3 ms·

> It absolutely needed a clear line since it employed no error correction. YMODEM-G was fast because it didn't do any error detection of its own, so it didn't

> It absolutely needed a clear line since it employed no error correction. YMODEM-G was fast because it didn't do any error detection of its own, so it didn't have the overhead of checksums and such. The usage scenario was that the connection would already have error detection and recovery by virtue of the modem and the connection... protocol? I forget what we called them.

gruturo 4y ago
>error detection and recovery by virtue of the modem and the connection... protocol? I forget what we called them. Yeah protocols. First ones to see widespread use (at least subjectively) were MNP4 and MNP5 for, respectively, Error correction (with a 25% speed increase as a bonus, since it was synchronous and would not therefore waste code space with start and stop bits) and Data Compression (a terrible one which would actually incur an overhead if data was already compressed). They got later replaced by v.42 and v.42bis, with the same respective purposes (but v.42bis was smarter than MNP5 and could switch to transparent mode when sending incompressible data). CARRIER 14400 COMPRESSION: V.42 bis PROTOCOL: LAPM CONNECT 57600/ARQ