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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 net-
     work interfaces using the SLIP protocol.

     To	use the	sl interface, the administrator	must first create the inter-
     face 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, automati-
		   cally 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 ad-
     dresses 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 su-
     perseded by the Point-to-Point Protocol (PPP), which does all of those
     things, and much more.

BSD				 July 9, 2006				   BSD

NAME | SYNOPSIS | DESCRIPTION | DIAGNOSTICS | SEE ALSO | HISTORY | BUGS

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