Microcom Networking Protocol D-3
Other Classes of MNP
Other Classes of MNP
There are several other classes of MNP. Table D-2 contains a description of each class.
Table D-2: Other MNP Classes
Class Name
Description
MNP Class 2
Uses standard asynchronous framing techniques for data
transmission and error correction. Due to this protocol
overhead, the actual throughput is less than the bps rate of
the modem.
MNP Class 3
Uses synchronous framing techniques. The modem
removes start and stop bits associated with each character
prior to transmitting by MNP. This results in a 20%
increase in performance over Class 2. Thus, the actual
throughput is greater than the modem’s bps rate.
Example:Microcom SX/2400 modems operating at Class 3
service transmits data at 2600 bps.
MNP Class 4
Uses synchronous framing techniques plus improvements
developed by Microcom: Adaptive Packet Assembly and
Optimized Data Phase. These enhancements result in better
performance for all types of connections.
Adaptive Packet Assembly automatically adjusts the size
of the data packets based on the quality of the telephone
line. When the line quality is good and there are few
retransmissions, the modem increases the packet size.
When the line quality is poor and retransmissions are
frequent, the size of the packet decreases in order to
maintain high throughput during error correction under
poor conditions.
Optimized Data Phase is the redesign of the MNP protocol
header that reduces the number of overhead bytes per data
packet.
Example:Modems operating at Class 4 service transmit data
at 2900 bps.
