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Outline of Presentation

• Introduction Inter-Agent Message Passing
• ARP Design and Analysis
• Generalization A Generic Framework
• Conclusion and Future Work

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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.

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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.

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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.

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MAP
?
MAP
MAP
MAP
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Inter-Agent Message Passing- Requirements

• Efficiency
• Low location updating overhead
• Low message delivery overhead
• Asynchrony
• Asynchronous execution
• Little constraint on the mobile agent mobility.
• Adaptability
• Suit different Communication and Migration Pattern

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• Introduction Inter-Agent Message Passing
• ARP Design and Analysis
• Design of ARP
• Analysis of ARP
• Improvements
• Generalization A Generic Framework
• Conclusion and Future Work

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Design of ARP (Adaptive and Reliable Protocol)

• Mobile IP solution
• Extention1 Mobile IP Synchronization
• Extension2 Distributed Home Scheme
• Extension3 Mailbox-Based Scheme ARP

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Mobile IP Solution
MAP
MAP-Home
MAP
MAP
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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

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Mobile IP Synchronization
MAP
MAP-Home
MAP
MAP
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Mobile IP Synchronization
MAP
MAP-Home
MAP
MAP
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Mobile IP Synchronization
MAP
MAP-Home
MAP
MAP
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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

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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

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Distributed Home Scheme
MAP-1
MAP-2
MAP-3
MAP-5
MAP-4
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Distributed Home Scheme
MAP-2
MAP-1
MAP-3
MAP-5
MAP-4
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Distributed Home Scheme
MAP-1
MAP-2
MAP-3
MAP-5
MAP-4
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Caching Mechanism
MAP-1
MAP-2
MAP-3
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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

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Design of ARP

• Mobile IP solution
• Extention1 Mobile IP Synchronization
• Extension2 Distributed Version
• Extension3 (ARP) Mailbox-Based Scheme

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Design of ARP-The Mailbox-Based Scheme
MB
MAP
MAP
MAP
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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

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ARP-Adaptive and Reliable Protocol
MB
MB
MAP-1
MAP-2
MAP-3
MB
MB
MAP-5
MAP-4
MAP-6
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MB
MB
MAP-1
MAP-2
MAP-3
MB
MB
MAP-4
MAP-5
MAP-6
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MB
MB
MAP-1
MAP-2
MAP-3
MB
MB
MAP-4
MAP-5
MAP-6
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Properties of ARP

• Location Transparency
• Home Caching Mechanism
• Reliability
• Synchronization is used
• Asynchronous Migration
• Adaptability
• Mobile IP Synchronization
• Distributed Home Scheme
• Efficiency

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• Introduction Inter-Agent Message Passing
• ARP Design and Analysis
• Design of ARP
• Analysis of ARP
• Improvements
• Generalization A Generic Framework
• Conclusion and Future Work

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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

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Impact of the migration frequency on the
performance
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• 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

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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

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Generalization A Generic Framework
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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

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• 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?

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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

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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

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Conclusion and Future Work

• Future work

• Modeling mobility of mobile agents
• Extend the mailbox-based scheme for mobile agents
  multicast

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• ???????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