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Tahan: An Open, Ethernet-Based Scale-Up Switch for Meta's MTIA Accelerators#

OCP Global Summit 2026 digest Program Core pick 12–15 October 2026

Abstract Recording

Ashutosh Grewal (Meta), Vimal Vasudevan (Meta Platforms inc.)

Play the recording: Tahan: An Open, Ethernet-Based Scale-Up Switch for Meta's MTIA Accelerators

  • Why: The best "show me the hardware" talk on scale-up Ethernet: a first-generation open scale-up switch with real numbers, and a rare case of one NOS (FBOSS) and one transport (RoCE) spanning both scale-out and scale-up.
  • What: Tahan, Meta's first scale-up switch for MTIA 300 accelerators: 6.4 Tbps per accelerator over 8× 800GbE passive copper links, 16 accelerators per liquid-cooled rack interconnected via 4 switches in a non-blocking topology, on merchant 25T/51.2 Tbps silicon running FBOSS (from abstract only).
  • How: Reuses the scale-out network's lossless RoCE transport (routed IPv6, PFC, AI-tuned QoS) on the scale-up fabric, eliminating separate software stacks and operational silos; next-gen targets 8 switches on 102.4 Tbps silicon, 72 accelerators per rack, adopting OCP ESUN as the dataplane.
  • Where applicable: Meta-specific (MTIA, FBOSS, in-rack passive copper reach), but the architecture pattern — unifying scale-up/scale-out under one Ethernet transport and NOS — is broadly instructive; note the passive-copper choice constrains it to in-rack distances.