ppp(ADMP)                                                          ppp(ADMP)


 Name

    ppp - Point-to-Point Protocol (PPP)

 Syntax

    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 compli-
    ant with RFC 1331, RFC 1332, and the Internet Draft ``The PPP Authentica-
    tion 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 not accepted; 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/strcf and are creat-
    ed and marked up when slink(ADMN) 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 PPPSM will notify
    the Point-to-Point Connection Information Daemon (PPCID), pppd (see
    pppd(ADMN)), 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(C) style login to the remote host and negotiates the line charac-
    teristics at both the local and remote hosts.  Once 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 count-down timer
    measuring continuous link inactivity has expired, or the link is broken
    by administrator command, i.e. using ifconfig(ADMN) to mark the interface
    down.

    During negotiation of a PPC, either side may require password authentica-
    tion to ensure authorization for a PPP connection.  The daemon pppd veri-
    fies authorization by consulting the /etc/pppauth file (see
    pppauth(SFF)).

    PPP provides a command, pppstat (see pppstat(ADMN)), for retrieving and
    displaying PPP interface statistics.

 See also

    asyhdlc(ADMP), hosts(SFF), ifconfig(ADMN), ppp(ADMN), pppd(ADMN),
    ppphosts(SFF), pppauth(SFF), pppstat(ADMN), slink(ADMN) and strcf(SFF).

    RFC 1331, RFC 1332 and the Internet Draft ``The PPP Authentication Proto-
    cols'' by B. Lloyd and W. Simpson.