Overcoming Challenge #4: Converged Testing for the LAN and SAN

The final of the four testing challenges developers of FCoE network equipment face when verifying equipment behavior, performance, and responsiveness is being able to not only test both the LAN and SAN components of the network simultaneously but to also combine test results and expertise onto a single, converged platform.

Currently, the LAN and SAN are separate networks which have their own tools and different testing focuses. For example, LAN testing focuses on the switch and network only. SAN testing, in contrast, requires network-to-end-device verification as all hosts, fabrics, and targets contribute to the overall performance of the network. Given that the LAN fabric is based on best effort delivery while the SAN has complete traffic control end-to-end governed by Fibre Channel’s protocol for zero frame loss, LAN QoS testing does not apply to storage networks. Rather, SAN testing measures the performance of Fibre Channel links through mechanisms such as buffer to buffer credit management from the host through the fabric to the storage. In addition, as SAN testing must verify the delivery of every single frame, it requires a wholly different dimension of performance and latency measurements compared to LAN testing.

Convergence of the LAN and SAN networks, however, needs to extend beyond simply carrying traffic out to all aspects of network management and testing. As the LAN and SAN become a single logical network under FCoE, analysis and monitoring tools need to accommodate this convergence as well, enabling developers to utilize a single test and development platform.

A common misconception is that as the network has converged on Enhanced Ethernet, converged testing should follow Ethernet’s traditional QoS-based structure. However, since all the new, enhanced features are designed to enable storage data to be converged with LAN data with performance comparable to a separate SAN, testing must actually focus on the SAN’s more stringent requirements. Thus, when designing a test setup for a converged Enhanced Ethernet network, developers must step away from QoS-based testing, which is a measure of lossy network performance, in order to focus on performance testing of a lossless network with zero tolerance for packet drop.

The challenge of testing Enhanced Ethernet is how to combine the expertise required for testing lossy traffic with that required for testing lossless traffic. As the testing focus of these two different types of traffic are difficult to reconcile, the analysis instrumentation itself must be integrated as a converged platform. In this way, it becomes possible to test the various convergence properties such as the priority groups and traffic classes as well as the influences these have on the converged network as a whole.