ppp(ADMP)                       19 June 1992                       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.  The protocol and configuration infor-
    mation is described in RFC171 and RFC172.  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 con-
    cerned with negotiating PPP operating parameters when PPCs are esta-
    blished 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 PPSM 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 it's 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.


 See also

    asyhdlc(ADMP), hosts(SFF), ifconfig(ADMN), ppp(ADMN), pppd(ADMN),
    ppphosts(SFF), slink(ADMN), strcf(SFF),

    System Administrator's Guide, RFC 1171, RFC 1172