src@scuzzy.uucp (Heiko Blume) (07/15/90)
jc@minya.UUCP (John Chambers) writes: >Be careful here. Where I work, we've been running SLIP over some modems >that do MNP, and we use raw mode. The reason is that the MNP comes with >software flow control, which means that any packet with a ^S causes the >link to die. It usually doesn't take too long for such a packet to come >along. that's not correct. the modem to modem link should be settable to 100% transparent. mnp doesnt care about what data is sent over the line. (at least if your modems are worth anything at all). your problem is the flow control between the modems and the serial ports. you *should* use hardware flow control (cts/rts). to do that your serial drivers must be capable to do that. some unix implementations and especially many multiport cards don't support that. it might be possible that some SL/IP implementations support XON/XOFF flow control, but i wouldn't try that anyway. however if you really want to use XON/XOFF your SL/IP must support it. (see below too). >I spent of bunch of time on the phone with Customer Support people at >the manufacturer (Codex), trying to figure out how to correctly configure >the modems, and all I got from them was "Of course you want flow control; >you'll lose data without it." They couldn't conceive of an application >that didn't care about lost data. If there's a way to do MNP that lets >*all* 8-bit values pass, they wouldn't or couldn't tell me how to do it. i've never heard of codex, but anyway: i assume that these are fast modems that use MNP class 5 or higher to yield speeds of 4800 bps or higher. i'll go into some depths now as far as i know about my hardware. however i think that good modems should work like this. i use US Robotics Courier HST modems that implement MNP 5 to achieve 14000 bps. to implement flow control HSTs offer a *lot* of options: - transmit data flow control can be set to - flow control disabled - hardware (cts) flow control - software flow control (XON/XOFF) - hardware AND software flow control. - received data (modem/other_host to host) software flow control can be - disabled - XON/XOFF to modem AND remote host - XON/XOFF to local modem only - HP protocol (ACK/NAK) - received data hardware flow control can be - disabled - pass received data on rts high remember that these are the options for *each* host/modem pair. all these can be set in any combination to yield lots of funny results. especially the XON/XOFF to modem AND remote host is dangerous, not to speak of using hardware and software flow control simultaneously.... therefore i strongly recommend using rts/cts on both sides. otherwise you'll have to do some serious planning/configuring. have a look at your modems manual. if they don't support hardware flow control, i'd buy other modems. good luck! -- Heiko Blume c/o Diakite blume@scuzzy.mbx.sub.org FAX (+49 30) 882 50 65 Kottbusser Damm 28 blume@netmbx.UUCP VOICE (+49 30) 691 88 93 D-1000 Berlin 61 blume@netmbx.de TELEX 184174 intro d "Have you bugged your source today?"
goldfarb@eola.ucf.edu (Benjamin I. Goldfarb) (07/19/90)
src@scuzzy.uucp (Heiko Blume) writes: >i've never heard of codex, but anyway: i assume that these are fast modems ^^^^^ Codex modems are made by Motorola. -- ------------------------------------------------------------------------------ Ben Goldfarb uucp: {decvax,uflorida}!ucf-cs!goldfarb University of Central Florida Internet: goldfarb@eola.ucf.edu Department of Computer Science BITNET: goldfarb@ucf1vm.BITNET