2.3.4.2. Serial-line communication
There are two protocols for serial-line communication: Serial Line IP
(SLIP) and Point-to-Point Protocol (PPP). These protocols let computers
transfer information using the serial port instead of a network card
and a serial cable in place of an Ethernet cable.
Under Linux, the SLIP driver is installed in the kernel. To
convert a serial line to SLIP mode, use the slattach program (details on slattach are available in Chapter 3, "Linux Commands"). Don't forget that after putting the line
in SLIP mode, you still have to run ifconfig to configure the network
interface. For example, if your machine is named tanuki and you have dialed in to ruby:
# ifconfig s10 tanuki pointopoint ruby
# route add ruby
# route add default gw ruby
This configures the interface as a point-to-point link to
ruby, adds the route to ruby, and makes it a default route, specifying
ruby as the gateway.
PPP was intended to remedy some of SLIP's failings; it can hold
packets from non-Internet protocols, it implements client
authorization and error detection/correction, and it dynamically
configures each network protocol that passes through it. Under Linux,
PPP exists as a driver in the kernel and as the daemon pppd. For more information on pppd, see Chapter 3, "Linux Commands".