PPP(7) PPP(7)
NAME
PPP - Point-to-Point Protocol (PPP)
SYNOPSIS
ppp
DESCRIPTION
The Point-to-Point protocol (PPP) is a method for transmitting
datagrams over point-to-point serial links. This
implementation of PPP is compliant with RFC 1331, RFC 1332,
and the Internet Draft ``The PPP Authentication Protocols''
with the following exceptions: the 32-Bit FCS (Frame Check
Sum) feature of RFC 1331 is not implemented; Link Quality
Control Protocol negotiation described in RFC 1331 is always
rejected; and the Challenge-Handshake Authentication Protocol
defined in the Internet Draft is not implemented. PPP is not
IP-specific like SLIP, but the current implementation only
supports transmission of IP datagrams over serial links.
The Point-to-Point protocol is implemented as a multiplexing
STREAMS driver (PPPSM) that is linked beneath IP when
internetworking is started. The PPPSM manages the routing of
IP datagrams between the interfaces presented to IP and the
physical links to remote hosts (PPC). It also performs PPP-
specific operations concerned with negotiating PPP operating
parameters when PPCs are established and tearing down PPCs
when they are no longer needed.
The interfaces presented to IP are specified in
/etc/confnet.d/inet/interface and are created and marked up
when slink(1M) is started. The PPC links are NOT established
to remote hosts until a pending datagram intended for a known
remote host is detected by the PPPSM. The interfaces
presented to IP are marked as point-to-point interfaces and as
such have a known destination IP address. There may be a
number of different physical links available that can be used
to reach the destination host. The PPC links are described in
the PPP and UUCP configuration files.
When a PPP data request (IP datagram) is detected, the PPSM
will notify the pppd [see pppd(1M)], that a pending datagram
exists for a specific destination IP address. pppd will then
check its configuration files for information on how to reach
the remote host. Using that information, pppd performs a
uucp(1C)-style login to the remote host and negotiates the
line characteristics at both the local and remote hosts. Once
Copyright 1994 Novell, Inc. Page 1
PPP(7) PPP(7)
the negotiation has finished and the PPC is established, the
tty representing the link is linked beneath the PPPSM and the
PPPSM is given information about the link. The PPPSM now uses
the link for its IP datagram traffic. The PPC will continue
to exist under the PPPSM until a pre-set countdown timer
measuring continuous link inactivity has expired, or the link
is broken by administrator command, i.e. using ifconfig(1M) to
mark the interface down.
During negotiation of a PPC, either side may require password
authentication to ensure authorization for a PPP connection.
The daemon pppd verifies authorization by consulting the
/etc/inet/pppauth file [see pppauth(4)].
PPP provides a command, pppstat [see pppstat(1M)], for
retrieving and displaying PPP interface statistics.
REFERENCES
ASYHDLC(7), hosts(4), ifconfig(1M), ppp(1M), pppauth(4),
pppd(1M), ppphosts(4), pppstat(1M), slink(1M), strcf(4)
RFC 1331, RFC 1332
Internet Draft ``The PPP Authentication Protocols'' by B.
Lloyd and W. Simpson
Copyright 1994 Novell, Inc. Page 2