Broadcom Tomahawk Ultra Low latency High performance and Reliable Ethernet for HPC and AI

Tomahawk Ultra shatters the myths about Ethernet’s ability to address high-performance networking. In this session we will show how we added features for lossless networking, reduced latency and increased performance – all while maintaining compatibility with Ethernet.

The presentation introduces the Broadcom Tomahawk Ultra, a 51.2 terabit per second switch chip designed to bring high-performance Ethernet to markets traditionally dominated by InfiniBand, specifically HPC and AI. Addressing perceived limitations of Ethernet such as high latency, small frame size constraints, packet overhead, and lossy nature, the Tomahawk Ultra is a clean-slate design focused on ultra-low latency, high packet rates, and reliability. The chip is pin-compatible with Tomahawk 5, enabling quick adoption by OEMs and ODMs, and it’s currently shipping to partners who are building boxes with it.

Key features of the Tomahawk Ultra include a 250 nanosecond ball-to-ball (first bit in to first bit out) latency, high packet-per-second processing optimized for small message sizes common in HPC and AI inferencing, and support for in-network collectives (INC) to offload computation from XPUs during AI training. The chip also incorporates an optimized header format to reduce packet overhead in managed networks and advanced reliability features like link-layer retry (LLR) and credit-based flow control (CBFC) for lossless networking. Topology aware routing, enabling optimized packet paths in complex HPC networks, is also implemented.

The speaker emphasized that the Tomahawk Ultra aims to provide an open and standards-based approach to high-performance networking, adhering to Ethernet standards for compatibility and ease of management. It utilizes standard Ethernet tools for configuration and monitoring, with features like LLR automatically negotiating between the switch and endpoints. Broadcom has contributed the Scale Up Ethernet (SUE) specification to OCP to encourage an open ecosystem. The Tomahawk Ultra is positioned as an end-to-end solution for high performance, offering an alternative to technologies like NVLink in scale-up architectures while ensuring compatibility and openness.