A Fibre Channel switch is logically positioned in the center of a SAN and is connected to hosts, storage, or other switches. The fabric infrastructure can be viewed as the foundation upon which the rest of the SAN is built. When a frame arrives from a device, a switch accepts and then routes that frame to the proper destination device. In fact, using the Brocade cut-through routing approach, a frame can begin to be forwarded even before it has been completely received. A fabric switch also contains a great deal of intelligence, providing services for locating other nodes in a network (the Simple Name Server [SNS]), automatically establishing routes between other switches in the fabric, compartmentalizing devices into zones (zoning), as well as monitoring and handling errors (basic Brocade Fabric OS functions and Fabric Watch). We discuss fabric services further in Chapter 2, Fibre Channel Basics.

Brocade switches also provide functionality that allows private loop devices to participate in a fabric and translate the communication between fabric devices and older private devices. In fact, the translative mode of operation for a port on a Brocade switch will automatically allow any private target node (such as a private loop JBOD) to function fully as part of a fabric. This feature is a core piece of the Fabric OS and does not require a license. Making this work for a private HBA, on the other hand, requires QuickLoop and/or Fabric Assist options.