Installing and Administering PPP

20 Chapter 1
Introduction
PPP and SLIP
PPP and SLIP
If you must link with a peer host that cannot use the point-to-point
protocol, you can use PPP’s SLIP option. SLIP, a non-standard but
popular protocol, is really only a framing convention for arranging IP
packets on a link. Many other PPP options are available when running
the SLIP option. Automatic dialing, idle line hangup, packet filtering, the
exec option, and most other management facilities can be invoked in
conjunction with SLIP.
However, SLIP provides few of the advanced facilities available with the
PPP protocol. pppd invoked with the SLIP option cannot provide the
following functions:
• Negotiations using link control protocol (LCP) and internet protocol
control protocol (IPCP).
• Authentication using password authentication protocol (PAP) and
challenge handshake authentication protocol (CHAP).
• Link quality monitoring (LQM).
• Asynchronous control character mapping or the escape option.
There are also the following connection restrictions when running PPP
with the SLIP option:
• Links must be asynchronous.
• Connections must be completely transparent to all 8-bit character
values.
• Flow control selection must be hardware only or no flow control at all.
• Link must not interpret passing data as flow control.
NOTE Earlier releases of HP-UX supported SLIP and other serial line IP
protocols with a facility called Point-to-Point Link (PPL), supplied with
the LAN/9000 product. PPL did not support point-to-point protocol
connections. If you are using SLIP to transfer data on serial IP lines, you
can migrate your SLIP connections to PPP connections. Migrating SLIP
to PPP connections is discussed in Chapter 3 of this manual.