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180 IBM ISDN PC Card:User’s Guide
6. Confirm your entries by clicking OK and close the modem window.
Connections to internet service providers (ISPs)
There is no binding standard for ISDN dial-in access to the Internet via Internet
providers. PPP/SLIP protocol variants, fixed or dynamically assigned IP
addresses, static or dynamic DNS and a variety of authentication techniques
make it impossible to set a universally valid Internet access configuration for the
ISDN CAPI Port Device Driver.
For TCP/IP connections using the ISDN CAPI Port Device Driver, you must also
use 32-bit client software (i.e., WWW browsers, FTP clients, etc.) rather than 16-bit
applications for Windows 3.x. Otherwise, no connection to the 32-bit TCP/IP
protocol stack integrated in Windows 95/98 is possible.
ISDN B-channel protocols and PPP variants
Many providers use the ”HDLC” or ”X.75” protocol on the ISDN B channel. Two
protocol variants are used for PPP connections: "PPP over ISDN" in accordance
with RFC 1618 (also known as synchronous PPP), and "PPP modem style" in
accordance with RFC 1162 (also called asynchronous PPP).
Note: Please ask your Internet provider which combination of protocols and
authentication procedures are required for ISDN dial-in access.
Incorrect protocol settings either result in an immediate termination of the
connection or prevent the ISDN connection from being established in the first
place (error message: "The computer you are dialing in to is not answering.").
Setting modem registers for ISDN B-channel protocols and PPP: The virtual
modem ISDN Internet (PPP over ISDN) is set by default to ”HDLC” and ”PPP
over ISDN” according to RFC 1618. If a different configuration is requested by
your Internet provider, you can change the B-channel ISDN protocol by setting
the register "S31":
• S31=0X.75 protocol
• S31=1HDLC protocol (default)
• S31=2V.110 protocol
• S31=7V.120 protocol
The registers ”S41”, ”S42” and ”S43” can also be used to set the B1, B2 and B3
protocol layers individually. However, this is not necessary in most cases.
The PPP protocol variant used can be configured using register "S51":
• S51=0 asynchronous PPP ("modem style", RFC 1162)
• S51=1 synchronous PPP ("PPP over ISDN", RFC 1618)
ISDNmst.fm Page 180 Wednesday, January 15, 2003 9:22 AM