On the efficiency of flexible ethernet client architectures in optical transport networks [invited]

The data-center interconnection (DCI) market has been rising sharply for some time, leading to the development of networking solutions tailored specifically for it. On the side of the transport network, DCI devices are characterized by simple, footprint-efficient designs focused on scalability, but still leverage the benefits of flexible-rate transponders on the line-side, to extract the most from costly optical transport infrastructures. Accompanying this evolution arose the need for a technology that could provide a flexible client layer where aggregation was done outside the transport device, but flows could still be efficiently mapped to flexible-rate transponder modules. In this context, the appearance of Flex Ethernet (FlexE) is targeted at decoupling the rates of interfaces connecting routers to transport boxes, from the actual flows traversing them. Through the introduction of an additional mapping/de-mapping layer, the capacity of multiple Ethernet interfaces can be virtualized in a resource pool for different flows. This paper addresses the application of FlexE to dense wavelength division multiplexing (DWDM) transport scenarios. Specifically, it evaluates how agnostic to FlexE a transport box should be, considering the potential trade-off between its complexity and the ability to efficiently fill lightpaths. Through a network simulation handling the provisioning of Ethernet flows in a DCI scenario, we evaluate the various FlexE use cases envisioned for transport networks, and how they affect the efficiency of router port usage and transport box provisioning, as well as their effect on the capacity of the DWDM layer.