• United States
Neal Weinberg
Contributing writer, Foundry

Riverstone 3000

Jul 29, 20033 mins

* The Reviewmeister sets about answering the question: What happens when you set filters on a router?

All router vendors claim that their products deliver wire speed throughput, but what happens when you set filters on a router? Does performance suffer?

The Reviewmeister set about answering this question. We took six access routers from five vendors and loaded the devices with progressively larger numbers of filters and routers.

We measured the performance effect of filtering with three metrics: throughput, average latency and maximum latency. To determine the router’s ability to recover from failure, we also measured reboot times under load for each device.

When it comes to throughput, there’s only one right result: line rate. The Riverstone 3000 delivered line rate throughput under all tests.

Next we tested for latency. In many ways, latency – the delay added by a device as a packet travels through it – is an even more important metric than throughput. Latency affects every packet, no matter how busy the network. Low and consistent latency is critical not just for voice and video applications, but for any application where response time matters. That definitely includes the roughly 90% of all Internet traffic that uses TCP. Because TCP requires timely acknowledgement of data, delays can lead to retransmissions or session loss.

Even at relatively slow T-1 rates, latency for 64-byte packets can theoretically be 500 microsec or less. The Riverstone 3000 stuck pretty close to that theoretical mark when we looked at average latency.

There’s no one good answer as to how much latency is acceptable. Humans perceive degraded video quality with delays of as little as 10,000 microsec, and degraded audio quality with delays of 50,000 to 200,000 microsec. For data applications, the threshold might be higher (sometimes much higher).

But this doesn’t excuse a router that adds, say, 100,000 microsec of latency. Keep in mind that these numbers are delays perceived by end users – and there are many other components, such as other routers, attached computers and software stacks, in play, each adding delay of their own. Any router that adds enough delay to mess with application performance is a problem.

Riverstone’s 3000 also had little difference between average and maximum. It also posted the lowest average latency across all tests with short frames and the least amount of variation among different test cases.

With 256-byte frames, Riverstone’s 3000 had the lowest average latencies across all test cases.

And the Riverstone’s 3000 registered relatively little difference between average and maximum delay – an indication of the device’s suitability for delay-sensitive applications. However, the Riverstone router’s maximum delays did spike upward when running large routing tables.

To assess how quickly devices recover from a loss of power, we loaded each router with the same line-rate stream of 64-byte traffic we used in the filtering tests. We did not set any filters or use dynamic routing, so we knew all routers were capable of forwarding traffic at line rate without loss.

Once a router began forwarding traffic, we used an automated power switch to power it off, wait 5 seconds and then power it up again. Because we offered traffic at a constant rate throughout the test, we were able to derive recovery time from frame-loss counts.

Riverstone’s box recovered in 123.7 seconds. For the full report, go to