An IBM interface specification for a serial transport protocol based on a ring topology and operating in full duplex (FDX) at a maximum of 20 MBps per channel, with as many as two channels per cable. SSA maps into the pre-existing Small Computer System Interface (SCSI) and SSA devices are SCSI devices.The Transport Layer protocol is non-return-to-zero (NRZ) and utilizes 8B/10B encoding. See also 8B/10B, FDX, NRZ, protocol, ring topology, SCSI, serial, and Transport Layer.