Universitat Autonoma` de Barcelona Departament d’Enginyeria de la Informacio´ i de les Comunicacions EFFICIENT MOBILITY AND INTEROPERABILITY OF SOFTWARE AGENTS SUBMITTED TO UNIVERSITAT AUTONOMA` DE BARCELONA IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN COMPUTER SCIENCE by Jordi Cucurull Juan Bellaterra, September 2008 Advisers: Dr. Joan Borrell Viader Dr. Guillermo Navarro Arribas c Copyright 2008 by Jordi Cucurull Juan I certify that I have read this thesis and that in my opinion it is fully adequate, in scope and in quality, as a dissertation for the degree of Doctor of Philosophy. Bellaterra, September 2008 Dr. Joan Borrell Viader (Principal Adviser) I certify that I have read this thesis and that in my opinion it is fully adequate, in scope and in quality, as a dissertation for the degree of Doctor of Philosophy. Bellaterra, September 2008 Dr. Guillermo Navarro Arribas (Adviser) Abstract Mobile agents are autonomous software entities that have the ability to stop and resume their execution in different network locations to accomplish a set of tasks. Despite their apparent simplicity, the fact of sharing a code in different places, in most cases heterogeneous, arises a set of issues which are far from have a simple solution. The proof is that after several years of efforts, a wide-scale deployment of mobile agents has not become a reality. In our opinion the main reasons which have hindered the adoption of mobile agents are: security, interoperability, and efficiency. Security may impose strong restrictions to the use of mobile agents. Nevertheless, enough research to satisfy the most common applications has been done in this field. Interoperability is absolutely indispensable to guarantee that different types of agents can run in different places and exchange information. And efficiency is a non functional requisite which favours the adoption of the technology. The suitability of mobile agents for distributed and heterogeneous environments is unique. The work presented in this thesis is motivated by this fact and comprises four objectives to improve, in this order, the interoperability, efficiency, and security of mo- bile agents in the context of the IEEE-FIPA standards. The first objective is the design of a flexible agent mobility specification. The second objective is the proposal of in- teroperability mechanisms to move and execute agents in several locations supporting different agent middlewares, programming languages, and underlying architectures tak- ing advantage of the previous mobility specification. The third objective is the proposal of methods to improve the efficiency of the agent mobility and interoperability. And finally, the last objective is the design of some protocols to deal with specific security issues of mobile agents. vii Acknowledgements In this preface I want to acknowledge several people for their support during my PhD studies. Since most of them are Catalan speakers I have written the rest of this section in Catalan. Nevertheless, before switching to it, I want to thank the people from the Vrije Universiteit (Benno, Michel, Reinier, Sander, Martijn, Thomas, Maik, Reza, Frances, Guido) their warm welcome during the three months I spent in Amsterdam. La vida esta` formada per una serie` d’etapes que, una vegada superades, solem anal- itzar, etiquetar i classificar en funcio´ d’on ens hagin conduit. Els estudis de doctorat facilment` es poden associar a una d’aquestes etapes que, a mes´ de la feina, inclouen tota una serie` de vivencies` personals. Es´ per aquest motiu que fare´ extensius aquests agra¨ıments, no tan sols a les persones que han tingut una relacio´ directa amb el desen- volupament d’aquesta tesi, sino´ tambe´ a les persones que han estat presents en aquesta etapa de la meva vida. Aix´ı en primer lloc voldria agra¨ır als meus pares, aix´ı com a la meva fam´ılia, el su- port i l’ajuda que sempre m’han donat, especialment en moments dif´ıcils. De la mateixa manera vull agra¨ır als meus amics mes´ propers (Raul,´ Oscar` i David) les estones que hem passat, tan en moments bons com en no tan bons. Agra¨ıments tambe´ a l’Anna per la seva aparicio´ del no res i per donar-me una mica de llum. Tambe´ vull donar les gracies` als meus companys del departament pels dinars, estones divertides i moments tan agrad- ables que m’han fet passar (Juan, Lino, Jorge, Joanet, Fernando, Cristina, Maria, Ra- mon, Guille, Sergi, Mari Carmen, Rosa Maria, Ian, Abraham, Carlos...). I una mencio´ especial al meu darrer company de despatx, en Carles, amb qui he compartit de molt a prop el proces´ de redaccio´ tan de la seva com de la meva tesi. I agra¨ır tambe´ les estones que hem passat als meus companys de les Jornades Doctorials. ix Respecte a la tesi, vull donar les gracies` en primer lloc al meu supervisor, en Joan Borrell, per haver-me guiat en la seva escriptura i desenvolupament. Tambe´ vull fer especial emfasi` amb en Guille, que a mes´ de ser un gran company ha estat un excel·lent codirector. Vull donar les gracies` a en Ramon per les seves correccions. A en Sergi per les seves suggerencies` i per dirigir el grup. I a en Joan Ametller per iniciar-me en la mobilitat dels agents. I un agraiment tambe´ als alumnes de projectes que he tingut (Ferran, V´ıctor i Gerard) i que han col·laborat activament en la implementacio´ d’alguns prototips relacionats amb la migracio´ dels agents. Donar les gracies,` tambe,´ a en Jaume Pujol per haver-me vingut a buscar quan encara no havia acabat la carrera. I finalment, un agra¨ıment a la resta de membres del departament per aportar, cadascu,´ el seu granet de sorra per a que` tot tiri endavant. Vull fer constar, a mes´ a mes,´ que aquest treball, a excepcio´ del que` es deriva de l’estada a la Vrije Universiteit, ha estat possible gracies` a la contribucio´ economica` que ha aportat el Departament d’Universitats, Recerca i Societat de la Informacio´ de la Generalitat de Catalunya mitjanc¸ant els Fons Socials Europeus. Destacar tambe´ el financ¸ament rebut dins del projecte Espanyol TSI2006-03481. Acronyms ACDS Agent Code Distribution Service ACL Agent Communication Language AID Agent Identifier AM Agent Middleware AMM Agent Mobility Manager AMS Agent Management System AP Agent Platform ASIPMS AgentScape Inter-Platform Mobility Service CAI Common Agent Interface CGID Code Group Identifier CID Code Identifier CDN Content Delivery Network DF Directory Facilitator DHT Distributed Hash Table EE Execution Environment FrTP Fragmented Transfer Protocol xi HAP Home Agent Platform HCID Hash Code Identifier JIPMS JADE Inter-Platform Mobility Service IPMA Inter-Platform Mobility Architecture IPMS Inter-Platform Mobility Service MA Mobile Agent MAS Mobile Agent System MID Migration Identifier MMP Main Migration Protocol ODTP On-Demand Transfer Protocol OSAAP One-Shot Agent Authentication Protocol P2P Peer to Peer PCTP Push Cache Transfer Protocol PL Programming Language PoP Point of Presence PS Protocol Sequences RESTTP REST Transfer Protocol SR Security Revision UA Underlying Architecture VM Virtual Machine Contents Abstract vii Acknowledgements ix Acronyms xi 1 Introduction 1 1.1 Objectives................................. 2 1.2 Structure.................................. 4 1.3 Publications................................ 5 2 Mobile Agents 7 2.1 Definition ................................. 7 2.2 TheAgent................................. 9 2.2.1 Agent Identification . 9 2.2.2 Agent Components . 10 2.2.3 AgentLifeCycle ......................... 11 2.2.4 The Mobile Agent System . 12 2.3 AgentMobility .............................. 13 2.3.1 MobilityBasics.......................... 13 2.3.2 Types of Agent Mobility . 14 2.3.3 Agent Itineraries . 15 2.4 Agent Interoperability . 16 2.4.1 Full Agent Interoperability . 16 xiii 2.4.2 AgentStandards ......................... 17 2.4.3 IEEE-FIPA ............................ 18 2.5 AgentSecurity .............................. 23 2.6 Summary ................................. 25 3 Inter-Platform Mobility Architecture 27 3.1 Introduction................................ 27 3.2 Relatedwork ............................... 28 3.3 Inter-Platform Mobility Architecture . ..... 30 3.3.1 MobilityModel.......................... 30 3.3.2 Mobility Architecture . 33 3.3.3 ErrorManagement . 40 3.4 MobilityProtocols ............................ 42 3.4.1 Push Cache Transfer Protocol . 44 3.4.2 On-Demand Transfer Protocol . 45 3.4.3 Fragmented Transfer Protocol . 48 3.4.4 RESTTransferProtocol . 50 3.4.5 Protocolsusage.......................... 54 3.5 Mobility services comparison . 55 3.6 JADE Inter-Platform Mobility Service . 59 3.6.1 JADE Introduction . 60 3.6.2 JIPMSBasics........................... 61 3.6.3 JIPMSStructure ......................... 61 3.6.4 JIPMSProtocols ......................... 65 3.6.5 JIPMSUsage........................... 68 3.7 AgentScape Inter-Platform Mobility Service . ...... 68 3.7.1 AgentScape introduction . 69 3.7.2 FIPA Message Transport Service . 69 3.7.3 ASIPMSStructure . 71 3.7.4 Openissues............................ 71 3.8 Conclusions................................ 73 4 Performance Analysis 75 4.1 Introduction................................ 75 4.2 Evaluationsetup.............................. 76 4.3 Performance evaluation 1: PCTP vs ODTP . 77 4.3.1 Lightweight agents . 77 4.3.2 Multi-class Heavyweight Agents . 81 4.4 Performance evaluation 2: PCTP vs FrTP . 84 4.4.1 Scenario 1: Local Area Network . 84 4.4.2 Scenario 2: Wide Area Network . 90 4.4.3 Scenario 3: Metropolitan Area Network . 93 4.5 Performance evaluation 3: PCTP vs RESTTP . 94 4.5.1 Scenario 1: Local Area Network . 95 4.5.2 Scenario 2: Wide Area Network . 97 4.5.3 Scenario 3: Metropolitan Area Network . 100 4.6 Conclusions................................ 100 5 Agent Code Distribution Service 103 5.1 Introduction................................ 103 5.2 RequirementsandRoles . 104 5.3 Agent Code Distribution Service . 106 5.3.1 Overview of the Architecture . 106 5.3.2 CodeManagement . 108 5.3.3 Code Distribution . 110 5.3.4 SecurityManagement . 111 5.3.5 ServiceInterface . 116 5.4 Implementation and performance . 120 5.4.1 Service implementation . 120 5.4.2 Performancetests.