An IMS subscriber location function for OpenBaton — A standards based MANO environment

In the past, virtualisation, and with it the move toward the cloud, has had a strong influence on the ICT (Information Communication Technology) sector, and now seems set to revolutionise the telecommunications sector as well. The virtualisation into software artefacts of functions that would usually be deployed as hardware has come to be known as Network Function Virtualisation (NFV), and the European Telecommunications Standards Institute (ETSI) through its MANO (Management and Orchestration) framework has outlined comprehensively how such functions could be orchestrated and managed over infrastructure such as the cloud. A set of functions of particular interest are the call session control functions (CSCFs) and HSS (Home Subscriber Server) of the IP Multimedia System (IMS) which perform signalling and authentication functions for multimedia calls in contexts such as Voice over LTE (VoLTE). IMS has enjoyed significant focus in the past from the research community, as such an implementation of an IMS service package has been provided in an open source MANO-compliant implementation called OpenBaton. While the service package provides the IMS CSCFs and HSS, it does not include a Subscriber Location Function (SLF) which provides a mapping function to map a subscriber identity to a hosting HSS. The SLF is an important element for building distributed networks that partition user data into multiple databases, and as such represents a useful inclusion to the developer community. This paper describes an extension to the OpenBaton service package that includes an SLF for partitioning large user populations across multiple HSSes and resolving individual addresses in real-time.