Technical data

ppp(7M) STREAMS Modules SunOS 5.5
NAME ppp, ppp_diag, ipd, ipdptp, ipdcm − STREAMS modules and drivers for the Point-to-
Point Protocol
AVAILABILITY SUNWpppk
DESCRIPTION ppp is a STREAMS module which implements the Point to Point Protocol (PPP). PPP is a
datalink protocol which provides a method for transmitting datagrams over serial point-
to-point links. PPP allows for various options to be negotiated between the two hosts of a
point-to-point link; theseoptions provide things such as peer authentication,header
compression, link quality monitoring, and mapping of control characters. The PPP
specifications are described in RFC 1331 The Point-to-Point Protocol (PPP) for the Transmis-
sion of Multi-protocol Datagrams over Point-to-Point Links and RFC 1332 The PPP Internet
Protocol Control Protocol (IPCP).
The pseudo device drivers /dev/ipd, /dev/ipdptp, and /dev/ipdcm form the IP-dialup
layer. This layer provides IP network interfaces for dialup (connect on demand) point-
to-point links. The ipd and ipdptp devices are the IP-dialup network interfaces. The ipd
device provides a point-to-multipoint interface, and theipdptp device provides a point-
to-point interface. The ipdcm device supplies an interface between the ipd or ipdptp
device and a link manager.
The ppp module and IP-dialup layer work together to provide IP connectivity over serial
point-to-point links. A "link manager" daemon is responsible for setting up and tearing
down these dialup connections. Connections are established when an IP packet needs to
be sent to the remote host, or the remote host has indicated its desire to establish a PPP
connection.
The ppp_diag module captures PPP layer packets and parses the contents for debugging
purposes. Usually, the parsed output is sent to the strlog facility from which it is
retrieved by the link manager. This module is pushed between the serial device and the
ppp module by the link manager when debuggingis enabled.
Operation When a packet is routed to an IP-dialup point-to-point interface which is not currently
connected to the remote host, the ipdcm driver sends a message to the link manager to
establish the connection. The link manager opens a communications channel and pushes
the ppp module onto the corresponding serial device. The ppp module negotiates with
the remote host on which options will be used for the link. When both hosts have agreed
on a set of options, the link manager links the ppp module and serial device underneath
the ipd or ipdptp interface which is providing the IP interface to the remote host.
Similarly, a remote host may initiate a connection on an enabled communications port.
In this case the linkmanager receives the request and pushes the ppp module onto the
corresponding device. Once the ppp module has successfully negotiated on the set of
options for the link with its peer, the link manager links the ppp module and serial device
underneath the ipd or ipdptp interface which is providing the IP-dialup interface.
7M-260 modified 18 Feb 1994