Bounded Protocols for Efficient Reliable Message Transmission

In the reliable message transmission problem (RMTP) processors communicate by exchanging messages, but the channel that connects two processors is subject to message loss, duplication, and reordering. Previous work focused on proposing protocols in asynchronous systems, where message size is finite and sequence numbers are bounded. However, if the channel can duplicate messages, lose messages, and arbitrarily reorder the messages, the problem is unsolvable. In this thesis, we consider a strengthening of the asynchronous model in which reordering of messages is bounded. In this model, we develop two efficient protocols to solve the RMTP: (1) when messages may be duplicated but not lost and (2) when messages may be duplicated and lost. This result is in contrast to the impossibility of such an algorithm when reordering is unbounded. Our protocols have the pleasing property that no messages need to be sent from the receiver to the sender

Virtual stationary timed automata for mobile networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 339-347).In this thesis, we formally define a programming abstraction for mobile networks called the Virtual Stationary Automata programming layer, consisting of real mobile clients, virtual timed I/O automata called virtual stationary automata (VSAs), and a communication service connecting VSAs and client nodes. The VSAs are located at prespecified regions that tile the plane, defining a static virtual infrastructure. We present a theory of self-stabilizing emulation and use this theory to prove correct a self-stabilizing algorithm to emulate a timed VSA using the real mobile nodes that are currently residing in the VSA's region. We also specify two important services for mobile networks: motion coordination and end-to-end routing. We split the implementation of the end-to-end routing service into three smaller pieces, consisting of geographic routing and location management services with an end-to-end routing service built on top of them. We provide stabilizing implementations of each of these services using the VSA abstraction, and provide formal correctness analyses for each implementation.by Tina Ann Nolte.Ph.D