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Extreme's Data Center Play: Page 2 of 2

Key to Extreme's Direct Attach is the 96-port fan out modules in the BlackDiamond chassis that can support high port counts when home running servers to a core switch. That's a lot of cable to run from rack to switch and may not be a viable option. It's one of the reasons why top-of-rack and end-of-row switches are used: the cable trays fill quickly as you approach the core.

The second necessary feature is Extreme's adoption of using a physical switch to move traffic between hosts, even within the same hypervisor. The idea, also promoted by HP and others, is to bypass the hypervisor soft-switch, which has limited functionality, and use the existing switch infrastructure. The argument is that doing so makes management better and simplifies the overall network topology. This is in contrast to Cisco's approach with the Nexus 1000V, which replaces the virtual switch in VMwares hypervisor, and Arista's approach of managing the soft-switch using their switch operating system.

Using the bypass method leverages the existing switch infrastructure but also has the potential to create hairpins where traffic between two or more VMs on the same hypervisor exits the server and then does a hairpin turn to come back to the same hypervisor. Work within the IEEE on 802.1 Qbg Edge Virtual Bridging  has just begun; the working group was approved in December of 2009. Given the typical working time within the IEEE, we can expect to see standards in 2-3 years. Extreme's Direct Attach is based on early work within 802.1Qbg, but it's a stretch to say it's standards-based. Direct Attach currently only works with the open source Kernel Virtual Machine (KVM) on RedHat, but Extreme plans support for other hypervisors in the future.

Whether virtual switching is going to be good enough or using Virtual Edge Bridging is going to be the way to go is yet undecided. What is clear that the network edge in the data center will have to increase capacity beyond Gb or multi-Gb connections, and that grooming traffic on a per VM basis will be necessary. Extreme, like other switching vendors, is getting their data center switching products ready.