) and G.827: Availability performance para- meters and objectives for end-to-end international constant bit-rate digital paths (https://www.itu.int/rec/T- REC-G.827/en). 5G Network Architecture 67 to this challenge by delivering new classes of PTP-aware nodes such as boundary clocks and transparent clocks. PTP-aware nodes are being increasingly deployed in wireless access networks around the world. While the packet delay variation is not a major concern for these deployments, timing error analysis remains a major point of focus. Timing error defines the difference between the time of a clock at any relevant part of the network and the time of a reference clock such as one delivered by a GPS source at another part of the network. It can result from network asymmetries and node configuration/performance issues [84]. In order to relax the excessive latency and capacity constraints on the fronthaul, the opera- tors and vendors have revisited the concept of C-RAN and considered more flexible distri- bution of baseband functionality between the RRH and the BBU pool. Instead of centralizing the entire BBU processing on the cloud, by dividing the physical receive and transmit chain in different blocks, it is possible to keep a subset of these blocks in the RRH. By gradually placing more and more BBU processing at the edge of the network, the fronthaul capacity requirement becomes less stringent. Nevertheless, partial centralization has two main drawbacks, both relating to the initially envisioned benefits of C-RAN: (1) RRHs become more complex, and thus more expensive; and (2) de-centralizing the BBU processing reduces the opportunities for multiplexing gains, coordinated signal proces- sing, and advanced interference avoidance schemes. Consequently, flexible or partial cen- tralization is a trade-off between what is gained in terms fronthaul requirements and what is lost in terms of C-RAN features. Another key question is how the information between the RRH and the BBU is transported over the fronthaul link. A number of