real hardware. Sub- sequently, the concept evolved to support more advanced management features, such as taking snapshots of a virtual machine state, failover, and migration. Apart from the economic benefits of decoupling software from hardware (and thus allow- ing one to source software and hardware components from different vendors), virtualized environments are typically more robust in the case of failures and provide better hardware utilization. 5G Radio Access Network Architecture: The Dark Side of 5G, First Edition. Edited by Sasha Sirotkin. © 2021 John Wiley & Sons Ltd. Published 2021 by John Wiley & Sons Ltd. 6 Enabling Technologies After virtualization had been extremely successful in the cloud and enterprise, there has been an increased interest in applying the same principles in networking. In fact, in many cases even 4G Evolved Packet Core (EPC) runs in virtualized environments and this trend is expected to continue with 5GC, which was designed with virtualization in mind. Once the core network is virtualized, the next logical step is to consider virtualizing (at least parts of) NG-RAN. While virtualized NG-RAN deployments are not explicitly defined in the standards, certain provisions have been made to make such implementations possible (see Chapter 4). In the present chapter we describe how NG-RAN virtualization may be realized. Note that the term "virtualization" is somewhat loosely defined and is often used in many different contexts to carry different meanings, especially in the area of networking. At least in some cases it means moving away from proprietary to a general purpose hardware, which may or may not require actual virtualization. Additionally, it may mean "softwariza- tion" - that is, moving parts of functionality from custom hardware to software. In the context of this section we describe various technologies that allow virtualization in its broad meaning, covering most of the cases mentioned above. 6.2.1 Key Ideas RAN virtualization refers to an ability to run the RAN protocol stack (