Update docs structure according to new guidelines in https://wiki.opnfv.org/display/DOC

Change-Id: I1c8c20cf85aa46269c5bc369f17ab0020862ddc5
Signed-off-by: Gerald Kunzmann <kunzmann@docomolab-euro.com>

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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+====================================
+Port data plane status
+====================================
+
+https://bugs.launchpad.net/neutron/+bug/1598081
+
+Neutron does not detect data plane failures affecting its logical resources.
+This spec addresses that issue by means of allowing external tools to report to
+Neutron about faults in the data plane that are affecting the ports. A new REST
+API field is proposed to that end.
+
+
+Problem Description
+===================
+
+An initial description of the problem was introduced in bug #159801 [1_]. This
+spec focuses on capturing one (main) part of the problem there described, i.e.
+extending Neutron's REST API to cover the scenario of allowing external tools
+to report network failures to Neutron. Out of scope of this spec are works to
+enable port status changes to be received and managed by mechanism drivers.
+
+This spec also tries to address bug #1575146 [2_]. Specifically, and argued by
+the Neutron driver team in [3_]:
+
+ * Neutron should not shut down the port completly upon detection of physnet
+   failure; connectivity between instances on the same node may still be
+   reachable. Externals tools may or may not want to trigger a status change on
+   the port based on their own logic and orchestration.
+
+ * Port down is not detected when an uplink of a switch is down;
+
+ * The physnet bridge may have multiple physical interfaces plugged; shutting
+   down the logical port may not be needed in case network redundancy is in
+   place.
+
+
+Proposed Change
+===============
+
+A couple of possible approaches were proposed in [1_] (comment #3). This spec
+proposes tackling the problema via a new extension API to the port resource.
+The extension adds a new attribute 'dp-down' (data plane down) to represent the
+status of the data plane. The field should be read-only by tenants and
+read-write by admins.
+
+Neutron should send out an event to the message bus upon toggling the data
+plane status value. The event is relevant for e.g. auditing.
+
+
+Data Model Impact
+-----------------
+
+A new attribute as extension will be added to the 'ports' table.
+
++------------+-------+----------+---------+--------------------+--------------+
+|Attribute   |Type   |Access    |Default  |Validation/         |Description   |
+|Name        |       |          |Value    |Conversion          |              |
++============+=======+==========+=========+====================+==============+
+|dp_down     |boolean|RO, tenant|False    |True/False          |              |
+|            |       |RW, admin |         |                    |              |
++------------+-------+----------+---------+--------------------+--------------+
+
+
+REST API Impact
+---------------
+
+A new API extension to the ports resource is going to be introduced.
+
+.. code-block:: python
+
+  EXTENDED_ATTRIBUTES_2_0 = {
+      'ports': {
+          'dp_down': {'allow_post': False, 'allow_put': True,
+                      'default': False, 'convert_to': convert_to_boolean,
+                      'is_visible': True},
+      },
+  }
+
+
+Examples
+~~~~~~~~
+
+Updating port data plane status to down:
+
+.. code-block:: json
+
+   PUT /v2.0/ports/<port-uuid>
+   Accept: application/json
+   {
+       "port": {
+           "dp_down": true
+       }
+   }
+
+
+
+Command Line Client Impact
+--------------------------
+
+::
+
+  neutron port-update [--dp-down <True/False>] <port>
+  openstack port set [--dp-down <True/False>] <port>
+
+Argument --dp-down is optional. Defaults to False.
+
+
+Security Impact
+---------------
+
+None
+
+Notifications Impact
+--------------------
+
+A notification (event) upon toggling the data plane status (i.e. 'dp-down'
+attribute) value should be sent to the message bus. Such events do not happen
+with high frequency and thus no negative impact on the notification bus is
+expected.
+
+Performance Impact
+------------------
+
+None
+
+IPv6 Impact
+-----------
+
+None
+
+Other Deployer Impact
+---------------------
+
+None
+
+Developer Impact
+----------------
+
+None
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+ * cgoncalves
+
+Work Items
+----------
+
+ * New 'dp-down' attribute in 'ports' database table
+ * API extension to introduce new field to port
+ * Client changes to allow for data plane status (i.e. 'dp-down' attribute')
+   being set
+ * Policy (tenants read-only; admins read-write)
+
+
+Documentation Impact
+====================
+
+Documentation for both administrators and end users will have to be
+contemplated. Administrators will need to know how to set/unset the data plane
+status field.
+
+
+References
+==========
+
+.. [1] RFE: Port status update,
+   https://bugs.launchpad.net/neutron/+bug/1598081
+
+.. [2] RFE: ovs port status should the same as physnet
+   https://bugs.launchpad.net/neutron/+bug/1575146
+
+.. [3] Neutron Drivers meeting, July 21, 2016
+   http://eavesdrop.openstack.org/meetings/neutron_drivers/2016/neutron_drivers.2016-07-21-22.00.html