ISO/IEC 14165-122 (2005-06)

Fibre Channel provides a general data transport vehicle for Upper Level Protocols (ULPs) such as Intelligent Peripheral Interface (IPI) and Small Computer System Interface (SCSI) command sets, the High-Performance Parallel Interface (HIPPI) data framing, IP (Internet Protocol), ANSI/IEEE 802.2, and others. This international standard, FC-AL-2, specifies an enhancement to the signaling protocol of the Fibre Channel Physical and Signalling Interface (FC-PH), ISO/IEC 14165-111, to support communication among two or more Ports without using the Fabric topology. It defines L_Ports that retain the functionality of Ports as specified in FC-PH. The Arbitrated Loop topology attaches multiple communicating points in a loop without requiring switches; it is a distributed topology where each L_Port includes the minimum necessary function to establish a Loop circuit. A single FL_Port connected to an Arbitrated Loop allows multiple NL_Ports to attach to a Fabric. Each L_Port may use a self-discovering procedure to find the correct operating mode without the need for external controls.