The results show FabricPath converges far faster than spanning tree. On average, the system rerouted traffic sent to a failed spine switch in 162 milliseconds, a big improvement over rapid spanning tree's 1 to 3 second convergence time.
We also tested convergence time when adding a switch to the FabricPath network by powering up each downed spine switch one at a time. In this test, convergence time was zero. The IS-IS protocol recognized each new path and began routing traffic over it, but the system dropped no frames during or after each route recalculation.
Data center Network manager
Our final set of tests examined the ability of Cisco's Data Center Network Manager (DCNM) software to configure and monitor FabricPath networks. DCNM uses Simple Object Access Protocol (SOAP), an XML-based method of representing data, which allows it to be called by any third-party Web services application. Cisco demonstrated this with functional tests of XML input and output to a DCNM server.
In our tests, we focused on DCNM's ability to perform common FabricPath management tasks. All the tasks tested are included with the base version of DCNM, supplied free for managing Nexus switches. Some additional functions such as configuration history management are available at extra cost but we did not test these. Also, DCNM is mainly useful for Nexus switch management; while it can discover non-Nexus switches using Cisco Discovery Protocol (CDP), the information it manages is limited to that supplied by CDP. With Nexus devices, the management toolkit is a lot more extensive.
In our first test, we configured DCNM to discover the six Nexus switches and populate its database. Second, we configured DCNM to send text and e-mails when traffic on a FabricPath link exceeded 80% utilization. Third, we configured DCNM to display an alarm on link failure (triggered by physically removing a cable between edge and spine switches). Finally, we configured DCNM to apply weighted random early detection queuing to all switch configurations, and then to remove the WRED section of all switches' configurations. DCNM successfully accomplished all these tasks.
While we would like to see FabricPath implemented on more than one switch, there's no question it represents a significant advancement in the state of the networking art. As these tests showed, FabricPath simplified network design while improving scalability and resiliency. For network architects looking to expand their data centers, flattening the network with FabricPath is now a real option.
Newman is a member of the Network World Lab Alliance and president of Network Test, an independent test lab and engineering services consultancy. He can be reached at firstname.lastname@example.org.
Network World gratefully acknowledges the support of Spirent Communications, which provided engineering and logistical assistance on this project.