21. Evolving Requirements and Trends of Datacenters Networks

In this manuscript, we present an overview of Google’s datacenter network, which has led and defined the industry over the past few decades. Starting inside the datacenter, we cover all aspects, from networking/topology to key hardware components of interconnect and switching, traffic/throughput, and energy usage/efficiency for intra-datacenter networks. Likewise, we discuss topology and interconnect for inter-datacenter networks. With particular focus on optical interconnect, we also discuss future technology directions for scaling bandwidth through a combination of higher baud rates, wavelength-division multiplexing (), coherent communication (polarization multiplexing, I/Q modulation), and space-division multiplexing (), along with the corresponding trade-offs between these various dimensions and how these trade-offs are adjusted at different length scales. Although questions remain on the exact implementation to be adopted in the future, one thing is clear: the evolution of datacenter networks and the underlying technologies have been and will remain a critical driver for enabling new compute capabilities in the cloud.