Non-Overlapping Rings: A New Architecture for Designing Switch Clusters in Data Centers

The data center network is an important component of the modular cloud data center. Currently, common practice is to have servers in the data center connected by switches arranged in a generalized tree topology. However, data center managers are considering adding "east-west" horizontal links between top of rack (TOR) switches to improve latency performance between groups of TOR switches and to off-load traffic from the tree network. One possible way in data center networking is to have TOR switches connected into clusters. Some clusters are high performance clusters providing low latency, while other clusters are optimized for cost but with adequate latency performance. In this paper, we present an algorithm for designing lower-cost network clusters using non-overlapping rings (NOR). We describe some of the performance characteristics of these NOR clusters such as coverage vs. number of rings. We show that cost savings can be achieved with minimal increase in end-to-end delay, and that good performance can also be maintained under failure conditions. We also describe how network growth can be easily accommodated using our algorithm. Cabling is a major practical consideration; we define a simple cabling architecture for such networks.