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NAME

     i4bipr - isdn4bsd IP over ISDN B-channel network driver

SYNOPSIS

     device "i4bipr" [count]

DESCRIPTION

     The i4bipr driver interfaces the IP subsystem of the operating system
     with the isdn4bsd package so that transport of IP packets over an ISDN
     link is possible.

     The driver just packs IP packets without anything appended or prepended
     into raw HDLC packets on the B channel and transfers them to a remote
     site.  IP packets received from the remote site are queued into the local
     IP protocol stack.

     The format of the resulting packet on the B channel is:

           (HDLC opening flag) (IP-packet) (CRC) (HDLC closing flag)

     In the case where an IP packet for a remote site arrives in the driver
     and no connection has been established yet, the driver communicates with
     the isdnd(8) daemon to establish a connection.

     The driver has support for interfacing to the bpf(4) subsystem for using
     tcpdump(1) with the ipr interfaces.

     The driver optionally (when compiled with the IPR_VJ option) provides Van
     Jacobsen header compression, under control of the link0 and link1 options
     to ifconfig(8):

           link0            Apply VJ compression to outgoing packets on this
                            interface, and assume that incoming packets
                            require decompression.
           link1            Check incoming packets for Van Jacobsen
                            compression; if they appear to be compressed,
                            automatically set link0.

     The default values are on for link1 and off for link0.

SEE ALSO

     tcpdump(1), bpf(4), isdnd.rc(5), isdnd(8)

AUTHORS

     The i4bipr device driver and this manpage were written by Hellmuth
     Michaelis 〈hm@FreeBSD.org〉.