er-plane separation makes it easy to deploy (and scale) both in a coherent manner. 4.4.4 Further Reading A comprehensive survey on SDN can be found in 'Software-defined networking: a compre- hensive survey'. 4 NG-RAN Architecture Full information about the CP/UP split NG-RAN architecture and related protocols described in this chapter can be found in the 3GPP technical specifications listed below. 3GPP TS 38.401 is the general stage 2 specification covering all NG-RAN aspects, includ- ing the CP/UP separation, and it is a good starting point for an interested reader to under- stand the details beyond what is described in this chapter. Once the reader has familiarized himself with the high-level aspects, we suggest learning the details of the E1AP, defined in 3GPP TS 38.463. Finally, 3GPP TS 28.541 can be used to gain an understanding of OAM aspects of the CP/UP separation, noting that the specification covers other nodes and archi- tectures as well. 3GPP TR 38.806 is a good source of background information about the study on control- and user-plane separation, their benefits, and deployment options. References 3GPP Technical Specification 23.214 (2019). Architecture enhancements for control and user plane separation of EPC nodes. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Report 38.806 (2019). Study of separation of NR Control Plane (CP) and User Plane (UP) for split option 2. Available at: www.3gpp.org (accessed May 29, 2020). O-RAN Alliance (2018). O-RAN: Towards an open and smart RAN. Available at: www.o-ran .org (accessed May 29, 2020). 3GPP Technical Specification 38.401 (2019). NG-RAN; Architecture description. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.460 (2019). NG-RAN; E1 general aspects and principles. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.461. (2019). NG-RAN; E1 layer 1. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.462 (2019). NG-RAN; E1 signalling trans