Quick custom optical networks

Fibre Channel and Gigabit Ethernet host-bus adapters that connect servers to storage systems. The adapters use 32-bit and 64-bit drivers for the Windows, Mac, Linux, and Solaris operating systems.

Develop a configurable network that lets a team of more than 40 test engineers run performance tests and verify adapter features such as data rate. Check that performance doesn't degrade with each new hardware or driver release. Test the hardware and software to ensure that they will handle packet faults and physical faults.

• Apcon: optical switches. www.apcon.com.
• EdenTree Technologies: network-configuration software. www.edentreetech.com.
• Finisar: Fibre Channel and Gigabit Ethernet analyzers and error generators. www.finisar.com.

Qlogic (Aliso Viejo, CA, www.qlogic.com) manufactures host-bus adapter cards that connect servers to storage devices and storage-area networks (SANs). Each time the company makes a design change, its test engineers must check performance, features, and error handling.

Host adapters connect to storage devices and SANs over Fibre Channel links at data rates up to 4 Gbps or over Ethernet at 1 Gbps. To configure a test SAN, test engineers had to manually connect fiber-optic cables from the device under test to networks and test equipment. Whenever an engineer needed to test for a lost optical link, he or she had to manually disconnect and reconnect the optical cables. To increase productivity, staff engineer Matt Holley designed a configurable network using software-controlled physical-layer switches.

Physical-layer switches and software let test engineers configure an optical network from their desks.

Ethernet connects the optical switches to a server running the configuration software. Engineers operate the configuration software over the company network, and the software schedules each use of the test system to avoid conflicts. Engineers can also invoke scripts that connect to the server to automate the test network's configuration.

During a test, the engineers introduce faults to verify that a host adapter recovers from errors. The error generators let engineers intercept and modify bits within frames or packets. They also break connections through the optical switches.

"If a connection is reestablished within 30 s, then the host adapter should continue to work normally," said Holley. "We also test for broken connections that go longer than 30 s. The connection should fail, but the host adapter should fail gracefully, without causing problems such as system crashes." Engineers verify that the host adapter can correct recoverable errors and provide error-free transmission.

After test engineers verify that a new product or updated product passes its tests, QLogic sends test results to Microsoft for device-driver certification. The company also sends test results to other software companies such as Red Hat and Novell for certification.

Although the optical switches can connect network devices in seconds as opposed to 15 minutes per test, Holley found the test engineers were somewhat reluctant to move to an automated network. The optical switches more than doubled the number of cables and transceivers interconnecting devices, which confused some test engineers because they didn't know the exact cables they were using. If a manually connected cable failed, they knew which one to replace. "We needed to train the test engineers on how the optical switches connect devices in the background," noted Holley.