What is Zero Bit Insertion?
Zero bit insertion is a bit stuffing technique in which a zero bit is inserted after a series of one bits to highlight a sequence change or interruption. Zero-bit insertion is used with other bit-oriented protocols to prevent the accidental occurrence of six consecutive one-bits between the two frame flags that indicate the beginning and the end of a transmission frame.
Zero-bit transmission is widely used in IBM's high-level data link control (HDLC) - a data link format structure. The HDLC format requires that the beginning and end of a frame be marked. The zero bit insertion is generally used to distinguish between the flag pattern and data of the same format. The flag byte normally contains the bit sequence '01111110'.
To prevent the flag byte bit sequence from occurring within the transmission frame, the HDLC transmitter inserts a zero after five consecutive bits. The only disadvantage of the zero bit insertion technique is its irregular code or information rate.