Time management in active networks

This paper investigates time management for distributed simulations in active networks. Time management is essentially the computation of the Lower Bound Time Stamp (LBTS) across federates in a distributed simulation, including in-transit (in-flight) messages. We show that the LBTS computation is an instance of the Distributed Termination Detection (DTD) problem and how DTD algorithms can be applied to LBTS in an active network. These algorithms are potentially much more efficient than traditional algorithms that rely on point-to-point communication. We demonstrate the potential of the Distinguished Root Node algorithm that can compute LBTS in O(logn) time in general network topologies using a prototype implemented in Java. While active network algorithms have the potential for improved functionality and superior performance, this potential will only be realized when "native" implementations are possible. For wide-scale deployment, real-world issues such as reliable delivery dynamic routing topologies, security and fault tolerance will have to be systematically addressed.