Showing papers by "Jon Crowcroft published in 2000"

Consideration of receiver interest for IP multicast delivery

Abstract: Large-scale applications are characterized by a large number of dynamic and often interactive group members. The nature of these applications is such that participants are not interested in all the content transmitted. We examine three currently available techniques to scope delivery of content to interested receivers in IP multicast: filtering, where data is filtered by middleware before being passed to the application; addressing, where data is routed only to those receivers that express their interest; and hybrid approaches. We propose a framework that models large-scale application behavior. We use this framework to evaluate the performance of these applications and related protocols when the network is capable of filtering or addressing. Our results show that the current Internet architecture does not efficiently support large-scale applications because it can not efficiently manage multiple multicast groups. We show that network-level addressing is preferred to filtering and hybrid approaches given that groups are easy to create and manage. We highlight areas of research in the multicast architecture to bring about this change.

An Architecture for Application Layer Routing

Abstract: We have previously proposed, implemented and demonstrated an Application Layer Active Network (ALAN) infrastructure. This infrastructure permits the dynamic deployment of active services in the network, but at the application level rather than the router level. Thus the advantages of active networking are realised, without the disadvantages of router level implementation. However we have previously left unsolved the issue of appropriate placement of ALAN supported services. This is an Application Layer Routing problem. In this paper we define this problem and show that, in contrast to IP, it is a multimetric problem. We then propose an architecture that helps conceptualise the problem and build solutions. We propose detailed approaches to the active node discovery and state maintenance aspects of Application Layer Routing (ALR).

The Internet Multimedia Conferencing Architecture

Abstract: This article provides an overview of multimedia conferencing on the Internet. The protocols mentioned are all specified elsewhere as internet-drafts or RFCs. Each RFC gives details of the protocol itself, how it works and what it does. This document attempts to provide the reader with an overview of how the components fit together and some of the assumptions made. The term “conferencing” is used in two different ways: firstly, to refer to bulletin boards and mail list style asynchronous exchanges of messages between multiple users; secondly, to refer to synchronous or so-called “real-time” conferencing, including audio, video, shared whiteboads and other applications. This document is about the architecture for this latter application, in the Internet. There are other infrastructures for conferencing in the world: POTS (Plain Old Telephone System) networks often provide voice conferencing and phone-bridges, while the ISDN provides H.320[1] for small, strictly organised video-telephony conferencing. The architecture that has evolved in the Internet is far more general as well as being scalable to very large groups, and permits the open introduction of new media and new applications as they are devised. There are a number of components to this architecture, and the rest of this document describes these as follows:

Component framework infrastructure for virtual environments

Abstract: Virtual Environments (VE) present a complex problem with interesting non-trivial challenges for system development, in particular when the VE is distributed and shared amongst multiple participants. Most problems are common to any VE system, however the development effort is replicated because current systems are neither evolutionary nor allow integration of code across different systems.This paper presents the Java Adaptive Dynamic Environment (JADE), which consists of a light-weight cross-platform kernel with inherent capabilities for dynamic extensibility in run-time. This kernel is the embodiment of a component framework for the underlying infrastructure of VE systems, addressing the problems of evolution and integration.

QoS-sensitive flows: issues in IP packet handling

Abstract: IP-based networks were never designed for real time traffic, yet QoS support in such networks is needed to accommodate both global use and the more demanding applications now emerging. Changes in packet handling, in particular, will help provide QoS support in IP networks. The article focuses on the issues and principles concerning router modification for IP packet handling.

Router level filtering for receiver interest delivery

Abstract: Delivering data to on-line game participants requires the game data to be “customized” in real-time to each participant's characteristics. Using multicast in such an environment might sound contradictory. But multicast is a very efficient communication paradigm to minimize the transmission delays. Also, multicast reduces the workload at the sender. Content delivery according to receiver interest can be achieved by group management in multicast. But the natural dynamics of the application results in numerous delays because of join/leave latencies. In this paper, we propose the Router Level Filtering as a solution to the above problem.RLF relies on an extension to the current IP multicast service model. It introduces “filters” in the router forwarding process thereby providing a simple effective mechanism to customize the data delivered to a multicast session receiver while minimizing the number of groups and the related management cost. Contrary to other router filtering proposals, the filter semantics is determined by the application. The paper discusses protocol specification and implementation details of RLF, and shows how it may be implemented in routers.

A method and apparatus for generating multiple watermarked copies of an information signal

Abstract: A method and apparatus for watermarking an information signal to generate multiple different watermarked copies of the information signal is disclosed. The information signal is segmented into information segments. The plurality of differently watermarked versions of each information segment is then generated and one of the watermarked versions for each segment is selected for each one of the multiple different copies to be generated to generate a sequence of differently watermarked segments which is different for each copy.

Optimised batch patching with classes of service

Abstract: In this paper we present a new technique called Optimised Batch Patching with Classes of Service(OBP with CoS) which can be used to leverage the benefits of multicast within the context of 'near' video-on-demand systems in IP networks. OBP with CoS builds on an earlier scheme, known as Optimised Patching, but is different in two respects. Firstly, in OBP with CoS, the server artificially delays requests in order to increase the probability of accumulating duplicates, thereby allowing greater exploitation of multicast compared to Optimised Patching albeit at the expense of higher latency until commencement of service. Secondly, the client is able to request a latency class of service which reflects how long the client is prepared to wait until playout of the video. The server scheduling algorithm attempts to minimise network bandwidth consumption within the constraints imposed by the class of each request. We present analysis and simulations of our scheme in order to validate its effectiveness.

Effects of interleaving on RTP header compression

Abstract: We discuss the use of interleaving as a bandwidth efficient means of protecting audio streams from the effects of packet loss on the Internet. The adverse effects of interleaving on IP/UDP/RTP header compression are noted and a number of schemes which remedy this problem are discussed.

Notes on the use of RTP for shared workspace applications

Abstract: The Real-time Transport Protocol, RTP, has become the dominant protocol for streaming audio and video in IP-based environments. A number of proposals have been made which attempt to build on this success and apply RTP for shared workspace applications. We discuss the needs of such applications and the features provided by RTP, with an aim to showing why RTP is not appropriate for such uses.

ALPINE - Application Level Programmable Inter-Network Environment

Abstract: Future requirements for a broadband multimedia network are likely to be very different from those of today. Three key changes are identified; rapid introduction of new services, dynamic customisation of services by clients, and minimal management overhead. Application layer active networking, perhaps the most pragmatic and immediately realisable active network proposal, is a potential solution to all three. In the management of multiservice networks project, BT and its academic partners are developing key middleware components required to support application layer active networking.

Quality of Future Internet Services: First COST 263 International Workshop, QofIS 2000 Berlin, Germany, September 25-26, 2000 Proceedings

Abstract: Queueing and Scheduling.- Delay Bounds in a Network with Aggregate Scheduling.- A Queue Management System for Differentiated-Services IP Routers.- Modeling the Dynamics of the RED Algorithm.- TCP,Flow and Congestion Control.- Random Early Marking.- A Markovian Model for TCP Analysis in a Differentiated Services Network.- The Direct Adjustment Algorithm: A TCP-Friendly Adaptation Scheme.- On ACK Filtering on a Slow Reverse Channel.- End-to-End.- Design, Implementation and Test of a RSVP Agent Based on a Generic QoS API1.- On the Feasibility of RSVP as General Signalling Interface.- Field-Trial of Dynamic SLA in Diffserv-Capable Network.- Traffic Engineering,QoS Routing.- Choosing the Objectives for Traffic Engineering in IP Backbone Networks Based on Quality-of-Service Requirements.- On the Cost of Using MPLS for Interdomain Trafic.- Mechanisms for Inter-domain QoS Routing in Differentiated Service Networks.- QoS Measurements and Measurement Based QoS Mechanisms.- Priority Queueing Applied to Expedited Forwarding: A Measurement-Based Analysis.- QoS/GOS Parameter Definitions and Measurement in IP/ATM Networks.- QoS Assessment and Measurement for End-to-End Services.- Fairness.- The Fairness Challenge in Computer Networks.- A Multi-color Marking Scheme to Achieve Fair Bandwidth Allocation.- Traffic Phase Effects with RED and Constant Bit Rate UDP-Based Traffic.- Adaptation.- Adaptive Hybrid Error Control for IP-Based Continuous Media Multicast Services.- Efficient Shaping of User-Specified QoS Using Aggregate-Flow Control.- On the Construction of Heterogeneous Multicast Distribution Trees Using Filtering in an Active Network.- Traffic Classes and Charging.- An Approach to Support Traffic Classes in IP Networks.- Elements of an Open Framework for Pricing in the Future Internet.- Evolution of Charging and Billing Models for GSM and Future Mobile Internet Services.- Resource Utilization and Performance.- Live Video Scheduling in Differentiated Services Internet.- Virtual Routers: A Novel Approach for QoS Performance Evaluation.- DSRUP: A Resource Updating Protocol for the Differentiated Services Environment.- Internet Charging.- Keynote Talk: Internet Charging.- Panel: Charging for QoS.

Herding cats:† modelling Quality of Service for Internet applications

Abstract: The art and science of tele–traffic modelling is quite mature. On the other hand, Internet traffic seems to defy all attempts to capture its essence in simple models. This is not so surprising when we consider that the Internet consists of a large number of self–organizing systems, each evolved almost independently, which is quite a different way to construct a network than the ground-up design associated with telecommunications. IP routing, TCP congestion control, Relative Transport Protocol playout and loss adaption, Web caching and load balancing, and user behaviour are all involved in a system of massive complexity. In this paper, we survey some of these mechanisms and some of the attempts to bring this unruly bunch of schemes into a more coherent whole. We argue that these attempts are misguided, and that the strength of the Internet design is in the loose organization of these components. As the commercial investors turn their eyes on the Internet with a view to pricing, we argue that they should take extreme care not to propose mechanisms that kill the goose that lays the golden egg. See http://www-mash.cs.berkeley.edu/ns/ for details about the network simulator. National Laboratory for Applied Network Research at http://www.nlanr.net. VBNS Network Topology at http://www.vbns.net/logical.html.