Communication protocol is an important mechanism in mobile agent systems since agents need to communicate each other to clinch and achieve their joint goal. In this research, we investigate communication issues between mobile agents, and propose a reliable communication protocol which integrates Session Initiation Protocol (SIP) as signaling protocol. With SIP, we present synchronous Invite model and asynchronous Subscribe&Notify model to establish a framework for interagent communication. The two models can solve communication failure and message chasing problems. We further analyze their communication costs and utilization rates.