outside in" against easily understood metrics. Chapter 10 Interoperability and test 341 Ethernet Traffic Generator O-DU Emulator Ethernet- O-CU (DUT) PDCP SDUs Switch FIGURE 10-7 PDCP throughput test setup. Throughput End-to-end performance tests involve recreating a complete user workflow to get an accurate picture of performance. Performance needs to be measured over a wide range of parameters, creating a matrix of test scenarios that consider: packet size (small, IMIX, large packets) protocol configuration (PDCP cipher mode, RLC mode, scheduling priority, etc.) carrier configuration (carrier aggregation, dual connectivity, etc.) DUT configuration (maximum number of users, UE per slot, etc.) Refer to RFC 2455, RFC 6349, and RFC 6815 for UDP and TCP performance measurement using different packets size and window sizes of TCP. Given the abovementioned example of PDCP (CU) testing, consider a test setup like in Fig. 10-7. PDCP performance is measured between the O-CU and UE/O-DU simulator. A standard Ethernet frame generator (either implemented as a software entity on a server or as dedi- cated test equipment such as from Spirent) is used as traffic generator, sourcing, and sinking GTP-U traffic for both the UL and DL streams. The UE/O-DU simulator processes GTP-U traffic related to O-DU over F1-U interface as well as GTP-U traffic related to an emulated (in the case of ENDC testing) eLTE entity over the Xn Interface, as well as PDCP traffic related to the UE. Refer to RFC 2455, RFC 6349, and RFC 6815 for UDP and TCP performance measurement using different packets size and window sizes of TCP. For this example, test configurations include a range of signaling/data radio bearer counts, packet sizes, cipher algorithmic configurations, and poll timer values. During development phase, throughput testing can be done in isolation for L1 or L2 sce- narios, for example, by so-called "L1 bypass" testing where the Physical Layer is bypassed through an emulated environment-for example, by communicating Transport Blocks over 