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Showing papers by "Jon Crowcroft published in 1994"


Journal ArticleDOI
TL;DR: An approach is developed to maximize the bandwidth utilization of a network for continually transmitting sources, such as video sources that use hierarchical encoding and can adapt their source coding rates in response to requests from the network congestion control algorithm.
Abstract: An approach is developed to maximize the bandwidth utilization of a network for continually transmitting sources, such as video sources. We assume that the sources use hierarchical encoding and can adapt their source coding rates in response to requests from the network congestion control algorithm, and we use this adaptability as the controlled input for a proportional control algorithm. We model flows entering or leaving the network as step inputs, and use the algorithm as the basis for admission control, using very little intelligence in the switches. We then present simulation results that demonstrate the algorithm working in a number of scenarios.

9 citations



Journal ArticleDOI
TL;DR: A tool for generating tours of the web to enable experts to become cyber-carto-graphers, mapmakers of the new virtual world, and share their findings with novice users.
Abstract: The World Wide Web is one of the fastest growing Networked Information Systems in history. The revolution has been brought about by use of GUIs such as NCSA's Mosaic, and the distributed hypertext language HTML, Universal Resource Locators, and with simple protocols for client server access. Another contributory factor has been the development of a number of filters that have permitted the introduction of material prepared using almost all the well known word processing and desk-top publishing tools. However, this growth has led to problems for new users finding the information they want. This paper is about a tool for generating tours of the web to enable experts to become cyber-carto-graphers, mapmakers of the new virtual world, and share their findings with novice users.

4 citations


01 Dec 1994
TL;DR: The conflicts between the emerging multiservice model for the Internet, which could operate in this future, and that for ATM, which address a bandwidth limited scenario arise because each is being designed with a view to being the all pervasive model, and not running recursively above the other.
Abstract: This paper is about the conflicts between two Multiservice Network architectures and to some extent, the Data Transfer Perspective for Congestion Control, in the context of an Internet with some (or most) paths provided by underlying ATM. In the limit, we believe that networks will have excess capacity, and that this will be the model for all traffic control - hence traffic control is about finding the operating point for a fair share of the network. The conflicts between the emerging multiservice model for the Internet, which could operate in this future, and that for ATM, which address a bandwidth limited scenario, arise because we foresee a period during which ATM available bitrate will be used as part of Internetwork paths, the rest of whose hops will either be best effort, or some new sub-service of integrated services internet, but that each is being designed with a view to being the all pervasive model, and not running recursively above the other.

2 citations


Journal ArticleDOI
TL;DR: The analysis shows that the mono-window model, which combines flow control and congestion control in a single window, can cause pipe breakdown after packet losses and is not suitable for high-speed and long-delay networks.
Abstract: This paper examines the window mechanism that has been widely used for flow and congestion control. The analysis shows that the mono-window model, which combines flow control and congestion control in a single window, can cause pipe breakdown after packet losses. A dual-window model is then presented, in which flow control and congestion control are decoupled. The dual-window model allows the traffic flow to be sustained while retransmission is being carried out. The dual-window model is particularly suitable for high-speed and long-delay networks where the pipelining of the packets is more crucial. The estimation of the window sizes, advance of the window edges, acknowledgement and retransmission are discussed in detail. Finally the performance of the dual-window model is examined with illustrated examples and by simulation.

2 citations


Journal Article
TL;DR: The changes the technology for the Internet is undergoing are about the changes the information Services, the access and transfer technology used to move the information round.
Abstract: This article is about the changes the technology for the Internet is undergoing. There are two aspects of the technology that we examine. The first in host software (applications and support). These form what one might call the information Services. The second is network support. This is the access and transfer technology used to move the information round. First a brief history of the Internet will give some clues as to its success

1 citations


Journal ArticleDOI
TL;DR: The hybrid model proposed by us combines the existing IDRP proposal with an alternative source routing proposal and believes that such a unified policy routing environment will be able to meet the most policy requirements outlined in the first part of the paper.
Abstract: In this paper we have attempted to synthesise the policy requirements of Administrative Domains and map them to the subject-object matrix normally used for access control models. This facilitates the analysis of the policy controls provided by the policy routing protocols. The hybrid model proposed by us combines the existing IDRP proposal with an alternative source routing proposal. We believe that such a unified policy routing environment will be able to meet the most policy requirements outlined in the first part of the paper.