OFAgent: Factor out switch implementation dependent code to sub-drivers

Change-Id: Iba22bea41d289077caa0a2f23bb0428e47e95f5a

specs/kilo/ofagent-sub-driver.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+=======================================================================
+OFAgent: Factor out switch implementation dependent code to sub-drivers
+=======================================================================
+
+https://blueprints.launchpad.net/neutron/+spec/ofagent-sub-driver
+
+Problem Description
+===================
+
+while ofagent aims to support plain openflow switches,
+some necessary operations like tunnel port creation is not covered
+by standards (yet?) and thus will be switch implementation dependent
+for the foreseeable future.
+
+Proposed Change
+===============
+
+- factor out OVS-dependent code into a sub-driver.
+
+- introduce an option to specify a sub-driver.  its default will be OVS.
+
+- OVS will likely be the only driver introduced as a part of this BP.
+  see "Work Items" section.
+
+Alternatives
+------------
+
+none
+
+Data Model Impact
+-----------------
+
+none
+
+REST API Impact
+---------------
+
+none
+
+Security Impact
+---------------
+
+none
+
+Notifications Impact
+--------------------
+
+none
+
+Other End User Impact
+---------------------
+
+none
+
+Performance Impact
+------------------
+
+none
+
+IPv6 Impact
+-----------
+
+none
+
+Other Deployer Impact
+---------------------
+
+a deployer who wants to use non-OVS driver needs to specify it
+via the newly introduced option.  one who wants to use OVS can
+just leave it default.
+
+Developer Impact
+----------------
+
+none
+
+Community Impact
+----------------
+
+none
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  yamamoto
+
+Other contributors:
+  kakuma
+
+Work Items
+----------
+
+see "Proposed Change" section.
+
+some research about non-OVS switches is necessary:
+
+- LINC doesn't match to some of ofagent's assumptions.
+  e.g. how ports are named
+
+- lagopus doesn't seem to support dynamic add/remove of ports.  (yet?)
+
+- IVS might be a good candidate.  it already seems to have nova/neutron
+  interface drivers.
+
+Dependencies
+============
+
+none
+
+Testing
+=======
+
+Tempest Tests
+-------------
+
+none
+
+Functional Tests
+----------------
+
+none
+
+API Tests
+---------
+
+none
+
+Documentation Impact
+====================
+
+User Documentation
+------------------
+
+The new option to specify sub driver needs to be documented.
+
+Developer Documentation
+-----------------------
+
+none
+
+References
+==========
+
+none