V.42bis Data compression, using "variable-length to fixed-length" block coding (codeword size constant)

MNP-10 Error correcting scheme for cellular transmission.

MNP-3/-4 A subset of the first error correction standards, developed by Microcom Inc. Proprietary error correction standard of Microcom

MNP4 Proprietary error correction standard of Microcom

MNP5 Proprietary data compression standard of Microcom. Using "run length encoding" and "adaptive frequency encoding" (codeword size varies) ARQ and MNP

MNP Level 1:asynchronous protocol, half duplex

MNP Level 2:asynchronous protocol, full duplex. Data divided into blocks. Actual data transmission speed somewhat lower than normal.

MNP Level 3:synchronous protocol, full duplex. Data in blocks. 10% higher speed with error-free transmissions.

MNP Level 4:data in blocks, block size according to line quality. Smaller blocks than Level 3 which results in a 20% faster transmission rate, when free from interference.

MNP Level 5:as in Level 4, but with data compression which results in up to double the speed.