--- /dev/null
+/*
+ * Copyright (c) 2015 Pantheon Technologies s.r.o. and others. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.openflowjava.protocol.api.connection;
+
+import com.google.common.annotations.Beta;
+import javax.annotation.Nonnull;
+import org.opendaylight.yang.gen.v1.urn.opendaylight.openflow.protocol.rev130731.BarrierInput;
+
+/**
+ * Handler of the outbound queue. The queue has a maximum depth assigned when the
+ * handler is registered.
+ */
+@Beta
+public interface OutboundQueueHandler {
+ /**
+ * Create a new {@link BarrierInput barrier} message. This callback is invoked
+ * when the queue is being flushed to the switch. The barrier ensures that any
+ * outstanding requests are detected as either completed or failed.
+ *
+ * @param xid XID for the barrier message
+ * @return New barrier message.
+ */
+ @Nonnull BarrierInput createBarrierRequest(@Nonnull Long xid);
+
+ /**
+ * Invoked whenever the underlying queue is refreshed. Implementations should
+ * ensure they are talking to the latest queue
+ * @param queue New queue instance, null indicates a shutdown, e.g. the queue
+ * is no longer available.
+ */
+ void onConnectionQueueChanged(OutboundQueue queue);
+}