| SL(4) | Device Drivers Manual | SL(4) | 
sl —
pseudo-device sl
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:
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.
sl device appeared in NetBSD
  1.0.
| January 18, 2020 | NetBSD 10.0 |