diff --git a/fw-update/inventory_manager.hpp b/fw-update/inventory_manager.hpp
index 953d7a4..ade1fcd 100644
--- a/fw-update/inventory_manager.hpp
+++ b/fw-update/inventory_manager.hpp
@@ -34,15 +34,21 @@
      *  @param[in] instanceIdDb - Managing instance ID for PLDM requests
      *  @param[out] descriptorMap - Populate the firmware identifiers for the
      *                              FDs managed by the BMC.
+     *  @param[out] downstreamDescriptorMap - Populate the downstream
+     *                                        identifiers for the FDs managed
+     *                                        by the BMC.
      *  @param[out] componentInfoMap - Populate the component info for the FDs
      *                                 managed by the BMC.
      */
     explicit InventoryManager(
         pldm::requester::Handler<pldm::requester::Request>& handler,
         InstanceIdDb& instanceIdDb, DescriptorMap& descriptorMap,
+        DownstreamDescriptorMap& downstreamDescriptorMap,
         ComponentInfoMap& componentInfoMap) :
         handler(handler), instanceIdDb(instanceIdDb),
-        descriptorMap(descriptorMap), componentInfoMap(componentInfoMap)
+        descriptorMap(descriptorMap),
+        downstreamDescriptorMap(downstreamDescriptorMap),
+        componentInfoMap(componentInfoMap)
     {}
 
     /** @brief Discover the firmware identifiers and component details of FDs
@@ -68,6 +74,33 @@
     void queryDeviceIdentifiers(mctp_eid_t eid, const pldm_msg* response,
                                 size_t respMsgLen);
 
+    /** @brief Handler for QueryDownstreamDevices command response
+     *
+     *  @param[in] eid - Remote MCTP endpoint
+     *  @param[in] response - PLDM response message
+     *  @param[in] respMsgLen - Response message length
+     */
+    void queryDownstreamDevices(mctp_eid_t eid, const pldm_msg* response,
+                                size_t respMsgLen);
+
+    /** @brief Handler for QueryDownstreamIdentifiers command response
+     *
+     *  @param[in] eid - Remote MCTP endpoint
+     *  @param[in] response - PLDM response message
+     *  @param[in] respMsgLen - Response message length
+     */
+    void queryDownstreamIdentifiers(mctp_eid_t eid, const pldm_msg* response,
+                                    size_t respMsgLen);
+
+    /** @brief Handler for GetDownstreamFirmwareParameters command response
+     *
+     *  @param[in] eid - Remote MCTP endpoint
+     *  @param[in] response - PLDM response message
+     *  @param[in] respMsgLen - Response message length
+     */
+    void getDownstreamFirmwareParameters(
+        mctp_eid_t eid, const pldm_msg* response, size_t respMsgLen);
+
     /** @brief Handler for GetFirmwareParameters command response
      *
      *  Handling the response of GetFirmwareParameters command and create
@@ -81,6 +114,45 @@
                                size_t respMsgLen);
 
   private:
+    /**
+     * @brief Sends QueryDeviceIdentifiers request
+     *
+     * @param[in] eid - Remote MCTP endpoint
+     */
+    void sendQueryDeviceIdentifiersRequest(mctp_eid_t eid);
+
+    /**
+     * @brief Sends QueryDownstreamDevices request
+     *
+     * @param[in] eid - Remote MCTP endpoint
+     */
+    void sendQueryDownstreamDevicesRequest(mctp_eid_t eid);
+
+    /**
+     * @brief Sends QueryDownstreamIdentifiers request
+     *
+     * The request format is defined at Table 16 – QueryDownstreamIdentifiers
+     * command format in DSP0267_1.1.0
+     *
+     * @param[in] eid - Remote MCTP endpoint
+     * @param[in] dataTransferHandle - Data transfer handle
+     * @param[in] transferOperationFlag - Transfer operation flag
+     */
+    void sendQueryDownstreamIdentifiersRequest(
+        mctp_eid_t eid, uint32_t dataTransferHandle,
+        enum transfer_op_flag transferOperationFlag);
+
+    /**
+     * @brief Sends QueryDownstreamFirmwareParameters request
+     *
+     * @param[in] eid - Remote MCTP endpoint
+     * @param[in] dataTransferHandle - Data transfer handle
+     * @param[in] transferOperationFlag - Transfer operation flag
+     */
+    void sendGetDownstreamFirmwareParametersRequest(
+        mctp_eid_t eid, uint32_t dataTransferHandle,
+        const enum transfer_op_flag transferOperationFlag);
+
     /** @brief Send GetFirmwareParameters command request
      *
      *  @param[in] eid - Remote MCTP endpoint
@@ -96,6 +168,9 @@
     /** @brief Device identifiers of the managed FDs */
     DescriptorMap& descriptorMap;
 
+    /** @brief Downstream Device identifiers of the managed FDs */
+    DownstreamDescriptorMap& downstreamDescriptorMap;
+
     /** @brief Component information needed for the update of the managed FDs */
     ComponentInfoMap& componentInfoMap;
 };