移动移动 agentagent 通信协议的通信协议的设计与分析设计与分析

答 辩 人： 冯 新 宇指导教师：吕 建 教授

南京大学计算机软件研究所2002 年 6月 4日

Outline of PresentationOutline of Presentation

Introduction: Inter-Agent Message PassingARP: Design and AnalysisGeneralization: A Generic FrameworkConclusion and Future Work

Introduction: Basic ConceptsIntroduction: Basic Concepts

Mobile Agents– Mobile Agents are autonomous objects or object cluster

s, 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 lay

er 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 PassingWhy 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 PassingInter-Agent Message Passing- - RequirementsRequirements

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.

MAPMAP

MAP

MAP

Inter-Agent Message PassingInter-Agent Message Passing- - RequirementsRequirements

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 Pa

ttern

Introduction: Inter-Agent Message PassingARP: Design and Analysis

– Design of ARP– Analysis of ARP– Improvements

Generalization: A Generic FrameworkConclusion and Future Work

Design of ARP (Adaptive and Design of ARP (Adaptive and Reliable Protocol)Reliable Protocol)

Mobile IP solutionExtention1: Mobile IP + SynchronizationExtension2: Distributed Home SchemeExtension3: Mailbox-Based Scheme = ARP

Mobile IP SolutionMobile IP Solution

MAP

MAP

MAP

MAP-Home

Reg

Design of ARPDesign of ARP

Mobile IP solution– No Reliability Support

Extention1: Mobile IP + Synchronization– The agent home coordinates message passing

and agent migration

Extension2: Distributed Home SchemeExtension3: Mailbox-Based Scheme = ARP

MAP

Mobile IP + SynchronizationMobile IP + Synchronization

MAP

MAP

MAP-Home

Dereg ACK Reg

MAP-Home

MAP

Mobile IP + SynchronizationMobile IP + Synchronization

MAP

MAP

Dereg ACK Reg

Mobile IP + SynchronizationMobile IP + Synchronization

MAP

MAP

MAP

MAP-Home

Dereg ACK

Mobile IP + SynchronizationMobile 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 ARPDesign of ARP

Mobile IP solutionExtention1: Mobile IP + SynchronizationExtension2: 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 SchemeDistributed Home Scheme

MAP-1 MAP-3MAP-2

MAP-5

MAP-4

MAP-3MAP-2MAP-1

Distributed Home SchemeDistributed Home Scheme

MAP-5

Distributed Home SchemeDistributed Home Scheme

MAP-4

MAP-1 MAP-3MAP-2

MAP-5

Caching MechanismCaching Mechanism

MAP-1

MAP-2 MAP-3

Distributed Home SchemeDistributed 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 ARPDesign of ARP

Mobile IP solutionExtention1: Mobile IP + SynchronizationExtension2: Distributed VersionExtension3 (ARP): Mailbox-Based

Scheme

Design of ARPDesign of ARP-The Mailbox-Based Scheme-The Mailbox-Based Scheme

MAP

MAP

MAP

MB

Design of ARPDesign of ARP-The Mailbox-Based Scheme-The Mailbox-Based Scheme

Communication between agents is divided into two steps– Message transmission from the sender to the

receiver’s 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

ARP-ARP-AAdaptive and daptive and RReliable eliable PProtocolrotocol

MAP-1 MAP-3

MAP-5MAP-4

MB

MB

MAP-2

MB

MAP-6

MB

MAP-4 MAP-5

MB

MAP-1

MB

MAP-2 MAP-3

MB

MAP-6

MB

MAP-4 MAP-5

MB

MAP-1

MB

MAP-2 MAP-3

MB

MAP-6

MB

Properties of ARPProperties of ARP

Location Transparency– Home + Caching Mechanism

Reliability– Synchronization is used

Asynchronous MigrationAdaptability

– Mobile IP + Synchronization– Distributed Home Scheme

Efficiency

Introduction: Inter-Agent Message PassingARP: Design and Analysis

– Design of ARP– Analysis of ARP– Improvements

Generalization: A Generic FrameworkConclusion and Future Work

ARP: Design and AnalysisARP: 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 PassingARP: Design and AnalysisGeneralization: A Generic Framework

– Design Space of the mailbox-based scheme– Three-Dimensional Framework– Particular Protocols

Conclusion and Future Work

Design Space of the Mailbox-Design Space of the Mailbox-based Schemebased Scheme

Migration of the mailboxInteraction between the agent and its

mailbox: Push or Pull?Synchronization

– Sender The mailbox– The mailbox Its owner agent

Generalization – A Generic Generalization – A Generic FrameworkFramework

NM JM FMX (Migration Frequency)

Y (Delivery Mode)

PL

PS

NSSHM (SMA)

FS

Z (Synchronization)

The Generic FrameworkThe Generic Framework-Particular Protocols-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 WorkConclusion 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 WorkConclusion 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 WorkConclusion and Future Work

– Modeling mobility of mobile agents– Extend the mailbox-based scheme for mobile a

gents multicast

Future work

致谢致谢感谢参加答辩的各位老师感谢我的导师吕建教授三年来的谆谆教

诲感谢陶先平博士对我工作上的指导和帮

助感谢软件所其他老师和各位同学对我生

活和学习上的关心和帮助

发表论文和参加项目发表论文和参加项目 发表论文

– 一种改进的移动 agent 通信算法，计算机学报， 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

参加项目– 基于 Internet 的移动 agent 技术及其在电子商务中的

应用– Design of Efficient Mobile Agent Communication Proto

cols