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3.0 Modem Setup Options
3.3.1 V.42 E
RROR
C
ORRECTION
O
PTIONS
The Modem supports both CCITT V.42 error correction and Microcom
Networking Protocol
®
(MNP
®
) error correction (classes 1 through 5).
V.42 and MNP provide end-to-end error correction through an automatic
repeat-transmission request algorithm. Both types of error correction
enable the Modem to detect data transmission errors and automatically
request retransmission of adversely affected data until it is received correctly.
Either error-correction standard (V.42 or MNP) may be enabled for dial
or leased-line operation. However, error correction can function only if
all of the following conditions are present:
• The modem that the Modem is communicating with must be equipped
with the same type of error correction (V.42/V.42 bis or MNP).
• The same type of error correction (V.42/V.42 bis or MNP) must be
enabled at both ends of the communication link.
• Both communicating modems must be configured for asynchronous
data format.
• The connected systems must support data flow control (have buffering
capabilities).
The V.42 and MNP error-correction options (listed and described below)
are effective only when all of the conditions listed above are present.
Error correction options cannot be changed when the modem is on-line.
For valid test results, disable error correction before running diagnostic tests.
User-selectable options allow you to configure the Modem for V.42 (LAPM)
error correction only, MNP error correction only, or V.42 error correction
with MNP as the fallback error correction protocol. Data compression may
also be enabled by selecting either V.42 bis or MNP class 5 error correction.
Other error-correction options are also available.