1.v.90, K56Flex, X2 data transmission. This is a few transport protocols related to 56K modeM. 2. Support V.42, MNP2-4 and MNP10 error correction protocols. V.42 is the error correction protocol launched by ITU-T. When communication is communicated, the information is transmitted in the form of a package (the package can be understood as a small information segment). The task of V.42 is when communicating two locations, if the package is sent due to some reason (such as telephone line interference), the clip can immediately ask the transfer party to reach the package, thus achieving zero error ideal state . MNP is a series of erroneous detection agreements that Microcon's presented in the event of errors when transmitting and can improve communication efficiency. Currently a total of 10 levels, the higher the level, the stronger, and is compatible, that is, the MNP10 includes all previous content. Among them, 1 to 4 levels have been made to the outside world for free from all manufacturers. Since its launch time is earlier than V.42, it is widely used. When the error correction cannot be completed using V.42, the MODEM will try to use MNP2 to 4 to perform error correction, and the main role of MNP10 is to be severely interfered in communication lines. Can still guarantee the quality of communication. 3.v.42bis and mnp5 data compression. V.42BIS is the compression protocol introduced by ITU-T (International Telecommunications Union), using the LZW algorithm to compress the data 4: 1, and further compress the file (such as .zip file) using overpassure When the compression ratio is less than 100%, the modem using V.42 BIS will automatically turn off its compression. The MNP5 adds the compression function on the basis of MNP4 error correction, and can use real-time adaptive way to calculate compressed data, optimize user data, and adjust the compressed parameters to achieve maximum data traffic. The compression ratio is up to 2: 1, but the compressed file cannot be further compressed. 4. DTE speed up to 115200 bps. Before talking about this problem, we will introduce another concept, the DCE (Data Communication Equipment Data Communication Equipment). It refers to the transmission speed between the two modems, the telephone line, and the 56K refers to this is this speed. The DTE (Data Terminal Equipment Data Terminal Death) refers to the transmission speed of the local computer to the MODEM. 4 = 115200bps, then transferred to the computer at this rate, which can be seen that the DTE speed of 56K cat (using V.42bis) should reach 115200 bps in an ideal state.
