IBM 19K5716 manual Remote access service RAS

The modem "ISDN SoftCompression X.75/V.42bis":

Using data compression according to V.42bis for X.75 connections

Using the virtual modem ISDN SoftCompression X.75/V.42bis connections can be established with activated data compression. This allows data to be transmitted at a rate up to four times higher, depending on the type of data to be transmitted.

Some basic conditions must be met, however:

•The latest CAPI 2.0 device drivers are required:

The CAPI 2.0 device drivers for your ISDN-Controller must support V.42bis. If this is not the case, the virtual modem ISDN SoftCompression X75/V42bis is not available for selection in the installation window.

•Only for X.75 connections:

Data compression according to V.42bis can be used only for X.75 connections. Possible applications include ISDN Point-to-Point connections and connections to ISDN BBSs. According to CAPI 2.0, a secured data link is imperative for V.42bis connections. As only the X.75 protocol guarantees this feature, V.42bis can be used only with this protocol. For connections to ISPs, HDLC is (nearly always) used as an ISDN B2 protocol. For this reason, a connection with data compression is not possible on ISDN protocol level.

•Automatic negotiation

When a connection to an X.75 remote site is established, the system automatically tries to negotiate V.42bis. If this does not succeed, e.g. because the remote site does not support V.42bis, a connection without data compression is made automatically.

Keep in mind that the V.42bis data compression algorithm of passive ISDN- Controllers is processed on the host's CPU and thus demands more powerful hardware. In the case of active controllers of the B1 family, the algorithm is processed completely on the Controller.

Note: With the command ATS42=8, V.42bis can be activated manually for X.75 connections as well.

Remote access service (RAS)

The ISDN CAPI Port Device Driver can be used for RAS connections to Windows 95/98/NT and Windows 2000 computers. The virtual modem ISDN RAS (PPP over ISDN) is provided for this purpose.

In Windows 95/98 Dial-Up Networking requires an additional server module to serve as a remote site. Windows NT computers can use the "NDIS WAN CAPI Device Driver for Windows NT" or the ISDN CAPI Port Device Driver for Windows NT to make WAN connections over ISDN.

Windows 2000 users can use the ISDN CAPI Port Device Driver or the NDIS WAN CAPI Device Driver installed with the CAPI 2.0 device drivers

13. ISDN CAPI Port Device Driver 201