  In this paper we present a model to study the end-to-end delay performance of
a satellite-ATM netowrk. We describe a satellite-ATM network architecture. The
architecture presents a trade-off between the on-board switching/processing
features and the complexity of the satellite communication systems. The
end-to-end delay of a connection passing through a satellite constellation
consists of the transmission delay, the uplink and downlink ground
terminal-satellite propagation delay, the inter-satellite link delays, the
on-board switching, processing and buffering delays. In a broadband satellite
network, the propagation and the buffering delays have the most impact on the
overall delay. We present an analysis of the propagation and buffering delay
components for GEO and LEO systems. We model LEO constellations as satellites
evenly spaced in circular orbits around the earth. A simple routing algorithm
for LEO systems calculates locally optimal paths for the end-to-end connection.
This is used to calculate the end-to-end propagation delays for LEO networks.
We present a simulation model to calculate the buffering delay for TCP/IP
traffic over ATM ABR and UBR service categories. We apply this model to
calculate total end-to-end delays for TCP/IP over satellite-ATM networks.
