ZyXEL U-1496S Plus User Guide - Page 11

V.42bis AND V.42

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interfaces and finds most of its use in Europe and IBM mainframe or mini environments which use synchronous communication. ERROR CORRECTION In synchronous data communication, data is checked and corrected in the host by the so called "link layer protocol" to ensure data integrity. Normally, no data checking is provided in the host for asynchronous data communication. Nowadays, intelligent modems incorporate error correction protocols inside the modem for asynchronous data communication and it is transparent to the host. The modem packs the asynchronous data characters into blocks, the data blocks are error checked at the remote end and the erroneous block is retransmitted. The commonly used error correction protocols are MNP (R) and V.42 protocols. DATA COMPRESSION Intelligent modems use redundancy removing methods to reduce the number of data bits actually sent for asynchronous character transmission. The full character data is recovered at the other end, thus the total throughput of the modem data transmission is increased. The commonly used data compression protocols by modems are MNP (R) class 5 and V.42bis. Data compression works on redundancy removing and its efficiency is both algorithm and data dependent. MNP (R) PROTOCOLS MNP (R) (Microcom Network Protocol) is a set of protocols first introduced by Microcom, Inc., and later used by many modem manufacturers. It consists of many classes. Classes 1 to 4 are for error correction, and class 5 is for data compression. MNP class 1 and 2 are obsolete. Normally class 4 is used for error correction and it uses class 3 internally. MNP class 5 is a data compression protocol with a maximum efficiency of 2 to 1. MNP-5 is used with MNP-4 for error correction. V.42bis AND V.42 V.42bis and V.42 are data compression and error correction standards set by the CCITT. V.42bis has a better data compression efficiency than MNP-5 and is a more advanced data compression scheme.

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interfaces and finds most of its use in Europe and IBM mainframe
or mini environments which use synchronous communication.
ERROR CORRECTION
In synchronous data communication, data is checked and corrected
in the host by the so called "link layer protocol" to ensure data
integrity. Normally, no data checking is provided in the host for
asynchronous data communication.
Nowadays, intelligent modems incorporate error correction
protocols inside the modem for asynchronous data communication
and it is transparent to the host. The modem packs the
asynchronous data characters into blocks, the data blocks are
error checked at the remote end and the erroneous block is
retransmitted.
The commonly used error correction protocols are MNP (R) and V.42
protocols.
DATA COMPRESSION
Intelligent modems use redundancy removing methods to reduce the
number of data bits actually sent for asynchronous character
transmission. The full character data is recovered at the other
end, thus the total throughput of the modem data transmission is
increased.
The commonly used data compression protocols by modems are MNP
(R) class 5 and V.42bis.
Data compression works on redundancy removing and its efficiency
is both algorithm and data dependent.
MNP (R) PROTOCOLS
MNP (R) (Microcom Network Protocol) is a set of protocols first
introduced by Microcom, Inc., and later used by many modem
manufacturers. It consists of many classes. Classes 1 to 4 are
for error correction, and class 5 is for data compression. MNP
class 1 and 2 are obsolete.
Normally class 4 is used for error
correction and it uses class 3 internally.
MNP class 5 is a data compression protocol with a maximum
efficiency of 2 to 1. MNP-5 is used with MNP-4 for error
correction.
V.42bis AND V.42
V.42bis and V.42 are data compression and error correction
standards set by the CCITT. V.42bis has a better data compression
efficiency than MNP-5 and is a more advanced data compression
scheme.