Saturday, April 07, 2007

Weaving a new fabric

My editors posted my latest story on Fibre Channel over enhanced Ethernet (FCoE) faster that I thought! The story gives a little more color on the Cisco patent mentioned below as well as some deeper details about the outlook for FCoE silicon.

Basically, if all goes well chips could hit as early as 2009 and systems perhaps 18 months later. The chips are likely to require an addition state machine to process congestion management algorithms as well as 3-5x deeper buffers to handle virtual channels, depending on the details of the final protocol. The chips are expected to be used widely in adapter cards, switches and gateways.

I had the chance late Friday to talk with Claudio DeSanti, vice-chair of the T11 committee and technical leader of Cisco's data center business unit. He made a couple interesting points.

Perhaps the most interesting was that the T11 work on FCoE will be based on existing traffic-pausing techniques in Ethernet. Ethernet enhancements being worked on in IEEE 802.1au and being discussed beyond that will be great, but not necessary.

"If we were forced to wait before we do our thing it could delay us a couple years, so what we are doing (in T11) has to be agnostic of any Ethernet extensions. If you have those extensions, things get even better," he said.

This is a practical approach, but I sense most products will be based on something closer to the whole enchilada including congestion management and priority-based pausing to make this work well. That will require vendors closely track work in T11, 802.1au, some efforts in the Internet Engineering Task Force and maybe other groups still to be decided. The priority pause work, for instance, doesn't have a defined forum yet.

That's an ambitious web to weave, but once that is in place, you can do a version of Ethernet that does not drop packets and has significantly better latency. Most observers expect the resulting technology will nibble at the low end of Infiniband in clusters and dampen enthusiasm for iSCSI at the high end of storage. But as we all know nothing ever goes away.

"We have and will continue to build iSCSI products. In no way do we see this as the end of iSCSI," said Anthony Faustini, a product line manager in the Cisco group. He might have said the same about Infiniband.

As my EE Times story says, the next big milestones will come in June with presentations on FCoE at the T11 meeting in Minneapolis and July when 802.11au hopes to select one of four proposals for Ethernet congestion management. Until then, stay tuned!

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