VL2

TLDR

Data centers must support agile, cost‑effective dynamic resource allocation, requiring a flat network abstraction that presents any server set as a separate, non‑interfering Ethernet switch. VL2 is introduced to provide such a flat, scalable network architecture that delivers uniform high‑capacity server connectivity, service‑level performance isolation, and Ethernet layer‑2 semantics. VL2 achieves this with flat addressing, Valiant load balancing across multiple paths, and end‑system address resolution, all informed by real‑world traffic and fault measurements and built on low‑cost, high‑speed hardware technologies. VL2 is deployable today, as demonstrated by a prototype that shuffles 2.7 TB of data among 75 servers in 395 s, sustaining 94 % of the theoretical maximum throughput.

Abstract

To be agile and cost effective, data centers must allow dynamic resource allocation across large server pools. In particular, the data center network should provide a simple flat abstraction: it should be able to take any set of servers anywhere in the data center and give them the illusion that they are plugged into a physically separate, noninterfering Ethernet switch with as many ports as the service needs. To meet this goal, we present VL2, a practical network architecture that scales to support huge data centers with uniform high capacity between servers, performance isolation between services, and Ethernet layer-2 semantics. VL2 uses (1) flat addressing to allow service instances to be placed anywhere in the network, (2) Valiant Load Balancing to spread traffic uniformly across network paths, and (3) end system--based address resolution to scale to large server pools without introducing complexity to the network control plane. VL2's design is driven by detailed measurements of traffic and fault data from a large operational cloud service provider. VL2's implementation leverages proven network technologies, already available at low cost in high-speed hardware implementations, to build a scalable and reliable network architecture. As a result, VL2 networks can be deployed today, and we have built a working prototype. We evaluate the merits of the VL2 design using measurement, analysis, and experiments. Our VL2 prototype shuffles 2.7 TB of data among 75 servers in 395 s---sustaining a rate that is 94% of the maximum possible.