Clearwater is an open source implementation of IMS (the IP Multimedia Subsystem) designed from the ground up for massively scalable deployment in the Cloud to provide voice, video and messaging services to millions of users. Clearwater combines the economics of over-the-top style service platforms with the standards compliance expected of telco-grade communications network solutions, and its Cloud-oriented design makes it extremely well suited for deployment in a Network Functions Virtualization (NFV) environment.