Why it matters

Network is often bottleneck. Understanding shapes pod design.

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The architecture

NVLink: intra-rack, ultra-high BW.

InfiniBand/RoCE: inter-rack scale.

Rail-optimized: dedicated per-rank link.

GPU pod networkNVLinkintra-rack 900GB/sInfiniBand / RoCEinter-rack 400+ Gb/sRail-optimizedtopologyMeta RSC, Microsoft Eagle scale to 20K+ GPUs; rail-optimized reduces hops
Pod network.
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How it works end to end

NVLink 5: 1.8 TB/s per B200.

InfiniBand HDR/NDR: 400/800 Gb/s.

RoCEv2: Ethernet-based alternative.

Rail-optimized: minimize congestion.