Testing TCP/IP Performance Optimizations Using NASA's Advanced
    Communications Technology Satellite Gigabit Satellite Network

			   David R. Beering
			      Principal
		 Infinite Global Infrastructures, LLC
			  Under contract to
	    Sterling Software, NASA Lewis Research Center

During two three-month experiments spanning 1996 and 1997, a group
of researchers from NASA and industry collaborated on a series of
TCP/IP performance optimization experiments using NASA's Advanced
Communications Technology Satellite (ACTS). The purpose of these
experiments was to examine the effect of geostationary delays on
TCP/IP data transfers after optimizations using the IETF's RFC 1323
TCP Extended Windows and RFC 2018 TCP Selective Acknowledgement, and
to use these performance optimizations as a baseline for experiments
on tape-to-tape transfer, and high-speed link encryption. The
satellite link, carried across the ACTS spacecraft at 622 Megabits per
second, was the fastest communications satellite link ever
established.
    Using equipment provided by Sun Microsystems, FORE Systems, Ampex
Data Systems, Secant Network Technologies, and NSC StorageTek, three
reference configurations were established: a Communications Satellite
model operating at 622 Mbps full-duplex; a Relay Satellite model with
a return link operating at 622 Mbps and a forward link operating at
1.544 Mbps; and a Global Broadcast Satellite model with a satellite
return link operating at 622 Mbps and a terrestrial forward link
operating at 155 Mbps.
    Experimental results confirmed that TCP/IP is a viable protocol
for networks operating in this performance regime. Memory-to-memory
user date rates in excess of 500 Mbps were demonstrated between two
Sun Ultra 2 workstations.
    Additional tests studied the effect of firewall and encryption
devices on the performance of the TCP/IP data transfer. Two different
155 Mbps encryption systems were studied, with performance benchmarked
in the Local Area Network, across a 2000-mile wide-area terrestrial
link, and finally across the geostationary satellite link.
    Additional performance tests were performed using Ampex
high-speed, high-density tape systems. These tests were benchmarked on
a Local Area Network, and repeated across the satellite link.
    This presentation will discuss the satellite reference
configurations used in the experiments, along with the data transfer
results acieved for each configuration. Finally, a review of current
work extending the original tests to other operating environments will
be presented.