Definition: MNP

(Microcom Networking Protocol) A family of communications protocols from Microcom, Inc., Norwood, MA, that have become de facto standards for error correction (classes 2 through 4) and data compression (class 5). In 1997, Compaq acquired Microcom.

Class 1
Half-duplex asynchronous transmission (earlier mode no longer used).

Class 2
Full-duplex asynchronous transmission.

Class 3
Full-duplex synchronous transmission using HDLC framing techniques and 64-byte blocks. Start/stop bits are stripped.

Class 4
Increased throughput. Shorter headers, frames up to 256 bytes. Some vendors adjust frame size based on line quality.

Class 5
Compresses data up to two times.

Class 6
Starts at V.22bis modulation and switches to V.29 if possible. Uses pseudo-duplexing ping-pong method for faster turnaround of V.29 transmission.

Class 7
Compresses data up to three times.

Class 8
Not in use.

Class 9 - Piggy-back Acknowledgment**
Includes selective retransmission for more efficient data transport. Better performance over a variety of links.

Class 10 - Adverse Channel Enhancements**
Better transmission on rural, cellular and noisy lines.

Class 9 and 10
** = Proprietary Microcom techniques