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Brocade, Cisco agree on Fibre Channel over Ethernet format

Posted: 24 Aug 2007 ?? ?Print Version ?Bookmark and Share

Keywords:Fibre Channel? Ethernet? Brocade-Cisco agreement?

Rivals Brocade Communications and Cisco Systems have agreed on a frame format for running Fibre Channel over Ethernet, clearing a major hurdle in the effort to develop a standard for the converged network. The Brocade-Cisco compromise marks the last major piece of the specification now in progress that might affect hardware, clearing the way for work to begin on chips that implement the standard.

A broad group of computer and communications companies have expressed support for Fibre Channel over Ethernet, kicking off earlier this year a standard effort in the T11 group that oversees Fibre Channel. The effort is one part of broader work on Converged Enhanced Ethernet (CEE), an advanced version of Ethernet geared for data centers.

Backers of CEE share a vision of consolidating the number of networks users need to support in tomorrow's data center. The first target of the group is to create a single adapter card for servers that would replace separate cards used today for Ethernet networking and Fibre Channel storage.

Multiple technologies
Today's data centers typically use Ethernet for networking, Fibre Channel for storage and Infiniband or proprietary interconnects for clustering. Increasingly companies are supporting all three technologies with separate products and trying to find ways they can streamline their ballooning product lines by supporting multiple technologies in individual products.

Brocade and Cisco arrived at the compromise during a T11 meeting last week and submitted a proposal that was accepted by the overall group. The compromise defined the key frame format for Fibre Channel over Ethernet taking elements from the separate proposals of both companies. In June, the two companies had submitted competing plans to T11.

"This is good news," said Renato Recio, a chief engineer in IBM Corp.'s eServer group. "The painful part is behind us now," he said.

"This was the last major decision which might impact ASIC design," Recio said. "I think both companies looked at their hardware in the works and decided it was better to bite the bullet now than keep arguing for a few more months and still have to rework their ASICs later," he added.

Compromise
As part of the compromise Cisco agreed to give up its request for a length field in the FCoE packet. Brocade argued including such a field would prohibit a switch's ability to do cross-through routing and more efficient buffering. Brocade said an end of frame character could supply packet length information.

For its part, Brocade relaxed its requirement for a time-stamp field in the FCoE packet intended to prevent re-transmission of an old packet. Cisco argued packets could use a timer facility already in Fibre Channel to perform the function, and both companies agreed they could leave space for an optional time-stamp field in the frame that could be used in the future.

The compromise basically follows a line of thinking proposed by EMC, Hewlett-Packard and IBM as part of a suggested compromise proposal.

Hard work ahead
Plenty of work still remains before the T11 committee can finish the FCoE standard, something it expects to do by April 2008. However, most of the remaining elements only impact the software design of systems supporting the draft spec.

Two key areas are now up for debate. Both center on whether certain features should be put into the spec now, even though they are not likely to be part of first-generation products.

One feature would describe how to directly attach storage devices to an Ethernet network supporting FCoE. The other involves defining a way to gang multiple FCoE switches into one virtual switch to support more robust automated backup capabilities.

"We think we should standardize these features now, otherwise people may try to differentiate themselves by implementing them early with various proprietary approaches," said Recio.

The T11 work is big chunk of a broader effort to create a version of Ethernet fully capable of handling Fibre Channel traffic. Separately, the IEEE 802.1au group is defining new congestion management techniques for Ethernet that would be needed to assure the kinds of performance defined by Fibre Channel.

- Rick Merritt
EE Times




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