Introducing Trust Establishment Protocol In Contract Net Protocol Aarti Singh , Dimple Juneja M.M.University, Mullana (Ambala) Haryana, India singh2208@gmail.com , dimplejunejagupta@gmail.com A.K. Sharma Y.M.C.A University of Science and Technology Faridabad , Haryana , India ashokakale2@rediffmail.com Abstract— Contract Net Protocol (CNP) is a means to specify problem-solving communication required in a distributed multi- agent environment. Although, FIPA standardized CNP addresses most of the issues with respect to communication happening among agents in a Multi-Agent Environment (MAE), issues related to establishing trust-worthy communication amongst agents is still prevailing. This work introduces a new Trust Establishment Protocol (TEP) in CNP, thereby improving CNP. The proposed new version shall be referred to as CNTEP Architecture. Introduction of TEP in existing CNP would help in ensuring truthfulness of agents which is crucial for open, dynamic and heterogeneous multi-agent systems. Keywords— Agent communication, Multi-Agent Systems, Trust, Interaction Protocols, Negotiations. I. INTRODUCTION Contract Net Protocol (CNP) [2, 17] facilitates interaction between agents for fully automated negotiations in the form of contracts. Foundation for Intelligent Physical Agents (FIPA) [6] has approved CNP as standard protocol for communication in Multi-Agent Systems (MAS). Although CNP addresses most of the issues related to agent communication in distributed environment, still shortcomings such as lack of formal coordination procedure for participants to follow is existing. Many variations in conventional CNP have been proposed by researchers [1, 12] to incorporate mechanisms for handling specialized interactions. However present variations of the communication protocol don’t ensure the truthfulness of agents which is very essential for open, dynamic and heterogeneous MAS. Establishing trust amongst agents in MAS would help them in choosing appropriate communication partners. Since, CNP do not consider the trust as a prime factor therefore, the necessity of TEP is apparent. This paper focuses on improving existing CNP by incorporating Trust Establishment Protocol (TEP) in CNP. The paper is organized in five sections. Section II contains introduction to state of the art CNP. Section III provides the work of eminent researcher in the related area. Section IV proposes the Trust Establishment Protocol (TEP) and hence an improved CNP. Finally section V concludes the paper. II. CONTRACT NET PROTOCOL (CNP): AN OVERVIEW Contract Net Protocol was originally proposed by Smith in 1980 [15] and was initially employed in a simulated distributed acoustic sensor network. It is a high level protocol which is concerned with the interpretation of the communication rather than the transmission of bit streams. It supports communication among agents in distributed MAS. High level protocols provide structure that help system designers decide what the agents should say while communicating rather than how they should say it. CNP being high level protocol facilitates distributed control of cooperative task execution with efficient inter node communication and also allows participation in fully automated competitive negotiations. It categorizes agents as either Initiator/Manager or Participant/Contractor. The agents can exchange their roles for different contracts as CNP allows further delegation of subcontracts to other agents. FIPA has standardized contract net interaction protocol and the flow diagram for the same is as depicted in fig.1. CNP exists mainly between an Initiator agent (IA) and a contractor agent (CA). Now the IA and CA undergo certain steps repeatedly until a contract gets negotiated and finalized. The steps are listed as follows: 1) The manager/initiator agent sends out a call for proposals (CFP) to m possible contractors. 2) Each CA reviews the received CFPs and bids on the most feasible contracts before the mentioned deadline. FIPA-Contract Net Protocol i<=n Reject proposal k<=j Inform-result: inform refuse Participant cfp n dead line j=n-i Accept proposal l=j-k failure Inform-done:inform Initiator m propose Figure 1. FIPA Contract Net Interaction Protocol 3) Out of the j proposals received, IA may reject k<=j proposals and might accept l=j-k proposals. For both cases a rejection message or acceptance message is forwarded to CAs. The initiator scans the best bid from the j received proposals 2010 International Conference on Advances in Computer Engineering 978-0-7695-4058-0/10 $26.00 © 2010 IEEE DOI 10.1109/ACE.2010.13 59