This International Standard specifies the frame structure for data communication systems using bit-oriented high-level data link con-trol (HDLC) procedures. It defines the relative positions of the various components of the basic frame and the bit combination for the frame delimiting sequence (flag). The mechanism used to achieve bit pattern independence within the frame is also defined. In ad-dition, two frame checking sequences (FCS) are specified; the rules for address field extension are defined; and the addressing con-ventions available are described.
Control field encodings and formats are defined in other International Standards.