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. IP, however, is used for in-band SNMP network management. Fibre Channel not only supports singlemode and multimode fiber connections, but coaxial cable and twisted pair as well.

Fibre Channel can be configured point-to-point, via a switched topology or in an arbitrated loop (FC-AL) with or without a hub, which can connect up to 127 nodes (see below). It supports transmission rates up to 2.12 Gbps in each direction, and 4.25 Gbps is expected. 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 of the architecture. See FCIP, 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.

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(storage, networking, communications)

Fibre Channel - An ANSI standard originally intended for high-speed SANs connecting servers, disc arrays, and backup devices, also later adapted to form the physical layer of Gigabit Ethernet. Development work on Fibre channel started in 1988 and it was approved by the ANSI standards committee in 1994, running at 100Mb/s. More recent innovations have seen the speed of Fibre Channel SANs increase to 10Gb/s. Several topologies are possible with Fibre Channel, the most popular being a number of devices attached to one (or two, for redundancy) central Fibre Channel switches, creating a reliable infrastructure that allows servers to share storage arrays or tape libraries. One common use of Fibre Channel SANs is for high availability databaseq clusters where two servers are connected to one highly reliable RAID array. Should one server fail, the other server can mount the array itself and continue operations with minimal downtime and loss of data. Other advanced features include the ability to have servers and hard drives seperated by hundreds of miles or to rapidly mirror data between servers and hard drives, perhaps in seperate geographic locations. Fibre Channel Industry Association (FCIA).