Fibre Channel's Five-Layered Structure

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FC-0 Physical Media

-- Optical cable with laser or LED transmitters for long-distance
   transmissions.
-- Copper coaxial cable for highest speeds over short distances using ECL. 
-- Twisted-pair cabling for 25-MBps data transfers to up to 50 meters.


FC-1 Byte Synchronization and Encoding
-- 8B/10B encoding/decoding scheme requires transmitting 25 percent
   more bytes total.
-- Developed by IBM, available to Fibre Channel developers at nominal cost.
-- 8B/10B code is extremely well balanced and simple to implement,
   and it provides useful error-detection capability.
-- A special code character maintains proper byte and word alignment.


FC-2 Actual Transport Mechanism
-- Framing protocol and flow control between nodes. four classes of
   ser
vice between ports:
    Class 1: Hard-wired or circuit-switched direct connection between devices.
    Class 2: Frame-switched through the fabric, with guaranteed delivery
    and receipt confirmation.
    Class 3: One-to-many, no confirmation of receipt.
    Class 4: This optional mode, Intermix, reserves the entire
    fabric bandwidth for a Class 1 connection but may also allow
    simultaneous connectionless traffic (i.e., a virtual switched,
    automatically routed connection) if bandwidth is available.
-- Frame controls ensure that Class 2 or Class 3 data arriving out
   of sequence is presented to the receiving port buffer in the
   appropriate order.


FC-3 Common Services Layer
-- Framing protocol and flow control between ports. Three services
   defined thus far, with more expected.
    Striping: Uses multiple N_ports in parallel to transmit a single
    information unit, achieving higher aggregate bandwidth. Most likely
    used for transferring large data sets in real time, a
s in video-imaging
    applications.
    Hunt Group: A set of N_ports attached to a single node. All set
    members are assigned an alias identifier that allows routing of data
    associated with a primary N-port to any port in the hunt group. Roughly
    equivalent to having a multiline telephone under a single business number.
    Broadcast, Multicast: Can send a single data transmission to all
    N_ports on a fabric (broadcast) or to a subset of the total
    (multicast). A single fabric may have up to 2 superscript 24 or just over
    16 million addresses.


FC-4 Upper Layer Protocols
-- Practically every significant channel, peripheral interface, and
   network protocol is already mapped to the Fibre Channel transport
   structure: 
    SCSI
    IPI (Intelligent Peripheral Interface)
    HIPPI (High Performance Parallel Interface)
    IP (Internet Protocol)
    AAL5 (ATM Adaptation Layer for computer data)
    FC-LE (Link Encapsulation)
    SBCCS (Single Byte Command Code Set M
apping)
    IEEE 802.2 (TCP/IP) data