diff --git a/tests/test_peer/test_connection.py b/tests/test_peer/test_connection.py
index 16a9fa4..6713209 100644
--- a/tests/test_peer/test_connection.py
+++ b/tests/test_peer/test_connection.py
@@ -1858,6 +1858,568 @@ def _on_receive_sabm(frame):
     assert frames == [frame]
 
 
+# RR Notification transmission, scheduling and cancellation
+
+
+def test_cancel_rr_notification_notpending():
+    """
+    Test _cancel_rr_notification does nothing if not pending.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    assert peer._rr_notification_timeout_handle is None
+
+    peer._cancel_rr_notification()
+
+    assert peer._rr_notification_timeout_handle is None
+
+
+def test_cancel_rr_notification_ispending():
+    """
+    Test _cancel_rr_notification cancels a pending notification.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    timeout = DummyTimeout(0, lambda: None)
+    peer._rr_notification_timeout_handle = timeout
+
+    peer._cancel_rr_notification()
+
+    assert peer._rr_notification_timeout_handle is None
+    assert timeout.cancelled is True
+
+
+def test_schedule_rr_notification():
+    """
+    Test _schedule_rr_notification schedules a notification.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._schedule_rr_notification()
+
+    assert peer._rr_notification_timeout_handle is not None
+
+
+def test_send_rr_notification_connected():
+    """
+    Test _send_rr_notification sends a notification if connected.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    peer._state = AX25PeerState.CONNECTED
+
+    peer._send_rr_notification()
+
+    assert count == dict(update_recv_seq=1)
+    assert len(transmitted) == 1
+    assert isinstance(transmitted[0], AX258BitReceiveReadyFrame)
+
+
+def test_send_rr_notification_disconnected():
+    """
+    Test _send_rr_notification sends a notification if connected.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    peer._state = AX25PeerState.DISCONNECTED
+
+    peer._send_rr_notification()
+
+    assert count == dict(update_recv_seq=0)
+    assert len(transmitted) == 0
+
+
+# RNR transmission
+
+
+def test_send_rnr_notification_connected():
+    """
+    Test _send_rnr_notification sends a notification if connected.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    peer._state = AX25PeerState.CONNECTED
+
+    peer._send_rnr_notification()
+
+    assert count == dict(update_recv_seq=1)
+    assert len(transmitted) == 1
+    assert isinstance(transmitted[0], AX258BitReceiveNotReadyFrame)
+
+
+def test_send_rnr_notification_connected_recent():
+    """
+    Test _send_rnr_notification skips notification if the last was recent.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    peer._state = AX25PeerState.CONNECTED
+    peer._last_rnr_sent = peer._loop.time() - (peer._rnr_interval / 2)
+
+    peer._send_rnr_notification()
+
+    assert count == dict(update_recv_seq=0)
+    assert len(transmitted) == 0
+
+
+def test_send_rnr_notification_disconnected():
+    """
+    Test _send_rnr_notification sends a notification if connected.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    peer._state = AX25PeerState.DISCONNECTED
+
+    peer._send_rnr_notification()
+
+    assert count == dict(update_recv_seq=0)
+    assert len(transmitted) == 0
+
+
+# I-Frame transmission
+
+
+def test_send_next_iframe_max_outstanding():
+    """
+    Test I-frame transmission is suppressed if too many frames are pending.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_send_seq=0, update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    def _update_send_seq():
+        count["update_send_seq"] += 1
+
+    peer._update_send_seq = _update_send_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    state_updates = []
+
+    def _update_state(**kwargs):
+        state_updates.append(kwargs)
+
+    peer._update_state = _update_state
+
+    peer._state = AX25PeerState.CONNECTED
+    peer._pending_iframes = {
+        0: (0xF0, b"Frame 1"),
+        1: (0xF0, b"Frame 2"),
+        2: (0xF0, b"Frame 3"),
+        3: (0xF0, b"Frame 4"),
+        4: (0xF0, b"Frame 5"),
+        5: (0xF0, b"Frame 6"),
+        6: (0xF0, b"Frame 7"),
+        7: (0xF0, b"Frame 8"),
+    }
+    peer._max_outstanding = 8
+
+    peer._send_next_iframe()
+
+    assert count == dict(update_send_seq=0, update_recv_seq=0)
+    assert state_updates == []
+    assert transmitted == []
+
+
+def test_send_next_iframe_nothing_pending():
+    """
+    Test I-frame transmission is suppressed no data is pending.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_send_seq=0, update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    def _update_send_seq():
+        count["update_send_seq"] += 1
+
+    peer._update_send_seq = _update_send_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    state_updates = []
+
+    def _update_state(**kwargs):
+        state_updates.append(kwargs)
+
+    peer._update_state = _update_state
+
+    peer._state = AX25PeerState.CONNECTED
+    peer._pending_iframes = {
+        0: (0xF0, b"Frame 1"),
+        1: (0xF0, b"Frame 2"),
+        2: (0xF0, b"Frame 3"),
+        3: (0xF0, b"Frame 4"),
+    }
+    peer._max_outstanding = 8
+    peer._send_state = 4
+
+    peer._send_next_iframe()
+
+    assert count == dict(update_send_seq=0, update_recv_seq=0)
+    assert state_updates == []
+    assert transmitted == []
+
+
+def test_send_next_iframe_create_next():
+    """
+    Test I-frame transmission creates a new I-frame if there's data to send.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_send_seq=0, update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    def _update_send_seq():
+        count["update_send_seq"] += 1
+
+    peer._update_send_seq = _update_send_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    state_updates = []
+
+    def _update_state(prop, **kwargs):
+        kwargs["prop"] = prop
+        state_updates.append(kwargs)
+
+    peer._update_state = _update_state
+
+    peer._state = AX25PeerState.CONNECTED
+    peer._pending_iframes = {
+        0: (0xF0, b"Frame 1"),
+        1: (0xF0, b"Frame 2"),
+        2: (0xF0, b"Frame 3"),
+        3: (0xF0, b"Frame 4"),
+    }
+    peer._pending_data = [
+        (0xF0, b"Frame 5"),
+    ]
+    peer._max_outstanding = 8
+    peer._send_state = 4
+
+    peer._send_next_iframe()
+
+    assert peer._pending_iframes == {
+        0: (0xF0, b"Frame 1"),
+        1: (0xF0, b"Frame 2"),
+        2: (0xF0, b"Frame 3"),
+        3: (0xF0, b"Frame 4"),
+        4: (0xF0, b"Frame 5"),
+    }
+    assert peer._pending_data == []
+    assert count == dict(update_send_seq=1, update_recv_seq=1)
+    assert state_updates == [
+        dict(prop="_send_state", delta=1, comment="send next I-frame")
+    ]
+    assert transmitted[1:] == []
+    frame = transmitted.pop(0)
+    assert isinstance(frame, AX258BitInformationFrame)
+    assert frame.payload == b"Frame 5"
+
+
+def test_send_next_iframe_existing_next():
+    """
+    Test I-frame transmission sends existing next frame.
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    peer._init_connection(False)
+
+    count = dict(update_send_seq=0, update_recv_seq=0)
+
+    def _update_recv_seq():
+        count["update_recv_seq"] += 1
+
+    peer._update_recv_seq = _update_recv_seq
+
+    def _update_send_seq():
+        count["update_send_seq"] += 1
+
+    peer._update_send_seq = _update_send_seq
+
+    transmitted = []
+
+    def _transmit_frame(frame):
+        transmitted.append(frame)
+
+    peer._transmit_frame = _transmit_frame
+
+    state_updates = []
+
+    def _update_state(prop, **kwargs):
+        kwargs["prop"] = prop
+        state_updates.append(kwargs)
+
+    peer._update_state = _update_state
+
+    peer._state = AX25PeerState.CONNECTED
+    peer._pending_iframes = {
+        0: (0xF0, b"Frame 1"),
+        1: (0xF0, b"Frame 2"),
+        2: (0xF0, b"Frame 3"),
+        3: (0xF0, b"Frame 4"),
+    }
+    peer._pending_data = [
+        (0xF0, b"Frame 5"),
+    ]
+    peer._max_outstanding = 8
+    peer._send_state = 3
+
+    peer._send_next_iframe()
+
+    assert peer._pending_iframes == {
+        0: (0xF0, b"Frame 1"),
+        1: (0xF0, b"Frame 2"),
+        2: (0xF0, b"Frame 3"),
+        3: (0xF0, b"Frame 4"),
+    }
+    assert peer._pending_data == [
+        (0xF0, b"Frame 5"),
+    ]
+    assert count == dict(update_send_seq=1, update_recv_seq=1)
+    assert state_updates == [
+        dict(prop="_send_state", delta=1, comment="send next I-frame")
+    ]
+    assert transmitted[1:] == []
+    frame = transmitted.pop(0)
+    assert isinstance(frame, AX258BitInformationFrame)
+    assert frame.payload == b"Frame 4"
+
+
+# Sequence number state updates
+
+
+def test_update_send_seq():
+    """
+    Test _update_send_seq copies V(S) to N(S).
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    state_updates = []
+
+    def _update_state(prop, **kwargs):
+        kwargs["prop"] = prop
+        state_updates.append(kwargs)
+
+    peer._update_state = _update_state
+
+    peer._send_seq = 2
+    peer._send_state = 6
+
+    peer._update_send_seq()
+    assert state_updates == [
+        dict(prop="_send_seq", value=6, comment="from V(S)")
+    ]
+
+
+def test_update_recv_seq():
+    """
+    Test _update_recv_seq copies V(R) to N(R).
+    """
+    station = DummyStation(AX25Address("VK4MSL", ssid=1))
+    peer = TestingAX25Peer(
+        station=station,
+        address=AX25Address("VK4MSL"),
+        repeaters=AX25Path(),
+    )
+
+    state_updates = []
+
+    def _update_state(prop, **kwargs):
+        kwargs["prop"] = prop
+        state_updates.append(kwargs)
+
+    peer._update_state = _update_state
+
+    peer._recv_state = 6
+    peer._recv_seq = 2
+
+    peer._update_recv_seq()
+    assert state_updates == [
+        dict(prop="_recv_seq", value=6, comment="from V(R)")
+    ]
+
+
 # SABM(E) handling