Host Identity Protocol (HIP) decouples IP addresses from higher layer Internet applications by proposing a new, cryptographic namespace for host identities. HIP has great potential in means of mobility and multihoming support, security, and performance, such making it quite a promising candidate as the basic architecture of the Future Internet. However, HIP is still in development and very early standardization phase: the protocol is continuously evolving due to its adaptivity to functional changes and extensions. Aiming to completely understand the protocol's behavior, its applicability to wide-scale usage and to analyze current and future improvements and enhancements, it is crucial to develop a proper, RFC-compliant, extensible simulation model for Host Identity Protocol. In this paper we present the structural design and the functional details of our HIP simulation framework (called HIPSim++) integrated into the INET/OMNeT++ discrete event simulation environment. In order to ...