The Care and Feeding of ISDN4BSD
3.2.9 misc	3 The Components of	4 Prerequisites

3.3 The Kernel Components

• [i4bq921]this driver is responsible for handling the ISDN D-channel layer 2 protocol specified in ITU recommendation Q.921. This driver is mandatory.
• [i4bq931]this driver is responsible for handling the ISDN D-channel layer 3 protocol specified in ITU recommendation Q.931. This driver is mandatory.
• [i4b]this driver is the interface to the isdnd daemon which is used for call setup, hang up and control. This driver is mandatory.
• [i4btrc]this driver is the interface to the isdntrace program which is used to display and capture traces of the ISDN protocol activities. The argument 4 specifies a maximum of 4 cards can be handled by this kernel. This driver is currently mandatory.
• [i4bctl]this driver is the interface for the isdndebug program, which is used to control several aspects of kernel driver debugging. This driver is currently mandatory.
• [i4brbch]this is the raw B channel interface to userland programs. One of its uses is to interface the userland ppp(8) daemon to isdn4bsd.
• [i4btel]this is the telephony interface to userland programs. In case you want to configure and use the isdn4bsd answering machine, you need to add this driver to your configuration file.
• [i4bipr]this is an interface to the BSD networking subsystem used to handle the ``IP over raw HDLC frames'' protocol. It is responsible for handling the ipr network interfaces. This driver is optional.
• [i4bisppp]this is an interface to the BSD networking subsystem used to handle the ``synchronous PPP'' protocol. It is responsible for handling the isp network interfaces. This driver is optional.
• [sppp]this is the real synchronous PPP driver required for proper operation of the above mentioned i4bisppp driver. It handles the core PPP protocol. This driver is mandatory in case the i4bisppp driver was added to the kernel configuration file.