Much ink has been spilled on the topic of what constitutes true “line rate,” and in the past we’ve advocated offering traffic at, and only at, 100.00 percent of theoretical line rate to determine if frame loss exists.

 However, the distinction between 99.99 percent (which we used in these tests) and 100.00 percent load is not all that meaningful, especially at higher Ethernet speeds, for a couple of reasons. First, Ethernet is inherently an asynchronous technology, meaning each device (in this case, the device under test and the test instrument) uses one or more of its own free-running clocks, without synchronization. Thus, throughput measurements may just be artifacts of minor differences in the speeds of clock chips, not descriptions of a system’s fabric capacity.

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The device under test for this project was the Cisco Nexus 9516 data center core switch/router, a 16-slot chassis equipped with 1,024 50-gigabit Ethernet interfaces and two supervisor modules. Cisco equipped the switch with its N9K-X9732C-EX line cards, each of which offers 32, 64, or 128 ports of 100-, 50-, and 25-gigabit Ethernet capacity.

The traffic generator/analyzer was Spirent TestCenter equipped with its 10/25/40/50/100G MX3 modules. The Spirent instrument has a measurement precision of +/- 2.5 nanoseconds.

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How many ports are enough at the core of the data center? How does 1,024 sound?

That’s the configuration we used to assess Cisco Systems’ Nexus 9516 data center core switch. In this exclusive Clear Choice test, we assessed the Cisco data center core switch with more than 1,000 50G Ethernet ports. That makes this by far the largest 50G test, and for that matter the highest-density switch test, Network World has ever published.

As its name suggests, the Nexus 9516 accepts up to 16 N9K-X9732C-EX line cards, built around Cisco’s CloudScale ASICs. These multi-speed chips can run at 100G rates, for up to 512 ports per chassis and either 25G or 50G rates for up to 1,024 ports. We picked the 50G rate, and partnered with test and measurement vendor Spirent Communications to fully load the switch’s control and data planes.

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Mention "home Wi-Fi router" and you’ll probably think of a cheap device with cruddy performance. But dramatic changes are coming, with big boosts in bandwidth, thanks to two new Wi-Fi technologies.

Both beamforming and MU-MIMO (an acronym for the mouthful that is “multi-user, multiple input, multiple output”) are transformational technologies. We tested them in the new Linksys EA-7500, the company’s first small office/home office router to support the so-called Wave 2 technologies.

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