This standard defines the physical layer of the Serial Storage Architecture (SSA). SSA defines a serial interface hierarchy to be used for purposes within its distance and performance characteristics, including but not limited to storage subsystems. This standard is intended to be used with an upper layer protocol and a transport layer.This standard defines the physical layer of the Serial Storage Architecture (SSA). SSA defines a serial interface hierarchy to be used for purposes within its distance and performance characteristics, including but not limited to storage subsystems.