User`s manual

U.S. Robotics I-modem Command Reference
Handshaking, Error Control, Data Compression, and Throughput • Page 11-12
¥ A Link Access Procedures for Modems (LAPM) nego-ti-ation phase, during which the
devices identify their capabilities concerning maximum data block size and the number
of outstanding data blocks allowed before an acknowledgment is required.
MNP Error Control
The Microcom Networking Protocol (MNP) is supported by the ITU-T V.42 Recom-
menda-tion. It was originally developed by Microcom, Inc. and is now in the public
domain.
MNP is based on special protocol
frames. If the remote device doesn't recognize an MNP
Link Request, error control isn't possible. (In HST asymmetrical mode, U.S. Robotics
devices use a proprietary scheme similar to MNP.)
Error Control and Flow Control
Flow control of data from the computer is required under error control for two reasons:
¥ The transmitting device buffers a copy of each frame it transmits to the remote end until
it is acknowledged by the receiving device.
¥ If errors are encountered, retransmis-sion activity can cause a steady stream of data from
the computer to overßow the buffer.