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ATM NICs: Ready To Sail, But Not Ready To Scale

By Joel Conover Enterprise computing demands scalability, and the enterprise server is one of the hardest-working devices in this carefully balanced system. For many years, vendors have sold ATM into the enterprise as the solution to address scalability and quality-of-service (QoS) nightmares.

We invited ATM vendors to put their hardware to the test at Network Computing's lab at the University of Wisconsin in Madison. We tested 155-Mbps solutions and one 622-Mbps solution in enterprise-class multiprocessor servers, running them through a battery of tests to determine how well these cards support high-bandwidth needs. The good news is ATM finally seems to have a degree of stability and interoperability, and it's ready to set sail. The bad news is ATM performance and scalability is far from what we expected.

To view the Report card.
FORE Systems, Interphase Corp., Madge Networks, Olicom USA and 3Com Corp. provided 155-Mbps ATM NICs that met our test requirements for enterprise ATM scalability (see "Setting Sail With ATM Network Interface Cards" on page 86). Other vendors couldn't participate for various reasons: Adaptec's adapter didn't support multiple adapter instances, and Allied Telesyn doesn't offer a twisted-pair adapter. Digital Equipment Corp. didn't have its new adapter ready in time for our tests, and Newbridge Networks stated it didn't have the hardware resources necessary to support our tests.

One vendor, Sun Microsystems Computer Corp., provided us with a 622-Mbps ATM adapter. Sun's adapter gets its own spotlight, since it was the only vendor with a 622-Mbps card in production during our test period (see "Sun's 155- and 622-Mbps SBUS Adapters" on page 90). The Sun 155 and 622 SBUS adapters, which operate in the Solaris OS environment, were tested separately from the Peripheral Component Interconnect (PCI) devices in this review. ATM performance and scalability in the Solaris environment was substantially better than that of Windows NT and IntranetWare: The Solaris-SBUS adapter combo pumped out nearly twice the throughput of the closest Intel-PCI competition.

Unable to Scale High Bandwidths Megabit for megabit, ATM NIC performance was no better than Fast Ethernet NIC performance on the same platform. By way of comparison, we were able to pump 140 Mbps out of Fast Ethernet adapters from 3Com. Average ATM performance fell in the range of 130 Mbps to 150 Mbps. We were disappointed with ATM's ability to scale on the Windows NT and IntranetWare platforms. Our Sun adapter fared much better in the tests, with top throughput coming in at about 253 Mbps.

In our testing, we were looking for scalable performance, ease of installation and effective management and diagnostic tools, as well as lo w cost. Our overall winner, Madge Networks' Collage ATM 155 PCI Adapter offered the best throughput in nine out of 12 of our tests with an aggregate speed of 150 Mbps. Strong runners-up are FORE Systems' ForeRunner PCA-200EPC PCI Bus ATM Adapter and 3Com's ATMLink PCI 155 Mbps Network Interface Card. These products offered easy setup and configuration and advanced features.

Madge Networks Collage ATM 155 PCI Adapter
The Madge PCI ATM Server Adapter stole the show in our tests. Top performance, simple installation and a range of driver support made the Collage ATM 155 PCI Adapter a clear winner.

Under Windows NT, the adapter managed 138 Mbps with four NICs. Although most vendors pegged both processors under heavy load, the Madge adapter left the second processor at only 60 percent utilization during our tests with one and two adapters. In the IntranetWare environment, the driver soft ware didn't fare as well--Symmetric Multiprocessing Protocol (SMP) support caused the server to crash when the drivers were loaded. Performance on a single processor was still higher than the competition--150 Mbps--the fastest of any adapter we tested.