mhw@fithp (Marc Weinstein) (05/15/91)
As a followup to my own article... In my last article, I stated that we had created a modem script which ran from inittab instead of calling uugetty directly. The script would apply HFC (and 19200, if needed) and would then exec uugetty. We have since found that this is NOT a good idea. For some reason unknown to us, if uugetty is not called directly from inittab, it can cause problems. For instance, after a failed outgoing call, the uugetty would not see the Carrier Detect go away, and wouldn't die and get restarted. So, HFC would never be reapplied. And, if the modem was confused, and the far end quit, the modem would stay connected for much longer because of something strange the hung uugetty would do to the port. We were even seeing the port/modem get hung for hours at a time - when the uugetty was killed manually, everything cleared up. Very strange. So, we modified our setup. We now are back to invoking uugetty directly from the inittab, and we changed the HFC program to a daemon. It runs out of inittab (as a respawn process, just to make sure) and reapplies HFC every ten seconds (or whatever you like). This makes it somewhat asynchronous with the uugetty restart, but it seems to work fine, albeit not in an ideal fashion. Things are working much better, and HFC (at least at 9600 baud) is working flawlessly. We're about to try 19200. Incidentally, for those of you with MNP modems, use MNP4 rather than MNP5 for sending compressed netnews batches. Apparently, the MNP5 compression is less efficient than the UNIX compress utility, so it ends up expanding the number of bytes in the file. Also, if it's possible to set the port speed to the modem higher than the DCE-to-DCE rate which the modem uses, you can get better than the expected rate. MNP apparently creates a "pseudo-synchronous" connection between the modems, and no start and stop bits are needed. This allows you to get 20% more throughput on the line (8 bits per byte rather than 10). But, you have to be able to supply the modem data at a faster rate. -- Marc Weinstein {simon,royko,tellab5}!linac!fithp!mhw Elmhurst, IL -or- {internet host}!linac.fnal.gov!fithp!mhw