.. _packetFormat:

NDNS Packet format
==================

NDNS Query
----------

Requests to the zone are made in the format of a standard NDN interest.

See `Interest section <http://named-data.net/doc/ndn-tlv/interest.html>`_ for details.


NDNS Response
-------------

NDNS Response is an ordinary `NDN-TLV Data packet <http://named-data.net/doc/ndn-tlv/data.html>`_
with specialized ``MetaInfo`` block:

::

    Data ::= DATA-TLV TLV-LENGTH
               Name
               MetaInfo (= NdnsMetaInfo)
               Content
               Signature

Every response from the NDNS system comes in the same generic form.
Specialization of different types of NDNS responses is accomplished through
``NDNS Type`` field of MetaInfo.

See :ref `NDNS Type section` <NDNS-Type> for details


NdnsMetaInfo
~~~~~~~~~~~~

``NdnsMetaInfo`` specified here represents portions that are specified in `MetaInfo
<http://named-data.net/doc/ndn-tlv/data.html#metainfo>`_ of any NDN-TLV Data packet with
NDNS specific additions.

::

    NdnsMetaInfo ::= META-INFO-TYPE TLV-LENGTH
                       ContentType (= 0)
                       FreshnessPeriod
                       NdnsType
                       AnswerCount


ContentType
+++++++++++

::

        ContentType ::= CONTENT-TYPE-TYPE TLV-LENGTH
                          nonNegativeInteger

For an NDNS packet the ``ContentType`` should always be ``BLOB`` (=0), specificity is accomplished
by NDNS-Type.

See :ref: `NDNS-Type` for details


FreshnessPeriod
+++++++++++++++

::

        FreshnessPeriod ::= FRESHNESS-PERIOD-TLV TLV-LENGTH
                              nonNegativeInteger


``FreshnessPeriod`` is required to be present in any NDNS response Data packets.  As in
any other Data packet, it specifies how long after the arrive of the data the recieving
node should wait before marking it stale.

See `NDN Packet Specification - Freshness Period <http://named-data.net/doc/ndn-tlv/data.html#freshnessperiod>`_


.. _NDNS-Type:

NDNS-Type
+++++++++

::

        NdnsType ::= NDNS-TYPE-TLV TLV-LENGTH
                       nonNegativeIntegear

There are 3 distinct types of NDNS Responses:

+-----------+------------------------------------------------------------------+
|    Type   | Description                                                      |
+===========+==================================================================+
| NDNS Data | indicates an answer was found, and that contains the requested   |
|           | content                                                          |
+-----------+------------------------------------------------------------------+
| NDNS NACK | indicates that the responding zone has no content matching the   |
|           | query.                                                           |
+-----------+------------------------------------------------------------------+
| NDNS AUTH | indicates that the zone has content, but a more specific         |
|           | question is need to determine the correct content to server.     |
+-----------+------------------------------------------------------------------+

.. _AnswerCount:

AnswerCount
+++++++++++

::

            AnswerCount ::= ANSWER-COUNT-TLV TLV-LENGTH
                    nonNegativeIntegear

This field is used to specify the number of answer in a response.


Content
~~~~~~~

::

            Content ::= CONTENT-TYPE TLV-LENGTH BYTE*