User's Guide for MS-DOS Clients

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Using Remote Access Service
Modems
Refer to your modem manual for the specific commands you use to do the
following:
• Recall factory settings.
• Track presence of data-carrier-detect (DCD high when carrier detected).
• Hang up and disable auto-answer when DTR goes from ON to OFF (high to low).
• Return result codes.
• Return verbose codes.
• Enable character echo in command state.
• Wait approximately 55 seconds for carrier.
• Make normal asynchronous connection (only needed if your modem supports
synchronous connections).
• Disable error control (disable MNP4, V42, or other error control scheme).
• Disable compression (disable MNP5, V.42bis, or other compression scheme).
• Disable +++ escape sequence.
• Disable software and hardware flow control.
• Modem Listen String (The specific command you use to make the modem answer
after one ring, needed for RAS servers and also for client workstations that will
be using callback.)
Error Control and Compression
RAS does not support error control and compression for the following
reasons:
• RAS for MS-DOS does not support Hardware Flow Control. Flow Control is
needed to regulate data transfer when compression is enabled.
• Not all processors can accommodate the 19200 or greater baud rate required to
make compression worthwhile at 9600 baud (see the table in the section, “Adding
a New Modem to MODEMS.INF,” earlier in this appendix). Note that the baud
rate specified in the MAXBAUD parameter of MODEMS.INF refers to the com-
puter-to-modem speed, not the modem-to-modem speed.
• Not all modems can accommodate the 19200 or greater baud rate required to en-
able compression. A 16450 or higher serial port chip is required.