Fibre Channel over Ethernet (FCoE) is the next evolution of the Fibre Channel networking and Small Computer System Interface (SCSI) block storage connectivity model. FCoE maps Fibre Channel onto Layer 2 Ethernet, allowing the combination of LAN and SAN traffic onto a link and enabling SAN users to take advantage of the economy of scale, robust vendor community and roadmap of Ethernet. The combination of LAN and SAN traffic on a link is called unified fabric. Unified fabric eliminates adapters, cables and devices, resulting in savings that can extend the life of the data center. FCoE enhances server virtualization initiatives with the availability of standard server I/O, which supports the LAN and all forms of Ethernet-based storage networking, eliminating specialized networks from the data center. FCoE is an industry standard developed by the same standards body that creates and maintains all Fibre Channel standards. FCoE is specified under INCITS as FC-BB-5.
FCoE is complemented by new facilities in Layer 2 Ethernet called Data Center Bridging (DCB). DCB is a collection of IEEE 802.1 standard enhancements that allows the LAN behavior of dropping packets upon congestion to co-exist with the SAN requirement of no loss of frames. Classes of service (CoSs) allow this behavior, and new bandwidth management tools enforce appropriate use of bandwidth among the classes. In this way, LAN scaling and the deterministic needs of SAN I/O are made compatible
FCoE is evolutionary in that it is compatible with the installed base of Fibre Channel as well as being the next step in capability. FCoE can be implemented in stages nondisruptively on installed SANs. FCoE simply tunnels a full Fibre Channel frame onto Ethernet. With the strategy of frame encapsulation and de-encapsulation, frames are moved, without overhead, between FCoE and Fibre Channel ports to allow connection to installed Fibre Channel. In support of FCoE, all the Fibre Channel network services, nomenclature, behaviors, and network tools remain intact. SAN administrators manage Fibre Channel flows in a manner very similar to that used today.
This sort of evolutionary transition has occurred before. In the mid 1990s, the SCSI protocol implemented over a bus architecture was the standard for block attached storage. However, storage assets coupled with individual servers used capacity inefficiently, so a networking model for storage was created, along with the capability to consolidate storage. Because valuable and robust driver and firmware technology needed to be preserved, not reinvented, the SCSI protocol became the upper-layer protocol of the Fibre Channel networking model.
Thus, a new physical infrastructure was created for SCSI with significant investment in creation of a robust networking model. This process is being repeated today but with the difficult work of network model creation done, and the porting of SCSI and Fibre Channel now occurring over proven 10 Gigabit Ethernet.