Fibre Channel Data Constructs Ordered Sets and Primitives
To maintain synchronization, the FC-1 layer generates continuous transmissions over each link to minimize latency and reduce the rate of errors on the link. These continuous transmissions consist of fill words:
• The IDLE signal assists with clock synchronization and retiming. At least six idles are transmitted between frames, and additional idles may be added between frames to assist in synchronization and retiming. Idles are sent continuously when no frames are being transmitted to maintain synchronization.
• The ARB (Arbitrate) signal is used only on arbitrated loops. ARB is part of the mechanism that loop ports use to decide which port has control over the loop at any particular time.