Fibre Channel over Ethernet
Fibre Channel over Ethernet (FCoE) is an encapsulation of Fibre Channel frames over Ethernet networks. This allows Fibre Channel to use 10 Gigabit Ethernet networks (or higher speeds) while preserving the Fibre Channel protocol. The specification, supported by a large number of network and storage vendors, is part of the International Committee for Information Technology Standards T11 FC-BB-5 standard.
FCoE maps Fibre Channel directly over Ethernet while being independent of the Ethernet forwarding scheme. The FCoE protocol specification replaces the FC0 and FC1 layers of the Fibre Channel stack with Ethernet. By retaining the native Fibre Channel constructs, FCoE was meant to integrate with existing Fibre Channel networks and management software.
Many data centers use Ethernet for TCP/IP networks and Fibre Channel for storage area networks (SANs). With FCoE, Fibre Channel becomes another network protocol running on Ethernet, alongside traditional Internet Protocol (IP) traffic. FCoE operates directly above Ethernet in the network protocol stack, in contrast to iSCSI which runs on top of TCP and IP. As a consequence, FCoE is not routable at the IP layer, and will not work across routed IP networks.
Since classical Ethernet had no priority-based flow control, unlike Fibre Channel, FCoE requires enhancements to the Ethernet standard to support a priority-based flow control mechanism (this prevents frame loss). The IEEE standards body is working on this in the Data Center Bridging Task Group.
Fibre Channel required three primary extensions to deliver the capabilities of Fibre Channel over Ethernet networks:
- Encapsulation of native Fibre Channel frames into Ethernet Frames.
- Extensions to the Ethernet protocol itself to enable an Ethernet fabric in which frames are not routinely lost during periods of congestion.
- Mapping between Fibre Channel N_port IDs (aka FCIDs) and Ethernet MAC addresses.
Computers connect to FCoE with Converged Network Adapters (CNAs), which contain both Fibre Channel Host Bus Adapter (HBA) and Ethernet Network Interface Card (NIC) functionality on the same adapter card. CNAs have one or more physical Ethernet ports. FCoE encapsulation can be done in software with a conventional Ethernet network interface card, however FCoE CNAs offload (from the CPU) the low level frame processing and SCSI protocol functions traditionally performed by Fibre Channel host bus adapters.
The main application of FCoE is in data center storage area networks (SANs). FCoE has particular application in data centers due to the cabling reduction it makes possible, as well as in server virtualization applications, which often require many physical I/O connections per server.
With FCoE, network (IP) and storage (SAN) data traffic can be consolidated using a single network. This consolidation can:
- reduce the number of network interface cards required to connect to disparate storage and IP networks
- reduce the number of cables and switches
- reduce power and cooling costs
Frame Format 
FCoE is encapsulated over Ethernet with the use of a dedicated Ethertype, 0x8906. A single 4-bit field (version) satisfies the IEEE sub-type requirements. The SOF (start of frame) and EOF (end of frame) are encoded as specified in RFC 3643. Reserved bits are present to guarantee that the FCoE frame meets the minimum length requirement of Ethernet. Inside the encapsulated Fibre Channel frame, the frame header is retained so as to allow connecting to a storage network by passing on the Fibre Channel frame directly after de-encapsulation.
The FIP (FCoE Initialization Protocol) is an integral part of FCoE. Its main goal is to discover and initialize FCoE capable entities connected to an Ethernet cloud. FIP uses a dedicated Ethertype of 0x8914.
Azul Technology developed early implementation and applied for a patent in October 2003. 
The FCoE standardization activity started in April 2007. The FCoE technology was defined as part of the INCITS T11 FC-BB-5 standard that was forwarded to ANSI for publication in June 2009. The FC-BB-5 standard was published in May 2010 as ANSI/INCITS 462-2010.
An early implementor was Nuova Systems, a subsidiary of Cisco Systems, which announced a switch in April 2008. Brocade Communications Systems also announced support in 2008. After the Late-2000s financial crisis, however, any new technology had a hard time getting established.
See also 
- Fibre Channel
- Converged Network Adapter
- ATA over Ethernet (AoE)
- LIO FCoE target driver
- SCST FCoE target driver
- "Fibre Channel: Backbone - 5 revision 2.00" (PDF). American National Standard for Information Technology International Committee for Information Technology Standards Technical Group T11. June 4, 2009. Retrieved May 5, 2011.
- "FCoE PatentApplication".
- "Information technology - Fibre Channel - Backbone - 5 (FC-BB-5)". ANSI/INCITS 462-2010. InterNational Committee for Information Technology Standards (formerly NCITS). May 13, 2010. Official standard.
- Paul Shread (April 10, 2008). "Cisco Buys Nuova as FCoE Heats Up". Enterprise Storage Forum. Retrieved May 5, 2011.
- "Cisco Announces Intent to Acquire Remaining Interest in Nuova Systems". Press release (Cisco Systems). April 8, 2008. Retrieved May 5, 2011.
- Dave Rowell (March 19, 2008). "Cisco, Brocade See One Big Happy Fabric". Enterprise Storage Forum. Retrieved May 5, 2011.
- Drew Robb (March 29, 2011). "FCoE Struggles to Gain Traction". Enterprise Storage Forum. Retrieved May 5, 2011.
- Henry Newman (April 25, 2011). "FCoE Gets Lost in Vendor Stupidity". Enterprise Storage Forum. Retrieved May 5, 2011.