio, video distortion and computation time in order to study the feasibility of a real time software videophone for 64 kbits/s channels, with exible user deened compression methods. We can combine and adjust the compression algorithms to the required bandwidth and video quality. We introduce the double logarithmic CORT Diagram , which is a novel, visual method to combine and evaluate video compression algorithms. The implemented algorithms are subsampling, block truncation coding (BTC), adaptive discrete cosine transform (ADTC) and conditional refreshment.

Pricing the Internet

Abstract: This is a paper about pricing the Internet. The focus is the use of pricing for usage of the infrastructure for transmitting and receiving IP packets, rather than of services such as WWW, FTP, Archie, Gopher, etc. In this we propose subscription based pricing, and a mechanism based on dynamic host address allocation drawn from a set of separately routed addresses to give priority levels. The idea of subscriptions here is not that all service pricing should be achieved through subscriptions per se. They are seen as a way of policing priority access to service bottlenecks, and thus can be deployed incrementally at weak interconnection points in a network, or between ISPs. Users of these subscriptions could easily be entire organisations (represented by network numbers, or CIDRized collections of network numbers, or ASs and so on). These organisations could employ refinement techniques to provide more usage oriented charging if needed.

High performance protocol architectures—HIPPARCH project and workshop

Abstract: The objective of the HIPPARCH project is to study and design high performance communication architectures and implementations, based particularly on the "Application Level Framing" and "Integrated Layer Processing" concepts. The HIPPARCH project holds annual workshops at which papers from leading communications research centers are presented. The papers in this issue of JHSN represent early results of the project and other groups engaged in similar research. 1. Introdnction HIPPARCH is an EC ESPRIT Basic Resarch project which began in january 1994 and is tasked with establishing a novel architectural design for communications protocols to be used for distributed applications over high speed networks. The project partners, INRIA, SICS, UCL and UTS, are all longstanding members of the research community working on improving our understanding and implementation of communications systems. The requirement for a new architecture is clear. Traditional layered protocol architectures such as the ISO OSI model (see for example [3]) and the ARPA Internet model (see for example [4]), are reaching the very end of their extended lifetimes. The problem can partly be blamed on an artificial separation of concerns in layers that represented interfaces between different service providers: The service/protocol concept derives historically from the model X.25 originally presented to the user of a network as inteiface. There would be a link, network, transport and session provider, perhaps all of which would be different potential vendors. This absurd extreme view of a potential "market" in layers in the stack has proved one thing: The costs of such a market in inefficiency mean buyers go to other markets the workable market appears to be in three layers: end system hardware and operating systems; end systems communications stacks; finally transmission networks. HIPPARCH concentrates its efforts on the second of these, to focus on end-to-end transmission control mechanisms and architecture. We are seeing a frantic flurry of effort piggybacked on the IPng effort to introduce a new architecture. Examples of such attempts include [5] and [6]. Some of these have led to partial attempts to address transport protocol problems as well [2]. While these address the network layer, they do not provide an integrated approach to designing the whole stack. We have adopted "Application Level Framing" and "Integrated Layer Processing" as intuitively reasonable guiding principles for selecting a new architecture that does address whole protocol stack design. In the initial year, we have carried out a number of tasks to deconstruct the problem. These fall roughly under the following headings: Adaptable transmission control mechanisms. Networks and End systems are and will probably always be heterogeneous. We should design systems that can operate for a large range of applications as well as TCP does now for a small one. 0926-6801/96/$8.00 © 1996 lOS Press. All rights reserved 106 1. Crowcr()ft / High peiformance protocol architectures HIPPARCH project and workshop Novel implementation techniques. We want to gather as many manual implementation techniques together as the basis of our decision on an architecture we want to maximise the "gene pool diversity" of the communications eco-system we are trying to build. In particular, we want to avoid pitfalls present in hidden assumptions about operating system structures (Unix, OS/2, Windows NT, etc) and about processor/memory architectures (uni versus multi, shared versus distributed memory) in the end system. In general, the final goal is a novel communication support architecture. This is not limited to implementation architecture, but to gain more from implementation techniques, the architecture itself has to be modified. Experiences with ALFIILP. While we seek new techniques, we would like to gain as much experience as possible using these particular guiding principles. Tools and description languages for protocol implementation. Initially, a lot of our efforts have involved manual programming of our new stacks. However, the objective is to eventually provide descriptions of application requirements, and automatically synthesize new protocols and protocol stacks to support the applications. To this end, initially, we wish to describe protocols and modules, and automatically generate working systems. Later this will permit verification/[8] and validation [8].

The Internet: a tutorial

Abstract: The Internet is a world-wide packet-switched network that connects together well over 10 million computers in over 100 countries for the purpose of information sharing. This paper is a tutorial on Internet technology-how it works now and how it is changing as the network becomes more commercial. It covers the underlying design of the Internet, the 'connectionless service model', and the applications that run over the network: the World Wide Web and other popular systems that have made the network growth so explosive in recent years.

Prospects for Internet technology

Abstract: This paper surveys the current developments in Internet technology, with a particular emphasis on performance, and the growing need for various guarantees of quality of service. It discusses hardware technologies for increased bandwidth, mechanisms for requesting and providing specific qualities of service, and various scaling issues. Finally it discusses mechanisms needed for (but not the economics of) the Internet in the mass market. To this end, we survey changes in the areas of addressing, and flow management.