If you have an unsupported modem or want to customize the Modem.inf file and want to use compression, and you are using RAS versions later than 1.x on the RAS server and client, it is recommended that you turn on V.42 bis modem compression and RAS software data compression. If you want to use RAS data compression, leave the most efficient error control protocol that is available on your modem turned on. For additional information, see the RAS Help topic "Modifying Modem.inf."
To use modem compression with an unsupported modem on the RAS 1.1a client (that does not have the RAS data compression feature), append a custom modem section to the MODEMS.INF file and create an initialization string that enables hardware flow control, V.42 bis compression, and V.42 error control, if available. Be sure to check that your modem is not already supported in the RAS 1.1a MCOMP.INF file that ships with RAS 1.1a. To create your custom modem section, model your section after an existing section in MCOMP.INF.