slip - Serial Line IP
The slip program implements an Internet network connection over a
bidirectional 8-bit transport, usually a serial line. The protocol used
for this connection is the Serial Line Internet Protocol, SLIP for short.
The pseudo-ip-device argument names one of the /dev/psip* devices that is
offered by the Minix TCP/IP driver inet(8). The slip program reads IP
packets from standard input and writes them to the pseudo IP device, and
reads packets from the pseudo IP device and writes them to standard
output. A typical use is like this:
stty raw 115200
slip /dev/psip2 &
} </dev/tty01 >/dev/tty01
The SLIP protocol is just a very simple packet framing protocol. It
defines two characters as markers on a byte stream to frame packets.
SLIP does not implement any higher level addressing, error detection, or
compression. Thanks to its simplicity it can be used under Minix, any
other system would prefer to use the Point-to-Point protocol: PPP.
The SLIP packet framing protocol as defined in RFC-1055 is as follows:
- Packets are delimited by an END character, octal 300. END is often
send at the start of a packet too to reset the logic of the
receiver, so that random noise isn't added to the beginning of a
- An ESC character (octal 333) is used to escape any END or ESC
characters that may occur in an IP packet. END and ESC are changed
to ESC 334 and ESC 335 in the data stream. (Note that END doesn't
occur within the data stream at all by escaping it this way, making
finding the framing END easier.)
/dev/psip* Pseudo-IP devices for use by slip.
Under Minix slip forks in two to handle the two data streams in or out of
the serial line. Under Minix-vmd it uses asynchronous I/O to handle the
two streams within one program.
Kees J. Bot <email@example.com>