--- /dev/null
+.. contents:: Table of Contents
+ :depth: 3
+
+======================================
+Group Command OFPGC_ADD_OR_MOD support
+======================================
+
+`Group ADD-MOD Reviews <https://git.opendaylight.org/gerrit/#/q/topic:group-add-mod>`__
+
+This spec addresses following enhancement in Openflowplugin module:
+
+Addition of new command OFPGC_ADD_OR_MOD for OFPT_GROUP_MOD message that adds a new group that
+does not exist (like ADD) or modifies an existing groups (like MODIFY).
+
+OFPGC_ADD_OR_MOD group command will be supported only for OVS2.6 and above.
+
+Problem description
+===================
+In OpenFlow 1.x the Group Mod commands OFPGC_ADD and OFPGC_MODIFY have strict semantics:
+ADD fails if the group exists, while MODIFY fails if the group does not exist. This requires
+a controller to exactly know the state of the switch when programming a group in order not run
+the risk of getting an OFP Error message in response. This is hard to achieve and maintain at
+all times in view of possible switch and controller restarts or other connection losses between
+switch and controller.
+
+Due to the un-acknowledged nature of the Group Mod message programming groups safely and
+efficiently at the same time is virtually impossible as the controller has to either query
+the existence of the group prior to each Group Mod message or to insert a Barrier Request/Reply
+after every group to be sure that no Error can be received at a later stage and require a
+complicated roll-back of any dependent actions taken between the failed Group Mod and the Error.
+
+Reconciliation
+--------------
+
+The current implementation of reconciliation is to read the complete set of groups from config inventory
+and start pushing the groups one by one. This will always end up in GROUP_ALREADY_EXITS error as the
+reconciliation will always send GROUP ADD.
+
+This can be avoided by reading the groups from switch and compare with the list from inventory config
+and push only the delta. This is an overhead comparision and can be simply avoided by updating the
+group command as OFPGC_ADD_OR_MOD.
+
+Use Cases
+---------
+
+a. Normal group provisioning via FRM: ADD/UPDATE group should send new command OFPGC_ADD_OR_MOD.
+
+b. Reconciliation of groups should send OFPGC_ADD_OR_MOD. Current implementation of openflowplugin will
+ always send group add OFPGC_ADD irrespective of the state of the switch.
+
+Proposed change
+---------------
+The implementation of OFPGC_ADD_OR_MOD command is specific to OVS2.6 and above and the same can be extended
+to other openflow switch based on the group command support by them.
+
+New configuration parameter will be introduced in openflowplugin.cfg file, which can be modified by users
+to enable the GROUP ADD MOD support.
+
+.. code-block:: none
+ :caption: openflowplugin.cfg
+
+ # GROUP ADD MOD Support for OVS2.6 and above
+ # group-add-mod-supported=false
+
+By default the group-add-mod-supported flag will be kept as false, which means existing group commands
+OFPGC_ADD/OFPGC_MODIFY will be used.
+
+GroupConverter will use the above flag to determine which group command should be sent out for add/update group.
+The changes will be done for both single layer and multilayer serialization.
+
+When flag is enabled, openflowplugin will always send OFPGC_ADD_OR_MOD for both group add and modify.
+
+Pipeline changes
+----------------
+None
+
+Yang changes
+------------
+
+Below yang changes is required to add new command support under typedef group-mod-command.
+New command OFPGC_ADD_OR_MOD will be added with value as 32768.
+
+.. code-block:: none
+ :caption: openflow-types.yang
+
+ typedef group-mod-command {
+ /* ofp_group_mod_command */
+ type enumeration {
+ enum OFPGC_ADD {
+ value 0;
+ description "New group.";
+ }
+ enum OFPGC_MODIFY {
+ value 1;
+ description "Modify all matching groups.";
+ }
+ enum OFPGC_DELETE {
+ value 2;
+ description "Delete all matching groups.";
+ }
+ enum OFPGC_ADD_OR_MOD {
+ /* Hexa value for OFPGC_ADD_OR_MOD = 0x8000 */
+ value 32768;
+ description "Create new or modify existing group.";
+ }
+ }
+ }
+
+Configuration impact
+--------------------
+None
+
+Clustering considerations
+-------------------------
+None
+
+Other Infra considerations
+--------------------------
+None
+
+Security considerations
+-----------------------
+None
+
+Scale and Performance Impact
+----------------------------
+Unknown
+
+Targeted Release
+----------------
+Oxygen
+
+Alternatives
+------------
+None
+
+Usage
+=====
+No external rpc/api will be provided. The implementation is internal to openflowplugin.
+
+REST API
+--------
+No new REST API is being added.
+
+CLI
+---
+
+No new CLI being added.
+
+Implementation
+==============
+Assignee(s)
+-----------
+Primary assignee:
+ D Arunprakash <d.arunprakash@ericsson.com>
+
+Other contributors:
+ Gobinath Suganthan <gobinath@ericsson.com
+
+Work Items
+----------
+* Implementation of GROUP ADD MOD support
+* Addition of configuration flag to enable/disable group add mod command
+
+Dependencies
+============
+No new dependencies.
+
+Testing
+=======
+Unit Tests
+----------
+#. Verify group provisioning via FRM with group-add-mod-supported disabled
+#. Verify group provisioning via FRM with group-add-mod-supported enabled
+#. Verify reconciliation via FRM with with group-add-mod-supported disabled
+#. Verify reconciliation via FRM with with group-add-mod-supported enabled
+
+CSIT
+----
+CSIT test cases will be added in future
+
+Documentation Impact
+====================
+None
+
+References
+==========
+`Openvswitch ADD_OR_MOD <https://github.com/openvswitch/ovs/commit/88b87a36123e5ce3704b5e79950e83651db43ef7>`__
Code Review / openflowplugin.git / commitdiff