Most of the real world deployment of Open RAN so far has focused on a standardized interface for fronthaul connections between radio units and basebands (centralized or distributed units). The O-RAN Alliance has specified Open Fronthaul, which is based on the eCPRI standard. But a fully interoperable, multivendor RAN will rely on a wider set of interfaces, to ensure open connections between every element. One of the most important is X2, which is the interface allowing handover between base stations. Although this is a 3GPP-defined interface, and so does not need to be specified by another body, it has been implemented in different ways by each base station vendor (in the same way that the CPRI specs for fronthaul have…