T11's FCoE defines the mapping of Fibre Channel frames over Ethernet so storage traffic can be converged onto a 10Gbps Ethernet network. The IEEE's DCB task force is defining three standards -- 802.1Qau for congestion notification, Qaz for enhanced transmission selection, and Qbb for priority-based flow control.

Where Ethernet standards fall short

Vendors say these standards should be solid enough to implement on products and deploy in data centers in late 2009/early 2010. The DCB standards will be final in March 2010, four months later than initially planned due to some outstanding, but not insurmountable issues, according to Pat Thaler, chair of the DCB Task Group in the IEEE.

But some leading-edge customer need a pre-standard lossless Ethernet implementation now, vendors say; and even when these standards are complete they will be incomplete, others say.

"A particular area where we feel these standards don't really address is the avoidance of congestion -- primarily with respect to load balancing traffic first before we rate limit traffic at the source," says Bert Tanaka, vice president of engineering for Woven Systems. "Qau and Qbb attempt to avoid congestion by slowing traffic from the source. But what we feel that they don't do is they don't actually try to avoid congestion by balancing traffic in the fabric. That is where we plan to couple [the standards] with our own technology."

Tanaka also says the DCB and FCoE standards are limited in the ability to scale to large networks.

"They are really targeted for a fairly small fabric -- maybe hundreds of nodes," he says. "But if you're trying to scale to multiple hops and larger fabrics, it's not clear it would scale to something like that. FCoE . . . is looking to a more constrained network size. It may not scale to the network the size of Google."

Thaler says no one ever proposed load balancing or congestion avoidance for inclusion in the DCB standards.

"I don't know any networks that have standardization for load balancing," she says. "Switch vendors like to keep that as their secret sauce."

And she disagrees with Tanaka's assertions that the standards will not scale: "I think that's (referring to) congestion notification but I don't entirely agree with that."