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

Synopsis
--------

::

    ndn-autoconfig


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 <http://named-data.net/ndn-testbed/>`_.

Overview
^^^^^^^^

This procedure contains three 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 for a large enterprise network.

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

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: find home router
^^^^^^^^^^^^^^^^^^^^^^^^^

This stage assumes that user has configured default certificate using `<http://ndncert.named-data.net/>`_ as described in `Certification Architecture <http://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
^^^^^^^

* 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.