diff --git a/api/src/main/java/org/opencord/olt/OltFlowServiceInterface.java b/api/src/main/java/org/opencord/olt/OltFlowServiceInterface.java
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+++ b/api/src/main/java/org/opencord/olt/OltFlowServiceInterface.java
@@ -0,0 +1,132 @@
+/*
+ * Copyright 2021-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.opencord.olt;
+
+import org.onosproject.net.Device;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.Port;
+import org.opencord.sadis.UniTagInformation;
+
+import java.util.Map;
+
+/**
+ * Interface for flow installation/removal methods for different types of traffic.
+ */
+public interface OltFlowServiceInterface {
+    /**
+     * Installs or removes default flows for the port to trap to controller.
+     * @param sub the information about the port
+     * @param defaultBpId the default bandwidth profile
+     * @param oltBandwidthProfile the olt bandwidth profile.
+     * @return true if successful
+     */
+    boolean handleBasicPortFlows(
+            DiscoveredSubscriber sub, String defaultBpId, String oltBandwidthProfile);
+
+    /**
+     * Installs or removes subscriber specific flows.
+     * @param sub the information about the subscriber
+     * @param defaultBpId the default bandwidth profile
+     * @param multicastServiceName the multicast service name.
+     * @return true if successful
+     */
+    boolean handleSubscriberFlows(DiscoveredSubscriber sub, String defaultBpId, String multicastServiceName);
+
+    /**
+     * Installs or removes flows on the NNI port.
+     * @param device the OLT
+     * @param port the NNI port
+     * @param action the operatio, ADD or REMOVE.
+     */
+    void handleNniFlows(Device device, Port port, FlowOperation action);
+
+    /**
+     * Checks if the default eapol flow is already installed.
+     * @param port the port
+     * @return true if installed, false otherwise.
+     */
+    boolean hasDefaultEapol(Port port);
+
+    /**
+     * Checks if the dhcp flows are installed.
+     * @param port the port
+     * @param uti the UniTagInformation to check for
+     * @return true if installed, false otherwise.
+     */
+    boolean hasDhcpFlows(Port port, UniTagInformation uti);
+
+    /**
+     * Checks if the pppoe flows are installed.
+     * @param port the port
+     * @param uti the UniTagInformation to check for
+     * @return true if installed, false otherwise.
+     */
+    boolean hasPppoeFlows(Port port, UniTagInformation uti);
+
+    /**
+     * Checks if the subscriber flows are installed.
+     * @param port the port
+     * @param uti the UniTagInformation to check for
+     * @return true if installed, false otherwise.
+     */
+    boolean hasSubscriberFlows(Port port, UniTagInformation uti);
+
+    /**
+     * Removes all device flows.
+     * @param deviceId the olt.
+     */
+    void purgeDeviceFlows(DeviceId deviceId);
+
+    /**
+     * Return the status of installation on the connect points.
+     * @return the status map
+     */
+    Map<ServiceKey, OltPortStatus> getConnectPointStatus();
+
+    /**
+     * Returns all the programmed subscribers.
+     * @return the subscribers
+     */
+    Map<ServiceKey, UniTagInformation> getProgrammedSubscribers();
+
+    /**
+     * Returns the list of requested subscribers to be installed with status.
+     * @return the list
+     */
+    Map<ServiceKey, Boolean> getRequestedSubscribers();
+
+    /**
+     * Returns if a subscriber on a port is provisioned or not.
+     * @param cp the port
+     * @return true if any service on that port is provisioned, false otherwise
+     */
+    boolean isSubscriberServiceProvisioned(AccessDevicePort cp);
+
+    /**
+     * Returns if a subscriber on a port is provisioned or not.
+     * @param sk the SubscriberKey
+     * @return true if provisioned, false otherwise
+     */
+    boolean isSubscriberServiceProvisioned(ServiceKey sk);
+
+    /**
+     * Updates the subscriber provisioning status.
+     * @param sk the SubscriberKey
+     * @param status the next status
+     */
+    void updateProvisionedSubscriberStatus(ServiceKey sk, Boolean status);
+}