capron@chiron.UUCP (Michael P. Capron) (05/19/89)
I had heard a rumor that Xmodem breaks down at high baud rates (>2400), something about the checksum algorithm. Does anyone know if there is any truth to this? Thanks in advance, Mike Capron ...uunet!chiron!capron
stripes@wam.UMD.EDU (05/21/89)
In article <187@chiron.UUCP> capron@chiron.UUCP (Michael P. Capron) writes: > >I had heard a rumor that Xmodem breaks down at high baud rates (>2400), >something about the checksum algorithm. Does anyone know if there is any truth >to this? The checksum does not cause it to breakdown at high speeds, but is not as good at finding errors as a CRC (a 16-bit CRC is supported by most XMODEM programs). It is not a good protocall for higher speeds, because the RTD becomes more and more important (or over LONG distantances, or through packet switched/mutiple networks, etc.). Ymodem (basicly 1K blocked XMODEM) is better at this, but still suffers with high RTD (Round Trip Delay). ZMODEM does not suffer from this (except durring error recovery, I think, and at inital handshakeing time), it also has a bunch of other goodie, but is a bit harder to implment. Sorces for a PD implimation of Xmodem, Ymodem, and Zmodem are all available *somewhere*, mabie SIMTEL20. -- stripes@wam.umd.edu Josh_Osborne@Real_World,The "The dyslexic porgramer" "Bones, help this man, He's hurt!" <-> <-> "Dammit, Jim, I'm a DOCTOR, not a.... Oh, yeah."
pozar@hoptoad.uucp (Tim Pozar) (05/22/89)
In article <187@chiron.UUCP> capron@chiron.UUCP (Michael P. Capron) writes: >I had heard a rumor that Xmodem breaks down at high baud rates (>2400), >something about the checksum algorithm. Does anyone know if there is any truth >to this? > No truth, but turn-around gets a bit ridiculous at speeds at or greater than 9600 with current high-speed modems. Tim -- ...sun!hoptoad!\ Tim Pozar >fidogate!pozar Fido: 1:125/406 ...lll-winken!/ PaBell: (415) 788-3904 USNail: KKSF / 77 Maiden Lane / San Francisco CA 94108