  We study the optimal control of propagation of packets in delay tolerant
mobile ad-hoc networks. We consider a two-hop forwarding policy under which the
expected number of nodes carrying copies of the packets obeys a linear
dynamics. We exploit this property to formulate the problem in the framework of
linear quadratic optimal control which allows us to obtain closed-form
expressions for the optimal control and to study numerically the tradeoffs by
varying various parameters that define the cost.
