Using the World Wide Web at 28.8 Kbps (or less) can be a frustrating experience: a multimedia page that takes a fraction of a second to download at Ethernet speeds takes many seconds at modem rates. Two enhancements to existing infrastructure have the potential to deliver more satisfactory residential Internet access: ISDN telephone service, and upgraded cable TV networks. While ISDN dedicates bandwidth to each user, cable networks support a shared bandwidth approach similar to that used in computer Local Area Networks (LANs). This report describes the technologies and evaluates qualitative differences between the two approaches. It presents quantitative results of capital cost models based on case studies of the PSICable deployment in Cambridge, MA, and the Internet over ISDN service offered by Internex, Inc. in the San Francisco, CA area. The report finds that cable''s shared-bandwidth approach has superior economic characteristics. For example, 500 Kbps Internet access over cable can provide the same average bandwidth and four times the peak bandwidth of ISDN access for less than half the capital cost per subscriber. The economy of the shared bandwidth approach is most evident when comparing the per-subscriber cost per bit of peak bandwidth: $0.60 for the 500 Kbps cable service versus close to $16 for ISDN. Cable-based access also has better service characteristics: it can support both full-time Internet connections and higher peak bandwidths, such as a 4 Mbps cable service that provides thirty-two times the peak bandwidth of ISDN. The report concludes with an analysis of the barriers to diffusion of cable and ISDN Internet access, including business and policy factors. It finds that the closed market structure for cable subscriber equipment has not been as effective as the open market for ISDN equipment at fostering the development of needed technology. Furthermore, monopoly control of residential communications infrastructure--whether manifest as high ISDN tariffs or simple lack of interest from cable operators--limits business opportunities for Internet service providers.

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Connecting Homes to the Internet: An Engineering Cost Model of Cable vs. ISDN

High-speed networks are capable of carrying many types of services such as voice, data, images, and video. These services have different requirements in terms of bandwidth, cell loss, delay, etc. The goal is to maximize the quality of service offered during periods of stress, as viewed by both the network provider and the customer. Many problems are created by these different requirements. This paper illustrates four bandwidth problems in high-speed networks, then describes several solutions to them. The first problem is topology design and bandwidth allocation, and it is concerned with the ability to dynamically reconfigure a network in order to efficiently benefit from network resources. The second problem is concerned with flow control and congestion avoidance. Bandwidth management (BWM) protocols are used to prevent congestion, essentially by accepting or refusing a new-arrival cell. The third problem, which is the most critical one, is bandwidth allocation, which is concerned with successful integration of link capacities through the different types of services. Given that a virtual path is a logical direct link, composed of a number of virtual circuits, between any two nodes, the last problem is concerned with how to assign bandwidth to each virtual path in the network, in order to optimize performance for all users. This paper may be a good guide to researchers concerned with high-speed networks in general.

Bandwidth problems in high-speed networks

Specially designed telecommunication networks like public switched telephone net­ work for speech, data networks for computer communications, and broadcast networks for television are very capable in supporting their intended services. These networks, however, are not well suited for other services like multimedia applications which involve the process­ ing and exchange of information in the various media of text, audio, and images. Broadband Integrated Services Digital Network (B-ISDN) provides a range of narrowband and broad­ band services for voice, video, and multimedia. It provides virtual connections for services which are distributive or interactive, constant bit rate or variable bit rate, and connection oriented or connectionless. Asynchronous Transfer Mode (ATM) has been selected by the standards bodies as the transfer mode for implementing B-ISDN. The ability to digitize images has lead to the prospect of reducing the physical space requirements, material costs, and manual labor of traditional film handling tasks in hospitals. The system which handles the acquisition, storage, and transmission of medical images is called a Picture Archiving and Communication System (FACS). A complete PACS system will require some means of transmission of the large amounts of digital data. The transmission system wUl directly impact the speed of image transfer. Today the most common transmision means used by acquisition and display station products is Ethernet. However, when considering network media, it is im portant to consider what the long term needs wiU be. Ethernet may be easily available, but sheer image data sizes will require most

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Application of Asynchronous Transfer Mode (Atm) technology to Picture Archiving and Communication Systems (Pacs): A survey

Concerns the economics of customer-premises agents that manage the bandwidth demanded by next-generation, high-speed networks. Models are proposed for the hypothetical prices of SONET and ATM telecommunication services. The ATM model builds on the SONET model, splitting the leased-line price into two components/spl mdash/a traffic-insensitive charge for port and access fees and a traffic-sensitive charge for delivering cells through the network/spl mdash/which are balanced so as to make the cost of ATM service at a pre-determined level of network utilization equal to the cost of a leased line. The models are extended to incorporate the rate at which transmission prices are expected to fall over time, the rate at which link traffic is expected to grow, and the degree of bandwidth conservation offered by the management system. The results show net economic efficiency over a wide range of circumstances, thereby suggesting the continued usefulness of customer-premises bandwidth management well into the future. >

The role of customer-premises bandwidth management

ATM networks and their applications at the NASA Lewis Research Center A case study

It is argued that the technology needed to support the emerging broadband integrated services digital network technology (B-ISDN) is on the horizon, but the deployment of this technology in the telecommunication plant will not be sufficient to make B-ISDN a commercial success. Two corequisites for ensuring the long-term success of the emerging B-ISDN include stimulating the demand for bandwidth by inventing and promoting new telecommunication applications, and enabling the interconnection or convergence of the emerging high-speed network and the existing cable television infrastructure. The author believes that this is necessary because no alternative seems to offer a workable base for financing the transition to B-ISDN and for reaching the needed economy of scale, and because the intrinsic value of the public network grows combinatorially with the number of subscribers. >

D.R. Irvin

Papers

Making broadband-ISDN successful

The role of customer-premises bandwidth management