, , . , , Xmodem
Kermit (. .3-9), . 9600 / , (), (), .
:
ARQ (Automatic ReQuest for repeat) - ;
MNP (Microcom Networking Protocol) - , , Microcom;
ITU-T V.42 - V.42, .
ARQ , . - , .
MNP , 9 : (Async/Sync); - (HDX, FDX); ; .
. V.42 , , , Hayes V, , MNP 1-4.
. :
MNP Class 5/6 ADC (Adaptive Data Compression) - 63% ( 2400-9600 / 4800-19200 /).
MNP Class 7/9 EDC (Enhanced Data Compression) - 63% ( 2400-9600 / 7200-28800 /).
ITU-T V.42bis - V.42bis - , BTLZ (British Telecom Lempel-Ziv), , Hayes (V) MNP . 5.
ITU-T V.44 - V.44 - V DCE, , V.42bis, , .
V V.42bis, V.44, . V.44 , LAPM (. ) 32- ( 16-) CRC (PCS).
LAPM
: MNP-2/3/4 ( Microcom) ITU-T V.42. V.42 : - MN1M, , . V.42, , , , MNP-4.
. V.42 LAPM - HDLC. LAPM (Link Access Procedure for Modems - ) ARQ . :
- CRC ( FCS .. (CRC-16) - CRC-32);
- ARQ;
- ( ) - ;
- "handshaking'a" - , DTE;
- ( ) DCE , . V. 14.
LAPM , HDLC (. .3-6).