Vendors hail Fibre Channel over Ethernet spec

A group of storage vendors on Thursday proposed the development of a new specification that would allow the Fibre Channel storage-area networking protocol to run over Ethernet.

Among the vendors proposing the Fibre Channel over Ethernet (FCoE) specification to the American National Standards Institute (ANSI) are Brocade, Cisco, EMC, Emulex, IBM, Intel, Nuova Systems, QLogic and Sun.

The vendor proposal would represent the first step toward a converged infrastructure consisting of both Ethernet and Fibre Channel that would be attractive to organizations that already have Fibre Channel SANs but want to run them over existing Ethernet infrastructures. The new Fibre Channel over Ethernet, unlike the iSCSI protocol, which transmits SCSI commands over TCP/IP, is designed for data center use. It will also be deployed in other specialized areas, vendors say.

"You can expect customers with bladed PCs or in high-performance computing who want to put in only one adapter to handle both Ethernet and storage traffic to adopt Fibre Channel over Ethernet," says Doug Ingraham, senior director of product management for Brocade.

FCoE will reduce the packet loss that plagues today's Ethernet networks. Because the Fibre Channel protocol does not tolerate the dropping of frames that Ethernet switches do, it will require the use of Ethernet switches with flow control enabled, says Luca Cafiero, a co-founder of Nuova Systems.

As Ethernet evolves, extensions to the Ethernet protocol that deal with pause mechanisms to ensure packets are not dropped or buffer-to-buffer credits may be implemented. These extensions are being considered by the IEEE.

Analysts applaud the move toward running Fibre Channel over standard Ethernet links.

“Fibre Channel over Ethernet is an interesting convergence point in that at the lowest physical layers, Fibre Channel and Ethernet leverage each others’ physical layer work,” says Greg Schulz, senior analyst for Storage I/O. “For those customers who are looking to unify their wiring and cabling infrastructures as well as their view of a unified network, Fibre Channel over Ethernet has great potential.”

The proposed specification likely would be implemented over 10Gbps Ethernet and require the use of specialized host bus adapters in servers that look to the server like a Fibre Channel adapter and to the network like an Ethernet adapter, says Mike Smith, director of marketing for Emulex.

FCoE differs from iSCSI because it runs over Layer 2 Data Link Ethernet instead of iSCSI. It also differs from the Internet Fibre Channel Protocol and the Fibre Channel over IP protocol, both of which also layer Fibre Channel frames on TCP/IP. Because FCoE runs as a Layer 2 service, it eliminates TCP/IP overhead.

The proposed specification also differs from Cisco's patent application for Data Center or Low Latency Ethernet, which proposes a converged I/O that can carry both Ethernet and Fibre Channel traffic in virtualized lanes, some which carry Ethernet data and allow for the dropping of frames and other lanes for Fibre Channel data, where dropped frames are not tolerated.