SDLC
An IBM standard SNA Layer 2 bit-oriented transmissions protocol. The SDLC data unit, called a frame, has both a header and trailer for data flow control and error correction. Defined to used half-duplex channels, it supports only synchronous polled transmission modes over point-to-point or multipoint lines. A methodology to manage the design and development of a computerized information system.
More: Synchronous Data Link Control System Development Life Cycle