Datacenter networking is currently dominated by two major trends. One is toward lossless, flat layer-2 fabrics based on Converged Enhanced Ethernet and InfiniBand, with benefits in efficiency and performance. The second trend aims at increasing flexibility by means of Software Defined Networking, which enables Overlay Virtual Networking. Although clearly complementary, these trends also exhibit conflicting traits: In contrast to physical fabrics, which avoid packet drops by means of flow control, almost all current virtual networks are lossy. We quantify these losses for several combinations of hypervisors and virtual switches, and show their detrimental effect on application performance. Moreover, we propose zOVN, a zero-loss Overlay Virtual Network, designed to reduce the flow completion time of latency-sensitive datacenter applications. We describe its architecture and detail the design of its key component, the zVALE lossless virtual switch. As a proof of concept, we have implemented a zOVN prototype, which we benchmark with Partition-Aggregate, achieving up to 19-fold reduction of the mean completion time using three widespread TCP versions. For larger scale validation and deeper introspection into zOVN’s operation, we developed an OMNeT++ model for accurate cross-layer simulations of a virtualized datacenter. The results obtained through simulation confirm the validity of the testbed findings.

By: D. Crisan, R. Birke, G. Cressier, C. Minkenberg, M. Gusat

Published in: RZ3840 in 2013


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