Test engineers face spectrum of networking issues

The challenges of testing high-performance networks are both big and broad. Just ask Dave Twinam, a manager of technical marketing and engineering for Cisco Systems Inc.'s core Catalyst 6500 local-area network (LAN) switch.

"Increasingly, we are trying to inject more and more real-world traffic into our test networks, as opposed to generic packet-processing routines. If you don't test systems at scale, you don't find problems until they crop up in deployed user networks," Twinam said.

For Cisco, "at scale" means internal test beds simulating more than 20,000 users networking with more than 60 Catalyst switches at its Research Triangle Park, N.C., and San Jose, Calif., test centers.

Testing throughput, quality of service, access control and failover mechanisms under real workloads is crucial, Twinam said. Test vendors are supporting Cisco with the tools to generate the network routes and routing tables as well as the IPv6 tools they now need.

"What's new are TCP state machines that run at gigabit-per-second data rates to let us take snapshots of real-world networks and incorporate that into our test beds. Vendors have delivered these at gigabit rates but they have not been able to do it yet at multigigabit rates," Twinam said.

"So I have to buy a lot of expensive test systems to tax our equipment. No one has cost-effectively delivered 10-Gbit TCP state machines in test gear yet. We need a few more generations of the ASICs to get there," he added.

Fred Niehaus, a technical marketing engineer at Cisco's wireless-networking business unit, sees similar challenges while testing 802.11a/b/g systems for large financial trading floors and other customers. Throughput, configuration and contention problems are top concerns. Creating wireless virtual LANs and, now, delivering voice with good quality of service are emerging issues.

Sometimes requirements dictate scaling back access points or clients to narrow, 1-milliwatt transmission ranges or dealing with the reality of .11b nets that only deliver an effective 6 Mbits/second of throughput, Niehaus said.

When EE Times asked top test vendors to tell us about the challenges they run into when testing high-performance networks, they came back with a grab bag of concerns all across the spectrum, as it were.

In this section, Tektronix Inc. calls for a new generation of test gear to handle 3G cellular networks, where data-link layer problems are taking on the aura of applications software debugging as users access multiple-logical-layer services, sometimes across multiple physical-layer connections. In the handset and basestation arena, Agilent Technologies contends new multichannel RF vector signal analyzers are required to test the emerging class of systems using so-called smart antennas. And National Instruments Corp. says handset OEMs need new firmware loading, test and feedback schemes to lower costs on their manufacturing lines.

In the wired world, Centillium Communications Inc. discusses two complementary methods for testing copper loops before deploying asymmetric digital subscriber line technology. Computer Access Technology Corp. details techniques for real-time protocol analysis on Ethernet links running at and above gigabit/second rates. And 3Ware Inc., which recently developed an enclosure specification for serial ATA hard-disk arrays, talks about chassis requirements for the emerging class of these storage-networking systems.

Finally, taking a look inside the box, OSA Technologies gives an update on the Intelligent Platform Management Interface, the internal test method used in a growing number of servers, server blades and network gear.