Testing Vendors Target NIC Performance Problems

As driver-caused issues become more relevant with the popularity of Gigabit Ethernet and VOIP, new tools help uncover bottlenecks.

Theres a dirty little secret in networking that many users have encountered but few talk about: NIC drivers can be a drag on performance and can even cause system crashes. But one small testing vendor is working to expose the problems and hold vendors accountable for the performance of their hardware and drivers.

To date, network-interface-card issues have been mostly an inconvenience. But the movement toward faster technologies such as Gigabit Ethernet, coupled with the increasing use of more latency-sensitive applications such as voice, video and storage over IP, is raising the profile of the problems caused by the drivers.

A number of factors have kept NIC performance issues on the back burner. At the desktop, the performance hit has not generally been felt.

"Five or six megabits per second is more than fast enough on the desktop. Your internal hard drive can only go so fast when youre copying from a network drive to your PC," said Ronald Knol, IT and VFX technical supervisor for postproduction and visual effects company Rainmaker Limited Partnership, in Vancouver, British Columbia.

In addition, performance-testing tools have not been able to isolate bottlenecks down to the driver level. "Most people cant see this, so they probably dont hear about it a lot," said Kelly Daniels, chief technology officer at Apparent Networks Inc., also in Vancouver.

Daniels said Apparent has developed a performance-testing tool called AppareNet and is working to bring the NIC driver issue to light. The company is testing a host of popular hardware and software combinations and reporting its findings to the manufacturers for resolution. Daniels said some companies, such as Intel Corp., have been good about making fixes, while others have been slower to react.

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In the meantime, experts agree network administrators should consider NIC conflicts when troubleshooting performance issues and should test drivers before deployment.

AppareNet can uncover such driver-based issues as full-/half-duplex mismatches, Message Transmission Unit conflicts, reordered packets and more. The tool goes in below the TCP protocol stack to isolate NIC and driver issues and measure the effect the NIC and its driver have on traffic flow.

"They bypass the ... operating system and reside on the interface. There is no overhead from the OS, nothing from the PC itself thats going to prevent it from driving [full bandwidth]," said Dana Richard, an AppareNet user at storage-over-IP vendor Computer Network Technology Corp., in Minneapolis. "Only the Ethernet driver itself could do that."

Richard said that when he tested various Fast Ethernet interface drivers, "you could see one give you 20M bps, another 50M bps, another 60M bps. In each case, when you hit the top end, packets would drop, get out of order or corrupt the driver—things you expect when overdriving an interface."

Next page: Addressing the bottleneck.