Simulation of two routing protocols operating in a low Earth orbit satellite network environment

Modern warfare is placing an increasing reliance on global communications. Currently under development are several low Earth orbit (LEO) satellite systems that propose to deliver voice and data traffic to subscribers anywhere on the globe. However, very little is known about the performance of conventional routing protocols under orbital conditions where the topology changes in minutes rather than days. This paper compares two routing protocols in a LEO environment. One (extended Bellman-Ford) is a conventional terrestrial routing protocol, while the other (Darting) is a new protocol which has been proposed as suitable for use in LEO networks. These protocols are compared via computer simulation in two of the proposed LEO systems (Globalstar and Iridium), under various traffic intensities. Comparative measures of packet delay, convergence speed, and protocol overhead are made. It is found that while both protocols have roughly equivalent end-to-end delay characteristics, Darting requires a much higher overhead. Darting also demonstrates higher instability at network update periods. Darting is handicapped by a strong correlation between data traffic and protocol overhead. Modifications to reduce this overhead would result in better performance.