|Most datacenter network (DCN) designs focus on maximizing bisection bandwidth
rather than minimizing server-to-server latency. They are, therefore, ill-suited
for important latency-sensitive applications, such as high performance
computing, realtime analytic systems and high-frequency financial trading.
Although there are a number of existing approaches to reduce network latency,
they are only partially effective, workload dependent, and often require
network protocol changes.
In this thesis, we explore architectural approaches to building a low-latency
DCN and introduce Quartz, a new optical design element consisting of a full
mesh of switches connected by an optical ring. We can reduce the network
latency of a hierarchical or random network by replacing portions of it with a
Quartz ring. Our analysis shows that, in a standard 3-tier DCN, replacing high
port-count core switches with Quartz can significantly reduce switching delays,
and replacing groups of top-of-rack and aggregation switches with Quartz can
significantly reduce congestion-related delays from cross-traffic. We overcome
the complexity of wiring a complete mesh by using low-cost optical multiplexers
that enable us to efficiently implement a logical mesh as a physical ring. We
evaluate our performance using both simulations and a small working prototype.
Our evaluation results confirm our analysis, and demonstrate that it is
possible to build low-latency DCNs using inexpensive commodity elements without
significant concessions to cost, scalability, or wiring complexity.