We present the design, implementation, and evaluation of B4, a private WAN connecting Google's data centers across the planet. B4 has a number of unique characteristics: i) massive bandwidth requirements deployed to a modest number of sites, ii) elastic traffic demand that seeks to maximize average bandwidth, and iii) full control over the edge servers and network, which enables rate limiting and demand measurement at the edge. These characteristics led to a Software Defined Networking architecture using OpenFlow to control relatively simple switches built from merchant silicon. B4's centralized traffic engineering service drives links to near 100% utilization, while splitting application flows among multiple paths to balance capacity against application priority/demands. We describe experience with three years of B4 production deployment, lessons learned, and areas for future work.
We present the design, implementation, and evaluation of B , a private WAN connecting Google's data centers across the planet. B has a number of unique characteristics: i) massive bandwidth requirements deployed to a modest number of sites, ii) elastic trafc demand that seeks to maximize average bandwidth, and iii) full control over the edge servers and network, which enables rate limiting and demand measurement at the edge. ese characteristics led to a So ware De ned Networking architecture using OpenFlow to control relatively simple switches built from merchant silicon. B 's centralized tra c engineering service drives links to near utilization, while splitting application ows among multiple paths to balance capacity against application priority/demands. We describe experience with three years of B production deployment, lessons learned, and areas for future work.
No abstract
Abstract-We present a "clean-slate" design for a networklayer routing and forwarding system intended to address shortcomings of the current Internet Protocol. Our design separates routing from both forwarding and topology discovery; requires only a flat, topology-independent namespace; and allows for policies of both users and service providers to be supported. Channels serve as the primary abstraction, allowing the network topology to be viewed at multiple levels of abstraction using the same identifiers. In this paper we present the basic design, which is based on loose source routing. Our routing and forwarding scheme is part of a larger project to produce a "clean-slate" network layer design.
Data Center topologies employ multiple paths among servers to deliver scalable, cost-effective network capacity. The simplest and the most widely deployed approach for load balancing among these paths, Equal Cost Multipath (ECMP), hashes flows among the shortest paths toward a destination. ECMP leverages uniform hashing of balanced flow sizes to achieve fairness and good load balancing in data centers. However, we show that ECMP further assumes a balanced, regular, and fault-free topology, which are invalid assumptions in practice that can lead to substantial performance degradation and, worse, variation in flow bandwidths even for same size flows.We present a set of simple algorithms that achieve Weighted Cost Multipath (WCMP) to balance traffic in the data center based on the changing network topology. The state required for WCMP is already disseminated as part of standard routing protocols and it can be readily implemented in the current switch silicon without any hardware modifications. We show how to deploy WCMP in a production OpenFlow network environment and present experimental and simulation results to show that variation in flow bandwidths can be reduced by as much as 25× by employing WCMP relative to ECMP.
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