Outline of Presentation Introduction: Inter-Agent Message Passing ARP: Design and Analysis Generalization: A Generic Framework Conclusion and Future Work
Introduction: Basic Concepts Mobile Agents – Mobile Agents are autonomous objects or object clusters, which are able to move between locations in a so-called mobile agent platform. (Mole, U of Stuttgart) Mobile Agent Platform – A mobile agent platform is a distributed abstraction layer that provides the concepts and mechanisms for mobility and communication on one hand, and security of the underlying system on the other hand.
Why Message Passing Mobile Agent System can be used as General-Purpose Distributed Computing Middleware Platform. Sometimes Message Passing is more efficient than migration There DO exist MA-based applications that needs remote message passing between cooperating agents.
Inter-Agent Message Passing - Requirements Location Transparency – Message sender does not need to know the physical location of the receiver agent, whose address changes frequently by moving from one host to another. Reliability – The concurrent and asynchronous nature of message forwarding and agent migration may cause message loss or chasing problem. – By reliability we mean the message can reach the target agent by a bounded number of forwarding.
Design of ARP Mobile IP solution – No Reliability Support Extention1: Mobile IP + Synchronization – The agent home coordinates message passing and agent migration Extension2: Distributed Home Scheme Extension3: Mailbox-Based Scheme = ARP
MAP Mobile IP + Synchronization MAP MAP-Home Dereg ACK Reg
MAP-Home MAP Mobile IP + Synchronization MAP Dereg ACK Reg
Mobile IP + Synchronization MAP MAP-Home Dereg ACK
Mobile IP + Synchronization Pros – Simple – Guarantee reliable message delivery Agent has received all the message on transmission before migration Message forwarding is suspended during agent migration Cons – Rely too much on the agent home Performance bottleneck Single-point-of-failure Asynchronous execution – Triangle Routing
Design of ARP Mobile IP solution Extention1: Mobile IP + Synchronization Extension2: Distributed Home Scheme – Decentralize the role of agent home to all the hosts on the migration Path – Caching Mechanism Extension3: Mailbox-Based Scheme = ARP
MAP-4 Distributed Home Scheme MAP-1 MAP-3 MAP-2 MAP-5
MAP-4 MAP-3 MAP-2 MAP-1 Distributed Home Scheme MAP-5
Distributed Home Scheme MAP-4 MAP-1 MAP-3 MAP-2 MAP-5
Distributed Home Scheme Pros – Location Transparency, Reliability – Reliance on the agent home is reduced – Locality of Communication (No Triangle Routing) Cons – Migration Cost is Un-Affordable – Delay of Migration is prohibitive
Design of ARP Mobile IP solution Extention1: Mobile IP + Synchronization Extension2: Distributed Version Extension3 (ARP): Mailbox-Based Scheme
Design of ARP -The Mailbox-Based Scheme Communication between agents is divided into two steps – Message transmission from the sender to the receivers mailbox Identical with inter-agent Communication Distributed Home Scheme is used – Delivery of the message from the mailbox to its owner agent Push or Pull
Properties of ARP Location Transparency – Home + Caching Mechanism Reliability – Synchronization is used Asynchronous Migration Adaptability – Mobile IP + Synchronization – Distributed Home Scheme Efficiency
Introduction: Inter-Agent Message Passing ARP: Design and Analysis – Design of ARP – Analysis of ARP – Improvements Generalization: A Generic Framework Conclusion and Future Work
ARP: Design and Analysis Analysis – Migration of the mailbox When to migrate Impact of migration frequency on the performance – Interaction between the mailbox and the agent Push or Pull Improvement – Path Compression and Garbage Collection – Fault-Tolerance Issues
Impact of the migration frequency on the performance
Introduction: Inter-Agent Message Passing ARP: Design and Analysis Generalization: A Generic Framework – Design Space of the mailbox-based scheme – Three-Dimensional Framework – Particular Protocols Conclusion and Future Work
Design Space of the Mailbox- based Scheme Migration of the mailbox Interaction between the agent and its mailbox: Push or Pull? Synchronization – Sender The mailbox – The mailbox Its owner agent
Generalization – A Generic Framework NM JM FM X (Migration Frequency) Y (Delivery Mode) PL PS NS SHM (SMA) FS Z (Synchronization)
The Generic Framework -Particular Protocols Parameter Combination – The three dimensions are orthogonal – Protocol: XX-YY-ZZ Home-Server Based Protocols – NM-PS-NS: Identical to Mobile IP – NM-PS-SMA: Mobile IP + Sync – NM-PL-NS: Pull mode is used
Forwarding Pointer Based Protocols – FM-*-NS – JM-PL-NS – JM-PS-NS Distributed Registration-Based Protocols – FM-*-SHM (Distributed Home Scheme) – JM-PS-FS – JM-PL-SHM (ARP) When to use which protocol?
Conclusion and Future Work The mailbox based scheme introduces – Flexibility and adaptability – Reduction of the constraint on the agent mobility. – Better balance between migration cost and message delivery cost
Conclusion and Future Work Based on the scheme – The Generic Framework can be used to: Describe and evaluate various MA communication protocols Help users to clearly specify their requirements Help users to design flexible and adaptive protocols which can be customized to meet their requirements – The ARP protocol derived from the framework can satisfy the requirements of a protocol Location Transparency Reliability Asynchrony Efficiency and Adaptability
Conclusion and Future Work – Modeling mobility of mobile agents – Extend the mailbox-based scheme for mobile agents multicast Future work
– agent Vol.25, No. 4, 2002, pp. 357-364 – An Efficient Mailbox-Based Algorithm for Message Delivery in Mobile Agent Systems Proc. of MA2001, pp. 135-151 – Internet agent – Design of Efficient Mobile Agent Communication Protocols