DiversiFi: Robust Multi-Link Interactive Streaming

ABSTRACT Real-time, interactive streaming for applications such as audio-video conferencing (e.g., Skype) and cloud-based gaming depends critically on the network providing low latency, jitter, and packet loss, much more so than on-demand streaming (e.g., YouTube) does. However, WiFi networks pose a challenge; our analysis of data from a large VoIP provider and from our own measurements shows that the WiFi access link is a significant cause of poor streaming experience. To improve streaming quality over WiFi, we present DiversiFi, which takes advantage of the diversity of WiFi links available in the vicinity, even when the individual links are poor. Leveraging such cross-link spatial and channel diversity outperforms both traditional link selection and the temporal diversity arising from retransmissions on the same link. It also provides significant gains over and above the PHY-layer spatial diversity provided by MIMO. Our experimental evaluation shows that, for a client with two NICs, enabling replication across two WiFi links helps cut down the poor call rate (PCR) for VoIP by 2.24x. Finally, we present the design and implementation of DiversiFi, which enables it to operate with single-NIC clients, and with either minimally modified APs or unmodified APs augmented with a middlebox. Over 61 runs, where the baseline average PCR is 4.9%, DiversiFi running with a single NIC, switching between two links, helps cut the PCR down to 0%, while duplicating wastefully only 0.62% of the packets and impacting competing TCP throughput by only 2.5%. Thus, DiversiFi provides the benefit of multi-link diversity for real-time interactive streaming in a manner that is deployable and imposes little overhead, thereby ensuring coexistence with other applications

A Remotely Operable Facility for Fabrication of Fuel Pins for test Irradiation

AbstractA laboratory scale facility has been set up for fabrication of test fuel pins through sol-gel route for irradiation in FBTR, Kalpakkam. The facility is a train of glove boxes fitted with master slave manipulators for carrying out various operations involved in the fuel fabricat ion process. The paper describes the design features of the equipment and mechanisms for automation, developed for microsphere production and other processes. The design features include control system and vision systems for man- machine interface

BU/NSF Workshop on Internet Measurement, Instrumentation and Characterization

OBJECTIVES AND OVERVIEW Because of its growth in size, scope, and complexity--as well as its increasingly central role in society--the Internet has become an important object of study and evaluation. Many significant innovations in the networking community in recent years have been directed at obtaining a more accurate understanding of the fundamental behavior of the complex system that is the Internet. These innovations have come in the form of better models of components of the system, better tools which enable us to measure the performance of the system more accurately, and new techniques coupled with performance evaluation which have delivered better system utilization. The continued development and improvement of our understanding of the properties of the Internet is essential to guide designers of hardware, protocols, and applications for the next decade of Internet growth. As a research community, an important next step involves an comprehensive look at the challenges that lie ahead in this area. This includes an an evaluation of both the current unsolved challenges and the upcoming challenges the Internet will present us with in the near future, and a discussion of the promising new techniques that innovators in the field are currently developing. To this end, the Web and InterNetworking Research Group at Boston University (WING@BU), with support from the National Science Foundation, (grant #9985484) organized a one-day workshop which was held at Boston University on Monday, August 30, 1999 (immediately preceding ACM SIGCOMM '99).National Science Foundation (9985484

Improving World Wide Web Latency

The HTTP protocol, as currently used in the World Wide Web, uses a separate TCP connection for each file requested. This adds significant and unnecessary overhead, especially in the number of network round trips required. We analyse the costs of this approach and propose simple modifications to HTTP that, while interoperating with unmodified implementations, avoid the unnecessary network costs. We have implemented our modifications, and our measurements show that they dramatically reduce latencies. We have also investigated the effectiveness of a scheme to mask network latency by prefetching files likely to be requested next, while the user is browsing through the currently displayed page. Our results indicate a significant benefit from prefetching at the cost of an increase in network traffic. 1 Introduction People use the World Wide Web (WWW) because it gives quick and easy access to a tremendous variety of information in remote locations. Users do not like to wait for their results..

Coordinating Congestion Management and Bandwidth Sharing for Heterogeneous Data Streams

Many of the busiest servers in the Internet consist of clusters of nodes that serve out data of heterogeneous types. At a given point in time, a user could be receiving multiple concurrent data streams, both real-time and nonreal -time, that originate at a single server node, multiple nodes in the same server cluster, or nodes in separate clusters. In this paper, we argue that significant performance benefits can accrue from a coordinated approach to congestion management and bandwidth sharing across the concurrent data streams. We discuss several challenges that arise in this context and outline a coordination architecture that addresses these challenges. 1 Introduction Many of the busiest servers 1 in the Internet consist of large clusters of nodes that serve out data of heterogeneous types. The kinds of information served include text, images, and streaming audio/video. The information is typically transferred from servers to clients via unicast. This tends to be the case even f..