Spineless Data Centers

In enterprises, CDNs, and increasingly in edge computing, most data centers have moderate scale. Recent research has developed designs such as expander graphs that are highly efficient compared to large-scale, 3-tier Clos networks, but moderate-scale data centers need to be constructed with standard hardware and protocols familiar to network engineers, and are overwhelmingly built with a leaf-spine architecture. This paper explores whether the performance efficiency that is known to be theoretically possible at large scale can be realized in a practical way for the common leaf-spine data center. First, we find that more efficient topologies indeed exist at moderate scale, showing through simulation and analysis that much of the benefit comes from choosing a 'flat' network that uses one type of switch rather than having separate roles for leafs and spines; indeed, even a simple ring-based topology outperforms leaf-spine for a wide range of traffic scenarios. Second, we design and prototype an efficient routing scheme for flat networks that uses entirely standard hardware and protocols. Our work opens new research directions in topology and routing design that can have significant impact for the most common data centers.