Agent Tcl: a Exible and Secure Mobile-agent System

A mobile agent is an autonomous program that can migrate under its own control from machine to machine in a heterogeneous network. In other words, the program can suspend its execution at an arbitrary point, transport itself to another machine, and then resume execution from the point of suspension. Mobile agents have the potential to provide a {\em single, general framework} in which a wide range of distributed applications can be implemented efficiently and easily. Several challenges must be faced, however, most notably reducing migration overhead, protecting a machine from malicious agents (and an agent from malicious machines), and insulating the agent against network and machine failures. Agent Tcl is a mobile-agent system under development at Dartmouth College that has evolved from a Tcl-only system into a multiple-language system that currently supports Tcl, Java, and Scheme. In this thesis, we examine the motivation behind mobile agents, describe the base Agent Tcl system and its security mechanisms for protecting a machine against malicious agents, and analyze the system''s current performance. Finally, we discuss the security, fault-tolerance and performance enhancements that will be necessary for Agent Tcl and mobile agents in general to realize their full potential.

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