Network Infrastructure

Private WANs are increasingly important to the operation of enterprises, telecoms, and cloud providers. For example, B4, Google’s private software-defined WAN, is larger and growing faster than our connectivity to the public Internet. In this paper, we present the five-year evolution of B4. We describe the techniques we employed to incrementally move from offering best-effort content-copy...

Clos topologies have been widely adopted for large-scale data center networks (DCNs), but it has been difficult to support incremental expansions of Clos DCNs. Some prior work has assumed that it is impossible to design DCN topologies that are both well-structured (non-random) and incrementally expandable at arbitrary granularities. We demonstrate that it is indeed possible to design such...

Modern networks have significantly outpaced the monitoring capabilities of SNMP and command-line scraping. Over the last three years we at Google have been working with members of the networking industry via the OpenConfig.net effort to redefine network monitoring. We have now deployed Streaming Telemetry in production to monitor devices from multiple vendors. We will talk about the experience...

By all accounts, today’s Internet is not moving data as well as it should. Most of the world’s cellular users experience delays of seconds to minutes; public Wi-Fi in airports and conference venues is often worse. Physics and climate researchers need to exchange petabytes of data with global collaborators but find their carefully engineered multi-Gbps infrastructure often delivers at only a few...

We present the design of Espresso, Google’s SDN-based Internet peering edge routing infrastructure. This architecture grew out of a need to exponentially scale the Internet edge cost-effectively and to enable application-aware routing at Internet-peering scale. Espresso utilizes commodity switches and host-based routing/packet processing to implement a novel fine-grained traffic engineering...

We increasingly depend on the availability of online services, either directly as users, or indirectly, when cloud-provider services support directly-accessed services. The availability of these "visible services" depends in complex ways on the availability of a complex underlying set of invisible infrastructure services. In our experience, most software engineers lack useful frameworks to...

Large flows like videos consume significant bandwidth. Some ISPs actively manage these high volume flows with techniques like policing, which enforces a flow rate by dropping excess traffic. While the existence of policing is well known, our contribution is an Internet-wide study quantifying its prevalence and impact on video quality metrics. We developed a heuristic to identify policing from...

Maintaining the highest levels of availability for content providers is challenging in the face of scale, network evolution, and complexity. Little, however, is known about the network failures large content providers are susceptible to, and what mechanisms they employ to ensure high availability. From a detailed analysis of over 100 high-impact failure events within Google’s network,...

Maglev is Google’s network load balancer. It is a large distributed software system that runs on commodity Linux servers. Unlike traditional hardware network load balancers, it does not require a specialized physical rack deployment, and its capacity can be easily adjusted by adding or removing servers. Network routers distribute packets evenly to the Maglev machines via Equal Cost Multipath...

As data centers grow larger and strive to provide tight performance and availability SLAs, their monitoring infrastructure must move from passive systems that provide aggregated inputs to human operators, to active systems that enable programmed control. In this paper, we propose Trumpet, an event monitoring system that leverages CPU resources and end-host programmability, to monitor every...

WAN bandwidth remains a constrained resource that is economically infeasible to substantially overprovision. Hence, it is important to allocate capacity according to service priority and based on the incremental value of additional allocation. For example, it may be the highest priority for one service to receive 10Gb/s of bandwidth but upon reaching such an allocation, incremental priority may...

The design space for large, multipath datacenter networks is large and complex, and no one design fits all purposes. Network architects must trade off many criteria to design cost-effective, reliable, and maintainable networks, and typically cannot explore much of the design space. We present Condor, our approach to enabling a rapid, efficient design cycle. Condor allows architects to express...

We present our approach for overcoming the cost, operational complexity, and limited scale endemic to datacenter networks a decade ago. Three themes unify the five generations of datacenter networks detailed in this paper. First, multi-stage Clos topologies built from commodity switch silicon can support cost-effective deployment of building-scale networks. Second, much of the general, but...

Datacenter transports aim to deliver low latency messaging together with high throughput. We show that simple packet delay, measured as round-trip times at hosts, is an effective congestion signal without the need for switch feedback. First, we show that advances in NIC hardware have made RTT measurement possible with microsecond accuracy, and that these RTTs are sufficient to estimate switch...