Liquid-Cooled Switching Doubles AI Network Bandwidth Per Rack

CoreWeave Brings Liquid Cooled Switching to AI Networking | CoreWeave Blog

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In modern AI cloud infrastructure, networking has become a strategic component, one that determines how effectively GPU compute translates into goodput for training and inference performance. That's a fundamental shift from traditional cloud infrastructure, where networking was often treated as plumbing, simply moving bits from one point to another. As liquid cooling enables rack-scale systems like NVIDIA Vera Rubin NVL72 to deliver exaflops of compute, the network must evolve alongside them. Just as compute has adopted liquid cooling, networking is following the same technique, with liquid cooling enabling new switch chipsets that deliver massive performance in a compact form factor. With liquid cooled switches, the network is no longer the limiting factor for what these accelerators can achieve. Trillion-parameter models, agentic systems running multi-step reasoning and parallel actions, and RL pipelines with their tight inference-training loops all depend on fast, low-latency communication between GPUs. Liquid-cooled switches let you push more bandwidth through denser rack configurations, so you can architect a network fabric that fully utilizes GPU and CPU resources within and across multiple racks. At CoreWeave, we design networking as a foundational layer of the AI cloud to ensure the fabric is never a bottleneck. With the deployment of Vera Rubin NVL72, we became one of the first cloud providers to deploy NVIDIA Spectrum-X Ethernet SN6600-LD, the industry's first fully liquid cooled 102.4 Tb/s Ethernet switch. Ultra high performance with liquid-cooled switching CoreWeave deployed the NVIDIA Spectrum-X SN6600-LD as the switching fabric for Vera Rubin NVL72. Built on the NVIDIA Spectrum-6 ASIC and fully liquid-cooled, the SN6600-LD delivers 102.4 Tb/s of switching capacity across 64 × 1.6 Tb/s ports using 200G SerDes, doubling the per-lane bandwidth of the previous generation while fitting into a compact 2U form factor. This combination of density and performance, made possible by liquid cooling, enables an unprecedented 1.64 Pb/s of switching capacity per rack. To put 1.64 Pb/s of switching capacity into perspective, the network could transfer the entire text collection of the Library of Congress approximately 160 times every second, sustained at full load and without congestion. Delivering the full networking bidirectional GPU-to-GPU bandwidth is needed when you are continuously improving your agents or training models. With the density and capacity of the SN6600-LD, CoreWeave provides a fully non-blocking, multi-plane, multi-rail spine and leaf fabric connecting Vera Rubin NVL72 GPUs without oversubscription. For customers running large scale training, this translates directly into higher model FLOPS utilization (MFU) by cutting network latency, giving every GPU full bandwidth, and keeping GPU idle time near zero For inference workloads, it delivers consistently low latency, which means faster response times, higher throughput, and better accelerator utilization.

NVIDIA Spectrum-X SN6600-LD deployed in CoreWeave Data Center Unified and programmable management for liquid cooling In “ A Deep Dive on CoreWeave Innovations for NVIDIA Vera Rubin NVL72 ,” we introduced Valvey and Racky , part of CoreWeave Mission Control, that manages Vera Rubin environmentals. Valvey and Racky’s management domain also includes the NVIDIA Spectrum-6 SPX rack, bringing the same unified monitoring and control to both Vera Rubin NVL72 and SN6600-LD Ethernet switches. Valvey is our patent-pending programmable per-rack liquid cooling valve assembly that monitors and controls flow rate, temperature, pressure, and leak detection. Extended now to the Spectrum-6 SPX switch rack, Valvey brings the network into the same thermal management loop as Vera Rubin NVL72. Racky , our rack control manager, aggregates power, cooling, and environmental sensors into a single interface. It monitors rack health, controls valves and power functions, and surfaces telemetry such as leak detection, flow rates, and temperature. Rather than monitoring each rack's subsystems independently, Racky presents everything through a unified management layer that connects directly to CoreWeave's broader infrastructure stack. In addition to Valvey and Racky, the Rack Lifecycle Controller (RLCC) automates the deployment, operation, and lifecycle management of AI infrastructure at the rack level. Rather than managing individual devices, RLCC treats an entire rack including GPUs, networking, power, and cooling systems as a single programmable resource. RLCC orchestrates firmware, configuration, health monitoring, and recovery across every component. That's what makes high-density AI infrastructure repeatable to deploy, without the operational complexity that usually comes with it. For customers, the operational result is simplicity through a unified rack management domain that is software-defined and programmable with one control surface, one observability layer, and one capacity model covering both compute and network fabric. Unlike air-cooled systems, the management overhead required for separate power monitoring, separate thermal management, and separate incident response workflows has been made obsolete with CoreWeave Mission Control. Once compute and network fabric run under a single observability and capacity model, the signal feeding the rest of the stack gets more reliable too. That's what lets a research and iteration agent like CoreWeave ARIA , built into Weights & Biases, give researchers cleaner answers when they're iterating on a model. The telemetry it's reasoning over comes from infrastructure that's already unified, making our entire stack a competitive advantage for AI researchers to work smarter and faster. Denser, faster, cooler: New efficiency gains Liquid-cooling allows the SN6600-LD to sustain line-rate switching performance at full density without thermal constraints. In a standard 48U rack, 16 SN6600-LD switches can be deployed, delivering...