Abbreviated SDLC. The data-link protocol most widely used in networks that conform to IBM's SNA (Systems Network Architecture).
SDLC is a bit-oriented synchronous protocol that organizes information into well-defined units known as frames. SDLC is similar to the HDLC (High-level Data Link Control) protocol defined by the International Organization for Standardization (ISO).
See also data-link layer; High-level Data Link Control; Systems Network Architecture.