diff --git a/internal/congestion/cubic_sender.go b/internal/congestion/cubic_sender.go
index 6f3d3289a..76706753e 100644
--- a/internal/congestion/cubic_sender.go
+++ b/internal/congestion/cubic_sender.go
@@ -66,7 +66,7 @@ var _ SendAlgorithm = &cubicSender{}
 var _ SendAlgorithmWithDebugInfo = &cubicSender{}
 
 // NewCubicSender makes a new cubic sender
-func NewCubicSender(clock Clock, rttStats *RTTStats, reno bool, initialCongestionWindow, initialMaxCongestionWindow protocol.ByteCount) SendAlgorithmWithDebugInfo {
+func NewCubicSender(clock Clock, rttStats *RTTStats, reno bool, initialCongestionWindow, initialMaxCongestionWindow protocol.ByteCount) *cubicSender {
 	return &cubicSender{
 		rttStats:                   rttStats,
 		initialCongestionWindow:    initialCongestionWindow,
diff --git a/internal/congestion/cubic_sender_test.go b/internal/congestion/cubic_sender_test.go
index de3b74fcc..1f1357dfd 100644
--- a/internal/congestion/cubic_sender_test.go
+++ b/internal/congestion/cubic_sender_test.go
@@ -26,7 +26,7 @@ const MaxCongestionWindow protocol.ByteCount = 200 * protocol.DefaultTCPMSS
 
 var _ = Describe("Cubic Sender", func() {
 	var (
-		sender            SendAlgorithmWithDebugInfo
+		sender            *cubicSender
 		clock             mockClock
 		bytesInFlight     protocol.ByteCount
 		packetNumber      protocol.PacketNumber
diff --git a/internal/congestion/interface.go b/internal/congestion/interface.go
index 7c27da64a..51e2e28dc 100644
--- a/internal/congestion/interface.go
+++ b/internal/congestion/interface.go
@@ -14,12 +14,7 @@ type SendAlgorithm interface {
 	MaybeExitSlowStart()
 	OnPacketAcked(number protocol.PacketNumber, ackedBytes protocol.ByteCount, priorInFlight protocol.ByteCount, eventTime time.Time)
 	OnPacketLost(number protocol.PacketNumber, lostBytes protocol.ByteCount, priorInFlight protocol.ByteCount)
-	SetNumEmulatedConnections(n int)
 	OnRetransmissionTimeout(packetsRetransmitted bool)
-	OnConnectionMigration()
-
-	// Experiments
-	SetSlowStartLargeReduction(enabled bool)
 }
 
 // SendAlgorithmWithDebugInfo adds some debug functions to SendAlgorithm
diff --git a/internal/mocks/congestion.go b/internal/mocks/congestion.go
index 774930eab..b98665931 100644
--- a/internal/mocks/congestion.go
+++ b/internal/mocks/congestion.go
@@ -61,18 +61,6 @@ func (mr *MockSendAlgorithmMockRecorder) MaybeExitSlowStart() *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "MaybeExitSlowStart", reflect.TypeOf((*MockSendAlgorithm)(nil).MaybeExitSlowStart))
 }
 
-// OnConnectionMigration mocks base method
-func (m *MockSendAlgorithm) OnConnectionMigration() {
-	m.ctrl.T.Helper()
-	m.ctrl.Call(m, "OnConnectionMigration")
-}
-
-// OnConnectionMigration indicates an expected call of OnConnectionMigration
-func (mr *MockSendAlgorithmMockRecorder) OnConnectionMigration() *gomock.Call {
-	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "OnConnectionMigration", reflect.TypeOf((*MockSendAlgorithm)(nil).OnConnectionMigration))
-}
-
 // OnPacketAcked mocks base method
 func (m *MockSendAlgorithm) OnPacketAcked(arg0 protocol.PacketNumber, arg1, arg2 protocol.ByteCount, arg3 time.Time) {
 	m.ctrl.T.Helper()
@@ -121,30 +109,6 @@ func (mr *MockSendAlgorithmMockRecorder) OnRetransmissionTimeout(arg0 interface{
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "OnRetransmissionTimeout", reflect.TypeOf((*MockSendAlgorithm)(nil).OnRetransmissionTimeout), arg0)
 }
 
-// SetNumEmulatedConnections mocks base method
-func (m *MockSendAlgorithm) SetNumEmulatedConnections(arg0 int) {
-	m.ctrl.T.Helper()
-	m.ctrl.Call(m, "SetNumEmulatedConnections", arg0)
-}
-
-// SetNumEmulatedConnections indicates an expected call of SetNumEmulatedConnections
-func (mr *MockSendAlgorithmMockRecorder) SetNumEmulatedConnections(arg0 interface{}) *gomock.Call {
-	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SetNumEmulatedConnections", reflect.TypeOf((*MockSendAlgorithm)(nil).SetNumEmulatedConnections), arg0)
-}
-
-// SetSlowStartLargeReduction mocks base method
-func (m *MockSendAlgorithm) SetSlowStartLargeReduction(arg0 bool) {
-	m.ctrl.T.Helper()
-	m.ctrl.Call(m, "SetSlowStartLargeReduction", arg0)
-}
-
-// SetSlowStartLargeReduction indicates an expected call of SetSlowStartLargeReduction
-func (mr *MockSendAlgorithmMockRecorder) SetSlowStartLargeReduction(arg0 interface{}) *gomock.Call {
-	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SetSlowStartLargeReduction", reflect.TypeOf((*MockSendAlgorithm)(nil).SetSlowStartLargeReduction), arg0)
-}
-
 // TimeUntilSend mocks base method
 func (m *MockSendAlgorithm) TimeUntilSend(arg0 protocol.ByteCount) time.Duration {
 	m.ctrl.T.Helper()