A CDE Definition
(Fibre Channel Over Ethernet) A protocol for transmitting Fibre Channel frames over 10G Ethernet. FCoE replaces the bottom Fibre Channel (FC) layers F0 and F1 with Enhanced Ethernet layers, enabling the same network port on a server to carry Fibre Channel frames to an FC storage device and Ethernet frames to the local network.
Rather than regular Ethernet adapters, FCoE requires Enhanced Ethernet adapters on all nodes that support FCoE, and these adapters are called "converged network adapters" (CNAs). Regular Ethernet can lose packets under heavy congestion, but Enhanced Ethernet prevents packet loss by providing flow control. The FC to Ethernet conversion also takes place in the FCoE engine within the CNA. See Fibre Channel.
Typical FCoE Topology
The FCoE Frame
A high-speed transport technology used to build storage area networks (SANs). Although Fibre Channel can be used as a general-purpose network carrying ATM, IP and other protocols, it has been primarily used for transporting SCSI traffic from servers to disk arrays. The Fibre Channel Protocol (FCP) serializes SCSI commands into Fibre Channel frames and uses IP for in-band SNMP network management (see SNMP). For more about storage networks, see SAN.
Using singlemode or multimode fibers, Fibre Channel can be configured point-to-point (FC-P2P), as a switched topology (FC-SW) or in an arbitrated loop (FC-AL) with or without a hub, which can connect up to 127 nodes (see below). Transmission rates up to 12.75 Gbps in each direction are supported.
Fibre Channel uses the Gigabit Ethernet physical layer and IBM's 8B/10B encoding method, where each byte is transmitted as 10 bits. Fibre Channel provides both connection-oriented and connectionless services. Following are the class and functional levels. See FCIP, FCoE, IP storage and Director-class switch.
Class 1 With acknowledgment, full bandwidth
Class 4 Virtual connections, QoS,
Class 6 Uni-directional
Class 2 With acknowledgment
Class 3 Without acknowledgment
FC-4 Translation between Fibre Channel and
command sets that use it: HiPPI, SCSI, IPI,
SBCCS, IP, IEEE 802.2, audio, video
FC-3 Common services across multiple ports
Port levels (FC-PH standard)
FC-2 Framing and flow control
FC-1 8B/10B encoding, error detection
FC-0 Electrical and optical characteristics
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