SL(4)							   BSD Kernel Interfaces Manual 						     SL(4)

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)

     J. Romkey, A Nonstandard for Transmission of IP Datagrams over Serial Lines: SLIP, RFC, 1055, June 1988.

     Van Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, RFC, 1144, February 1990.

HISTORY

     The sl device appeared in NetBSD 1.0.

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     superseded by the Point-to-Point Protocol (PPP), which does all of those things, and much more.

BSD
								   July 9, 2006 							       BSD