186 IBM ISDN PC Card:User’s Guide
• 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. As HDLC is nearly
always used as an ISDN B2 protocol in connections to Internet providers, it is
not possible to establish connections with data compression 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.
• Cannot yet be applied to connections to AOL or CompuServe:
The PoPs (points of presence) of AOL and CompuServe do support the X.75
protocol, but, at the time this document was printed, did not yet allow the use
of V.42bis. Should problems arise in dialing up these services, select the
virtual modem AVM ISDN Mailbox (X.75) rather than the modem ISDN
SoftCompression X.75/V.42bis.
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 and Windows NT 3.51/4.0 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 3.51/4.0 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.
Connections and caller authentication are managed by the PPP protocol (PPP over
ISDN, RFC 1618) for both operating systems. HDLC is the specified ISDN B2
protocol. The remote computer is then accessible over ISDN using network
protocols such as TCP/IP, SPX/IPX or NetBEUI.
Remote access service (RAS) with Windows 95/98
See the Windows 95/98 documentation for instructions about how to configure
Remote Access Service (RAS). Should any problems with RAS arise, contact your
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