NAME
sl
- Serial Line IP (SLIP) network interface
SYNOPSIS
pseudo-device sl
DESCRIPTION
The
sl
interface allows asynchronous serial lines to be used as
IPv4
network interfaces using the
SLIP
protocol.
To use the
sl
interface, the administrator must first create the interface and assign
a tty line to it.
The
sl
interface is created using the
ifconfig(8)
create
subcommand, and
slattach(8)
is used to assign a tty line to the interface.
Once the interface is attached, network source and destination addresses and
other parameters are configured via
ifconfig(8).
The
sl
interface can use Van Jacobson
TCP
header compression and
ICMP
filtering.
The following flags to
ifconfig(8)
control these properties of a SLIP link:
- link0
-
Turn on Van Jacobson header compression.
- -link0
-
Turn off header compression. (default)
- link1
-
Don't pass through ICMP packets.
- -link1
-
Do pass through ICMP packets. (default)
- link2
-
If a packet with a compressed header is received, automatically enable
compression of outgoing packets. (default)
- -link2
-
Don't auto-enable compression.
DIAGNOSTICS
- sl%d: af%d not supported
- .
The interface was handed
a message with addresses formatted in an unsuitable address
family; the packet was dropped.
SEE ALSO
inet(4),
intro(4),
ppp(4),
strip(4),
ifconfig(8),
slattach(8),
sliplogin(8),
slstats(8)
HISTORY
The
sl
device appeared in
NetBSD1.0.
BUGS
SLIP
can only transmit
IPv4
packets between preconfigured hosts on an asynchronous serial link.
It has no provision for address negotiation,
carriage of additional protocols (e.g.
XNS,
AppleTalk,
DECNET),
and is not designed for synchronous serial links.
This is why
SLIP
has been superseded by the Point-to-Point Protocol
(PPP),
which does all of those things, and much more.