Microcom Networking Protocol
Another de facto standard is the Microcom Networking Protocol (MNP) which was originally developed by Microcom, Inc.
Available in versions (called classes) 1-9, MNP is a high-performance, high-speed protocol that was available before the advent of the ITU-TSS standards. With MNP, errors in the transmitted data packets are detected by the remote modem causing it to request a retransmission of the data packet in error. The capability to recognize and quickly correct data errors makes MNP one of today's most common protocols.
The following table specifies MNP communication standards.
| Item | Description |
|---|---|
| MNP Class 1 | An asynchronous, half-duplex, byte-oriented method of transferring data realizing about 70% efficiency. This standard is uncommon in modern modems. |
| MNP Class 2 | A full-duplex counterpart to MNP Class 1 which is also uncommon in modern modems. |
| MNP Class 3 | A synchronous, bit-oriented full-duplex method of transferring data realizing about 108% efficiency. Efficiency greater than 100% is realized because the start/stop bits required for an asynchronous connection are eliminated. The DTE/DCE between the modem and the system are still asynchronous. |
| MNP Class 4 | An enhancement to MNP Class 3 including a mechanism for varying the packet size (adaptive packet assembly) and a means of eliminating redundant administrative overhead (data phase optimization). An MNP Class 4 modem offers approximately 120% efficiency. |
| MNP Class 5 | Includes data compression along with Class 4 features. An MNP Class 5 modem offers 200% efficiency. |
| MNP Class 6 | Allows incorporation of multiple, incompatible modulation techniques into one modem (universal link negotiation). This allows MNP Class 6 modems to begin communication at a slower speed and negotiate a transition to a higher speed. Class 6 also includes a statistical duplexing scheme which dynamically allocates utilization of half-duplex modulation to simulate full-duplex service. All features of MNP Class 5 are supported. |
| MNP Class 7 | Incorporates enhanced data compression. Combined with Class 4, efficiencies of 300% can be realized. |
| MNP Class 8 | Not Applicable. |
| MNP Class 9 | Combine enhanced data compression with V.32 technology to allow data rates up to 28,800 bps. |