###### Abstract
This goal is not easy to accomplish, as various technologies mutually interoperate; the RR transport is just a segment of the network providing services to customers. It is always the case that there are segments that are not over-provisioned and can therefore become congested. Consequently, if in the transmission chain only a single aggregation RR link branches to access RR links leading towards a number of base stations, does this enable the simultaneous desired throughput to all base stations, especially in the condition of insufficient throughput of the aggregating RR connection? Should all traffic types and applications (video, VoIP, Internet, FTP, IPTV, etc.) be treated equally, or should some traffic engineering be done to ensure optimization and prioritization based on the importance and sensitivity of each application to packet loss, latency, and jitter [9]? Should TDM voice traffic be put at a higher priority in case of reduced throughput of the link? Rather than reviewing well-known classical properties of microwave RR Carrier Ethernet, however, this research was motivated by more recent and relevant issues coming out of wide deployment--more than 60% globally of RR Ethernet links are 4G (i.e., long-term evolution (LTE)) and 5G backhaul connections [10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. This is the main reviving force of RR links, fueled by their high spectral efficiency (i.e., usage of higher-order QAM modulations), automatic transmit power control (ATPC), and ACM. As a matter of fact, in this actual and research-motivating framework, we explored the cross-layer consistency (articulated as correlation) between the practical RR performance (availability) and the corresponding QoS at the Ethernet (and IP) layer. To the best of our knowledge, apart from some simulation studies, there have been few (if any) similar experimental cross-layer investigations--that combine in-service and out-of-service testing in a live hybrid (with all three interoperating technologies) RR Ethernet backhaul of a major operator network--reported in the public literature [10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. Therefore, our motivation for this research, the relevance and actuality of which arise from real-life engineering practices (e.g., the sometimes quite unexpected uncoupling of Ethernet QoS from the RR performance, which we explored by the according statistical analysis), was to pave the way for network operators to apply such an approach while making their proactive conformance tests and analyses comply with the latest updated RR Carrier Ethernet recommendations [1, 2], which specify actions needed to achieve the best QoS figures (and QoE of their users). This way, the proposed correlative cross-layer testing could be further developed on a larger scale in terms of test diversity, repeating rate, and impact of any specific real-time propagation impairments, such as fading or ducting, which impact the RR performance and hence the Ethernet (IP) QoS. Finally, the main task of this work is to answer whether such a diverse RR system can satisfy the quality norms for Ethernet-based services, meaning whether an acceptable RR availability will necessarily enable the according Ethernet-based QoS in terms of packet loss, delay, and jitter. This question is addressed by comprehensive in-service and out-of-service testing of the operating heterogeneous RR system. Out-of-service testing was conducted during installation of the actual RR links connecting 12 base stations, as even temporarily shutting down the revenue-generating traffic was not an option. Accordingly, in Section 2, the basics of Ethernet testing are reviewed, while the system being tested is described in Section 3. Test results of both RR system reliability and end-to-end Ethernet QoS are presented in Section 4, and their consistency is explored and discussed through statistical analysis in Section 5. Conclusions are drawn in Section 6.