Serial Attached SCSI partially coincident with Serial ATA
Serial SCSI Protocol (SSP) –  for command-level communication with SCSI devices.
Serial ATA Tunneling Protocol (STP) –  for command-level communication with SATA devices.
Serial Management Protocol (SMP) –  for managing the SAS fabric.For the Link and PHY layers, SAS defines its own unique protocol.
At the physical layer, the SAS standard defines connectors and voltage levels. The physical characteristics of the SAS wiring and signaling are compatible with and have loosely tracked that of SATA up to the 6 Gbit/s rate, although SAS defines more rigorous physical signaling specifications as well as a wider allowable differential voltage swing intended to allow longer cabling. While SAS-1.0 and SAS-1.1 adopted the physical signaling characteristics of SATA at the 3 Gbit/s rate with 8b/10b encoding, SAS-2.0 development of a 6 Gbit/s physical rate led the development of an equivalent SATA speed. In 2013, 12 Gbit/s followed in the SAS-3 specification. SAS-4 is slated to introduce 22.5 Gbit/s signaling with a more efficient 128b/150b encoding scheme to realize a usable data rate of 2,400 MB/s while retaining compatibility with 6 and 12 Gbit/s.Additionally, SCSI Express takes advantage of the PCI Express infrastructure to directly connect SCSI devices over a more universal interface.
partially overlapping with partially intersecting with partially sharing with partially matching with partially aligning with