AZIMAS: ALMOST ZERO INFRASTRUCTURE MOBILE AGENT

74 Pages·2001·0.17 MB·English

AZIMAS: ALMOST ZERO INFRASTRUCTURE MOBILE AGENT SYSTEM

By

AMAR NALLA

A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2001
Copyright 2001

by

Amar Nalla
ACKNOWLEDGMENTS
I would like to express my thanks to Dr. Abdelsalam (Sumi) Helal for all his
support and motivation. I would also like to thank Dr. Michael Frank and Dr. Joachim
Hammer for agreeing to serve in my committee and for reviewing my work.
I extend special thanks to my parents for being patient and for understanding my
efforts that kept me away from home for a long time. I would also like to thank
Choonhwa Lee for providing help with my Unix account in the Harris Lab. I also thank
Sonali for understanding that this work was important and for letting me stay in the lab
for long hours.
I also thank members of the Apache mailing list, the Agents mailing list and the
Java-res mailing list for answering all of my questions and for helping me solve some
tough problems. I also thank all the users of Java usenet groups for providing valuable
suggestions. This work would not have been possible without all of this help.

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TABLE OF CONTENTS

page

ACKNOWLEDGMENTS..................................................................................................iii
LIST OF FIGURES...........................................................................................................vii
ABSTRACT.....................................................................................................................viii
INTRODUCTION...............................................................................................................1
1.1Vision of AZIMAS.....................................................................................................2
1.2 Goal of Thesis...........................................................................................................2

SURVEY OF RELATED WORK......................................................................................5
2.1 Mobile Agents Research Issues.................................................................................5
2.1.1Taxonomy of Mobile Agents..............................................................................5
2.1.2 Java Based Agents..............................................................................................6
2.1.3 Non Java-Based Agents.....................................................................................7
2.2 Agent Servers............................................................................................................8
2.2.1 Ajanta Server Architecture.................................................................................8
2.2.2 Aglets Runtime Layer........................................................................................9
2.3 Web Servers............................................................................................................11
2.4 Mobile Agents on Web Servers..............................................................................12

INFRASTRUCTURE REQUIREMENTS AND SECURITY ISSUES...........................15
3.1 Infrastructure Requirements....................................................................................15
3.2 Security Issues.........................................................................................................16
3.2.1 Agent and Server Authentication.....................................................................17
3.2.2 Access Control.................................................................................................17
3.2.3 Protection of Agents.........................................................................................18
3.3 Resource Usage and Availability of Server............................................................19
3.4 Generic Agent Server..............................................................................................19

AZIMAS ARCHITECTURE............................................................................................21
4.1 Introduction.............................................................................................................21
4.2 Overall Architecture................................................................................................21
4.3 AZIMAS agents......................................................................................................22
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4.4 Mobility of AZIMAS Agents..................................................................................24
4.5 Encapsulation of Agents as MIME contents...........................................................25
4.5.1 Mobile Agent Constituents...............................................................................25
4.5.2 HTTP Message Structure.................................................................................26
4.6 Client Components..................................................................................................27
4.7 Server Components.................................................................................................28
4.7.1 Apache: An Ideal Web Server..........................................................................30
4.7.2 How Apache Works.........................................................................................30
4.7.3 Apache Server Components.............................................................................31
4.7.4 RunTime Layer Components...........................................................................32

IMPLEMENTATION.......................................................................................................35
5.1 Apache Module.......................................................................................................35
5.1.1 Handler Functionality.......................................................................................35
5.1.2 Apache Server – Agent Runtime Interface......................................................36
5.2 Runtime Layer Implementation..............................................................................38
5.3 Agent Execution......................................................................................................39
5.4 AzimasAgent API...................................................................................................41
5.4.1 The go() API.....................................................................................................41
5.4.2 The launch() API..............................................................................................42
5.4.3 The mail() API.................................................................................................42
5.5 Implementation Of Security Policies......................................................................42
5.5.2 Access Control.................................................................................................43
5.5.3 Protection of Agents.........................................................................................44
5.5.4 Resource Usage Policies..................................................................................44

PERFORMANCE EVALUATION..................................................................................46
6.1 Introduction.............................................................................................................46
6.2 Experiment Setup....................................................................................................46
6.2.1 Web Server Performance Measuring Tools.....................................................46
6.2.2 Agent Launcher................................................................................................48
6.3 Simulation Results...................................................................................................49
6.3.1 Response Time.................................................................................................49
6.3.2 Saturation Level Of Web Server......................................................................50
6.3.3 Agent Benchmarking........................................................................................51
6.4 Performance Analysis.............................................................................................53

APPLICATION SCENARIOS.........................................................................................55
7.1 Application Interface...............................................................................................55
7.2 Agent Interface........................................................................................................56

CONCLUSION AND FUTURE WORK..........................................................................59
8.1 Current Status..........................................................................................................59
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8.2 Future Work............................................................................................................60
8.2.1 Platform Extensions.........................................................................................60
8.2.2 Security Model Extensions...............................................................................60
8.2.3 Denial-Of-Service Attacks...............................................................................61
8.3 Applications For AZIMAS.....................................................................................62

LIST OF REFERENCES..................................................................................................63
BIOGRAPHICAL SKETCH............................................................................................65

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LIST OF FIGURES

Figure Page

2-1 Ajanta server architecture [TRI99].................................................................................9
2-2 Aglets runtime layer and communication API [LAN96]................................................10
2-3 WASP architecture [STE98]...........................................................................................13
4-1 Overall AZIMAS architecture.........................................................................................22
4-2 Agent encapsulated in a multipart MIME message........................................................27
4-3 Client components in the AZIMAS system....................................................................28
4-4 Agent Runtime Layer components..................................................................................33
5-1 Components of the Apache server extension module and the interface with the Agent
Runtime Layer.....................................................................................................36
6-1 Httperf invocation...........................................................................................................47
6-2 Experiment setup............................................................................................................48
6-3 Response time of web servers under varying load of HTTP requests and agents...........49
6-4 Requests served by web server.......................................................................................50
6-5 Replies sent by the web server........................................................................................50
6-6 Response Time vs. Request Rate (load on web server by agents with different
resource consumption)........................................................................................51
6-7 Comparison of response time (Interactive Agents and Non-Interactive Agents)...........52
7-1 User interface for “Thesis Defense Scheduling Tool”....................................................56
7-2 Scheduler Agent’s applet interface.................................................................................57
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Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
AZIMAS: ALMOST ZERO INFRASTRUCTURE MOBILE AGENT SYSTEM
By
Amar Nalla
August, 2001

Chairman: Abdelsalam (Sumi) Helal
Major Department: Computer and Information Science and Engineering
Mobile agents promise to bring in a new era in the field of World Wide Web and
Internet Computing. Many mobile agent systems have been developed but none of them
are widely deployed on the Internet. Although these systems have been around for
sometime, their full potential has not been realized because of the lack of a suitable
infrastructure that would allow for the seamless integration of mobile agents on the
Internet. Most of the developed systems advocate the use of proprietary architectures and
protocols and it is difficult to integrate the new systems with the existing Internet
architecture and well-established protocols like Hyper Text Transfer Protocol (HTTP).
Thus, there is a need for a simple but effective mobile agent system that can be easily
deployed on the Internet without requiring extensive additions or modifications to the
present infrastructure.
This thesis presents the design and implementation of the, Almost Zero
Infrastructure Mobile Agent System (AZIMAS), a mobile agent system that is easy to
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deploy on the Internet. The platform that has been developed enables mobile agents to
move at will on the Internet by extending the role of existing Apache web servers to act
as hosts for visiting mobile agents. Hyper Text Transfer Protocol, which is a widely used
transfer protocol on the Internet is used to enable the mobility of the agents. This
infrastructure enables developers to build effective Internet agents that will open a whole
new world of web applications based on mobile agents. The performance implications of
using the developed infrastructure on a web server are also presented. Some of the
problems faced while developing the system and the future developments necessary to
extend the system are outlined.
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CHAPTER 1
INTRODUCTION
There has been much interest in mobile agents for a long time. Their predicted
emergence as the key future technologies for the Internet has not materialized for a
number of valid reasons. Although many different mobile agent systems have been
developed they have not been deployed on the World Wide Web (WWW) on a large
scale because of the lack of a suitable infrastructure supporting their operation. Most of
the current systems necessitate the existence of a specialized “agent server” at each host
supporting a mobile agent. This presents an administrative overhead, and more seriously,
an interoperability nightmare given the lack of standards for agent systems. This has
seriously hindered the deployment of mobile agents on the Internet. Another problem in
deploying mobile agents are the various security issues that need to be considered when
building an agent system. Webmasters are reluctant to support agent systems because of
security concerns, which adds to the problem. In addition to these problems, there is a
dearth of agent-based applications that are popular among users and hence there is no
demand on the network administrators to install support for agent-based systems. There is
a need to develop a system that can be easily blended into the existing infrastructure and
yet be powerful to present new ideas and application scenarios. This thesis presents
AZIMAS (Almost Zero Infrastructure Mobile Agent System), an HTTP [BER99] based
infrastructure that supports mobile agents on the Internet. This is achieved by making
suitable extensions to existing web servers to support mobile agents with almost zero
additional infrastructure.
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