The ANSI-approved Serial Attached SCSI (SAS) standard divides the SAS architecture into six layers and defines the function of each layer. From lowest to highest in the SAS architecture, these layers are: the physical layer, the phy layer, the link layer, the port layer, the transport layer, and the application layer. This is Part 2 of a 5-part white paper series that describes in detail each of the layers in the SAS architecture as defined in the SAS standard. This white paper discusses the SAS link layer, which is the third-lowest layer of the SAS architecture.