Internet Delivery System (IDS),

[attachment=17572]

1. INTRODUCTION

Satellites have been used for years to provide communication network links. Historically, the use of satellites in the Internet can be divided into two generations. In the first generation, satellites were simply used to provide commodity links (e.g., T1) between countries. Internet Protocol (IP) routers were attached to the page link endpoints to use the links as single-hop alternatives to multiple terrestrial hops. Two characteristics marked these first-generation systems: they had limited bandwidth, and they had large latencies that were due to the propagation delay to the high orbit position of a geosynchronous satellite.
In the second generation of systems now appearing, intelligence is added at the satellite page link endpoints to overcome these characteristics. This intelligence is used as the basis for a system for providing Internet access engineered using a collection or fleet of satellites, rather than operating single satellite channels in isolation. Examples of intelligent control of a fleet include monitoring which documents are delivered over the system to make decisions adaptively on how to schedule satellite time; dynamically creating multicast groups based on monitored data to conserve satellite bandwidth; caching documents at all satellite channel endpoints; and anticipating user demands to hide latency.



Can international Internet access using a geosynchronous satellite be competitive with today's terrestrial networks?
The first question is whether it makes sense today to use geosynchronous satellite links for Internet access. Alternatives include wired terrestrial connections, low earth orbiting (LEO) satellites, and wireless wide area network technologies (such as Local Multipoint Distribution Service or 2.4-GHz radio links in the U.S.).


What elements constitute an "intelligent control" for a satellite-based Internet link?

The basic architecture behind intelligent control for a satellite fleet is to augment the routers at each end of a satellite page link with a bank of network-attached servers that implement algorithms appropriate for the types of traffic carried over the links. We use certain terminology in our discussion. First, given the argument above for asymmetric traffic, our discussion is framed in terms of connecting content providers (in a few countries) to end users (in all countries). In some cases (e.g., two-way audio), however, the traffic may be symmetrical. Second, we refer to the content-provider endpoint of a satellite page link as a warehouse, and the end-user endpoint as a kiosk.