Mobile Agents: Understanding Weak Mobility and Aglets, Slides of Multiagent Systems

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Mobile agents

Weak mobility

Challenges in soft mobility

• Platform independent code
  • How do I handle heterogeneous systems?
  • What about extremely heterogeneous systems?
• How to collect state / data?
• How to mark checkpoints (when is mobility possible)?
• Authorization, security, resource management
• Reliability problems
• How do I handle open files and other local resources?
• How do I handle global names? How do I send a message to a mobile agent? What is the address of the agent?

Agent systems with weak mobility

• Most agent system designers considered that migration is a relatively rare even in the life of the agent system. - Thus: weak mobility
• The agent system is allowed to migrate, but migration is not a fundamental type of operation, but a problem to be solved - In Telescript, migration was the basic communication primitive!
• Examples:
  • Aglets, Jade, Concordia, Grasshopper, Bond 2, aIsland (JXTA)
  • About 60 agent systems on the Mobile Agent List
  • http://mole.informatik.uni-stuttgart.de/mal/mal.html

Aglets

• Java based mobile agent system
  • I have chosen to present this because of its major focus on mobility
• Research project at IBM Japan (from 1996)
  • Danny Lange and Mitsuro Oshima
  • http://www.trl.ibm.com/aglets/index_e.htm
• As IBM decided to phase out the project it was released as an Open Source project - http://aglets.sourceforge.net/

Aglets (cont’d)

• Goal: “Provide an easy and comprehensive model for programming mobile agents without requiring modifications to Java VM or native code”

Agent lifecycle

• Instantiating:
  • Creating a new aglet from the codebase
  • Cloning (the clone has the same state as the original but different identity)
• An aglet can dispatch itself to a remote server by calling the Aglet.dispatch(URL dest) primitive. To be more precise, an aglet occupies the aglet context and can move from this context to others during its execution. Because the server may serve multiple contexts within one Java VM, and one host may serve multiple servers in one host the context are named as the following set Docsity.com

Aglet lifecycle (cont’d)

• Dispatching causes an aglet to suspend its execution, serialize its internal state and bytecode into the standard form and then to be transported to the destination. On the receiver side, the Java object is reconstructed according to the data received from the origin, and a new thread is assigned and executed.
• Aglets can be persistent. Since a mobile aglet needs to be serializable into a bit-stream, all mobile aglet can be persistent in nature. TheDocsity.com

Security issues in aglets / mobile

agents

• For secure agent execution, the agent system must provide the following security services:
• Authentication of the Sender, the Manufacturer and the Owner of the Agent. - Who is responsible for this agent? - Who is responsible for the agent code? - Has the agent (code and state) been tampered with?
• Authorization of the Agent (or Its Owner)
  • What can this agent do? (E.g, can this agent access files?)
• Secure Communication between Agent Docsity.com