diff --git a/xos/synchronizer/helpers.py b/xos/synchronizer/helpers.py
new file mode 100755
index 0000000..3cbedb8
--- /dev/null
+++ b/xos/synchronizer/helpers.py
@@ -0,0 +1,82 @@
+# Copyright 2020-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.
+
+from xossynchronizer.steps.syncstep import DeferredException
+
+class DtHelpers():
+    @staticmethod
+    def validate_onu(model_accessor, log, dt_si):
+        """
+        This method validate an ONU against the whitelist and set the appropriate state.
+        It's expected that the deferred exception is managed in the caller method,
+        for example a model_policy or a sync_step.
+
+        :param dt_si: DtWorkflowDriverServiceInstance
+        :return: [boolean, string]
+        """
+
+        oss_service = dt_si.owner.leaf_model
+
+        # See if there is a matching entry in the whitelist.
+        matching_entries = model_accessor.DtWorkflowDriverWhiteListEntry.objects.filter(
+            owner_id=oss_service.id,
+        )
+        matching_entries = [e for e in matching_entries if e.serial_number.lower() == dt_si.serial_number.lower()]
+
+        if len(matching_entries) == 0:
+            log.warn("ONU not found in whitelist", object=str(dt_si), serial_number=dt_si.serial_number, **dt_si.tologdict())
+            return [False, "ONU not found in whitelist"]
+
+        whitelisted = matching_entries[0]
+        try:
+            onu = model_accessor.ONUDevice.objects.get(serial_number=dt_si.serial_number)
+            pon_port = onu.pon_port
+        except IndexError:
+            raise DeferredException("ONU device %s is not know to XOS yet" % dt_si.serial_number)
+
+        if onu.admin_state == "ADMIN_DISABLED":
+            return [False, "ONU has been manually disabled"]
+
+        if pon_port.port_no != whitelisted.pon_port_id or dt_si.of_dpid != whitelisted.device_id:
+            log.warn("ONU disable as location don't match",
+                     object=str(dt_si),
+                     serial_number=dt_si.serial_number,
+                     pon_port=pon_port.port_no,
+                     whitelisted_pon_port=whitelisted.pon_port_id,
+                     device_id=dt_si.of_dpid,
+                     whitelisted_device_id=whitelisted.device_id,
+                     **dt_si.tologdict())
+            return [False, "ONU activated in wrong location"]
+
+        return [True, "ONU has been validated"]
+
+    @staticmethod
+    def find_or_create_dt_si(model_accessor, log, event):
+        try:
+            dt_si = model_accessor.DtWorkflowDriverServiceInstance.objects.get(
+                serial_number=event["serialNumber"]
+            )
+            log.debug("DtHelpers: Found existing DtWorkflowDriverServiceInstance", si=dt_si)
+        except IndexError:
+            # create an DtWorkflowDriverServiceInstance, the validation will be
+            # triggered in the corresponding sync step
+            dt_si = model_accessor.DtWorkflowDriverServiceInstance(
+                serial_number=event["serialNumber"],
+                of_dpid=event["deviceId"],
+                uni_port_id=long(event["portNumber"]),
+                # we assume there is only one DtWorkflowDriverService
+                owner=model_accessor.DtWorkflowDriverService.objects.first()
+            )
+            log.debug("DtHelpers: Created new DtWorkflowDriverServiceInstance", si=dt_si)
+        return dt_si