Latency is the key variable for high-frequency trading; all use cut-through switching to keep latency as low as possible. Arista’s switches and the Mellanox SX1036 had set the low-latency benchmark, at around 400 nanoseconds over 10-Gbps links. Cisco’s Nexus 3000 switches clocked in closer to 1,000 nanoseconds. The Nexus 3548 employs what Cisco calls Algo Boost (algorithm boost) to push latency down to 250 nanoseconds and below 200 ns in Warp mode. Warp mode restricts the size of the forwarding table, allowing the switch to make faster forwarding decisions. Feed replication (sending the same data out multiple ports) can incur latencies as low as 50 nsec.
Algo Boost is now part of Cisco's ASIC design library, and the company says the performance numbers above are valid for unicast, multicast and Layer 2 and 3 switching. Cisco also provides precision time synchronization, which can be required by regulation in trading applications. In other words, the switch is fast, and that speed isn't dependent on turning off management functionality, according to Cisco. The Nexus 3548 also supports a bigger packet buffer than its predecessor, at 18 MB of shared buffer space.
The fixed-configuration, 48-port switch is just the first in the product line; Cisco will add to it, as it did with the Nexus 3000 series, and we’re told that Algo Boost will probably show up in other switch designs. With this product rollout, Cisco is reminding the market that it can to things with its custom silicon capabilities that might take others a while to catch up--but catch up they will, as the vendors leapfrog each other for this fairly lucrative market.
The one thing the Cisco 3548 isn’t is cheap. The Arista 7148SX lists for $26,395, while Cisco’s switch starts at $41,000 for the Layer 2 version and runs up to $66,000 for the fully loaded Layer 3 version. Applications go well beyond financial trading, including high-performance computing and private cloud pods.