Alan Freedman -- The Computer Language Company - Computer Desktop Encyclopedia
Computer Desktop Encyclopedia
Longest-Running Tech Reference on the Planet

A CDE Definition

You'll love The Computer Desktop Encyclopedia (CDE) for Tech Term of the Day (TTOD)

LOOK UP ANOTHER TERM


FCoE

(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.

Enhanced Ethernet
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
Both IP traffic for the LAN and FC traffic for the SAN (storage network) ride over the same FCoE-based Ethernet port. Although a CNA may have two 10G Ethernet ports, they exist for redundancy, not to separate IP from FC traffic. Both the server and switch perform the FC to Ethernet and Ethernet to FC conversion in their respective CNAs.






The FCoE Frame
Each Fibre Channel (FC) frame is encapsulated within an FCoE frame, which becomes the payload of the Ethernet frame.






Fibre Channel

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.

Specifications
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.



 Connection-oriented services
 Class 1    With acknowledgment, full bandwidth
 Class 4    Virtual connections, QoS,
             fractional bandwidth
 Class 6    Uni-directional

 Connectionless services
 Class 2    With acknowledgment
 Class 3    Without acknowledgment


 Node levels
 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





Arbitrated Loop
The arbitrated loop is widely used and can connect up to 127 nodes without using a switch. All devices share the bandwidth, and only two can communicate with each other at the same time, with each node repeating the data to its adjacent node. TX means transmit, and RX means receive.






Switch Fabric
A switch fabric is the most flexible topology, enabling all servers and storage devices to communicate with each other. It also provides for a failover architecture in the event a server or disk array ceases to operate.






Point-to-Point
This is the simplest topology connecting two Fibre Channel devices that communicate at full bandwidth.






Personal Use Only

Before/After Your Search Term
BeforeAfter
FC-P2PFCP
FC-SWFD
FCAPSFD/HD
FCCFD-LTE
FCC auctionFD:OCA
FCC ClassFDD
FCFSFDDI
fciFDISK
FCIFFDIV bug
FCIPFDM

Terms By Topic
Click any of the following categories for a list of fundamental terms.
Computer Words You Gotta KnowSystem design
Job categoriesUnix/Linux
Interesting stuffPersonal computers
InternetIndustrial Automation/Process Control
Communications & networkingAssociations/Standards organizations
HistoryDesktop publishing
Audio/VideoGraphics
MainframesSecurity
ProgrammingHealthcare IT
System design