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. In earlier versions of i4b, this was a separate component of the i4bisppp driver; beginning with i4b versions greater than 0.90, the sppp driver was integrated into the i4bisppp driver (for FreeBSD only).
• [i4bing]this is an interface to the FreeBSD Netgraph subsystem. This driver is optional.