diff --git a/xos/synchronizer/event_steps/onos_event.py b/xos/synchronizer/event_steps/onos_event.py
new file mode 100644
index 0000000..574413d
--- /dev/null
+++ b/xos/synchronizer/event_steps/onos_event.py
@@ -0,0 +1,90 @@
+
+# Copyright 2017-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.
+
+
+import datetime
+import json
+import time
+from xossynchronizer.event_steps.eventstep import EventStep
+from xosconfig import Config
+from xoskafka import XOSKafkaProducer
+from multistructlog import create_logger
+
+log = create_logger(Config().get('logging'))
+
+
+class OnosPortEventStep(EventStep):
+    topics = ["onos.events.port"]
+    technology = "kafka"
+
+    def __init__(self, *args, **kwargs):
+        super(OnosPortEventStep, self).__init__(*args, **kwargs)
+
+    def subscriber_olt_closure(self, olt):
+        subscribers = []
+        for pon_port in olt.pon_ports.all():
+            for onu_device in pon_port.onu_devices.all():
+                for si in onu_device.volt_service_instances.all():
+                    for subscriber in si.westbound_service_instances:
+                        subscribers.append(subscriber)
+        return subscribers
+
+
+    def send_alarm(self, olt, value):
+        timestamp = time.mktime(datetime.datetime.strptime(value["timestamp"], "%Y-%m-%dT%H:%M:%S.%fZ").timetuple())
+        state = "RAISED" if olt.link_status == "down" else "CLEARED"
+
+        # Hypothetically, a maximum of 64 subscribers per pon port, 16 pon ports, and 32 characters
+        # per subscriber name = 32KB of subscriber names in the event.
+        subscribers = self.subscriber_olt_closure(olt)
+        subscribers = [x.name for x in subscribers]
+
+        alarm = {"category": "OLT",
+                 "reported_ts": time.time(),
+                 "raised_ts": timestamp,
+                 "state": state,
+                 "alarm_type_name": "OLT.LOSS_OF_AGGSWITCH",
+                 "severity": "MAJOR",
+                 "resource_id": olt.device_id,
+                 "logical_device_id": olt.dp_id,
+                 "context": {"affected_subscribers": subscribers},
+                 "type": "COMMUNICATION",
+                 "id": "xos.voltservice.%s.OLT_LOSS_OF_AGGWSWITCH" % olt.device_id,
+                 "description": "xos.voltservice.%s - OLT LOSS OF AGGSWITCH Alarm - OLT_LOSS_OF_AGGSWITCH - %s" % (olt.device_id, state)}
+
+        topic = "xos.alarms.olt-service"
+        key = olt.device_id
+        value = json.dumps(alarm, default=lambda o: repr(o))
+
+        XOSKafkaProducer.produce(topic, key, value)
+
+    def process_event(self, event):
+        log.info("Received ONOS Port Event", kafka_event=event)
+
+        value = json.loads(event.value)
+
+        olt = self.model_accessor.OLTDevice.objects.filter(switch_datapath_id=value["deviceId"],
+                                                           switch_port=value["portId"])
+        if not olt:
+            log.info("Onos port event not for a known olt", deviceId=value["deviceId"], portId=value["portId"])
+            return
+
+        olt = olt[0]
+
+        link_status = "up" if value["enabled"] else "down"
+        if link_status != olt.link_status:
+            olt.link_status = link_status
+            olt.save_changed_fields()
+            self.send_alarm(olt, value)
diff --git a/xos/synchronizer/event_steps/test_onos_event.py b/xos/synchronizer/event_steps/test_onos_event.py
new file mode 100644
index 0000000..8f8f0d8
--- /dev/null
+++ b/xos/synchronizer/event_steps/test_onos_event.py
@@ -0,0 +1,235 @@
+# Copyright 2017-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.
+
+import unittest
+import json
+from mock import patch, Mock, MagicMock, ANY
+
+import datetime
+import os
+import sys
+import time
+
+test_path = os.path.abspath(os.path.dirname(os.path.realpath(__file__)))
+
+
+class TestOnosPortEvent(unittest.TestCase):
+
+    def setUp(self):
+        global DeferredException
+
+        self.sys_path_save = sys.path
+
+        # Setting up the config module
+        from xosconfig import Config
+        config = os.path.join(test_path, "../test_config.yaml")
+        Config.clear()
+        Config.init(config, "synchronizer-config-schema.yaml")
+
+        # Mock the kafka producer
+        self.mockxoskafka = MagicMock()
+        modules = {
+            'xoskafka': self.mockxoskafka,
+            'xoskafka.XOSKafkaProducer': self.mockxoskafka.XOSKafkaProducer,
+        }
+        self.module_patcher = patch.dict('sys.modules', modules)
+        self.module_patcher.start()
+
+        from xossynchronizer.mock_modelaccessor_build import mock_modelaccessor_config
+        mock_modelaccessor_config(test_path, [("olt-service", "volt.xproto"),
+                                              ("rcord", "rcord.xproto")])
+
+        import xossynchronizer.modelaccessor
+        import mock_modelaccessor
+        reload(mock_modelaccessor)  # in case nose2 loaded it in a previous test
+        reload(xossynchronizer.modelaccessor)  # in case nose2 loaded it in a previous test
+
+        from mock_modelaccessor import MockObjectList
+        from xossynchronizer.modelaccessor import model_accessor
+        self.model_accessor = model_accessor
+
+        # necessary to reset XOSKafkaProducer's call_count
+        import onos_event
+        reload(onos_event)
+
+        from onos_event import OnosPortEventStep, XOSKafkaProducer
+        from onos_event import XOSKafkaProducer
+        self.XOSKafkaProducer = XOSKafkaProducer
+
+        # import all class names to globals
+        for (k, v) in model_accessor.all_model_classes.items():
+            globals()[k] = v
+
+        self.event_step = OnosPortEventStep
+
+        self.volt_service = VOLTService(name="volt",
+                                        id=1112,
+                                        backend_code=1,
+                                        backend_status="succeeded")
+
+        self.oltdevice = OLTDevice(name="myolt",
+                                   device_id="of:0000000000000001",
+                                   switch_dsatapath_id="of:0000000000000001",
+                                   switch_port="1")
+
+        self.ponport = PONPort(olt_device = self.oltdevice)
+
+        self.onudevice = ONUDevice(pon_port = self.ponport)
+
+        self.subscriber = RCORDSubscriber(name="somesubscriber")
+        self.voltsi = VOLTServiceInstance()
+
+        # chain it all together
+        self.oltdevice.pon_ports = MockObjectList([self.ponport])
+        self.ponport.onu_devices = MockObjectList([self.onudevice])
+        self.onudevice.volt_service_instances = MockObjectList([self.voltsi])
+        self.voltsi.westbound_service_instances = [self.subscriber]
+
+        self.log = Mock()
+
+    def tearDown(self):
+        sys.path = self.sys_path_save
+
+    def test_process_event_enable(self):
+        with patch.object(OLTDevice.objects, "get_items") as olt_objects:
+            olt_objects.return_value = [self.oltdevice]
+
+            event_dict = {"timestamp":"2019-03-21T18:00:26.613Z",
+                          "deviceId": self.oltdevice.switch_datapath_id,
+                          "portId": self.oltdevice.switch_port,
+                          "enabled": True}
+            event = Mock()
+            event.value = json.dumps(event_dict)
+
+            step = self.event_step(model_accessor=self.model_accessor, log=self.log)
+            step.process_event(event)
+
+            self.assertEqual(self.oltdevice.link_status, "up")
+
+    def test_process_event_disable(self):
+        with patch.object(OLTDevice.objects, "get_items") as olt_objects:
+            olt_objects.return_value = [self.oltdevice]
+
+            event_dict = {"timestamp":"2019-03-21T18:00:26.613Z",
+                          "deviceId": self.oltdevice.switch_datapath_id,
+                          "portId": self.oltdevice.switch_port,
+                          "enabled": False}
+            event = Mock()
+            event.value = json.dumps(event_dict)
+
+            step = self.event_step(model_accessor=self.model_accessor, log=self.log)
+            step.process_event(event)
+
+            self.assertEqual(self.oltdevice.link_status, "down")
+
+    def test_process_event_no_olt(self):
+        with patch.object(OLTDevice.objects, "get_items") as olt_objects:
+            olt_objects.return_value = [self.oltdevice]
+
+            event_dict = {"timestamp":"2019-03-21T18:00:26.613Z",
+                          "deviceId": "doesnotexist",
+                          "portId": self.oltdevice.switch_port,
+                          "enabled": True}
+            event = Mock()
+            event.value = json.dumps(event_dict)
+
+            step = self.event_step(model_accessor=self.model_accessor, log=self.log)
+            step.process_event(event)
+
+            # should not have changed
+            self.assertEqual(self.oltdevice.link_status, None)
+
+    def test_send_alarm(self):
+        self.oltdevice.link_status = "down"
+        value = {"timestamp":"2019-03-21T18:00:26.613Z",
+                 "deviceId":"of:0000000000000001",
+                 "portId":"2",
+                 "enabled":False,
+                 "speed":10000,
+                 "type":"COPPER"}
+
+        step = self.event_step(model_accessor=self.model_accessor, log=self.log)
+        step.send_alarm(self.oltdevice, value)
+
+        self.assertEqual(self.XOSKafkaProducer.produce.call_count, 1)
+        topic = self.XOSKafkaProducer.produce.call_args[0][0]
+        key = self.XOSKafkaProducer.produce.call_args[0][1]
+        event = json.loads(self.XOSKafkaProducer.produce.call_args[0][2])
+
+        self.assertEqual(topic, "xos.alarms.olt-service")
+        self.assertEqual(key, "of:0000000000000001")
+
+        raised_ts = time.mktime(datetime.datetime.strptime(value["timestamp"], "%Y-%m-%dT%H:%M:%S.%fZ").timetuple())
+
+        self.maxDiff = None
+
+        expected_alarm = {
+                 u"category": u"OLT",
+                 u"reported_ts": ANY,
+                 u"raised_ts": raised_ts,
+                 u"state": u"RAISED",
+                 u"alarm_type_name": u"OLT.LOSS_OF_AGGSWITCH",
+                 u"severity": u"MAJOR",
+                 u"resource_id": unicode(self.oltdevice.device_id),
+                 u"logical_device_id": self.oltdevice.dp_id,
+                 u"context": {u'affected_subscribers': [u'somesubscriber']},
+                 u"type": u"COMMUNICATION",
+                 u"id": u"xos.voltservice.%s.OLT_LOSS_OF_AGGWSWITCH" % self.oltdevice.device_id,
+                 u"description": u"xos.voltservice.%s - OLT LOSS OF AGGSWITCH Alarm - OLT_LOSS_OF_AGGSWITCH - RAISED" % self.oltdevice.device_id}
+
+        self.assertDictEqual(expected_alarm, event)
+
+    def test_clear_alarm(self):
+        self.oltdevice.link_status = "up"
+        value = {"timestamp":"2019-03-21T18:00:26.613Z",
+                 "deviceId":"of:0000000000000001",
+                 "portId":"2",
+                 "enabled":True,
+                 "speed":10000,
+                 "type":"COPPER"}
+
+        step = self.event_step(model_accessor=self.model_accessor, log=self.log)
+        step.send_alarm(self.oltdevice, value)
+
+        self.assertEqual(self.XOSKafkaProducer.produce.call_count, 1)
+        topic = self.XOSKafkaProducer.produce.call_args[0][0]
+        key = self.XOSKafkaProducer.produce.call_args[0][1]
+        event = json.loads(self.XOSKafkaProducer.produce.call_args[0][2])
+
+        self.assertEqual(topic, "xos.alarms.olt-service")
+        self.assertEqual(key, "of:0000000000000001")
+
+        raised_ts = time.mktime(datetime.datetime.strptime(value["timestamp"], "%Y-%m-%dT%H:%M:%S.%fZ").timetuple())
+
+        self.maxDiff = None
+
+        expected_alarm = {
+                 u"category": u"OLT",
+                 u"reported_ts": ANY,
+                 u"raised_ts": raised_ts,
+                 u"state": u"CLEARED",
+                 u"alarm_type_name": u"OLT.LOSS_OF_AGGSWITCH",
+                 u"severity": u"MAJOR",
+                 u"resource_id": unicode(self.oltdevice.device_id),
+                 u"logical_device_id": self.oltdevice.dp_id,
+                 u"context": {u'affected_subscribers': [u'somesubscriber']},
+                 u"type": u"COMMUNICATION",
+                 u"id": u"xos.voltservice.%s.OLT_LOSS_OF_AGGWSWITCH" % self.oltdevice.device_id,
+                 u"description": u"xos.voltservice.%s - OLT LOSS OF AGGSWITCH Alarm - OLT_LOSS_OF_AGGSWITCH - CLEARED" % self.oltdevice.device_id}
+
+        self.assertDictEqual(expected_alarm, event)
+
+
+if __name__ == '__main__':
+    unittest.main()