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Spectrum-2 Debuts 200GbE

July 31, 2017

Author: Loring Wirbel

The second-generation Ethernet switch from Mellanox, Spectrum-2, strongly supports the emerging IEEE 802.3bs 200GbE and 400GbE standards. The company has provided Ethernet adapters since 2007, though only the two switch generations are designed with Ethernet in mind. It introduced dedicated Ethernet chips two years ago by offering the first Spectrum generation.

Spectrum-2 offers 16x400GbE ports or 32x200GbE ports, the latter standard being oft neglected. It’s a single-chip device with 300ns latency and an aggregate L2 switching/L3 routing capacity of 6.4Tbps, or 9.52 billion packets per second. Spectrum-2 uses 128 native 50Gbps PAM4 serdes, which can also operate in optional 25Gbps NRZ mode, to provide the most port configurations. Its architecture allows “smart cut-through” between ports of different speeds—for example, 25GbE to 100GbE in a top-of-rack (ToR) topology.

Mellanox distinguishes the 16nm Spectrum-2 not only through port diversity but also through a large shared-memory packet buffer. It adds load-balancing and quality-of-service (QoS) features relative to Spectrum. Adaptive Flowlet Routing (the company’s name for flowlet switching) improves the load balancing of equal-cost-multipath (ECMP) routing, and the new chip implements a dynamic flow-prioritization scheme to distinguish long-lived (“elephant”) packet flows from short-lived (“mice”) flows.

The memory and QoS enhancements will appeal to hyperscale data-center operators and their OEM/ODM suppliers. Mellanox offers OEMs a choice of system-level products or chips; these customers can start with its system-level SN3xxx switches and later move to an in-house system design using the standalone Spectrum-2. Still, to take on Broadcom’s Tomahawk switch directly, Mellanox must become as visible in switch-chip sales as it is in switching-system sales. In the near term, Spectrum-2 will face Innovium’s Teralynx switch chips, which also uses 50Gbps PAM4 serdes to enable 200GbE and 400GbE ports.

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