Modeling and Analysis of Active Messages in Volatile Networks

Interest in and development of mobile agent software systems has burgeoned in the past ve years. Code mobility has many attractive attributes for performance and dynamic deployment of new distributed computing and information management applications. An active message is a datagram encapsulated as a mobile agent. The agent is persistent in the network, moving from node to node under its own internal routing logic and control at the application layer. Active messages are particularly attractive in networks that have very unreliable links such as wireless networks in which the nodes are mobile. Such networks experience frequent link failures and other changes in topology. Active messages allow data to propagate between nodes that may never have viable TCP/IP type connections. In spite of the growing implementation interest in mobile agents and active messaging, there are essentially no analytic models or results dealing with their performance. This paper presents a simple model for active messages in a network with frequent link failures. Using this model, we develop expressions for the expected delivery time of an active message along one path as well as expected delivery time for duplicated messages traversing disjoint paths between source and destination nodes.