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Fibre Channel, a family of ANSI standards, is a common,
efficient transportsystem supporting multiple protocols.
ANSI -- American National Standards InstituteFibre Channel is
structured with independent layers.
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FC0 Physical interface, transmission, signaling,
cables/connectors
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OFC (Open Fiber Control) vs Non-OFC
What is OFC?
OFC is a start-up protocol implemented through handshaking
hardware toallow the use of non-eye safe optical power levels
between duplex links. FibreChannel short-wave and long-wave
originally implemented with OFC, to allow
use of non-eye safe signal levels. Non-OFC was technologically
challengingat the time because receivers required higher signal
levels.
What is non-OFC?Advances in receiver sensitivity and safety
lasers allowed the laser power
levels to decrease. The non-OFC design features signal integrity
at eye-safe power levels. The simplicity, cost and reliability of
non-OFC
implementation exceeds its OFC alternative. Non-OFC-state
machines are
less expensive, simpler and more reliable because there is no
10-second timedelay handshake per node and there are no additional
hard/lower power
lasers.
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FC1- The data link layer, which implements the 8b/10b encoding
anddecoding of signals
Data is expanded using an algorithm that creates one of two
possible 10-bitoutput values for each input 8-bit value. Each 8-bit
input value can map eitherto a 10-bit output value with odd
disparity, or to one with even disparity. This
mapping is usually done at the time when parallel input data is
converted intoa serial output stream for transmission over a fibre
channel link. The odd/even
selection is done in such a way that a long-term zero disparity
between onesand zeroes is maintained. This is often called "DC
balancing".
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FC2 - The network layer, defined by the FC-PI-2 standard,
consists of thecore of Fibre Channel, and defines the main
protocols
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FC3 - The common services layer, a thin layer that could
eventuallyimplement functions like encryption or RAID
Name Server
Provides a directory of N_Ports within a FabricDatabase of ID,
World-wide Name, Supported FC-4's per N_PortN_Port may query the
Name Server to discover other N_Ports attached tothe Fabric
Alias Server
Multicast- Assigns alias IDs to multicast groups and hunt
groups
- Multicast frames are delivered to all N_Ports assigned to the
alias IDfor the multicast
Hunt Group- A hunt group is a set of associated N_Ports attached
to a single node
- Assigns alias ID that allow any frame containing the alias ID
to berouted to any available (non-busy) N_Port within a set
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FC4 - The Protocol Mapping layer. Layer in which other
protocols, such asSCSI, are encapsulated into an information unit
for delivery to FC2
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Fibre Channel had been defined by the T11 organization to
communicate in
different classes of service. These class of services each have
a variety ofdifferent properties, making each one unique.
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