This American National Standard for FC-AL specifies signaling interface enhancements for ANSI X3, FC-PH-xto allow L-Ports to operate with an Arbitrated Loop topology. This standard defines L-Ports that retain thefunctionality of Ports as specified in ANSI X3, FC-PH-x. The Arbitrated Loop topology attaches multiplecommunicating points in a Loop without requiring switches.The Arbitrated Loop topology is a distributed topology where each L-Port includes the minimum necessaryfunction to establish a Loop circuit. A single FL-Port connected to an Arbitrated Loop allows multiple NL-Portsto attach to a Fabric.When an L-Port is operating on a Loop with at least one other L-Port, the L-Port uses the protocol extensionsto ANSI X3, FC-PH-x that are specified in this standard.When an L-Port is connected with an N-Port or an F-Port, the L-Port communicates using the protocoldefined in ANSI X3, FC-PH-x.?Each L-Port may use a self-discovering procedure to find the correct operating mode without the need forexternal controls.