Bisync

Bisync is a communication protocol used in computer networks to synchronize data between two devices. It was developed by IBM in the 1960s and is often used in mainframe environments. Bisync, also known as Binary Synchronous Communication, is a half-duplex protocol, meaning that data can be transmitted in only one direction at a time. This protocol uses a character-oriented framing technique, where each frame of data is enclosed between special control characters, known as SYN (synchronous idle) and ETX (end of text).

The Bisync protocol operates in three modes: character mode, block mode, and transparent mode. In character mode, data is transmitted one character at a time. In block mode, data is transmitted in blocks, which can improve efficiency. Transparent mode allows for the transmission of any type of data, including binary data, without the need for special encoding.

Bisync uses a simple error detection mechanism, known as longitudinal redundancy check (LRC), to ensure data integrity. The LRC is a single byte that is calculated based on the data in the frame and is appended to the end of the frame. The receiving device can then use this byte to verify the integrity of the data.

Bisync has been largely replaced by more modern protocols, such as TCP/IP, but it remains in use in certain legacy systems. Its simplicity and reliability made it a popular choice for early computer networks, and it continues to be studied and implemented in educational and research settings.