LAPB

LAPB, or Link Access Procedure, Balanced, is a data link layer protocol used in telecommunications. It was developed by the International Organization for Standardization (ISO) and is defined in the ISO/IEC 4335 standard. LAPB is a bit-oriented synchronous protocol, meaning it operates over a synchronous serial link and uses bit patterns to delimit frames.

LAPB is designed to provide reliable, error-free communication between two stations. It uses a sliding window mechanism to control the flow of data, allowing multiple frames to be sent before an acknowledgment is required. This helps to improve efficiency and reduce the overhead associated with acknowledgments.

LAPB employs a combination of error detection and correction techniques to ensure data integrity. It uses a cyclic redundancy check (CRC) to detect errors in received frames. If an error is detected, the receiving station will discard the frame and request a retransmission. LAPB also supports selective reject, allowing the receiving station to request retransmission of only the frames that were received in error.

LAPB is commonly used in various telecommunications applications, including X.25 packet-switched networks and Integrated Services Digital Network (ISDN) services. It provides a reliable and efficient means of data transmission over synchronous serial links, making it a valuable protocol in the field of telecommunications.