Voice over Internet Protocol (VoIP) in Mobile Ad-hoc NETwork (MANET) is challenging because MANET is an infrastructure-less network. VoIP requires a signaling protocol like the Session Initiation Protocol (SIP) for session establishment and management. In infrastructure network, SIP utilizes the centralized proxy, register and redirect servers for session establishment. MANET is a decentralized network of mobile nodes. Hence SIP cannot adopt as it is to MANETs. In this paper, the authors have described the SIP implementation for MANET using network simulator 2 NS2.