Use distinct enums for distinct ticket types

7 files changed, 172 insertions, 111 deletions

diff --git a/src/python/src/grpc/_adapter/_links_test.py b/src/python/src/grpc/_adapter/_links_test.py
index 5d7e677243..49fd1f7a1c 100644
--- a/src/python/src/grpc/_adapter/_links_test.py
+++ b/src/python/src/grpc/_adapter/_links_test.py
@@ -60,9 +60,11 @@ class RoundTripTest(unittest.TestCase):
     test_fore_link = _test_links.ForeLink(None, None)
     def rear_action(front_to_back_ticket, fore_link):
       if front_to_back_ticket.kind in (
-          tickets.Kind.COMPLETION, tickets.Kind.ENTIRE):
+          tickets.FrontToBackPacket.Kind.COMPLETION,
+          tickets.FrontToBackPacket.Kind.ENTIRE):
         back_to_front_ticket = tickets.BackToFrontPacket(
-            front_to_back_ticket.operation_id, 0, tickets.Kind.COMPLETION, None)
+            front_to_back_ticket.operation_id, 0,
+            tickets.BackToFrontPacket.Kind.COMPLETION, None)
         fore_link.accept_back_to_front_ticket(back_to_front_ticket)
     test_rear_link = _test_links.RearLink(rear_action, None)
 
@@ -81,20 +83,24 @@ class RoundTripTest(unittest.TestCase):
     rear_link.start()
 
     front_to_back_ticket = tickets.FrontToBackPacket(
-        test_operation_id, 0, tickets.Kind.ENTIRE, test_method,
-        interfaces.ServicedSubscription.Kind.FULL, None, None, _TIMEOUT)
+        test_operation_id, 0, tickets.FrontToBackPacket.Kind.ENTIRE,
+        test_method, interfaces.ServicedSubscription.Kind.FULL, None, None,
+        _TIMEOUT)
     rear_link.accept_front_to_back_ticket(front_to_back_ticket)
 
     with test_fore_link.condition:
       while (not test_fore_link.tickets or
-             test_fore_link.tickets[-1].kind is tickets.Kind.CONTINUATION):
+             test_fore_link.tickets[-1].kind is
+                 tickets.BackToFrontPacket.Kind.CONTINUATION):
         test_fore_link.condition.wait()
 
     rear_link.stop()
     fore_link.stop()
 
     with test_fore_link.condition:
-      self.assertIs(test_fore_link.tickets[-1].kind, tickets.Kind.COMPLETION)
+      self.assertIs(
+          test_fore_link.tickets[-1].kind,
+          tickets.BackToFrontPacket.Kind.COMPLETION)
 
   def testEntireRoundTrip(self):
     test_operation_id = object()
@@ -109,11 +115,15 @@ class RoundTripTest(unittest.TestCase):
       else:
         payload = test_back_to_front_datum
       terminal = front_to_back_ticket.kind in (
-          tickets.Kind.COMPLETION, tickets.Kind.ENTIRE)
+          tickets.FrontToBackPacket.Kind.COMPLETION,
+          tickets.FrontToBackPacket.Kind.ENTIRE)
       if payload is not None or terminal:
+        if terminal:
+          kind = tickets.BackToFrontPacket.Kind.COMPLETION
+        else:
+          kind = tickets.BackToFrontPacket.Kind.CONTINUATION
         back_to_front_ticket = tickets.BackToFrontPacket(
-            front_to_back_ticket.operation_id, rear_sequence_number[0],
-            tickets.Kind.COMPLETION if terminal else tickets.Kind.CONTINUATION,
+            front_to_back_ticket.operation_id, rear_sequence_number[0], kind,
             payload)
         rear_sequence_number[0] += 1
         fore_link.accept_back_to_front_ticket(back_to_front_ticket)
@@ -135,14 +145,15 @@ class RoundTripTest(unittest.TestCase):
     rear_link.start()
 
     front_to_back_ticket = tickets.FrontToBackPacket(
-        test_operation_id, 0, tickets.Kind.ENTIRE, test_method,
-        interfaces.ServicedSubscription.Kind.FULL, None,
+        test_operation_id, 0, tickets.FrontToBackPacket.Kind.ENTIRE,
+        test_method, interfaces.ServicedSubscription.Kind.FULL, None,
         test_front_to_back_datum, _TIMEOUT)
     rear_link.accept_front_to_back_ticket(front_to_back_ticket)
 
     with test_fore_link.condition:
       while (not test_fore_link.tickets or
-             test_fore_link.tickets[-1].kind is not tickets.Kind.COMPLETION):
+             test_fore_link.tickets[-1].kind is not
+                 tickets.BackToFrontPacket.Kind.COMPLETION):
         test_fore_link.condition.wait()
 
     rear_link.stop()
@@ -172,11 +183,15 @@ class RoundTripTest(unittest.TestCase):
         else:
           response = None
       terminal = front_to_back_ticket.kind in (
-          tickets.Kind.COMPLETION, tickets.Kind.ENTIRE)
+          tickets.FrontToBackPacket.Kind.COMPLETION,
+          tickets.FrontToBackPacket.Kind.ENTIRE)
       if response is not None or terminal:
+        if terminal:
+          kind = tickets.BackToFrontPacket.Kind.COMPLETION
+        else:
+          kind = tickets.BackToFrontPacket.Kind.CONTINUATION
         back_to_front_ticket = tickets.BackToFrontPacket(
-            front_to_back_ticket.operation_id, rear_sequence_number[0],
-            tickets.Kind.COMPLETION if terminal else tickets.Kind.CONTINUATION,
+            front_to_back_ticket.operation_id, rear_sequence_number[0], kind,
             response)
         rear_sequence_number[0] += 1
         fore_link.accept_back_to_front_ticket(back_to_front_ticket)
@@ -199,25 +214,29 @@ class RoundTripTest(unittest.TestCase):
     rear_link.start()
 
     commencement_ticket = tickets.FrontToBackPacket(
-        test_operation_id, 0, tickets.Kind.COMMENCEMENT, test_method,
-        interfaces.ServicedSubscription.Kind.FULL, None, None, _TIMEOUT)
+        test_operation_id, 0, tickets.FrontToBackPacket.Kind.COMMENCEMENT,
+        test_method, interfaces.ServicedSubscription.Kind.FULL, None, None,
+        _TIMEOUT)
     fore_sequence_number = 1
     rear_link.accept_front_to_back_ticket(commencement_ticket)
     for request in scenario.requests():
       continuation_ticket = tickets.FrontToBackPacket(
-          test_operation_id, fore_sequence_number, tickets.Kind.CONTINUATION,
-          None, None, None, request, None)
+          test_operation_id, fore_sequence_number,
+          tickets.FrontToBackPacket.Kind.CONTINUATION, None, None, None,
+          request, None)
       fore_sequence_number += 1
       rear_link.accept_front_to_back_ticket(continuation_ticket)
     completion_ticket = tickets.FrontToBackPacket(
-        test_operation_id, fore_sequence_number, tickets.Kind.COMPLETION, None,
-        None, None, None, None)
+        test_operation_id, fore_sequence_number,
+        tickets.FrontToBackPacket.Kind.COMPLETION, None, None, None, None,
+        None)
     fore_sequence_number += 1
     rear_link.accept_front_to_back_ticket(completion_ticket)
 
     with test_fore_link.condition:
       while (not test_fore_link.tickets or
-             test_fore_link.tickets[-1].kind is not tickets.Kind.COMPLETION):
+             test_fore_link.tickets[-1].kind is not
+                 tickets.BackToFrontPacket.Kind.COMPLETION):
         test_fore_link.condition.wait()
 
     rear_link.stop()
diff --git a/src/python/src/grpc/_adapter/_lonely_rear_link_test.py b/src/python/src/grpc/_adapter/_lonely_rear_link_test.py
index 77821ba71a..29c95d1d0a 100644
--- a/src/python/src/grpc/_adapter/_lonely_rear_link_test.py
+++ b/src/python/src/grpc/_adapter/_lonely_rear_link_test.py
@@ -76,22 +76,26 @@ class LonelyRearLinkTest(unittest.TestCase):
     with fore_link.condition:
       while True:
         if (fore_link.tickets and
-            fore_link.tickets[-1].kind is not packets.Kind.CONTINUATION):
+            fore_link.tickets[-1].kind is not
+                packets.BackToFrontPacket.Kind.CONTINUATION):
           break
         fore_link.condition.wait()
 
     rear_link.stop()
 
     with fore_link.condition:
-      self.assertIsNot(fore_link.tickets[-1].kind, packets.Kind.COMPLETION)
+      self.assertIsNot(
+          fore_link.tickets[-1].kind,
+          packets.BackToFrontPacket.Kind.COMPLETION)
 
   @unittest.skip('TODO(nathaniel): This seems to have broken in the last few weeks; fix it.')
   def testLonelyClientCommencementPacket(self):
     self._perform_lonely_client_test_with_ticket_kind(
-        packets.Kind.COMMENCEMENT)
+        packets.FrontToBackPacket.Kind.COMMENCEMENT)
 
   def testLonelyClientEntirePacket(self):
-    self._perform_lonely_client_test_with_ticket_kind(packets.Kind.ENTIRE)
+    self._perform_lonely_client_test_with_ticket_kind(
+        packets.FrontToBackPacket.Kind.ENTIRE)
 
 
 if __name__ == '__main__':
diff --git a/src/python/src/grpc/_adapter/fore.py b/src/python/src/grpc/_adapter/fore.py
index 339c0ef216..16e5a2018c 100644
--- a/src/python/src/grpc/_adapter/fore.py
+++ b/src/python/src/grpc/_adapter/fore.py
@@ -128,7 +128,7 @@ class ForeLink(ticket_interfaces.ForeLink, activated.Activated):
         self._response_serializers[method])
 
     ticket = tickets.FrontToBackPacket(
-        call, 0, tickets.Kind.COMMENCEMENT, method,
+        call, 0, tickets.FrontToBackPacket.Kind.COMMENCEMENT, method,
         interfaces.ServicedSubscription.Kind.FULL, None, None,
         service_acceptance.deadline - time.time())
     self._rear_link.accept_front_to_back_ticket(ticket)
@@ -146,13 +146,13 @@ class ForeLink(ticket_interfaces.ForeLink, activated.Activated):
     rpc_state.sequence_number += 1
     if event.bytes is None:
       ticket = tickets.FrontToBackPacket(
-          call, sequence_number, tickets.Kind.COMPLETION, None, None, None,
-          None, None)
+          call, sequence_number, tickets.FrontToBackPacket.Kind.COMPLETION,
+          None, None, None, None, None)
     else:
       call.read(call)
       ticket = tickets.FrontToBackPacket(
-          call, sequence_number, tickets.Kind.CONTINUATION, None, None, None,
-          rpc_state.deserializer(event.bytes), None)
+          call, sequence_number, tickets.FrontToBackPacket.Kind.CONTINUATION,
+          None, None, None, rpc_state.deserializer(event.bytes), None)
 
     self._rear_link.accept_front_to_back_ticket(ticket)
 
@@ -181,7 +181,8 @@ class ForeLink(ticket_interfaces.ForeLink, activated.Activated):
       sequence_number = rpc_state.sequence_number
       rpc_state.sequence_number += 1
       ticket = tickets.FrontToBackPacket(
-          call, sequence_number, tickets.Kind.TRANSMISSION_FAILURE, None, None,
+          call, sequence_number,
+          tickets.FrontToBackPacket.Kind.TRANSMISSION_FAILURE, None, None,
           None, None, None)
       self._rear_link.accept_front_to_back_ticket(ticket)
 
@@ -200,16 +201,17 @@ class ForeLink(ticket_interfaces.ForeLink, activated.Activated):
     rpc_state.sequence_number += 1
     if code is _low.Code.CANCELLED:
       ticket = tickets.FrontToBackPacket(
-          call, sequence_number, tickets.Kind.CANCELLATION, None, None, None,
-          None, None)
+          call, sequence_number, tickets.FrontToBackPacket.Kind.CANCELLATION,
+          None, None, None, None, None)
     elif code is _low.Code.EXPIRED:
       ticket = tickets.FrontToBackPacket(
-          call, sequence_number, tickets.Kind.EXPIRATION, None, None, None,
-          None, None)
+          call, sequence_number, tickets.FrontToBackPacket.Kind.EXPIRATION,
+          None, None, None, None, None)
     else:
       # TODO(nathaniel): Better mapping of codes to ticket-categories
       ticket = tickets.FrontToBackPacket(
-          call, sequence_number, tickets.Kind.TRANSMISSION_FAILURE, None, None,
+          call, sequence_number,
+          tickets.FrontToBackPacket.Kind.TRANSMISSION_FAILURE, None, None,
           None, None, None)
     self._rear_link.accept_front_to_back_ticket(ticket)
 
@@ -351,9 +353,9 @@ class ForeLink(ticket_interfaces.ForeLink, activated.Activated):
       if self._server is None:
         return
 
-      if ticket.kind is tickets.Kind.CONTINUATION:
+      if ticket.kind is tickets.BackToFrontPacket.Kind.CONTINUATION:
         self._continue(ticket.operation_id, ticket.payload)
-      elif ticket.kind is tickets.Kind.COMPLETION:
+      elif ticket.kind is tickets.BackToFrontPacket.Kind.COMPLETION:
         self._complete(ticket.operation_id, ticket.payload)
       else:
         self._cancel(ticket.operation_id)
diff --git a/src/python/src/grpc/_adapter/rear.py b/src/python/src/grpc/_adapter/rear.py
index 62703fab30..38936ed7ae 100644
--- a/src/python/src/grpc/_adapter/rear.py
+++ b/src/python/src/grpc/_adapter/rear.py
@@ -154,7 +154,7 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
       rpc_state.active = False
       ticket = tickets.BackToFrontPacket(
           operation_id, rpc_state.common.sequence_number,
-          tickets.Kind.TRANSMISSION_FAILURE, None)
+          tickets.BackToFrontPacket.Kind.TRANSMISSION_FAILURE, None)
       rpc_state.common.sequence_number += 1
       self._fore_link.accept_back_to_front_ticket(ticket)
 
@@ -165,7 +165,8 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
 
       ticket = tickets.BackToFrontPacket(
           operation_id, rpc_state.common.sequence_number,
-          tickets.Kind.CONTINUATION, rpc_state.common.deserializer(event.bytes))
+          tickets.BackToFrontPacket.Kind.CONTINUATION,
+          rpc_state.common.deserializer(event.bytes))
       rpc_state.common.sequence_number += 1
       self._fore_link.accept_back_to_front_ticket(ticket)
 
@@ -175,7 +176,7 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
       rpc_state.active = False
       ticket = tickets.BackToFrontPacket(
           operation_id, rpc_state.common.sequence_number,
-          tickets.Kind.TRANSMISSION_FAILURE, None)
+          tickets.BackToFrontPacket.Kind.TRANSMISSION_FAILURE, None)
       rpc_state.common.sequence_number += 1
       self._fore_link.accept_back_to_front_ticket(ticket)
 
@@ -188,17 +189,16 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
     """Handle termination of an RPC."""
     # TODO(nathaniel): Cover all statuses.
     if event.status.code is _low.Code.OK:
-      category = tickets.Kind.COMPLETION
+      kind = tickets.BackToFrontPacket.Kind.COMPLETION
     elif event.status.code is _low.Code.CANCELLED:
       # TODO(issue 752): Use a CANCELLATION ticket kind here.
-      category = tickets.Kind.SERVICER_FAILURE
+      kind = tickets.BackToFrontPacket.Kind.SERVICER_FAILURE
     elif event.status.code is _low.Code.EXPIRED:
-      category = tickets.Kind.EXPIRATION
+      kind = tickets.BackToFrontPacket.Kind.EXPIRATION
     else:
-      category = tickets.Kind.TRANSMISSION_FAILURE
+      kind = tickets.BackToFrontPacket.Kind.TRANSMISSION_FAILURE
     ticket = tickets.BackToFrontPacket(
-        operation_id, rpc_state.common.sequence_number, category,
-        None)
+        operation_id, rpc_state.common.sequence_number, kind, None)
     rpc_state.common.sequence_number += 1
     self._fore_link.accept_back_to_front_ticket(ticket)
 
@@ -372,17 +372,17 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
       if self._completion_queue is None:
         return
 
-      if ticket.kind is tickets.Kind.COMMENCEMENT:
+      if ticket.kind is tickets.FrontToBackPacket.Kind.COMMENCEMENT:
         self._commence(
             ticket.operation_id, ticket.name, ticket.payload, ticket.timeout)
-      elif ticket.kind is tickets.Kind.CONTINUATION:
+      elif ticket.kind is tickets.FrontToBackPacket.Kind.CONTINUATION:
         self._continue(ticket.operation_id, ticket.payload)
-      elif ticket.kind is tickets.Kind.COMPLETION:
+      elif ticket.kind is tickets.FrontToBackPacket.Kind.COMPLETION:
         self._complete(ticket.operation_id, ticket.payload)
-      elif ticket.kind is tickets.Kind.ENTIRE:
+      elif ticket.kind is tickets.FrontToBackPacket.Kind.ENTIRE:
         self._entire(
             ticket.operation_id, ticket.name, ticket.payload, ticket.timeout)
-      elif ticket.kind is tickets.Kind.CANCELLATION:
+      elif ticket.kind is tickets.FrontToBackPacket.Kind.CANCELLATION:
         self._cancel(ticket.operation_id)
       else:
         # NOTE(nathaniel): All other categories are treated as cancellation.
diff --git a/src/python/src/grpc/framework/base/packets/_reception.py b/src/python/src/grpc/framework/base/packets/_reception.py
index becbef828d..697095961a 100644
--- a/src/python/src/grpc/framework/base/packets/_reception.py
+++ b/src/python/src/grpc/framework/base/packets/_reception.py
@@ -35,6 +35,11 @@ from grpc.framework.base import interfaces as base_interfaces
 from grpc.framework.base.packets import _interfaces
 from grpc.framework.base.packets import packets
 
+_INITIAL_FRONT_TO_BACK_PACKET_KINDS = (
+    packets.FrontToBackPacket.Kind.COMMENCEMENT,
+    packets.FrontToBackPacket.Kind.ENTIRE,
+)
+
 
 class _Receiver(object):
   """Common specification of different packet-handling behavior."""
@@ -151,15 +156,15 @@ class _BackReceiver(_Receiver):
       A base_interfaces.Outcome value describing operation abortion if the
         packet is abortive or None if the packet is not abortive.
     """
-    if packet.kind is packets.Kind.CANCELLATION:
+    if packet.kind is packets.FrontToBackPacket.Kind.CANCELLATION:
       return base_interfaces.Outcome.CANCELLED
-    elif packet.kind is packets.Kind.EXPIRATION:
+    elif packet.kind is packets.FrontToBackPacket.Kind.EXPIRATION:
       return base_interfaces.Outcome.EXPIRED
-    elif packet.kind is packets.Kind.SERVICED_FAILURE:
+    elif packet.kind is packets.FrontToBackPacket.Kind.SERVICED_FAILURE:
       return base_interfaces.Outcome.SERVICED_FAILURE
-    elif packet.kind is packets.Kind.RECEPTION_FAILURE:
+    elif packet.kind is packets.FrontToBackPacket.Kind.RECEPTION_FAILURE:
       return base_interfaces.Outcome.SERVICED_FAILURE
-    elif (packet.kind in (packets.Kind.COMMENCEMENT, packets.Kind.ENTIRE) and
+    elif (packet.kind in _INITIAL_FRONT_TO_BACK_PACKET_KINDS and
           self._first_packet_seen):
       return base_interfaces.Outcome.RECEPTION_FAILURE
     elif self._last_packet_seen:
@@ -179,14 +184,14 @@ class _BackReceiver(_Receiver):
     if packet.timeout is not None:
       self._expiration_manager.change_timeout(packet.timeout)
 
-    if packet.kind is packets.Kind.COMMENCEMENT:
+    if packet.kind is packets.FrontToBackPacket.Kind.COMMENCEMENT:
       self._first_packet_seen = True
       self._ingestion_manager.start(packet.name)
       if packet.payload is not None:
         self._ingestion_manager.consume(packet.payload)
-    elif packet.kind is packets.Kind.CONTINUATION:
+    elif packet.kind is packets.FrontToBackPacket.Kind.CONTINUATION:
       self._ingestion_manager.consume(packet.payload)
-    elif packet.kind is packets.Kind.COMPLETION:
+    elif packet.kind is packets.FrontToBackPacket.Kind.COMPLETION:
       self._last_packet_seen = True
       if packet.payload is None:
         self._ingestion_manager.terminate()
@@ -239,11 +244,11 @@ class _FrontReceiver(_Receiver):
       A base_interfaces.Outcome value describing operation abortion if the
         packet is abortive or None if the packet is not abortive.
     """
-    if packet.kind is packets.Kind.EXPIRATION:
+    if packet.kind is packets.BackToFrontPacket.Kind.EXPIRATION:
       return base_interfaces.Outcome.EXPIRED
-    elif packet.kind is packets.Kind.SERVICER_FAILURE:
+    elif packet.kind is packets.BackToFrontPacket.Kind.SERVICER_FAILURE:
       return base_interfaces.Outcome.SERVICER_FAILURE
-    elif packet.kind is packets.Kind.RECEPTION_FAILURE:
+    elif packet.kind is packets.BackToFrontPacket.Kind.RECEPTION_FAILURE:
       return base_interfaces.Outcome.SERVICER_FAILURE
     elif self._last_packet_seen:
       return base_interfaces.Outcome.RECEPTION_FAILURE
@@ -259,9 +264,9 @@ class _FrontReceiver(_Receiver):
 
   def receive(self, packet):
     """See _Receiver.receive for specification."""
-    if packet.kind is packets.Kind.CONTINUATION:
+    if packet.kind is packets.BackToFrontPacket.Kind.CONTINUATION:
       self._ingestion_manager.consume(packet.payload)
-    elif packet.kind is packets.Kind.COMPLETION:
+    elif packet.kind is packets.BackToFrontPacket.Kind.COMPLETION:
       self._last_packet_seen = True
       if packet.payload is None:
         self._ingestion_manager.terminate()
diff --git a/src/python/src/grpc/framework/base/packets/_transmission.py b/src/python/src/grpc/framework/base/packets/_transmission.py
index 002519b9a1..9922213d0a 100644
--- a/src/python/src/grpc/framework/base/packets/_transmission.py
+++ b/src/python/src/grpc/framework/base/packets/_transmission.py
@@ -47,15 +47,33 @@ _BACK_TO_FRONT_NO_TRANSMISSION_OUTCOMES = (
     interfaces.Outcome.SERVICED_FAILURE,
     )
 
-_ABORTION_OUTCOME_TO_PACKET_KIND = {
-    interfaces.Outcome.CANCELLED: packets.Kind.CANCELLATION,
-    interfaces.Outcome.EXPIRED: packets.Kind.EXPIRATION,
-    interfaces.Outcome.RECEPTION_FAILURE: packets.Kind.RECEPTION_FAILURE,
-    interfaces.Outcome.TRANSMISSION_FAILURE: packets.Kind.TRANSMISSION_FAILURE,
-    interfaces.Outcome.SERVICED_FAILURE: packets.Kind.SERVICED_FAILURE,
-    interfaces.Outcome.SERVICER_FAILURE: packets.Kind.SERVICER_FAILURE,
+_ABORTION_OUTCOME_TO_FRONT_TO_BACK_PACKET_KIND = {
+    interfaces.Outcome.CANCELLED:
+        packets.FrontToBackPacket.Kind.CANCELLATION,
+    interfaces.Outcome.EXPIRED:
+        packets.FrontToBackPacket.Kind.EXPIRATION,
+    interfaces.Outcome.RECEPTION_FAILURE:
+        packets.FrontToBackPacket.Kind.RECEPTION_FAILURE,
+    interfaces.Outcome.TRANSMISSION_FAILURE:
+        packets.FrontToBackPacket.Kind.TRANSMISSION_FAILURE,
+    interfaces.Outcome.SERVICED_FAILURE:
+        packets.FrontToBackPacket.Kind.SERVICED_FAILURE,
+    interfaces.Outcome.SERVICER_FAILURE:
+        packets.FrontToBackPacket.Kind.SERVICER_FAILURE,
 }
 
+_ABORTION_OUTCOME_TO_BACK_TO_FRONT_PACKET_KIND = {
+    interfaces.Outcome.EXPIRED:
+        packets.BackToFrontPacket.Kind.EXPIRATION,
+    interfaces.Outcome.RECEPTION_FAILURE:
+        packets.BackToFrontPacket.Kind.RECEPTION_FAILURE,
+    interfaces.Outcome.TRANSMISSION_FAILURE:
+        packets.BackToFrontPacket.Kind.TRANSMISSION_FAILURE,
+    interfaces.Outcome.SERVICED_FAILURE:
+        packets.BackToFrontPacket.Kind.SERVICED_FAILURE,
+    interfaces.Outcome.SERVICER_FAILURE:
+        packets.BackToFrontPacket.Kind.SERVICER_FAILURE,
+}
 
 
 class _Packetizer(object):
@@ -120,24 +138,28 @@ class _FrontPacketizer(_Packetizer):
   def packetize(self, operation_id, sequence_number, payload, complete):
     """See _Packetizer.packetize for specification."""
     if sequence_number:
+      if complete:
+        kind = packets.FrontToBackPacket.Kind.COMPLETION
+      else:
+        kind = packets.FrontToBackPacket.Kind.CONTINUATION
       return packets.FrontToBackPacket(
-          operation_id, sequence_number,
-          packets.Kind.COMPLETION if complete else packets.Kind.CONTINUATION,
-          self._name, self._subscription_kind, self._trace_id, payload,
-          self._timeout)
+          operation_id, sequence_number, kind, self._name,
+          self._subscription_kind, self._trace_id, payload, self._timeout)
     else:
+      if complete:
+        kind = packets.FrontToBackPacket.Kind.ENTIRE
+      else:
+        kind = packets.FrontToBackPacket.Kind.COMMENCEMENT
       return packets.FrontToBackPacket(
-          operation_id, 0,
-          packets.Kind.ENTIRE if complete else packets.Kind.COMMENCEMENT,
-          self._name, self._subscription_kind, self._trace_id, payload,
-          self._timeout)
+          operation_id, 0, kind, self._name, self._subscription_kind,
+          self._trace_id, payload, self._timeout)
 
   def packetize_abortion(self, operation_id, sequence_number, outcome):
     """See _Packetizer.packetize_abortion for specification."""
     if outcome in _FRONT_TO_BACK_NO_TRANSMISSION_OUTCOMES:
       return None
     else:
-      kind = _ABORTION_OUTCOME_TO_PACKET_KIND[outcome]
+      kind = _ABORTION_OUTCOME_TO_FRONT_TO_BACK_PACKET_KIND[outcome]
       return packets.FrontToBackPacket(
           operation_id, sequence_number, kind, None, None, None, None, None)
 
@@ -147,17 +169,19 @@ class _BackPacketizer(_Packetizer):
 
   def packetize(self, operation_id, sequence_number, payload, complete):
     """See _Packetizer.packetize for specification."""
+    if complete:
+      kind = packets.BackToFrontPacket.Kind.COMPLETION
+    else:
+      kind = packets.BackToFrontPacket.Kind.CONTINUATION
     return packets.BackToFrontPacket(
-        operation_id, sequence_number,
-        packets.Kind.COMPLETION if complete else packets.Kind.CONTINUATION,
-        payload)
+        operation_id, sequence_number, kind, payload)
 
   def packetize_abortion(self, operation_id, sequence_number, outcome):
     """See _Packetizer.packetize_abortion for specification."""
     if outcome in _BACK_TO_FRONT_NO_TRANSMISSION_OUTCOMES:
       return None
     else:
-      kind = _ABORTION_OUTCOME_TO_PACKET_KIND[outcome]
+      kind = _ABORTION_OUTCOME_TO_BACK_TO_FRONT_PACKET_KIND[outcome]
       return packets.BackToFrontPacket(
           operation_id, sequence_number, kind, None)
 
diff --git a/src/python/src/grpc/framework/base/packets/packets.py b/src/python/src/grpc/framework/base/packets/packets.py
index 9e2d4080b8..d3f9a92aa0 100644
--- a/src/python/src/grpc/framework/base/packets/packets.py
+++ b/src/python/src/grpc/framework/base/packets/packets.py
@@ -36,22 +36,6 @@ import enum
 from grpc.framework.base import interfaces  # pylint: disable=unused-import
 
 
-@enum.unique
-class Kind(enum.Enum):
-  """Identifies the overall kind of a ticket."""
-
-  COMMENCEMENT = 'commencement'
-  CONTINUATION = 'continuation'
-  COMPLETION = 'completion'
-  ENTIRE = 'entire'
-  CANCELLATION = 'cancellation'
-  EXPIRATION = 'expiration'
-  SERVICER_FAILURE = 'servicer failure'
-  SERVICED_FAILURE = 'serviced failure'
-  RECEPTION_FAILURE = 'reception failure'
-  TRANSMISSION_FAILURE = 'transmission failure'
-
-
 class FrontToBackPacket(
     collections.namedtuple(
         'FrontToBackPacket',
@@ -66,9 +50,7 @@ class FrontToBackPacket(
       packet's place among all the packets sent from front to back for this
       particular operation. Must be zero if kind is Kind.COMMENCEMENT or
       Kind.ENTIRE. Must be positive for any other kind.
-    kind: One of Kind.COMMENCEMENT, Kind.CONTINUATION, Kind.COMPLETION,
-      Kind.ENTIRE, Kind.CANCELLATION, Kind.EXPIRATION, Kind.SERVICED_FAILURE,
-      Kind.RECEPTION_FAILURE, or Kind.TRANSMISSION_FAILURE.
+    kind: A Kind value describing the overall kind of ticket.
     name: The name of an operation. Must be present if kind is Kind.COMMENCEMENT
       or Kind.ENTIRE. Must be None for any other kind.
     subscription: An interfaces.ServicedSubscription.Kind value describing the
@@ -88,6 +70,21 @@ class FrontToBackPacket(
       operations.
   """
 
+  @enum.unique
+  class Kind(enum.Enum):
+    """Identifies the overall kind of a FrontToBackPacket."""
+
+    COMMENCEMENT = 'commencement'
+    CONTINUATION = 'continuation'
+    COMPLETION = 'completion'
+    ENTIRE = 'entire'
+    CANCELLATION = 'cancellation'
+    EXPIRATION = 'expiration'
+    SERVICER_FAILURE = 'servicer failure'
+    SERVICED_FAILURE = 'serviced failure'
+    RECEPTION_FAILURE = 'reception failure'
+    TRANSMISSION_FAILURE = 'transmission failure'
+
 
 class BackToFrontPacket(
     collections.namedtuple(
@@ -101,11 +98,21 @@ class BackToFrontPacket(
     sequence_number: A zero-indexed integer sequence number identifying the
       packet's place among all the packets sent from back to front for this
       particular operation.
-    kind: One of Kind.CONTINUATION, Kind.COMPLETION, Kind.EXPIRATION,
-      Kind.SERVICER_FAILURE, Kind.RECEPTION_FAILURE, or
-      Kind.TRANSMISSION_FAILURE.
+    kind: A Kind value describing the overall kind of ticket.
     payload: A customer payload object. Must be present if kind is
-      Kind.CONTINUATION. May be None if kind is Kind.COMPLETION. Must be None if
-      kind is Kind.EXPIRATION, Kind.SERVICER_FAILURE, Kind.RECEPTION_FAILURE, or
-      Kind.TRANSMISSION_FAILURE.
+      Kind.CONTINUATION. May be None if kind is Kind.COMPLETION. Must be None
+      otherwise.
   """
+
+  @enum.unique
+  class Kind(enum.Enum):
+    """Identifies the overall kind of a BackToFrontPacket."""
+
+    # TODO(issue 752): Add CANCELLATION.
+    CONTINUATION = 'continuation'
+    COMPLETION = 'completion'
+    EXPIRATION = 'expiration'
+    SERVICER_FAILURE = 'servicer failure'
+    SERVICED_FAILURE = 'serviced failure'
+    RECEPTION_FAILURE = 'reception failure'
+    TRANSMISSION_FAILURE = 'transmission failure'