.. _ndn-autoconfig:

ndn-autoconfig
==============

Usage
-----

::

    ndn-autoconfig [options]

Description
-----------

Client tool to run :ref:`NDN hub discovery procedure`.

Options
-------

``-d`` or ``--daemon``
  Run ndn-autoconfig in daemon mode, detecting network change events and re-running
  auto-discovery procedure.  In addition, the auto-discovery procedure is unconditionally
  re-run every hour.

  NOTE: if connection to NFD fails, the daemon will be terminated.

``-c [FILE]`` or ``--config=[FILE]``
  Use the specified configuration file. If `enabled = true` is not specified in the
  configuration file, no actions will be performed.

``--ndn-fch-url=[URL]``
  Use the specified URL to find the closest hub (NDN-FCH protocol).  If not specified,
  ``http://ndn-fch.named-data.net`` will be used.  Only ``http://`` URLs are supported.

``-h`` or ``--help``
  Print help message and exit.

``-V`` or ``--version``
  Show version information and exit.

.. _NDN hub discovery procedure:

NDN hub discovery procedure
---------------------------

When an end host starts up, or detects a change in its network environment, it MAY use
this procedure to discover a local or home NDN router, in order to gain connectivity to
`the NDN research testbed <https://named-data.net/ndn-testbed/>`_.

Overview
^^^^^^^^

This procedure contains four methods to discover a NDN router:

1.  Look for a local NDN router by multicast.
    This is useful in a home or small office network.

2.  Look for a local NDN router by DNS query with default suffix.
    This allows network administrator to configure a NDN router in a large enterprise network.

3.  Find closest hub by sending an HTTP request to NDN-FCH server.

4.  Connect to the home NDN router according to user certificate.
    This ensures connectivity from anywhere.

After connecting to an NDN router, two prefixes will be automatically registered:

- ``/ndn``
- ``/localhop/nfd`` --- this to inform RIB manager that there is connectivity to the hub

Stage 1: multicast discovery
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Request
+++++++

The end host sends an Interest over a multicast face.

Interest Name is ``/localhop/ndn-autoconf/hub``.

Response
++++++++

A producer app on the HUB answer this Interest with a Data packet that contains a
TLV-encoded `Uri` block.  The value of this block is the URI for the HUB, preferrably a
UDP tunnel.

Stage 2: DNS query with default suffix
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Request
+++++++

The end host sends a DNS query that is equivalent to this command::

    dig +search +short +cmd +tries=2 +ndots=10 _ndn._udp srv

Response
++++++++

The DNS server should answer with an SRV record that contains the hostname and UDP port
number of the NDN router.

Stage 3: HTTP Request to NDN-FCH server
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This stage uses a simple HTTP-based API.  For more information about NDN-FCH server, refer
to the `NDN-FCH README file <https://github.com/named-data/ndn-fch>`__.

Request
+++++++

HTTP/1.0 request for the NDN-FCH server URI (``http://ndn-fch.named-data.net`` by default)

Response
++++++++

The HTTP response is expected to be a hostname or an IP address of the closest hub,
inferred using IP-geo approximation service.


Stage 4: find home router
^^^^^^^^^^^^^^^^^^^^^^^^^

This stage assumes that user has configured default certificate using
`<https://ndncert.named-data.net/>`_ as described in `Certification Architecture
<https://redmine.named-data.net/attachments/download/23/CertificationArchitecture.pptx>`_.

Request
+++++++

The end host loads the default user identity (eg. ``/ndn/edu/ucla/cs/afanasev``), and
converts it to DNS format.

The end host sends a DNS query for an SRV record of name ``_ndn._udp.`` + user identity in
DNS format + ``_homehub._autoconf.named-data.net``. For example::

    _ndn._udp.afanasev.cs.ucla.edu.ndn._homehub._autoconf.named-data.net

Response
++++++++

The DNS server should answer with an SRV record that contains the hostname and UDP port
number of the home NDN router of this user's site.

Client procedure
----------------

Stage 1
^^^^^^^

Send a multicast discovery Interest.

If this Interest is answered, connect to the HUB and terminate auto-discovery.

Stage 2
^^^^^^^

Send a DNS query with default suffix.

If this query is answered, connect to the HUB and terminate auto-discovery.

Stage 3
^^^^^^^

Send HTTP request to NDN-FCH server.

If request succeeds, attempt to connect to the discovered HUB and terminate
auto-discovery.

Stage 4
^^^^^^^

* Load default user identity, and convert it to DNS format; if either fails, the
  auto-discovery fails.

* Send a DNS query to find home HUB.
  If this query is answered, connect to the home HUB and terminate auto-discovery.
  Otherwise, the auto-discovery fails.

Exit status
-----------

0: No error.

1: An unspecified error occurred.

2: Malformed command line, e.g., invalid, missing, or unknown argument.

4: Insufficient privileges.

See also
--------

:ref:`ndn-autoconfig-server`, :doc:`ndn-autoconfig.conf`