David Michael Turner

A market-based bandwidth charging framework

The increasing demand for high-bandwidth applications such as video-on-demand and grid computing is reviving interest in bandwidth reservation schemes. Earlier attempts did not catch on for a number of reasons, notably lack of interest on the part of the bandwidth providers. This, in turn, was partially caused by the lack of an efficient way of charging for bandwidth. Thus, the viability of bandwidth reservation depends on the existence of an efficient market where bandwidth-related transactions can take place. For this market to be effective, it must be efficient for both the provider (seller) and the user (buyer) of the bandwidth. This implies that: (a) the buyer must have a wide choice of providers that operate in a competitive environment, (b) the seller must be assured that a QoS transaction will be paid by the customer, and (c) the QoS transaction establishment must have low overheads so that it may be used by individual customers without a significant burden to the provider. In order to satisfy these requirements, we propose a framework that allows customers to purchase bandwidth using an open market where providers advertise links and capacities and customers bid for these services. The model is close to that of a commodities market that offers both advance bookings (futures) and a spot market. We explore the mechanisms that can support such a model.

The bandwidth exchange architecture

New applications for the Internet such as video on demand, grid computing etc. depend on the availability of high bandwidth connections with acceptable quality of service (QoS). There appears to be, therefore, a requirement for a market where bandwidth-related transactions can take place. For this market to be effective, it must be efficient for both the provider (seller) and the user (buyer) of the bandwidth. This implies that: (a) the buyer must have a wide choice of providers that operate in a competitive environment, (b) the seller must be assured that a QoS transaction will be paid by the customer, and (c) the QoS transaction establishment must have low overheads so that it may be used by individual customers without a significant burden to the provider. In order to satisfy these requirements, we propose a framework that allows customers to purchase bandwidth using an open market where providers advertise links and capacities and customers bid for these services. The model is close to that of a commodities market that offers both advance bookings (futures) and a spot market. We explore the mechanisms that can support such a model.

Efficient computation of the angularly resolved chord length distributions and lineal path functions in large microstructure datasets

Chord length distributions (CLDs) and lineal path functions (LPFs) have been successfully utilized in prior literature as measures of the size and shape distributions of the important microscale constituents in the material system. Typically, these functions are parameterized only by line lengths, and thus calculated and derived independent of the angular orientation of the chord or line segment. We describe in this paper computationally efficient methods for estimating chord length distributions and lineal path functions for 2D (two dimensional) and 3D microstructure images defined on any number of arbitrary chord orientations. These so called fully angularly resolved distributions can be computed for over 1000 orientations on large microstructure images (5003 voxels) in minutes on modest hardware. We present these methods as new tools for characterizing microstructures in a statistically meaningful way.

An audio stream redirector for the Ethernet Speaker

The authors have developed the “Ethernet Speaker” (ES), a network‐enabled single board computer embedded into a conventional audio speaker. Audio streams are transmitted in the local area network using multicast packets, and the ES can select any one of them and play it back. A key requirement for the ES is that it must be capable of playing any type of audio stream, independent of the streaming protocol, or the encoding used. The authors achieved this by providing a streaming audio server built using the kernel‐based audio stream redirector (ASR) in the OpenBSD kernel. The ASR accepts input from any of the existing audio file players, or streaming audio clients. Since all audio applications have to be able to use the system audio driver, this system can accommodate any protocol or file format, provided that there exists some compatible player running under OpenBSD. This paper discusses the design and implementation of the server as an ASR, the streaming protocol developed for this application, and the implementation of the client.

Microstructure Analysis Tools for Quantification of Key Structural Properties of Fuel Cell Materials

The objective of this work is to develop advanced microstructure analysis tools for direct quantification of the key structural properties of complex fuel cell materials. Computationally efficient algorithms have been developed to extract the key structural parameters from measured microstructure datasets of these materials. In addition to determination of the traditional structural measures (e.g., porosity, surface area, phase connectivity), two novel microstructure analysis techniques are introduced for the quantification of pore size and tortuosity distributions. For initial demonstration purposes, the methods developed are applied to a digitally reconstructed sample of the micro-porous layer (MPL) of a polymer electrolyte fuel cell (PEFC). The results produced from these analyses are compared to previously reported experimental and model-derived values where applicable.

Bridging the Network Reservation Gap Using Overlays

We propose the concept of Overlay-linked IntServ (OLIntServ), a system architecture that combines network overlays with intra-domain QoS to provide assured communications over the Internet, while allowing ISPs to extend the reach of their currently under-utilized IntServ services. We describe our system prototype, and provide some preliminary experimental results on its efficacy.