Specifications

V.3229 / V.3229L <C#>-1
8
Protocols
Chapter 8
Protocols
CCITT V.42 bis
ERROR CONTROL
PROTOCOL
V.42 bis is an industry standard for error control
adopted by the Consultative Committee for Interna-
tional Telephone and Telegraph (CCITT). The
CCITT V.42 bis protocol incorporates two error con-
trol algorithms, LAPM and MNP. LAPM is a CCITT
Link Access Protocol family member related to
LAPB and LAPD currently in use in other commu-
nications applications. MNP is Microcom Network-
ing Protocol that has become an industry standard by
the number of its users.
The use of V.42 bis requires both local and remote
modems to be V.42 bis compatible. Error control
protocol is transparent to the user and requires no
special hardware or software. Data to be transmitted
is put in a buffer so the modem can retransmit it if an
error occurs. The modem also buffers data received
from the remote modem in case an error occurs and
the data is retransmitted. To avoid overfilling the
buffer, flow control is used to control data between
the modem and the terminal. V.42 bis protocol
options can be set by AT commands.
RELIABLE