This paper explores the issues involved in designing and developing network software architectures for large scale virtual environments. We present our ideas in the context of NPSNET-IV, the first 3D virtual environment that incorporates both the IEEE 1278 Distributed Interactive Simulation (DIS) application protocol and the IP Multicast network protocol for multi-player simulation over the Internet.

The advent of high speed networks in the wide and local area enables multimedia traffic to be easily carried between workstation class machines. This dissertation considers an architecture for a workstation to support such traffic effectively. In addition to presenting the information to a human user the architecture allows processing to be done on continuous media streams. The proposed workstation architecture, known as the Desk Area Network (DAN), extends ideas from Asynchronous Transfer Mode (ATM) networks into the end system. All processors and devices are connected to an ATM interconnect. This is shown to be capable of supporting both multimedia data streams and more traditional CPU cache line traffic. The advocated extension of the CPU cache which allows caching of multimedia data streams is shown to provide a natural programming abstraction and a mechanism for synchronising the processor with the stream. A prototype DAN workstation has been built. Experiments have been done to ...

Emerging high-speed networks provide several hundred megabits per second to several gigabits per second of raw communication bandwidth. However, the maximum achievable throughput available to the end-user or application is quite limited. In order to fully utilize the network bandwidth and to improve the performance at the application level, a careful examination of I/O subsystems is essential. In this paper, we study one emerging high-speed network, the Fibre Channel network. The objectives of this study are : 1) to understand how the I/O subsystem relates to network operations, 2) to evaluate and analyze the performance of such a subsystem, and 3) to propose possible approaches for improving the maximum achievable bandwidth and reducing end-to-end communication latency. We will show (by simply modifying device driver code) a 75% maximum achievable bandwidth improvement and a 15.9% latency reduction for short packets. Other ways of improving network performance are also disc...

The rapidly advancing technology of cellular communication and wireless LAN makes ubiquitous computing feasible where the mobile users can have access to the location independent information and the computing resources. Multimedia networking is another emerging technological trend of the 1990s and there is an increasing demand for supporting continuous media traffic in wireless personal communication environment. In order to guarantee the strict performance requirements of realtime traffic, the connection-oriented approaches are proving to be more efficient compared to the conventional datagram based networking. This dissertation deals with a network architecture and its design issues for implementing the connection-oriented services in a mobile radio environment. The wired backbone of the proposed wireless LAN comprises of high speed ATM switching elements, connected in a modular fashion, where the new switches and the user devices can be dynamically added and reconnected for maintai...

This paper is a retrospective on the design of Xunet 2, one of the earliest functional wide-area ATM networks. Work on Xunet 2 began in 1989 and the network, consisting of experimental ATM switches, IP routers, and 45 Mbps transmission lines, has been operational since October 1991. The network serves as a "laboratory without walls" for eight research groups across the United States. While Xunet 2 has only a small number of nodes, it was designed as a prototype of a nationwide ATM network. This paper reviews some of the design decisions and lessons learned in the project and points out the research directions motivated by this work, focusing on the areas of traffic management, ATM switch design, network control, and the implementation of an IP router. 1. Introduction The Experimental University Network (Xunet) program began in 1986 when AT&T Bell Laboratories formed a research collaboration with the University of California at Berkeley, the University of Illinois at Urbana-Champaign, ...

This document outlines the plans to support IP-based multicast applications on Xunet. This extension would allow multicast--based multimedia programs, including nevot (network voice terminal), vat (visual audio tool), nv (network video), and wb (whiteboard), to run unmodified over Xunet. These plans involve extending the Mbone across Xunet. By surrounding Xunet with reasonable thresholds, it is possible to confine high-bandwidth traffic within Xunet. With an expected Mbone load of 0.5 Mbps, the multicast traffic will occupy only a small portion of Xunet's available bandwidth and network resources. In addition to allowing audio and video conferencing between Xunet sites, usage measurements could provide interesting statistics on multicast traffic and traffic patterns. By setting the metrics on the links near unity, many Xunet links will become primary links for multicast traffic originating near Xunet routers. Larger metrics will cause the shortest path algorithm to use the existing Int...

This thesis describes the Dynamic Time Windows congestion control and avoidance system. This system is designed to mitigate the effects of network congestion on today's networks and the networks of the future by directly controlling source burstiness. This chapter will discuss the need for congestion control in computer networks, identify the aspects of congestion control that present particular challenges in high speed networks, and introduce the Dynamic Time Windows system (DTW). It will also provide an overview of the remainder of the thesis.