Showing papers by "Jon Crowcroft published in 1997"

Core Based Trees (CBT) An Architecture for Scalable Inter-Domain Multicast Routing

Abstract: One of the central problems in one-to-many wide-area communications is forming the delivery tree the collection of nodes and links that a multicast packet traverses. Significant problems remain to be solved in the area of multicast tree formation, the problem of scaling being paramount among these. In this paper we show how the current 1P multicast arctiltecture scales poorly (by scale poorly, we mean consume too much memory, bandwidth, or too many processing resources), and subsequently present a multicaat protocol based on a new scalable architecture that is low-cost, relatively simple, and efficient. We also show how this architecture is decoupled from (though dependent on) unicast routing, and is therefore easy to install in an internet that comprises multiple heterogeneous unicast routing algorithms.

Multipoint communication: a survey of protocols, functions, and mechanisms

Abstract: Group communication supports information transfer between a set of participants. It is becoming more and more relevant in distributed environments. For distributed or replicated data, it provides efficient communication without overloading the network. For some types of multimedia applications, it is the only way to control data transmission to group members. This paper surveys protocol functions and mechanisms for data transmission within a group, from multicast routing problems up to end-to-end multipoint transmission control. We provide a bibliography which is organized by topic.

Building shared trees using a one-to-many joining mechanism

Abstract: This paper presents a new approach for building shared trees which have the capability of providing multiple routes from the joining node onto an existing tree. The approach follows a design parameter of CBT and PIM in that it operates independently of any unicast routing protocol. However, a paradigm shift is introduced such that trees are built in an on-demand basis through the use of a one-to-many joining mechanism. In addition, the paper presents optimisations of the new mechanism to help constrain its impact in the case where many receivers exist for a given multicast group.

Ticket based service access for the mobile user

Abstract: Traditional mechanisms for service access, by mobile hosts across muhiple service domains, rely on the concept of a home location and cross domain authentication using roaming agreements. The reasons for requiring a home location are considered and it is argued that with recent developmenrs in elecn-onic payment schemes an alternative is possible. In an environment with many service providers, a wide range of services, and a diverse user population, roaming agreements based on a home location provide a far from ideal solution. An allernative “homeless” mechanism based on the notion of tickets is proposed. The requirements and impacts of such a scheme are considered. The proposed scheme is described and anaiysed to show robusrness against specific problems. A description of a protogpe implemenration is included, together with ideas for firm-e work.

Network text editor (NTE): A scalable shared text editor for the MBone

Abstract: IP Multicast, Lightweight Sessions and Application Level Framing provide guidelines by which multimedia conferencing tools can be designed, but they do not provide specific solutions. In this paper, we use these design principles to guide the design of a multicast based shared editor, and examine the consequences of taking a loose consistency approach to achieve good performance in the face of network failures and losses.

The integrated services in the Internet: state of the art

Abstract: This paper is about the evolution of the Internet from a simple data network into a true multiservice network that can support the emerging multimedia applications and their protocols with appropriate performance and costs. The real-time delivery and specific bandwidth requirements of these multimedia applications have created a need for an integrated services Internet in which traditional best effort datagram delivery can coexist with additional enhanced quality of service delivery classes. The integrated services Internet will be able to commit to meet bandwidth, packet loss, and delay specifications for individual data flows by using the resource reservation protocol together with appropriate packet forward scheduling policies.

IPv4 Address Behaviour Today

Abstract: The main purpose of this note is to clarify the current interpretation of the 32-bit IP version 4 address space, whose significance has changed substantially since it was originally defined. A short section on IPv6 addresses mentions the main points of similarity with, and difference from, IPv4.

Reservations about Reservations

Abstract: The panel discussed the current state and likely future development of how to provide differentiated quality of service in an Internet context, primarily through reservations. The panel agreed that it appears unlikely that a single approach will fit all applications, with different trade-offs between complexity, level of guarantee and scaling

Real-time audio and video transmission of IEEE GLOBECOM '96 over the Internet

Abstract: Discusses experiences of the authors in transmitting the proceedings of some events at IEEE GLOBECOM '96 in London, England, during November 17-22, 1996. Live video and audio of all the events in the Churchill Auditorium of the Queen Elizabeth II Conference Center were captured and transmitted, in real time, as well as stored and transmitted later, for remote participants in three continents, over the Internet. Two independent systems were used simultaneously, one supplied by researchers from NTT Laboratories in Japan and the other by researchers from University College London. The former system is based on a server model of distribution, while the latter is based on the use of network-level packet multicast. Both systems employ compression algorithms, so the network capacity requirement in each case was on the order of 100 kb/s to 200 kb/s total, thus enabling remote participants without very high-end network connectivity to take part. Receivers only need software for a PC running most popular versions of Windows or a UNIX workstation to be able to receive either type of transmission, or to retrieve the recorded sessions from NTT Laboratories servers. The multimedia transmission was carried over carefully engineered links that traversed many different subnet technologies, including point-to-point circuits, SMDS networks, ATM networks, and fast Ethernet switches. This was both to give a high level of assurance that the traffic would not experience too much interference from other traffic, and to ensure very low packet store and forward delays. The system ran for four days continuously, and was generally very successful.

Bibliography of recent publications on computer communication

Abstract: Due to an error in the simulation used to conduct removal policy experiments, one of the primary conclusions from our SIGCOMM'96 paper is in error. We present here the corrections, and some new results. The conclusion "sorting by SIZE is the best policy to maximize hit rate," is correct. However, the other primary conclusion "sorting by SIZE is the best policy to maximize weighted hit rate," is incorrect. In fact, sorting by SIZE was found to be the worst policy. A brief description of changes in each of the four experiments conducted follows. The text of the revised paper can be found at http:-//www.cs.vt.edu/~chitra/docs/96sigcomm/.

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.