Java-based mobile agents

Institute for Visualization and Perception ResearchI VPR 1

© Copyright 1999 Haim Levkowitz

Java-based mobile agents



Java effective for mobile agents in e-commerce



Earlier technologies

• “Fathered” mobile agents

• Dev’d to improve RPC for distributed programming

• Process migration

• Remote evaluation

• Mobile objects



Process migration

• Move entire address space among computers

• Reduce net BW compared to RPC• Multiple RPCs to execute app

• ==> Entire process can migrate• No way to return data back to source

node wo entire process returning



Remote evaluation

• Send request in form of program (not entire process address space)

• Remote executes + returns results

• No need to transmit process control data

• Lack ability to encapsulate more state info into program



Mobile objects

• Extend remote eval

• Capture more program behavior within mobile object

• Objects migrate, carrying executable code, data (object specific properties), other objects

• Mobile agents improved …



Mobile agents improved

• Reduce net traffic for app’s processing large quantities of data

• Earlier: client/server• Ship data to program source

• Agents: ship program to data• Also, autonomy: decide dynamically,

where, when to travel



Client/server vs. agent computing modelsClient Server

NetworkInteraction

Client Server

NetworkInteraction

Agent



Mobile agents improvements (cont.)

• Adapt to changes in program state + net environment

• Asynchrounous interaction• User can disconnect from net• Store-and-forward mechanism

• Async + autonom ==> protect mission-critical app’s form unreliable net’s



Mobile agent advantages (cont.)

• Traveling user

• Connect/disconnect

• Fault tolerance

• Security



Java as a language for mobile agent dev

• Concordia

• Odyssey

• Voyager



Java for mobile agents

• Multiplatform support

• “Write once, run anywhere”

• Ubiquity of JVM

• ==> Facilitate dissemination



Java unique features

• Object serialization

• ==> Convert agent + state -->suitable form for net transmission

• Remote sys reconstruct



Java unique features (cont.)

• Persistent agent state info

• Serialize agent’s state

• Write to persistent storage

• Retrieve state + use to reconstruct agent



Java unique features (cont.)• Network support

• Sockets

• URL comm.

• Distributed object protocol

• RMI: Remote method invocation

• Prog. Access to dist. object simple

• RMI handled by local proxy



Java unique features (cont.)

• Class loading mechanism

• ==> Facilitate migration of code + state

• Dynamically load classes

• Classpath / net

• Code subject to security restrictions

• Fine-grain, configurable security policies

• Tight integration with Web ...



Tight integration with Web• Applets can launch mobile agents• Receive returning agents when done• Servlets: function like CGI script• May launch + receive mobile agents• JNDI: Java Naming & Directory Interface

==> seamless connectivity via unified access to multi naming + directory services



Generic mobile agent architecture

SecurityManager

GenericMobile Agent Server

GenericMobile Agent Server

InteragentCommunication Manager

ApplicationGateway

DirectoryManager

Agent

Reliability Manager

Agent ManagerNetwork

ExternalApplication

Generic Mobile Agent Server



Generic mobile agent architecture• Six major components

• Agent manager

• Interagent communications manager

• Security manager

• Reliability manager

• Application gateway

• Directory manager



Agent manager• Send agents to remote hosts• Receive agents for execution on local host• Serialize agent prior to transport• Pass serialized form to counterpart on

destination• Really to reliability manager

• Ensure reception on other side



Agent manager• Upon reception

• Reconstruct

• Agent + objects ref’d

• Create execution context



Mobile agent system (JVM)

• Auto invoke security manager

• Authorize any op’s using sys resources

• Request agent manager to transport agent to correct location



Security manager• Protect host + mobile agents against

unauthorized code• Authenticate received agent• Encrypt agents before

• Transmission • Saving to storage

• Digitally sign agents• Exchange certificates



Reliability manager• Ensure robustness of mobile agent system

• Shield agents from server / sys crash

• Guarantee persistence of

• State associated with agents

• Mobile agent sys

• Use transactional queuing to ensure agents reach destination even during sys crashes



Interagent communications manager



Application gateway



Directory manager



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A killer opp



What’s next?

Documents

Java-based mobile agents