n. CPRI is defined by a consortium consisting of a small number of RAN vendors. Although the specification is public, the actual implementation of the upper layers and the contents of the messages are mostly proprietary. This means that there is no opportunity for multi-vendor inter- operability in the traditional front-haul even when every device is using CPRI. As it basically represents the raw form of the radio signals, CPRI is quite an inefficient way to transmit high-data-rate traffic. One analogy is that it is like sending photos of an email printout rather than the much smaller ASCII (or Unicode) data making up the message. With the increas- ing focus of 5G on much higher data rates to support eMBB, CPRI is showing its limitations and the amount of bandwidth it consumes is increasing more quickly than the increase in the user data traffic-it has simply reached the end of its scalability. Another shortcoming is that because CPRI was traditionally designed to connect the RU with the BBU, it is fundamentally a point-to-point, TDM-style synchronous protocol. For this reason, there is very little flexibility in CPRI to build complex networks and adopt efficiencies like multiplexing (aggregating lower-bandwidth signals together into a single higher speed link). Other systems, such as those based on packet technology, do this very easily. In summary, the CPRI protocol is not efficient enough to support 5G bandwidth demands or flexible enough to implement a scalable RAN architecture. So, the CPRI approach has to either evolve or be replaced. Two evolutions are underway that resolve these shortcomings with CPRI in the 5G RAN: The separation of functions inside the RAN is being changed SO that not as much data needs to be carried over the front-haul network (see the upcoming section "RAN Functional Splits"). CPRI is being migrated from a TDM-based to a packet-based protocol (such as Ethernet) to gain efficiencies and allow statistical multiplexing and increased flexibility. The participants in the CPRI consortium ha