FCoE maps Fibre Channel natively 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 allows a seamless integration with existing Fibre Channel networks and management software.

 <!--more-->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, it is not routable at the IP layer, and will not work across routed IP networks.

 Since classical Ethernet has no flow control, unlike Fibre Channel, FCoE requires enhancements to the Ethernet standard to support a flow control mechanism (this prevents congestion and ensuing frame loss.) The IEEE standards body is working on this in the Data Center Bridging Task Group.

 Servers using FCoE are initially expected to use 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 in combination with 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.