  The sensitivity of LISA depends on the suppression of several noise sources;
dominant one is laser frequency noise. It has been shown that the six Doppler
data streams obtained from three space-crafts can be appropriately time delayed
and optimally combined to cancel this laser frequency noise. We show that the
optimal data combinations when operated in a network mode improves the
sensitivity over Michelson ranging from 40 % to 100 %. In this article, we
summarize these results. We further show that the residual laser noise in the
optimal data combination due to typical arm-length inaccuracy of 200 m is much
below the level of optical path and the proof mass noises.
