diff --git a/tricircle/network/central_plugin.py b/tricircle/network/central_plugin.py
index a466b50e..3111eb28 100644
--- a/tricircle/network/central_plugin.py
+++ b/tricircle/network/central_plugin.py
@@ -297,9 +297,8 @@ class TricirclePlugin(db_base_plugin_v2.NeutronDbPluginV2,
                                             'comparator': 'eq',
                                             'value': network_id}])
 
-        session = context.session
-        with session.begin(subtransactions=True):
-            self.type_manager.release_network_segments(session, network_id)
+        with context.session.begin(subtransactions=True):
+            self.type_manager.release_network_segments(context, network_id)
             super(TricirclePlugin, self).delete_network(context, network_id)
 
     def update_network(self, context, network_id, network):
diff --git a/tricircle/network/drivers/type_local.py b/tricircle/network/drivers/type_local.py
index 6d07ddb7..e31b7d3e 100644
--- a/tricircle/network/drivers/type_local.py
+++ b/tricircle/network/drivers/type_local.py
@@ -31,13 +31,13 @@ class LocalTypeDriver(driver_api.TypeDriver):
     def validate_provider_segment(self, segment):
         pass
 
-    def reserve_provider_segment(self, session, segment):
+    def reserve_provider_segment(self, context, segment):
         return segment
 
-    def allocate_tenant_segment(self, session):
+    def allocate_tenant_segment(self, context):
         return {driver_api.NETWORK_TYPE: constants.NT_LOCAL}
 
-    def release_segment(self, session, segment):
+    def release_segment(self, context, segment):
         pass
 
     def get_mtu(self, physical):
diff --git a/tricircle/network/drivers/type_shared_vlan.py b/tricircle/network/drivers/type_shared_vlan.py
index ce65667f..3ea8e09a 100644
--- a/tricircle/network/drivers/type_shared_vlan.py
+++ b/tricircle/network/drivers/type_shared_vlan.py
@@ -45,15 +45,15 @@ class SharedVLANTypeDriver(type_vlan.VlanTypeDriver):
     def get_type(self):
         return constants.NT_SHARED_VLAN
 
-    def reserve_provider_segment(self, session, segment):
+    def reserve_provider_segment(self, context, segment):
         res = super(SharedVLANTypeDriver,
-                    self).reserve_provider_segment(session, segment)
+                    self).reserve_provider_segment(context, segment)
         res[driver_api.NETWORK_TYPE] = constants.NT_SHARED_VLAN
         return res
 
-    def allocate_tenant_segment(self, session):
+    def allocate_tenant_segment(self, context):
         res = super(SharedVLANTypeDriver,
-                    self).allocate_tenant_segment(session)
+                    self).allocate_tenant_segment(context)
         res[driver_api.NETWORK_TYPE] = constants.NT_SHARED_VLAN
         return res
 
diff --git a/tricircle/network/managers.py b/tricircle/network/managers.py
index 6b7ebfc9..a64ebef7 100644
--- a/tricircle/network/managers.py
+++ b/tricircle/network/managers.py
@@ -87,11 +87,11 @@ class TricircleTypeManager(managers.TypeManager):
             if segments:
                 for segment_index, segment in enumerate(segments):
                     segment = self.reserve_provider_segment(
-                        session, segment)
+                        context, segment)
                     self._add_network_segment(context, network_id, segment,
                                               segment_index)
             else:
-                segment = self._allocate_tenant_net_segment(session)
+                segment = self._allocate_tenant_net_segment(context)
                 self._add_network_segment(context, network_id, segment)
 
     def extend_networks_dict_provider(self, context, networks):