Daniel Halperin, Srikanth Kandula, Jitendra Padhye, Paramvir Bahl, and David Whetherall
10 August 2011
The 60GHz wireless technology that is now emerging
has the potential to provide dense and extremely fast connectivity
at low cost. In this paper, we explore its use to relieve hotspots
in oversubscribed data center (DC) networks. By experimenting
with prototype equipment, we show that the DC environment is well
suited to a deployment of 60GHz links contrary to concerns about
interference and link reliability. Using directional antennas, many
wireless links can run concurrently at multi-Gbps rates on top-ofrack
(ToR) switches. The wired DC network can be used to sidestep
several common wireless problems. By analyzing production traces
of DC traffic for four real applications, we show that adding a small
amount of network capacity in the form of wireless flyways to the
wired DC network can improve performance. However, to be of
significant value, we find that one hop indirect routing is needed.
Informed by our 60GHz experiments and DC traffic analysis, we
present a design that uses DC traffic levels to select and adds flyways
to the wired DC network. Trace-driven evaluations show that
network-limited DC applications with predictable traffic workloads
running on a 1:2 oversubscribed network can be sped up by 45%
in 95% of the cases, with just one wireless device per ToR switch.
With two devices, in 40% of the cases, the performance is identical
to that of a non-oversubscribed network.