New channels, old concerns: Scalable and reliable data dissemination

Abstract

An interesting trend in the continuing convergence of information technologies is the emergence of the Internet as a content provider in its own right, as opposed to its simply being one of many delivery channels. For example, it is increasingly the primary source for items such as court rulings and software releases. Unfortunately the IP protocols normally employed for reliable data transfer are of the point-to-point type and not well suited to large-scale one-to-many dissemination. Sudden rushes to obtain new items can cause severe traffic congestion and degrade network service across a whole region. Even worse, sites which are routinely popular cause routine congestion. Broadcast technologies should be able to provide a better solution in terms of scalability. The Internet has a mature protocol suite for IP multicast and more recently the traditional wireless broadcast industry has started moving from analog to digital transmission formats. However, in both these cases the emphasis in protocol development has been on support for continuous media, which requires timeliness of delivery rather than bit-perfect data integrity. A further problem with the new digital broadcast channels is their lack of support for integration with the Internet. This paper examines some of the issues involved in providing both reliable and scalable dissemination across broadcast channels and describes the DABWeb architecture for Internet content dissemination via digital broadcast.