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Broadcom Opens New Switch SDK

February 13, 2018

Author: Bob Wheeler

In a bold departure, Broadcom is publishing the source code of its new software-development kit (SDK) for switch-chip drivers. The SDK is the company’s third set of open driver APIs, but it’s the first that allows others to modify and redistribute the source code. It also adopts a new API approach based on logical tables, so Broadcom calls it the SDKLT. The initial drivers only support the first-generation Tomahawk (BCM56960), however, and Broadcom has declined to reveal a roadmap for supporting other switch chips.

Because of the new logical-table design, the company developed the SDKLT from scratch. For more than a decade, its SDK has used function-based APIs, which are the foundation for OpenNSL. The problem with this approach is that every new switch feature requires a new function, causing an explosion of API functions to more than 700 in OpenNSL. In the SDKLT, logical tables abstract device resources, hiding physical-table details from the programmer. The result is that tens of API functions now manage switch behavior versus hundreds in the function-based SDK. The logical-table API carries an Apache 2.0 license, whereas all other SDKLT code is restricted to use on Broadcom silicon.

Where the SDKLT goes from here will depend in part on the developer community outside Broadcom. Because Tomahawk is the de facto standard for 100G Ethernet white-box switches, many ODMs, OEMs, and cloud-service providers already have experience with it. Broadcom claims the new API and associated documentation negates the need for most developers to access the Tomahawk programmer’s guide, which remains confidential. The company is making all SDKLT code readily available on GitHub and lowering the licensing barrier for customers; doing so will encourage development and sharing.

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