CacheCloud: Towards Speed-of-light Datacenter Communication.

The network is continuing to advance unabated, with 100- Gb/s Ethernet already a commercial reality, and now 400- Gb/s in the standardization process. Within a single rack, inter-server latency will soon be in the range of 250ns, trending ever closer towards the fundamental propagation delay of light in a fiber. In this paper we argue that in this environment, a major performance bottleneck is DRAM latency, which has stagnated at 100ns per access. Consequently, data should be kept entirely in the CPU cache which has an order of magnitude lower latency and RAM should be considered a slower backing store. We describe the implications of designing a "speed of light" datacenter network stack that can keep up with ever increasing link speeds with the goal of keeping latency as close to the speed of light propagation time as possible.