Defines the SCSI commands that are mandatory and optional for all SCSI devices. This standard also defines the SCSI commands that may apply to any device model. The set of SCSI standards specifies the interfaces, functions, and operations necessary to ensure interoperability between conforming SCSI implementations. This standard is a functional description. Conforming implementations may employ any design technique that does not violate interoperability.This Standard describes the physical interface portions of a high performance serial link that supports the higher Upper Level Protocols (ULPs) associated with HIPPI, IPI, SCSI, IP and others. This Standard incorporates features from the standards described in clause 2. Where needed, changes are or have been proposed to the appropriate ANSI NCITS technical committees to ensure this document remains a strict ANSI standard.