+ <table name="Flow_Table" title="OpenFlow table configuration">
+ <p>Configuration for a particular OpenFlow table.</p>
+
+ <column name="name">
+ The table's name. Set this column to change the name that controllers
+ will receive when they request table statistics, e.g. <code>ovs-ofctl
+ dump-tables</code>. The name does not affect switch behavior.
+ </column>
+
+ <column name="flow_limit">
+ If set, limits the number of flows that may be added to the table. Open
+ vSwitch may limit the number of flows in a table for other reasons,
+ e.g. due to hardware limitations or for resource availability or
+ performance reasons.
+ </column>
+
+ <column name="overflow_policy">
+ <p>
+ Controls the switch's behavior when an OpenFlow flow table modification
+ request would add flows in excess of <ref column="flow_limit"/>. The
+ supported values are:
+ </p>
+
+ <dl>
+ <dt><code>refuse</code></dt>
+ <dd>
+ Refuse to add the flow or flows. This is also the default policy
+ when <ref column="overflow_policy"/> is unset.
+ </dd>
+
+ <dt><code>evict</code></dt>
+ <dd>
+ Delete the flow that will expire soonest. See <ref column="groups"/>
+ for details.
+ </dd>
+ </dl>
+ </column>
+
+ <column name="groups">
+ <p>
+ When <ref column="overflow_policy"/> is <code>evict</code>, this
+ controls how flows are chosen for eviction when the flow table would
+ otherwise exceed <ref column="flow_limit"/> flows. Its value is a set
+ of NXM fields or sub-fields, each of which takes one of the forms
+ <code><var>field</var>[]</code> or
+ <code><var>field</var>[<var>start</var>..<var>end</var>]</code>,
+ e.g. <code>NXM_OF_IN_PORT[]</code>. Please see
+ <code>nicira-ext.h</code> for a complete list of NXM field names.
+ </p>
+
+ <p>
+ When a flow must be evicted due to overflow, the flow to evict is
+ chosen through an approximation of the following algorithm:
+ </p>
+
+ <ol>
+ <li>
+ Divide the flows in the table into groups based on the values of the
+ specified fields or subfields, so that all of the flows in a given
+ group have the same values for those fields. If a flow does not
+ specify a given field, that field's value is treated as 0.
+ </li>
+
+ <li>
+ Consider the flows in the largest group, that is, the group that
+ contains the greatest number of flows. If two or more groups all
+ have the same largest number of flows, consider the flows in all of
+ those groups.
+ </li>
+
+ <li>
+ Among the flows under consideration, choose the flow that expires
+ soonest for eviction.
+ </li>
+ </ol>
+
+ <p>
+ The eviction process only considers flows that have an idle timeout or
+ a hard timeout. That is, eviction never deletes permanent flows.
+ (Permanent flows do count against <ref column="flow_limit"/>.
+ </p>
+
+ <p>
+ Open vSwitch ignores any invalid or unknown field specifications.
+ </p>
+
+ <p>
+ When <ref column="overflow_policy"/> is not <code>evict</code>, this
+ column has no effect.
+ </p>
+ </column>
+ </table>
+