  In this paper, we investigate an important research problem facing the
upcoming satellite Internet: from a network perspective, how many satellites
exactly do we need to construct a survivable and performant LSN? To answer this
question, we first formulate the survivable and performant LSN design (SPLD)
problem, which aims to find the minimum number of needed satellites to
construct an LSN that can provide sufficient amount of redundant paths,
required link capacity and acceptable latency for traffic carried by the LSN.
Second, to efficiently solve the tricky SPLD problem, we propose MEGAREDUCE, a
requirement-driven constellation optimization mechanism, which can calculate
feasible solutions for SPLD in polynomial time. Finally, we conduct extensive
trace-driven simulations to verify MEGAREDUCE's cost-effectiveness in
constructing survivable and performant LSNs on demand, and showcase how
MEGAREDUCE can help optimize the incremental deployment and long-term
maintenance of future satellite Internet.
