.. _ppp:

Point-to-Point Protocol (PPP) Support
#####################################

.. contents::
    :local:
    :depth: 2

Overview
********

`Point-to-Point Protocol
<https://en.wikipedia.org/wiki/Point-to-Point_Protocol>`_ (PPP) is a data link
layer (layer 2) communications protocol used to establish a direct connection
between two nodes. PPP is used over many types of serial links since IP packets
cannot be transmitted over a modem line on their own, without some data link
protocol.

In Zephyr, each individual PPP link is modelled as a network interface. This
is similar to how Linux implements PPP.

PPP support must be enabled at compile time by setting option
:kconfig:option:`CONFIG_NET_PPP` and :kconfig:option:`CONFIG_NET_L2_PPP`.
The PPP support in Zephyr 2.0 is still experimental and the implementation
supports only these protocols:

* LCP (Link Control Protocol,
  `RFC1661 <https://tools.ietf.org/html/rfc1661>`__)
* HDLC (High-level data link control,
  `RFC1662 <https://tools.ietf.org/html/rfc1662>`__)
* IPCP (IP Control Protocol,
  `RFC1332 <https://tools.ietf.org/html/rfc1332>`__)
* IPV6CP (IPv6 Control Protocol,
  `RFC5072 <https://tools.ietf.org/html/rfc5072>`__)

See also the :zephyr_file:`samples/net/sockets/echo_server/overlay-ppp.conf`
file for configuration option examples.
For using PPP with GSM modem, see :ref:`gsm_modem` for additional information.

Testing
*******

See the `net-tools README`_ file for more details on how to test the Zephyr PPP
against pppd running in Linux.

.. _net-tools README:
   https://github.com/zephyrproject-rtos/net-tools/blob/master/README.md#ppp-connectivity
