diff --git a/api/data_channel_interface.h b/api/data_channel_interface.h
index 4f74918ff9..35ef8e4f0d 100644
--- a/api/data_channel_interface.h
+++ b/api/data_channel_interface.h
@@ -100,6 +100,17 @@ class DataChannelObserver {
   // The data channel's buffered_amount has changed.
   virtual void OnBufferedAmountChange(uint64_t sent_data_size) {}
 
+  // Override this to get callbacks directly on the network thread.
+  // An implementation that does that must not block the network thread
+  // but rather only use the callback to trigger asynchronous processing
+  // elsewhere as a result of the notification.
+  // The default return value, `false`, means that notifications will be
+  // delivered on the signaling thread associated with the peerconnection
+  // instance.
+  // TODO(webrtc:11547): Eventually all DataChannelObserver implementations
+  // should be called on the network thread and this method removed.
+  virtual bool IsOkToCallOnTheNetworkThread() { return false; }
+
  protected:
   virtual ~DataChannelObserver() = default;
 };
diff --git a/pc/data_channel_controller.cc b/pc/data_channel_controller.cc
index 36e8be1411..20d5fe98b0 100644
--- a/pc/data_channel_controller.cc
+++ b/pc/data_channel_controller.cc
@@ -29,8 +29,15 @@ DataChannelController::~DataChannelController() {
 }
 
 bool DataChannelController::HasDataChannelsForTest() const {
-  RTC_DCHECK_RUN_ON(signaling_thread());
-  return !sctp_data_channels_.empty();
+  auto has_channels = [&] {
+    RTC_DCHECK_RUN_ON(network_thread());
+    return !sctp_data_channels_n_.empty();
+  };
+
+  if (network_thread()->IsCurrent())
+    return has_channels();
+
+  return network_thread()->BlockingCall(std::move(has_channels));
 }
 
 bool DataChannelController::HasUsedDataChannels() const {
@@ -66,11 +73,15 @@ void DataChannelController::RemoveSctpDataStream(StreamId sid) {
 void DataChannelController::OnChannelStateChanged(
     SctpDataChannel* channel,
     DataChannelInterface::DataState state) {
-  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK_RUN_ON(network_thread());
   if (state == DataChannelInterface::DataState::kClosed)
     OnSctpDataChannelClosed(channel);
 
-  pc_->OnSctpDataChannelStateChanged(channel->internal_id(), state);
+  signaling_thread()->PostTask(
+      SafeTask(signaling_safety_.flag(),
+               [this, channel_id = channel->internal_id(), state = state] {
+                 pc_->OnSctpDataChannelStateChanged(channel_id, state);
+               }));
 }
 
 void DataChannelController::OnDataReceived(
@@ -82,27 +93,22 @@ void DataChannelController::OnDataReceived(
   if (HandleOpenMessage_n(channel_id, type, buffer))
     return;
 
-  signaling_thread()->PostTask(
-      SafeTask(signaling_safety_.flag(), [this, channel_id, type, buffer] {
-        RTC_DCHECK_RUN_ON(signaling_thread());
-        // TODO(bugs.webrtc.org/11547): The data being received should be
-        // delivered on the network thread.
-        auto it = FindChannel(StreamId(channel_id));
-        if (it != sctp_data_channels_.end())
-          (*it)->OnDataReceived(type, buffer);
-      }));
+  auto it = absl::c_find_if(sctp_data_channels_n_, [&](const auto& c) {
+    return c->sid_n().stream_id_int() == channel_id;
+  });
+
+  if (it != sctp_data_channels_n_.end())
+    (*it)->OnDataReceived(type, buffer);
 }
 
 void DataChannelController::OnChannelClosing(int channel_id) {
   RTC_DCHECK_RUN_ON(network_thread());
-  signaling_thread()->PostTask(
-      SafeTask(signaling_safety_.flag(), [this, channel_id] {
-        RTC_DCHECK_RUN_ON(signaling_thread());
-        // TODO(bugs.webrtc.org/11547): Should run on the network thread.
-        auto it = FindChannel(StreamId(channel_id));
-        if (it != sctp_data_channels_.end())
-          (*it)->OnClosingProcedureStartedRemotely();
-      }));
+  auto it = absl::c_find_if(sctp_data_channels_n_, [&](const auto& c) {
+    return c->sid_n().stream_id_int() == channel_id;
+  });
+
+  if (it != sctp_data_channels_n_.end())
+    (*it)->OnClosingProcedureStartedRemotely();
 }
 
 void DataChannelController::OnChannelClosed(int channel_id) {
@@ -112,48 +118,44 @@ void DataChannelController::OnChannelClosed(int channel_id) {
   auto it = absl::c_find_if(sctp_data_channels_n_,
                             [&](const auto& c) { return c->sid_n() == sid; });
 
-  if (it != sctp_data_channels_n_.end())
+  if (it != sctp_data_channels_n_.end()) {
+    rtc::scoped_refptr<SctpDataChannel> channel = std::move(*it);
     sctp_data_channels_n_.erase(it);
-
-  signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this, sid] {
-    RTC_DCHECK_RUN_ON(signaling_thread());
-    auto it = FindChannel(sid);
-    // Remove the channel from our list, close it and free up resources.
-    if (it != sctp_data_channels_.end()) {
-      rtc::scoped_refptr<SctpDataChannel> channel = std::move(*it);
-      // Note: this causes OnSctpDataChannelClosed() to not do anything
-      // when called from within `OnClosingProcedureComplete`.
-      sctp_data_channels_.erase(it);
-
-      channel->OnClosingProcedureComplete();
-    }
-  }));
+    channel->OnClosingProcedureComplete();
+  }
 }
 
 void DataChannelController::OnReadyToSend() {
   RTC_DCHECK_RUN_ON(network_thread());
-  signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this] {
-    RTC_DCHECK_RUN_ON(signaling_thread());
-    auto copy = sctp_data_channels_;
-    for (const auto& channel : copy)
+  auto copy = sctp_data_channels_n_;
+  for (const auto& channel : copy) {
+    if (channel->sid_n().HasValue()) {
       channel->OnTransportReady();
-  }));
+    } else {
+      // This happens for role==SSL_SERVER channels when we get notified by
+      // the transport *before* the SDP code calls `AllocateSctpSids` to
+      // trigger assignment of sids. In this case OnTransportReady() will be
+      // called from within `AllocateSctpSids` below.
+      RTC_LOG(LS_INFO) << "OnReadyToSend: Still waiting for an id for channel.";
+    }
+  }
 }
 
 void DataChannelController::OnTransportClosed(RTCError error) {
   RTC_DCHECK_RUN_ON(network_thread());
-  signaling_thread()->PostTask(
-      SafeTask(signaling_safety_.flag(), [this, error] {
-        RTC_DCHECK_RUN_ON(signaling_thread());
-        OnTransportChannelClosed(error);
-      }));
+  // This loop will close all data channels and trigger a callback to
+  // `OnSctpDataChannelClosed` which will modify `sctp_data_channels_n_`, so
+  // we create a local copy while we do the fan-out.
+  auto copy = sctp_data_channels_n_;
+  for (const auto& channel : copy)
+    channel->OnTransportChannelClosed(error);
 }
 
 void DataChannelController::SetupDataChannelTransport_n() {
   RTC_DCHECK_RUN_ON(network_thread());
 
   // There's a new data channel transport.  This needs to be signaled to the
-  // `sctp_data_channels_` so that they can reopen and reconnect.  This is
+  // `sctp_data_channels_n_` so that they can reopen and reconnect.  This is
   // necessary when bundling is applied.
   NotifyDataChannelsOfTransportCreated();
 }
@@ -165,11 +167,12 @@ void DataChannelController::PrepareForShutdown() {
 
 void DataChannelController::TeardownDataChannelTransport_n() {
   RTC_DCHECK_RUN_ON(network_thread());
-  if (data_channel_transport()) {
-    data_channel_transport()->SetDataSink(nullptr);
+  if (data_channel_transport_) {
+    data_channel_transport_->SetDataSink(nullptr);
+    set_data_channel_transport(nullptr);
   }
-  set_data_channel_transport(nullptr);
   sctp_data_channels_n_.clear();
+  weak_factory_.InvalidateWeakPtrs();
 }
 
 void DataChannelController::OnTransportChanged(
@@ -185,7 +188,7 @@ void DataChannelController::OnTransportChanged(
       new_data_channel_transport->SetDataSink(this);
 
       // There's a new data channel transport.  This needs to be signaled to the
-      // `sctp_data_channels_` so that they can reopen and reconnect.  This is
+      // `sctp_data_channels_n_` so that they can reopen and reconnect.  This is
       // necessary when bundling is applied.
       NotifyDataChannelsOfTransportCreated();
     }
@@ -194,10 +197,10 @@ void DataChannelController::OnTransportChanged(
 
 std::vector<DataChannelStats> DataChannelController::GetDataChannelStats()
     const {
-  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK_RUN_ON(network_thread());
   std::vector<DataChannelStats> stats;
-  stats.reserve(sctp_data_channels_.size());
-  for (const auto& channel : sctp_data_channels_)
+  stats.reserve(sctp_data_channels_n_.size());
+  for (const auto& channel : sctp_data_channels_n_)
     stats.push_back(channel->GetStats());
   return stats;
 }
@@ -219,28 +222,38 @@ bool DataChannelController::HandleOpenMessage_n(
                         << channel_id;
   } else {
     config.open_handshake_role = InternalDataChannelInit::kAcker;
-    signaling_thread()->PostTask(
-        SafeTask(signaling_safety_.flag(),
-                 [this, label = std::move(label), config = std::move(config)] {
-                   RTC_DCHECK_RUN_ON(signaling_thread());
-                   OnDataChannelOpenMessage(label, config);
-                 }));
+    auto channel_or_error = CreateDataChannel(label, config);
+    if (channel_or_error.ok()) {
+      signaling_thread()->PostTask(SafeTask(
+          signaling_safety_.flag(),
+          [this, channel = channel_or_error.MoveValue(),
+           ready_to_send = data_channel_transport_->IsReadyToSend()] {
+            RTC_DCHECK_RUN_ON(signaling_thread());
+            OnDataChannelOpenMessage(std::move(channel), ready_to_send);
+          }));
+    } else {
+      RTC_LOG(LS_ERROR) << "Failed to create DataChannel from the OPEN message."
+                        << ToString(channel_or_error.error().type());
+    }
   }
   return true;
 }
 
 void DataChannelController::OnDataChannelOpenMessage(
-    const std::string& label,
-    const InternalDataChannelInit& config) {
-  auto channel_or_error = InternalCreateDataChannelWithProxy(label, config);
-  if (!channel_or_error.ok()) {
-    RTC_LOG(LS_ERROR) << "Failed to create DataChannel from the OPEN message."
-                      << ToString(channel_or_error.error().type());
-    return;
-  }
+    rtc::scoped_refptr<SctpDataChannel> channel,
+    bool ready_to_send) {
+  has_used_data_channels_ = true;
+  auto proxy = SctpDataChannel::CreateProxy(channel);
 
-  pc_->Observer()->OnDataChannel(channel_or_error.MoveValue());
+  pc_->Observer()->OnDataChannel(proxy);
   pc_->NoteDataAddedEvent();
+
+  if (ready_to_send) {
+    network_thread()->PostTask([channel = std::move(channel)] {
+      if (channel->state() != DataChannelInterface::DataState::kClosed)
+        channel->OnTransportReady();
+    });
+  }
 }
 
 // RTC_RUN_ON(network_thread())
@@ -269,6 +282,31 @@ RTCError DataChannelController::ReserveOrAllocateSid(
   return RTCError::OK();
 }
 
+// RTC_RUN_ON(network_thread())
+RTCErrorOr<rtc::scoped_refptr<SctpDataChannel>>
+DataChannelController::CreateDataChannel(const std::string& label,
+                                         InternalDataChannelInit& config) {
+  StreamId sid(config.id);
+  RTCError err = ReserveOrAllocateSid(sid, config.fallback_ssl_role);
+  if (!err.ok())
+    return err;
+
+  // In case `sid` has changed. Update `config` accordingly.
+  config.id = sid.stream_id_int();
+
+  rtc::scoped_refptr<SctpDataChannel> channel = SctpDataChannel::Create(
+      weak_factory_.GetWeakPtr(), label, data_channel_transport_ != nullptr,
+      config, signaling_thread(), network_thread());
+  RTC_DCHECK(channel);
+  sctp_data_channels_n_.push_back(channel);
+
+  // If we have an id already, notify the transport.
+  if (sid.HasValue())
+    AddSctpDataStream(sid);
+
+  return channel;
+}
+
 RTCErrorOr<rtc::scoped_refptr<DataChannelInterface>>
 DataChannelController::InternalCreateDataChannelWithProxy(
     const std::string& label,
@@ -283,29 +321,25 @@ DataChannelController::InternalCreateDataChannelWithProxy(
   bool ready_to_send = false;
   InternalDataChannelInit new_config = config;
   StreamId sid(new_config.id);
-  auto weak_ptr = weak_factory_.GetWeakPtr();
-  RTC_DCHECK(weak_ptr);  // Associate with current thread.
   auto ret = network_thread()->BlockingCall(
       [&]() -> RTCErrorOr<rtc::scoped_refptr<SctpDataChannel>> {
         RTC_DCHECK_RUN_ON(network_thread());
-        RTCError err = ReserveOrAllocateSid(sid, new_config.fallback_ssl_role);
-        if (!err.ok())
-          return err;
-
-        // In case `sid` has changed. Update `new_config` accordingly.
-        new_config.id = sid.stream_id_int();
+        auto channel = CreateDataChannel(label, new_config);
+        if (!channel.ok())
+          return channel;
         ready_to_send =
             data_channel_transport_ && data_channel_transport_->IsReadyToSend();
-
-        rtc::scoped_refptr<SctpDataChannel> channel(SctpDataChannel::Create(
-            std::move(weak_ptr), label, data_channel_transport_ != nullptr,
-            new_config, signaling_thread(), network_thread()));
-        RTC_DCHECK(channel);
-        sctp_data_channels_n_.push_back(channel);
-
-        // If we have an id already, notify the transport.
-        if (sid.HasValue())
-          AddSctpDataStream(sid);
+        if (ready_to_send) {
+          // If the transport is ready to send because the initial channel
+          // ready signal may have been sent before the DataChannel creation.
+          // This has to be done async because the upper layer objects (e.g.
+          // Chrome glue and WebKit) are not wired up properly until after
+          // `InternalCreateDataChannelWithProxy` returns.
+          network_thread()->PostTask([channel = channel.value()] {
+            if (channel->state() != DataChannelInterface::DataState::kClosed)
+              channel->OnTransportReady();
+          });
+        }
 
         return channel;
       });
@@ -313,114 +347,71 @@ DataChannelController::InternalCreateDataChannelWithProxy(
   if (!ret.ok())
     return ret.MoveError();
 
-  if (ready_to_send) {
-    // Checks if the transport is ready to send because the initial channel
-    // ready signal may have been sent before the DataChannel creation.
-    // This has to be done async because the upper layer objects (e.g.
-    // Chrome glue and WebKit) are not wired up properly until after this
-    // function returns.
-    signaling_thread()->PostTask(
-        SafeTask(signaling_safety_.flag(), [channel = ret.value()] {
-          if (channel->state() != DataChannelInterface::DataState::kClosed)
-            channel->OnTransportReady();
-        }));
-  }
-
-  sctp_data_channels_.push_back(ret.value());
   has_used_data_channels_ = true;
   return SctpDataChannel::CreateProxy(ret.MoveValue());
 }
 
 void DataChannelController::AllocateSctpSids(rtc::SSLRole role) {
-  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK_RUN_ON(network_thread());
+
+  const bool ready_to_send =
+      data_channel_transport_ && data_channel_transport_->IsReadyToSend();
 
   std::vector<std::pair<SctpDataChannel*, StreamId>> channels_to_update;
   std::vector<rtc::scoped_refptr<SctpDataChannel>> channels_to_close;
-
-  network_thread()->BlockingCall([&] {
-    RTC_DCHECK_RUN_ON(network_thread());
-    for (auto it = sctp_data_channels_n_.begin();
-         it != sctp_data_channels_n_.end();) {
-      if (!(*it)->sid_n().HasValue()) {
-        StreamId sid = sid_allocator_.AllocateSid(role);
-        if (sid.HasValue()) {
-          (*it)->SetSctpSid_n(sid);
-          AddSctpDataStream(sid);
-          channels_to_update.push_back(std::make_pair((*it).get(), sid));
-        } else {
-          channels_to_close.push_back(std::move(*it));
-          it = sctp_data_channels_n_.erase(it);
-          continue;
+  for (auto it = sctp_data_channels_n_.begin();
+       it != sctp_data_channels_n_.end();) {
+    if (!(*it)->sid_n().HasValue()) {
+      StreamId sid = sid_allocator_.AllocateSid(role);
+      if (sid.HasValue()) {
+        (*it)->SetSctpSid_n(sid);
+        AddSctpDataStream(sid);
+        if (ready_to_send) {
+          RTC_LOG(LS_INFO) << "AllocateSctpSids: Id assigned, ready to send.";
+          (*it)->OnTransportReady();
         }
+        channels_to_update.push_back(std::make_pair((*it).get(), sid));
+      } else {
+        channels_to_close.push_back(std::move(*it));
+        it = sctp_data_channels_n_.erase(it);
+        continue;
       }
-      ++it;
     }
-  });
+    ++it;
+  }
 
   // Since closing modifies the list of channels, we have to do the actual
   // closing outside the loop.
   for (const auto& channel : channels_to_close) {
     channel->CloseAbruptlyWithDataChannelFailure("Failed to allocate SCTP SID");
-    // The channel should now have been removed from sctp_data_channels_.
-    RTC_DCHECK(absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
-                 return c.get() == channel.get();
-               }) == sctp_data_channels_.end());
-  }
-
-  for (auto& pair : channels_to_update) {
-    auto it = absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
-      return c.get() == pair.first;
-    });
-    RTC_DCHECK(it != sctp_data_channels_.end());
-    (*it)->SetSctpSid_s(pair.second);
   }
 }
 
 void DataChannelController::OnSctpDataChannelClosed(SctpDataChannel* channel) {
-  RTC_DCHECK_RUN_ON(signaling_thread());
-
-  network_thread()->BlockingCall([&] {
-    RTC_DCHECK_RUN_ON(network_thread());
-    // After the closing procedure is done, it's safe to use this ID for
-    // another data channel.
-    if (channel->sid_n().HasValue()) {
-      sid_allocator_.ReleaseSid(channel->sid_n());
-    }
-
-    auto it = absl::c_find_if(sctp_data_channels_n_, [&](const auto& c) {
-      return c.get() == channel;
-    });
-
-    if (it != sctp_data_channels_n_.end())
-      sctp_data_channels_n_.erase(it);
-  });
-
-  for (auto it = sctp_data_channels_.begin(); it != sctp_data_channels_.end();
-       ++it) {
-    if (it->get() == channel) {
-      // Since this method is triggered by a signal from the DataChannel,
-      // we can't free it directly here; we need to free it asynchronously.
-      rtc::scoped_refptr<SctpDataChannel> release = std::move(*it);
-      sctp_data_channels_.erase(it);
-      signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(),
-                                            [release = std::move(release)] {}));
-      return;
-    }
+  RTC_DCHECK_RUN_ON(network_thread());
+  // After the closing procedure is done, it's safe to use this ID for
+  // another data channel.
+  if (channel->sid_n().HasValue()) {
+    sid_allocator_.ReleaseSid(channel->sid_n());
   }
+  auto it = absl::c_find_if(sctp_data_channels_n_,
+                            [&](const auto& c) { return c.get() == channel; });
+  if (it != sctp_data_channels_n_.end())
+    sctp_data_channels_n_.erase(it);
 }
 
 void DataChannelController::OnTransportChannelClosed(RTCError error) {
-  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK_RUN_ON(network_thread());
   // Use a temporary copy of the SCTP DataChannel list because the
   // DataChannel may callback to us and try to modify the list.
   // TODO(tommi): `OnTransportChannelClosed` is called from
   // `SdpOfferAnswerHandler::DestroyDataChannelTransport` just before
   // `TeardownDataChannelTransport_n` is called (but on the network thread) from
-  // the same function. Once `sctp_data_channels_` moves to the network thread,
-  // we can get rid of this function (OnTransportChannelClosed) and run this
-  // loop from within the TeardownDataChannelTransport_n callback.
+  // the same function. We can now get rid of this function
+  // (OnTransportChannelClosed) and run this loop from within the
+  // TeardownDataChannelTransport_n callback.
   std::vector<rtc::scoped_refptr<SctpDataChannel>> temp_sctp_dcs;
-  temp_sctp_dcs.swap(sctp_data_channels_);
+  temp_sctp_dcs.swap(sctp_data_channels_n_);
   for (const auto& channel : temp_sctp_dcs) {
     channel->OnTransportChannelClosed(error);
   }
@@ -444,16 +435,10 @@ RTCError DataChannelController::DataChannelSendData(
     StreamId sid,
     const SendDataParams& params,
     const rtc::CopyOnWriteBuffer& payload) {
-  // TODO(bugs.webrtc.org/11547): Expect method to be called on the network
-  // thread instead. Remove the BlockingCall() below and move associated state
-  // to the network thread.
-  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK_RUN_ON(network_thread());
   RTC_DCHECK(data_channel_transport());
-
-  return network_thread()->BlockingCall([this, sid, params, payload] {
-    return data_channel_transport()->SendData(sid.stream_id_int(), params,
-                                              payload);
-  });
+  return data_channel_transport()->SendData(sid.stream_id_int(), params,
+                                            payload);
 }
 
 void DataChannelController::NotifyDataChannelsOfTransportCreated() {
@@ -463,22 +448,8 @@ void DataChannelController::NotifyDataChannelsOfTransportCreated() {
   for (const auto& channel : sctp_data_channels_n_) {
     if (channel->sid_n().HasValue())
       AddSctpDataStream(channel->sid_n());
+    channel->OnTransportChannelCreated();
   }
-
-  signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this] {
-    RTC_DCHECK_RUN_ON(signaling_thread());
-    for (const auto& channel : sctp_data_channels_) {
-      channel->OnTransportChannelCreated();
-    }
-  }));
-}
-
-std::vector<rtc::scoped_refptr<SctpDataChannel>>::iterator
-DataChannelController::FindChannel(StreamId stream_id) {
-  RTC_DCHECK_RUN_ON(signaling_thread());
-  return absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
-    return c->sid_s() == stream_id;
-  });
 }
 
 rtc::Thread* DataChannelController::network_thread() const {
diff --git a/pc/data_channel_controller.h b/pc/data_channel_controller.h
index fa6c13e6ec..074b1feadb 100644
--- a/pc/data_channel_controller.h
+++ b/pc/data_channel_controller.h
@@ -107,6 +107,11 @@ class DataChannelController : public SctpDataChannelControllerInterface,
   rtc::Thread* signaling_thread() const;
 
  private:
+  // Creates a new SctpDataChannel object on the network thread.
+  RTCErrorOr<rtc::scoped_refptr<SctpDataChannel>> CreateDataChannel(
+      const std::string& label,
+      InternalDataChannelInit& config) RTC_RUN_ON(network_thread());
+
   // Parses and handles open messages.  Returns true if the message is an open
   // message and should be considered to be handled, false otherwise.
   bool HandleOpenMessage_n(int channel_id,
@@ -114,8 +119,8 @@ class DataChannelController : public SctpDataChannelControllerInterface,
                            const rtc::CopyOnWriteBuffer& buffer)
       RTC_RUN_ON(network_thread());
   // Called when a valid data channel OPEN message is received.
-  void OnDataChannelOpenMessage(const std::string& label,
-                                const InternalDataChannelInit& config)
+  void OnDataChannelOpenMessage(rtc::scoped_refptr<SctpDataChannel> channel,
+                                bool ready_to_send)
       RTC_RUN_ON(signaling_thread());
 
   // Accepts a `StreamId` which may be pre-negotiated or unassigned. For
@@ -139,9 +144,6 @@ class DataChannelController : public SctpDataChannelControllerInterface,
   // (calls OnTransportChannelCreated on the signaling thread).
   void NotifyDataChannelsOfTransportCreated();
 
-  std::vector<rtc::scoped_refptr<SctpDataChannel>>::iterator FindChannel(
-      StreamId stream_id);
-
   // Plugin transport used for data channels.  Pointer may be accessed and
   // checked from any thread, but the object may only be touched on the
   // network thread.
@@ -149,21 +151,16 @@ class DataChannelController : public SctpDataChannelControllerInterface,
   // thread.
   DataChannelTransportInterface* data_channel_transport_ = nullptr;
   SctpSidAllocator sid_allocator_ RTC_GUARDED_BY(network_thread());
-  std::vector<rtc::scoped_refptr<SctpDataChannel>> sctp_data_channels_
-      RTC_GUARDED_BY(signaling_thread());
-  // TODO(bugs.webrtc.org/11547): This vector will eventually take over from
-  // `sctp_data_channels_`. While we're migrating away from thread hops
-  // between the signaling and network threads, we need both, so this is
-  // a temporary situation.
   std::vector<rtc::scoped_refptr<SctpDataChannel>> sctp_data_channels_n_
       RTC_GUARDED_BY(network_thread());
   bool has_used_data_channels_ RTC_GUARDED_BY(signaling_thread()) = false;
 
   // Owning PeerConnection.
   PeerConnectionInternal* const pc_;
-  // The weak pointers must be dereferenced and invalidated on the signalling
+  // The weak pointers must be dereferenced and invalidated on the network
   // thread only.
-  rtc::WeakPtrFactory<DataChannelController> weak_factory_{this};
+  rtc::WeakPtrFactory<DataChannelController> weak_factory_
+      RTC_GUARDED_BY(network_thread()){this};
   ScopedTaskSafety signaling_safety_;
 };
 
diff --git a/pc/data_channel_controller_unittest.cc b/pc/data_channel_controller_unittest.cc
index 9b66faccd4..fd3deae0d7 100644
--- a/pc/data_channel_controller_unittest.cc
+++ b/pc/data_channel_controller_unittest.cc
@@ -131,44 +131,6 @@ TEST_F(DataChannelControllerTest, CloseAfterControllerDestroyed) {
   channel->Close();
 }
 
-TEST_F(DataChannelControllerTest, AsyncChannelCloseTeardown) {
-  DataChannelControllerForTest dcc(pc_.get());
-  auto ret = dcc.InternalCreateDataChannelWithProxy(
-      "label", InternalDataChannelInit(DataChannelInit()));
-  ASSERT_TRUE(ret.ok());
-  auto channel = ret.MoveValue();
-  SctpDataChannel* inner_channel =
-      DowncastProxiedDataChannelInterfaceToSctpDataChannelForTesting(
-          channel.get());
-  // Grab a reference for testing purposes.
-  inner_channel->AddRef();
-
-  channel = nullptr;  // dcc still holds a reference to `channel`.
-  EXPECT_TRUE(dcc.HasDataChannelsForTest());
-
-  // Trigger a Close() for the channel. This will send events back to dcc,
-  // eventually reaching `OnSctpDataChannelClosed` where dcc removes
-  // the channel from the internal list of data channels, but does not release
-  // the reference synchronously since that reference might be the last one.
-  inner_channel->Close();
-  // Now there should be no tracked data channels.
-  EXPECT_FALSE(dcc.HasDataChannelsForTest());
-  // But there should be an async operation queued that still holds a reference.
-  // That means that the test reference, must not be the last one.
-  ASSERT_NE(inner_channel->Release(),
-            rtc::RefCountReleaseStatus::kDroppedLastRef);
-  // Grab a reference again (using the pointer is safe since the object still
-  // exists and we control the single-threaded environment manually).
-  inner_channel->AddRef();
-  // Now run the queued up async operations on the signaling (current) thread.
-  // This time, the reference formerly owned by dcc, should be release and the
-  // truly last reference is now held by the test.
-  run_loop_.Flush();
-  // Check that this is the last reference.
-  EXPECT_EQ(inner_channel->Release(),
-            rtc::RefCountReleaseStatus::kDroppedLastRef);
-}
-
 // Allocate the maximum number of data channels and then one more.
 // The last allocation should fail.
 TEST_F(DataChannelControllerTest, MaxChannels) {
diff --git a/pc/data_channel_unittest.cc b/pc/data_channel_unittest.cc
index fe75d385f3..2582561282 100644
--- a/pc/data_channel_unittest.cc
+++ b/pc/data_channel_unittest.cc
@@ -40,18 +40,19 @@ static constexpr int kDefaultTimeout = 10000;
 
 class FakeDataChannelObserver : public DataChannelObserver {
  public:
-  FakeDataChannelObserver()
-      : messages_received_(0),
-        on_state_change_count_(0),
-        on_buffered_amount_change_count_(0) {}
+  FakeDataChannelObserver() {
+    // This implementation relies on the SctpDataChannel::ObserverAdapter
+    // implementation to post events to the signaling thread.
+    RTC_DCHECK(!IsOkToCallOnTheNetworkThread());
+  }
 
-  void OnStateChange() { ++on_state_change_count_; }
+  void OnStateChange() override { ++on_state_change_count_; }
 
-  void OnBufferedAmountChange(uint64_t previous_amount) {
+  void OnBufferedAmountChange(uint64_t previous_amount) override {
     ++on_buffered_amount_change_count_;
   }
 
-  void OnMessage(const DataBuffer& buffer) { ++messages_received_; }
+  void OnMessage(const DataBuffer& buffer) override { ++messages_received_; }
 
   size_t messages_received() const { return messages_received_; }
 
@@ -68,9 +69,9 @@ class FakeDataChannelObserver : public DataChannelObserver {
   }
 
  private:
-  size_t messages_received_;
-  size_t on_state_change_count_;
-  size_t on_buffered_amount_change_count_;
+  size_t messages_received_ = 0u;
+  size_t on_state_change_count_ = 0u;
+  size_t on_buffered_amount_change_count_ = 0u;
 };
 
 class SctpDataChannelTest : public ::testing::Test {
@@ -93,11 +94,17 @@ class SctpDataChannelTest : public ::testing::Test {
 
   void SetChannelReady() {
     controller_->set_transport_available(true);
-    inner_channel_->OnTransportChannelCreated();
-    if (!inner_channel_->sid_s().HasValue()) {
-      SetChannelSid(inner_channel_, StreamId(0));
-    }
+    StreamId sid(0);
+    network_thread_.BlockingCall([&]() {
+      RTC_DCHECK_RUN_ON(&network_thread_);
+      if (!inner_channel_->sid_n().HasValue()) {
+        inner_channel_->SetSctpSid_n(sid);
+        controller_->AddSctpDataStream(sid);
+      }
+      inner_channel_->OnTransportChannelCreated();
+    });
     controller_->set_ready_to_send(true);
+    run_loop_.Flush();
   }
 
   // TODO(bugs.webrtc.org/11547): This mirrors what the DataChannelController
@@ -108,9 +115,10 @@ class SctpDataChannelTest : public ::testing::Test {
   void SetChannelSid(const rtc::scoped_refptr<SctpDataChannel>& channel,
                      StreamId sid) {
     RTC_DCHECK(sid.HasValue());
-    network_thread_.BlockingCall(
-        [&]() { controller_->AddSctpDataStream(sid); });
-    channel->SetSctpSid_s(sid);
+    network_thread_.BlockingCall([&]() {
+      channel->SetSctpSid_n(sid);
+      controller_->AddSctpDataStream(sid);
+    });
   }
 
   void AddObserver() {
@@ -146,11 +154,13 @@ TEST_F(SctpDataChannelTest, VerifyConfigurationGetters) {
 
   // Check the non-const part of the configuration.
   EXPECT_EQ(channel_->id(), init_.id);
-  EXPECT_EQ(inner_channel_->sid_s(), StreamId());
+  network_thread_.BlockingCall(
+      [&]() { EXPECT_EQ(inner_channel_->sid_n(), StreamId()); });
 
   SetChannelReady();
   EXPECT_EQ(channel_->id(), 0);
-  EXPECT_EQ(inner_channel_->sid_s(), StreamId(0));
+  network_thread_.BlockingCall(
+      [&]() { EXPECT_EQ(inner_channel_->sid_n(), StreamId(0)); });
 }
 
 // Verifies that the data channel is connected to the transport after creation.
@@ -158,13 +168,15 @@ TEST_F(SctpDataChannelTest, ConnectedToTransportOnCreated) {
   controller_->set_transport_available(true);
   rtc::scoped_refptr<SctpDataChannel> dc =
       controller_->CreateDataChannel("test1", init_);
-
   EXPECT_TRUE(controller_->IsConnected(dc.get()));
+
   // The sid is not set yet, so it should not have added the streams.
-  EXPECT_FALSE(controller_->IsStreamAdded(dc->sid_s()));
+  StreamId sid = network_thread_.BlockingCall([&]() { return dc->sid_n(); });
+  EXPECT_FALSE(controller_->IsStreamAdded(sid));
 
   SetChannelSid(dc, StreamId(0));
-  EXPECT_TRUE(controller_->IsStreamAdded(dc->sid_s()));
+  sid = network_thread_.BlockingCall([&]() { return dc->sid_n(); });
+  EXPECT_TRUE(controller_->IsStreamAdded(sid));
 }
 
 // Tests the state of the data channel.
@@ -183,7 +195,7 @@ TEST_F(SctpDataChannelTest, StateTransition) {
   channel_->Close();
   // The (simulated) transport close notifications runs on the network thread
   // and posts a completion notification to the signaling (current) thread.
-  // Allow that ooperation to complete before checking the state.
+  // Allow that operation to complete before checking the state.
   run_loop_.Flush();
   EXPECT_EQ(DataChannelInterface::kClosed, channel_->state());
   EXPECT_EQ(observer_->on_state_change_count(), 3u);
@@ -201,6 +213,7 @@ TEST_F(SctpDataChannelTest, BufferedAmountWhenBlocked) {
   EXPECT_TRUE(channel_->Send(buffer));
   size_t successful_send_count = 1;
 
+  run_loop_.Flush();
   EXPECT_EQ(0U, channel_->buffered_amount());
   EXPECT_EQ(successful_send_count,
             observer_->on_buffered_amount_change_count());
@@ -217,6 +230,7 @@ TEST_F(SctpDataChannelTest, BufferedAmountWhenBlocked) {
             observer_->on_buffered_amount_change_count());
 
   controller_->set_send_blocked(false);
+  run_loop_.Flush();
   successful_send_count += number_of_packets;
   EXPECT_EQ(0U, channel_->buffered_amount());
   EXPECT_EQ(successful_send_count,
@@ -337,10 +351,9 @@ TEST_F(SctpDataChannelTest, LateCreatedChannelTransitionToOpen) {
   SetChannelReady();
   InternalDataChannelInit init;
   init.id = 1;
-  rtc::scoped_refptr<SctpDataChannel> dc =
-      controller_->CreateDataChannel("test1", init);
-  EXPECT_EQ(DataChannelInterface::kConnecting, dc->state());
-  EXPECT_TRUE_WAIT(DataChannelInterface::kOpen == dc->state(), 1000);
+  auto dc = webrtc::SctpDataChannel::CreateProxy(
+      controller_->CreateDataChannel("test1", init));
+  EXPECT_EQ(DataChannelInterface::kOpen, dc->state());
 }
 
 // Tests that an unordered DataChannel sends data as ordered until the OPEN_ACK
@@ -352,21 +365,23 @@ TEST_F(SctpDataChannelTest, SendUnorderedAfterReceivesOpenAck) {
   init.ordered = false;
   rtc::scoped_refptr<SctpDataChannel> dc =
       controller_->CreateDataChannel("test1", init);
+  auto proxy = webrtc::SctpDataChannel::CreateProxy(dc);
 
-  EXPECT_EQ_WAIT(DataChannelInterface::kOpen, dc->state(), 1000);
+  EXPECT_EQ_WAIT(DataChannelInterface::kOpen, proxy->state(), 1000);
 
   // Sends a message and verifies it's ordered.
   DataBuffer buffer("some data");
-  ASSERT_TRUE(dc->Send(buffer));
+  ASSERT_TRUE(proxy->Send(buffer));
   EXPECT_TRUE(controller_->last_send_data_params().ordered);
 
   // Emulates receiving an OPEN_ACK message.
   rtc::CopyOnWriteBuffer payload;
   WriteDataChannelOpenAckMessage(&payload);
-  dc->OnDataReceived(DataMessageType::kControl, payload);
+  network_thread_.BlockingCall(
+      [&] { dc->OnDataReceived(DataMessageType::kControl, payload); });
 
   // Sends another message and verifies it's unordered.
-  ASSERT_TRUE(dc->Send(buffer));
+  ASSERT_TRUE(proxy->Send(buffer));
   EXPECT_FALSE(controller_->last_send_data_params().ordered);
 }
 
@@ -379,15 +394,17 @@ TEST_F(SctpDataChannelTest, SendUnorderedAfterReceiveData) {
   init.ordered = false;
   rtc::scoped_refptr<SctpDataChannel> dc =
       controller_->CreateDataChannel("test1", init);
+  auto proxy = webrtc::SctpDataChannel::CreateProxy(dc);
 
-  EXPECT_EQ_WAIT(DataChannelInterface::kOpen, dc->state(), 1000);
+  EXPECT_EQ_WAIT(DataChannelInterface::kOpen, proxy->state(), 1000);
 
   // Emulates receiving a DATA message.
   DataBuffer buffer("data");
-  dc->OnDataReceived(DataMessageType::kText, buffer.data);
+  network_thread_.BlockingCall(
+      [&] { dc->OnDataReceived(DataMessageType::kText, buffer.data); });
 
   // Sends a message and verifies it's unordered.
-  ASSERT_TRUE(dc->Send(buffer));
+  ASSERT_TRUE(proxy->Send(buffer));
   EXPECT_FALSE(controller_->last_send_data_params().ordered);
 }
 
@@ -440,7 +457,10 @@ TEST_F(SctpDataChannelTest, ReceiveDataWithValidId) {
   AddObserver();
 
   DataBuffer buffer("abcd");
-  inner_channel_->OnDataReceived(DataMessageType::kText, buffer.data);
+  network_thread_.BlockingCall([&] {
+    inner_channel_->OnDataReceived(DataMessageType::kText, buffer.data);
+  });
+  run_loop_.Flush();
   EXPECT_EQ(1U, observer_->messages_received());
 }
 
@@ -455,8 +475,9 @@ TEST_F(SctpDataChannelTest, NoMsgSentIfNegotiatedAndNotFromOpenMsg) {
   SetChannelReady();
   rtc::scoped_refptr<SctpDataChannel> dc =
       controller_->CreateDataChannel("test1", config);
+  auto proxy = webrtc::SctpDataChannel::CreateProxy(dc);
 
-  EXPECT_EQ_WAIT(DataChannelInterface::kOpen, dc->state(), 1000);
+  EXPECT_EQ_WAIT(DataChannelInterface::kOpen, proxy->state(), 1000);
   EXPECT_EQ(0, controller_->last_sid());
 }
 
@@ -480,9 +501,10 @@ TEST_F(SctpDataChannelTest, VerifyMessagesAndBytesReceived) {
   EXPECT_EQ(0U, channel_->bytes_received());
 
   // Receive three buffers while data channel isn't open.
-  inner_channel_->OnDataReceived(DataMessageType::kText, buffers[0].data);
-  inner_channel_->OnDataReceived(DataMessageType::kText, buffers[1].data);
-  inner_channel_->OnDataReceived(DataMessageType::kText, buffers[2].data);
+  network_thread_.BlockingCall([&] {
+    for (int i : {0, 1, 2})
+      inner_channel_->OnDataReceived(DataMessageType::kText, buffers[i].data);
+  });
   EXPECT_EQ(0U, observer_->messages_received());
   EXPECT_EQ(0U, channel_->messages_received());
   EXPECT_EQ(0U, channel_->bytes_received());
@@ -496,9 +518,11 @@ TEST_F(SctpDataChannelTest, VerifyMessagesAndBytesReceived) {
   EXPECT_EQ(bytes_received, channel_->bytes_received());
 
   // Receive three buffers while open.
-  inner_channel_->OnDataReceived(DataMessageType::kText, buffers[3].data);
-  inner_channel_->OnDataReceived(DataMessageType::kText, buffers[4].data);
-  inner_channel_->OnDataReceived(DataMessageType::kText, buffers[5].data);
+  network_thread_.BlockingCall([&] {
+    for (int i : {3, 4, 5})
+      inner_channel_->OnDataReceived(DataMessageType::kText, buffers[i].data);
+  });
+  run_loop_.Flush();
   bytes_received += buffers[3].size() + buffers[4].size() + buffers[5].size();
   EXPECT_EQ(6U, observer_->messages_received());
   EXPECT_EQ(6U, channel_->messages_received());
@@ -516,8 +540,9 @@ TEST_F(SctpDataChannelTest, OpenAckSentIfCreatedFromOpenMessage) {
   SetChannelReady();
   rtc::scoped_refptr<SctpDataChannel> dc =
       controller_->CreateDataChannel("test1", config);
+  auto proxy = webrtc::SctpDataChannel::CreateProxy(dc);
 
-  EXPECT_EQ_WAIT(DataChannelInterface::kOpen, dc->state(), 1000);
+  EXPECT_EQ_WAIT(DataChannelInterface::kOpen, proxy->state(), 1000);
 
   EXPECT_EQ(config.id, controller_->last_sid());
   EXPECT_EQ(DataMessageType::kControl,
@@ -554,9 +579,8 @@ TEST_F(SctpDataChannelTest, OpenWhenSendBufferFull) {
     EXPECT_TRUE(channel_->Send(packet));
   }
 
-  // The sending buffer shoul be full, send returns false.
+  // The sending buffer should be full, `Send()` returns false.
   EXPECT_FALSE(channel_->Send(packet));
-
   EXPECT_TRUE(DataChannelInterface::kOpen == channel_->state());
 }
 
@@ -580,10 +604,12 @@ TEST_F(SctpDataChannelTest, ClosedWhenReceivedBufferFull) {
   rtc::CopyOnWriteBuffer buffer(1024);
   memset(buffer.MutableData(), 0, buffer.size());
 
-  // Receiving data without having an observer will overflow the buffer.
-  for (size_t i = 0; i < 16 * 1024 + 1; ++i) {
-    inner_channel_->OnDataReceived(DataMessageType::kText, buffer);
-  }
+  network_thread_.BlockingCall([&] {
+    // Receiving data without having an observer will overflow the buffer.
+    for (size_t i = 0; i < 16 * 1024 + 1; ++i) {
+      inner_channel_->OnDataReceived(DataMessageType::kText, buffer);
+    }
+  });
   EXPECT_EQ(DataChannelInterface::kClosed, channel_->state());
   EXPECT_FALSE(channel_->error().ok());
   EXPECT_EQ(RTCErrorType::RESOURCE_EXHAUSTED, channel_->error().type());
@@ -604,7 +630,8 @@ TEST_F(SctpDataChannelTest, SendEmptyData) {
 // Tests that a channel can be closed without being opened or assigned an sid.
 TEST_F(SctpDataChannelTest, NeverOpened) {
   controller_->set_transport_available(true);
-  inner_channel_->OnTransportChannelCreated();
+  network_thread_.BlockingCall(
+      [&] { inner_channel_->OnTransportChannelCreated(); });
   channel_->Close();
 }
 
@@ -634,7 +661,8 @@ TEST_F(SctpDataChannelTest, TransportDestroyedWhileDataBuffered) {
   // transition to the "closed" state.
   RTCError error(RTCErrorType::OPERATION_ERROR_WITH_DATA, "");
   error.set_error_detail(RTCErrorDetailType::SCTP_FAILURE);
-  inner_channel_->OnTransportChannelClosed(error);
+  network_thread_.BlockingCall(
+      [&] { inner_channel_->OnTransportChannelClosed(error); });
   controller_.reset(nullptr);
   EXPECT_EQ_WAIT(DataChannelInterface::kClosed, channel_->state(),
                  kDefaultTimeout);
@@ -654,7 +682,8 @@ TEST_F(SctpDataChannelTest, TransportGotErrorCode) {
   error.set_error_detail(RTCErrorDetailType::SCTP_FAILURE);
   error.set_sctp_cause_code(
       static_cast<uint16_t>(cricket::SctpErrorCauseCode::kProtocolViolation));
-  inner_channel_->OnTransportChannelClosed(error);
+  network_thread_.BlockingCall(
+      [&] { inner_channel_->OnTransportChannelClosed(error); });
   controller_.reset(nullptr);
   EXPECT_EQ_WAIT(DataChannelInterface::kClosed, channel_->state(),
                  kDefaultTimeout);
diff --git a/pc/legacy_stats_collector.cc b/pc/legacy_stats_collector.cc
index 6829e359b8..7ce85e411c 100644
--- a/pc/legacy_stats_collector.cc
+++ b/pc/legacy_stats_collector.cc
@@ -670,7 +670,7 @@ void LegacyStatsCollector::UpdateStats(
   // to fetch stats, then applies them on the signaling thread. See if we need
   // to do this synchronously or if updating the stats without blocking is safe.
   std::map<std::string, std::string> transport_names_by_mid =
-      ExtractSessionInfo();
+      ExtractSessionAndDataInfo();
 
   // TODO(tommi): All of these hop over to the worker thread to fetch
   // information.  We could post a task to run all of these and post
@@ -681,7 +681,6 @@ void LegacyStatsCollector::UpdateStats(
   ExtractBweInfo();
   ExtractMediaInfo(transport_names_by_mid);
   ExtractSenderInfo();
-  ExtractDataInfo();
   UpdateTrackReports();
 }
 
@@ -856,19 +855,26 @@ StatsReport* LegacyStatsCollector::AddCandidateReport(
   return report;
 }
 
-std::map<std::string, std::string> LegacyStatsCollector::ExtractSessionInfo() {
-  TRACE_EVENT0("webrtc", "LegacyStatsCollector::ExtractSessionInfo");
+std::map<std::string, std::string>
+LegacyStatsCollector::ExtractSessionAndDataInfo() {
+  TRACE_EVENT0("webrtc", "LegacyStatsCollector::ExtractSessionAndDataInfo");
   RTC_DCHECK_RUN_ON(pc_->signaling_thread());
 
   SessionStats stats;
+  StatsCollection::Container data_report_collection;
   auto transceivers = pc_->GetTransceiversInternal();
   pc_->network_thread()->BlockingCall(
       [&, sctp_transport_name = pc_->sctp_transport_name(),
        sctp_mid = pc_->sctp_mid()]() mutable {
         stats = ExtractSessionInfo_n(
             transceivers, std::move(sctp_transport_name), std::move(sctp_mid));
+        StatsCollection data_reports;
+        ExtractDataInfo_n(&data_reports);
+        data_report_collection = data_reports.DetachCollection();
       });
 
+  reports_.MergeCollection(std::move(data_report_collection));
+
   ExtractSessionInfo_s(stats);
 
   return std::move(stats.transport_names_by_mid);
@@ -1292,8 +1298,8 @@ void LegacyStatsCollector::ExtractSenderInfo() {
   }
 }
 
-void LegacyStatsCollector::ExtractDataInfo() {
-  RTC_DCHECK_RUN_ON(pc_->signaling_thread());
+void LegacyStatsCollector::ExtractDataInfo_n(StatsCollection* reports) {
+  RTC_DCHECK_RUN_ON(pc_->network_thread());
 
   rtc::Thread::ScopedDisallowBlockingCalls no_blocking_calls;
 
@@ -1301,7 +1307,7 @@ void LegacyStatsCollector::ExtractDataInfo() {
   for (const auto& stats : data_stats) {
     StatsReport::Id id(StatsReport::NewTypedIntId(
         StatsReport::kStatsReportTypeDataChannel, stats.id));
-    StatsReport* report = reports_.ReplaceOrAddNew(id);
+    StatsReport* report = reports->ReplaceOrAddNew(id);
     report->set_timestamp(stats_gathering_started_);
     report->AddString(StatsReport::kStatsValueNameLabel, stats.label);
     // Filter out the initial id (-1).
diff --git a/pc/legacy_stats_collector.h b/pc/legacy_stats_collector.h
index cedd36c853..e905b39d48 100644
--- a/pc/legacy_stats_collector.h
+++ b/pc/legacy_stats_collector.h
@@ -165,11 +165,13 @@ class LegacyStatsCollector : public LegacyStatsCollectorInterface {
                                        const StatsReport::Id& channel_report_id,
                                        const cricket::ConnectionInfo& info);
 
-  void ExtractDataInfo();
+  void ExtractDataInfo_n(StatsCollection* reports);
 
   // Returns the `transport_names_by_mid` member from the SessionStats as
-  // gathered and used to populate the stats.
-  std::map<std::string, std::string> ExtractSessionInfo();
+  // gathered and used to populate the stats. Contains one synchronous hop
+  // to the network thread to get this information along with querying data
+  // channel stats at the same time and populating `reports_`.
+  std::map<std::string, std::string> ExtractSessionAndDataInfo();
 
   void ExtractBweInfo();
   void ExtractMediaInfo(
diff --git a/pc/peer_connection.cc b/pc/peer_connection.cc
index fdbd32bbce..82c5914a52 100644
--- a/pc/peer_connection.cc
+++ b/pc/peer_connection.cc
@@ -2286,7 +2286,7 @@ bool PeerConnection::GetTransportDescription(
 }
 
 std::vector<DataChannelStats> PeerConnection::GetDataChannelStats() const {
-  RTC_DCHECK_RUN_ON(signaling_thread());
+  RTC_DCHECK_RUN_ON(network_thread());
   return data_channel_controller_.GetDataChannelStats();
 }
 
diff --git a/pc/proxy.h b/pc/proxy.h
index 2be115fdf3..ebe60c0293 100644
--- a/pc/proxy.h
+++ b/pc/proxy.h
@@ -450,6 +450,24 @@ class ConstMethodCall {
     return c_->method();                     \
   }
 
+// Allows a custom implementation of a method where the otherwise proxied
+// implementation can do a more efficient, yet thread-safe, job than the proxy
+// can do by default or when more flexibility is needed than can be provided
+// by a proxy.
+// Note that calls to these methods should be expected to be made from unknown
+// threads.
+#define BYPASS_PROXY_METHOD0(r, method) \
+  r method() override {                 \
+    TRACE_BOILERPLATE(method);          \
+    return c_->method();                \
+  }
+
+// The 1 argument version of `BYPASS_PROXY_METHOD0`.
+#define BYPASS_PROXY_METHOD1(r, method, t1) \
+  r method(t1 a1) override {                \
+    TRACE_BOILERPLATE(method);              \
+    return c_->method(std::move(a1));       \
+  }
 }  // namespace webrtc
 
 #endif  //  PC_PROXY_H_
diff --git a/pc/rtc_stats_collector.cc b/pc/rtc_stats_collector.cc
index 429e9d0268..574e1cc6ec 100644
--- a/pc/rtc_stats_collector.cc
+++ b/pc/rtc_stats_collector.cc
@@ -1499,7 +1499,6 @@ void RTCStatsCollector::ProducePartialResultsOnSignalingThreadImpl(
   RTC_DCHECK_RUN_ON(signaling_thread_);
   rtc::Thread::ScopedDisallowBlockingCalls no_blocking_calls;
 
-  ProduceDataChannelStats_s(timestamp, partial_report);
   ProduceMediaStreamStats_s(timestamp, partial_report);
   ProduceMediaStreamTrackStats_s(timestamp, partial_report);
   ProduceMediaSourceStats_s(timestamp, partial_report);
@@ -1519,6 +1518,8 @@ void RTCStatsCollector::ProducePartialResultsOnNetworkThread(
   // `network_report_event_` is reset before this method is invoked.
   network_report_ = RTCStatsReport::Create(timestamp);
 
+  ProduceDataChannelStats_n(timestamp, network_report_.get());
+
   std::set<std::string> transport_names;
   if (sctp_transport_name) {
     transport_names.emplace(std::move(*sctp_transport_name));
@@ -1653,10 +1654,10 @@ void RTCStatsCollector::ProduceCertificateStats_n(
   }
 }
 
-void RTCStatsCollector::ProduceDataChannelStats_s(
+void RTCStatsCollector::ProduceDataChannelStats_n(
     Timestamp timestamp,
     RTCStatsReport* report) const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   rtc::Thread::ScopedDisallowBlockingCalls no_blocking_calls;
   std::vector<DataChannelStats> data_stats = pc_->GetDataChannelStats();
   for (const auto& stats : data_stats) {
diff --git a/pc/rtc_stats_collector.h b/pc/rtc_stats_collector.h
index ac0453fb7c..34962bf5f7 100644
--- a/pc/rtc_stats_collector.h
+++ b/pc/rtc_stats_collector.h
@@ -186,7 +186,7 @@ class RTCStatsCollector : public rtc::RefCountInterface {
       const std::map<std::string, CertificateStatsPair>& transport_cert_stats,
       RTCStatsReport* report) const;
   // Produces `RTCDataChannelStats`.
-  void ProduceDataChannelStats_s(Timestamp timestamp,
+  void ProduceDataChannelStats_n(Timestamp timestamp,
                                  RTCStatsReport* report) const;
   // Produces `RTCIceCandidatePairStats` and `RTCIceCandidateStats`.
   void ProduceIceCandidateAndPairStats_n(
diff --git a/pc/sctp_data_channel.cc b/pc/sctp_data_channel.cc
index 623a153067..892eca9aa7 100644
--- a/pc/sctp_data_channel.cc
+++ b/pc/sctp_data_channel.cc
@@ -38,8 +38,8 @@ int GenerateUniqueId() {
 // Define proxy for DataChannelInterface.
 BEGIN_PROXY_MAP(DataChannel)
 PROXY_PRIMARY_THREAD_DESTRUCTOR()
-PROXY_METHOD1(void, RegisterObserver, DataChannelObserver*)
-PROXY_METHOD0(void, UnregisterObserver)
+BYPASS_PROXY_METHOD1(void, RegisterObserver, DataChannelObserver*)
+BYPASS_PROXY_METHOD0(void, UnregisterObserver)
 BYPASS_PROXY_CONSTMETHOD0(std::string, label)
 BYPASS_PROXY_CONSTMETHOD0(bool, reliable)
 BYPASS_PROXY_CONSTMETHOD0(bool, ordered)
@@ -50,20 +50,18 @@ BYPASS_PROXY_CONSTMETHOD0(absl::optional<int>, maxPacketLifeTime)
 BYPASS_PROXY_CONSTMETHOD0(std::string, protocol)
 BYPASS_PROXY_CONSTMETHOD0(bool, negotiated)
 // Can't bypass the proxy since the id may change.
-PROXY_CONSTMETHOD0(int, id)
+PROXY_SECONDARY_CONSTMETHOD0(int, id)
 BYPASS_PROXY_CONSTMETHOD0(Priority, priority)
-PROXY_CONSTMETHOD0(DataState, state)
-PROXY_CONSTMETHOD0(RTCError, error)
-PROXY_CONSTMETHOD0(uint32_t, messages_sent)
-PROXY_CONSTMETHOD0(uint64_t, bytes_sent)
-PROXY_CONSTMETHOD0(uint32_t, messages_received)
-PROXY_CONSTMETHOD0(uint64_t, bytes_received)
-PROXY_CONSTMETHOD0(uint64_t, buffered_amount)
-PROXY_METHOD0(void, Close)
-// TODO(bugs.webrtc.org/11547): Change to run on the network thread.
-PROXY_METHOD1(bool, Send, const DataBuffer&)
+BYPASS_PROXY_CONSTMETHOD0(DataState, state)
+PROXY_SECONDARY_CONSTMETHOD0(RTCError, error)
+PROXY_SECONDARY_CONSTMETHOD0(uint32_t, messages_sent)
+PROXY_SECONDARY_CONSTMETHOD0(uint64_t, bytes_sent)
+PROXY_SECONDARY_CONSTMETHOD0(uint32_t, messages_received)
+PROXY_SECONDARY_CONSTMETHOD0(uint64_t, bytes_received)
+PROXY_SECONDARY_CONSTMETHOD0(uint64_t, buffered_amount)
+PROXY_SECONDARY_METHOD0(void, Close)
+PROXY_SECONDARY_METHOD1(bool, Send, const DataBuffer&)
 END_PROXY_MAP(DataChannel)
-
 }  // namespace
 
 InternalDataChannelInit::InternalDataChannelInit(const DataChannelInit& base)
@@ -142,6 +140,78 @@ void SctpSidAllocator::ReleaseSid(StreamId sid) {
   used_sids_.erase(sid);
 }
 
+// A DataChannelObserver implementation that offers backwards compatibility with
+// implementations that aren't yet ready to be called back on the network
+// thread. This implementation posts events to the signaling thread where
+// events are delivered.
+// In the class, and together with the `SctpDataChannel` implementation, there's
+// special handling for the `state()` property whereby if that property is
+// queried on the channel object while inside an event callback, we return
+// the state that was active at the time the event was issued. This is to avoid
+// a problem with calling the `state()` getter on the proxy, which would do
+// a blocking call to the network thread, effectively flushing operations on
+// the network thread that could cause the state to change and eventually return
+// a misleading or arguably, wrong, state value to the callback implementation.
+// As a future improvement to the ObserverAdapter, we could do the same for
+// other properties that need to be read on the network thread. Eventually
+// all implementations should expect to be called on the network thread though
+// and the ObserverAdapter no longer be necessary.
+class SctpDataChannel::ObserverAdapter : public DataChannelObserver {
+ public:
+  explicit ObserverAdapter(DataChannelObserver* delegate,
+                           SctpDataChannel* channel)
+      : delegate_(delegate), channel_(channel) {}
+
+  bool IsInsideStateNotification() const {
+    RTC_DCHECK_RUN_ON(signaling_thread());
+    return inside_state_change_;
+  }
+
+  DataChannelInterface::DataState cached_state() const {
+    RTC_DCHECK_RUN_ON(signaling_thread());
+    RTC_DCHECK(IsInsideStateNotification());
+    return cached_state_;
+  }
+
+ private:
+  void OnStateChange() override {
+    RTC_DCHECK_RUN_ON(network_thread());
+    signaling_thread()->PostTask(
+        SafeTask(safety_.flag(), [this, new_state = channel_->state()] {
+          RTC_DCHECK_RUN_ON(signaling_thread());
+          cached_state_ = new_state;
+          inside_state_change_ = true;
+          delegate_->OnStateChange();
+          inside_state_change_ = false;
+        }));
+  }
+
+  void OnMessage(const DataBuffer& buffer) override {
+    RTC_DCHECK_RUN_ON(network_thread());
+    signaling_thread()->PostTask(
+        SafeTask(safety_.flag(),
+                 [this, buffer = buffer] { delegate_->OnMessage(buffer); }));
+  }
+
+  void OnBufferedAmountChange(uint64_t sent_data_size) override {
+    RTC_DCHECK_RUN_ON(network_thread());
+    signaling_thread()->PostTask(
+        SafeTask(safety_.flag(), [this, sent_data_size] {
+          delegate_->OnBufferedAmountChange(sent_data_size);
+        }));
+  }
+
+  rtc::Thread* signaling_thread() const { return channel_->signaling_thread_; }
+  rtc::Thread* network_thread() const { return channel_->network_thread_; }
+
+  DataChannelObserver* const delegate_;
+  SctpDataChannel* const channel_;
+  ScopedTaskSafety safety_;
+  bool inside_state_change_ RTC_GUARDED_BY(signaling_thread()) = false;
+  DataChannelInterface::DataState cached_state_
+      RTC_GUARDED_BY(signaling_thread()) = DataChannelInterface::kConnecting;
+};
+
 // static
 rtc::scoped_refptr<SctpDataChannel> SctpDataChannel::Create(
     rtc::WeakPtr<SctpDataChannelControllerInterface> controller,
@@ -175,7 +245,6 @@ SctpDataChannel::SctpDataChannel(
     rtc::Thread* network_thread)
     : signaling_thread_(signaling_thread),
       network_thread_(network_thread),
-      id_s_(config.id),
       id_n_(config.id),
       internal_id_(GenerateUniqueId()),
       label_(label),
@@ -207,19 +276,81 @@ SctpDataChannel::SctpDataChannel(
   }
 }
 
-SctpDataChannel::~SctpDataChannel() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
-}
+SctpDataChannel::~SctpDataChannel() {}
 
 void SctpDataChannel::RegisterObserver(DataChannelObserver* observer) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
-  observer_ = observer;
-  DeliverQueuedReceivedData();
+  // Note: at this point, we do not know on which thread we're being called
+  // from since this method bypasses the proxy. On Android in particular,
+  // registration methods are called from unknown threads.
+
+  // Check if we should set up an observer adapter that will make sure that
+  // callbacks are delivered on the signaling thread rather than directly
+  // on the network thread.
+  const auto* current_thread = rtc::Thread::Current();
+  // TODO(webrtc:11547): Eventually all DataChannelObserver implementations
+  // should be called on the network thread and IsOkToCallOnTheNetworkThread().
+  if (!observer->IsOkToCallOnTheNetworkThread()) {
+    auto prepare_observer = [&]() {
+      RTC_DCHECK(!observer_adapter_);
+      observer_adapter_ = std::make_unique<ObserverAdapter>(observer, this);
+      return observer_adapter_.get();
+    };
+    // Instantiate the adapter in the right context and then substitute the
+    // observer pointer the SctpDataChannel will call back on, with the adapter.
+    if (signaling_thread_ == current_thread) {
+      observer = prepare_observer();
+    } else {
+      observer = signaling_thread_->BlockingCall(std::move(prepare_observer));
+    }
+  }
+
+  // Now do the observer registration on the network thread.
+  auto register_observer = [&] {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    observer_ = observer;
+    DeliverQueuedReceivedData();
+  };
+
+  if (network_thread_ == current_thread) {
+    register_observer();
+  } else {
+    network_thread_->BlockingCall(std::move(register_observer));
+  }
 }
 
 void SctpDataChannel::UnregisterObserver() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
-  observer_ = nullptr;
+  // Note: As with `RegisterObserver`, the proxy is being bypassed.
+  const auto* current_thread = rtc::Thread::Current();
+  // Callers must not be invoking the unregistration from the network thread
+  // (assuming a multi-threaded environment where we have a dedicated network
+  // thread). That would indicate non-network related work happening on the
+  // network thread or that unregistration is being done from within a callback
+  // (without unwinding the stack, which is a requirement).
+  // The network thread is not allowed to make blocking calls to the signaling
+  // thread, so that would blow up if attempted. Since we support an adapter
+  // for observers that are not safe to call on the network thread, we do
+  // need to check+free it on the signaling thread.
+  RTC_DCHECK(current_thread != network_thread_ ||
+             network_thread_ == signaling_thread_);
+
+  auto unregister_observer = [&] {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    observer_ = nullptr;
+  };
+
+  if (current_thread == network_thread_) {
+    unregister_observer();
+  } else {
+    network_thread_->BlockingCall(std::move(unregister_observer));
+  }
+
+  auto clear_observer = [&]() { observer_adapter_.reset(); };
+
+  if (current_thread != signaling_thread_) {
+    signaling_thread_->BlockingCall(std::move(clear_observer));
+  } else {
+    clear_observer();
+  }
 }
 
 std::string SctpDataChannel::label() const {
@@ -261,8 +392,11 @@ bool SctpDataChannel::negotiated() const {
 }
 
 int SctpDataChannel::id() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
-  return id_s_.stream_id_int();
+  RTC_DCHECK_RUN_ON(network_thread_);
+  // TODO(tommi): Once an ID has been assigned, it won't change (can be
+  // considered const). We could do special handling of this and allow bypassing
+  // the proxy so that we can return a valid id without thread hopping.
+  return id_n_.stream_id_int();
 }
 
 Priority SctpDataChannel::priority() const {
@@ -270,12 +404,12 @@ Priority SctpDataChannel::priority() const {
 }
 
 uint64_t SctpDataChannel::buffered_amount() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   return queued_send_data_.byte_count();
 }
 
 void SctpDataChannel::Close() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   if (state_ == kClosing || state_ == kClosed)
     return;
   SetState(kClosing);
@@ -284,40 +418,58 @@ void SctpDataChannel::Close() {
 }
 
 SctpDataChannel::DataState SctpDataChannel::state() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
-  return state_;
+  // Note: The proxy is bypassed for the `state()` accessor. This is to allow
+  // observer callbacks to query what the new state is from within a state
+  // update notification without having to do a blocking call to the network
+  // thread from within a callback. This also makes it so that the returned
+  // state is guaranteed to be the new state that provoked the state change
+  // notification, whereby a blocking call to the network thread might end up
+  // getting put behind other messages on the network thread and eventually
+  // fetch a different state value (since pending messages might cause the
+  // state to change in the meantime).
+  const auto* current_thread = rtc::Thread::Current();
+  if (current_thread == signaling_thread_) {
+    if (observer_adapter_ && observer_adapter_->IsInsideStateNotification())
+      return observer_adapter_->cached_state();
+  }
+
+  auto return_state = [&] {
+    RTC_DCHECK_RUN_ON(network_thread_);
+    return state_;
+  };
+
+  return current_thread == network_thread_
+             ? return_state()
+             : network_thread_->BlockingCall(std::move(return_state));
 }
 
 RTCError SctpDataChannel::error() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   return error_;
 }
 
 uint32_t SctpDataChannel::messages_sent() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   return messages_sent_;
 }
 
 uint64_t SctpDataChannel::bytes_sent() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   return bytes_sent_;
 }
 
 uint32_t SctpDataChannel::messages_received() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   return messages_received_;
 }
 
 uint64_t SctpDataChannel::bytes_received() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   return bytes_received_;
 }
 
 bool SctpDataChannel::Send(const DataBuffer& buffer) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
-  // TODO(bugs.webrtc.org/11547): Expect this method to be called on the network
-  // thread. Bring buffer management etc to the network thread and keep the
-  // operational state management on the signaling thread.
+  RTC_DCHECK_RUN_ON(network_thread_);
 
   if (state_ != kOpen) {
     return false;
@@ -335,25 +487,17 @@ bool SctpDataChannel::Send(const DataBuffer& buffer) {
   return true;
 }
 
-void SctpDataChannel::SetSctpSid_s(StreamId sid) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
-  RTC_DCHECK(!id_s_.HasValue());
-  RTC_DCHECK(sid.HasValue());
-  RTC_DCHECK_NE(handshake_state_, kHandshakeWaitingForAck);
-  RTC_DCHECK_EQ(state_, kConnecting);
-
-  id_s_ = sid;
-}
-
 void SctpDataChannel::SetSctpSid_n(StreamId sid) {
   RTC_DCHECK_RUN_ON(network_thread_);
   RTC_DCHECK(!id_n_.HasValue());
   RTC_DCHECK(sid.HasValue());
+  RTC_DCHECK_NE(handshake_state_, kHandshakeWaitingForAck);
+  RTC_DCHECK_EQ(state_, kConnecting);
   id_n_ = sid;
 }
 
 void SctpDataChannel::OnClosingProcedureStartedRemotely() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   if (state_ != kClosing && state_ != kClosed) {
     // Don't bother sending queued data since the side that initiated the
     // closure wouldn't receive it anyway. See crbug.com/559394 for a lengthy
@@ -369,7 +513,7 @@ void SctpDataChannel::OnClosingProcedureStartedRemotely() {
 }
 
 void SctpDataChannel::OnClosingProcedureComplete() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   // If the closing procedure is complete, we should have finished sending
   // all pending data and transitioned to kClosing already.
   RTC_DCHECK_EQ(state_, kClosing);
@@ -378,12 +522,12 @@ void SctpDataChannel::OnClosingProcedureComplete() {
 }
 
 void SctpDataChannel::OnTransportChannelCreated() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
-
+  RTC_DCHECK_RUN_ON(network_thread_);
   connected_to_transport_ = true;
 }
 
 void SctpDataChannel::OnTransportChannelClosed(RTCError error) {
+  RTC_DCHECK_RUN_ON(network_thread_);
   // The SctpTransport is unusable, which could come from multiple reasons:
   // - the SCTP m= section was rejected
   // - the DTLS transport is closed
@@ -392,7 +536,7 @@ void SctpDataChannel::OnTransportChannelClosed(RTCError error) {
 }
 
 DataChannelStats SctpDataChannel::GetStats() const {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
   DataChannelStats stats{internal_id_,        id(),         label(),
                          protocol(),          state(),      messages_sent(),
                          messages_received(), bytes_sent(), bytes_received()};
@@ -401,25 +545,25 @@ DataChannelStats SctpDataChannel::GetStats() const {
 
 void SctpDataChannel::OnDataReceived(DataMessageType type,
                                      const rtc::CopyOnWriteBuffer& payload) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
 
   if (type == DataMessageType::kControl) {
     if (handshake_state_ != kHandshakeWaitingForAck) {
       // Ignore it if we are not expecting an ACK message.
       RTC_LOG(LS_WARNING)
           << "DataChannel received unexpected CONTROL message, sid = "
-          << id_s_.stream_id_int();
+          << id_n_.stream_id_int();
       return;
     }
     if (ParseDataChannelOpenAckMessage(payload)) {
       // We can send unordered as soon as we receive the ACK message.
       handshake_state_ = kHandshakeReady;
       RTC_LOG(LS_INFO) << "DataChannel received OPEN_ACK message, sid = "
-                       << id_s_.stream_id_int();
+                       << id_n_.stream_id_int();
     } else {
       RTC_LOG(LS_WARNING)
           << "DataChannel failed to parse OPEN_ACK message, sid = "
-          << id_s_.stream_id_int();
+          << id_n_.stream_id_int();
     }
     return;
   }
@@ -428,7 +572,7 @@ void SctpDataChannel::OnDataReceived(DataMessageType type,
              type == DataMessageType::kText);
 
   RTC_DLOG(LS_VERBOSE) << "DataChannel received DATA message, sid = "
-                       << id_s_.stream_id_int();
+                       << id_n_.stream_id_int();
   // We can send unordered as soon as we receive any DATA message since the
   // remote side must have received the OPEN (and old clients do not send
   // OPEN_ACK).
@@ -459,7 +603,7 @@ void SctpDataChannel::OnDataReceived(DataMessageType type,
 }
 
 void SctpDataChannel::OnTransportReady() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
 
   // TODO(bugs.webrtc.org/11547): The transport is configured inside
   // `PeerConnection::SetupDataChannelTransport_n`, which results in
@@ -472,6 +616,7 @@ void SctpDataChannel::OnTransportReady() {
   // be on for the below `Send*` calls, which currently do a BlockingCall
   // from the signaling thread to the network thread.
   RTC_DCHECK(connected_to_transport_);
+  RTC_DCHECK(id_n_.HasValue());
 
   SendQueuedControlMessages();
   SendQueuedDataMessages();
@@ -480,7 +625,7 @@ void SctpDataChannel::OnTransportReady() {
 }
 
 void SctpDataChannel::CloseAbruptlyWithError(RTCError error) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
+  RTC_DCHECK_RUN_ON(network_thread_);
 
   if (state_ == kClosed) {
     return;
@@ -501,13 +646,14 @@ void SctpDataChannel::CloseAbruptlyWithError(RTCError error) {
 
 void SctpDataChannel::CloseAbruptlyWithDataChannelFailure(
     const std::string& message) {
+  RTC_DCHECK_RUN_ON(network_thread_);
   RTCError error(RTCErrorType::OPERATION_ERROR_WITH_DATA, message);
   error.set_error_detail(RTCErrorDetailType::DATA_CHANNEL_FAILURE);
   CloseAbruptlyWithError(std::move(error));
 }
 
+// RTC_RUN_ON(network_thread_).
 void SctpDataChannel::UpdateState() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
   // UpdateState determines what to do from a few state variables. Include
   // all conditions required for each state transition here for
   // clarity. OnTransportReady(true) will send any queued data and then invoke
@@ -535,7 +681,7 @@ void SctpDataChannel::UpdateState() {
           DeliverQueuedReceivedData();
         }
       } else {
-        RTC_DCHECK(!id_s_.HasValue());
+        RTC_DCHECK(!id_n_.HasValue());
       }
       break;
     }
@@ -551,11 +697,9 @@ void SctpDataChannel::UpdateState() {
           // to complete; after calling RemoveSctpDataStream,
           // OnClosingProcedureComplete will end up called asynchronously
           // afterwards.
-          if (!started_closing_procedure_ && id_s_.HasValue()) {
+          if (!started_closing_procedure_ && id_n_.HasValue()) {
             started_closing_procedure_ = true;
-            network_thread_->BlockingCall([c = controller_.get(), sid = id_s_] {
-              c->RemoveSctpDataStream(sid);
-            });
+            controller_->RemoveSctpDataStream(id_n_);
           }
         }
       } else {
@@ -572,8 +716,8 @@ void SctpDataChannel::UpdateState() {
   }
 }
 
+// RTC_RUN_ON(network_thread_).
 void SctpDataChannel::SetState(DataState state) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
   if (state_ == state) {
     return;
   }
@@ -587,8 +731,8 @@ void SctpDataChannel::SetState(DataState state) {
     controller_->OnChannelStateChanged(this, state_);
 }
 
+// RTC_RUN_ON(network_thread_).
 void SctpDataChannel::DeliverQueuedReceivedData() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
   if (!observer_) {
     return;
   }
@@ -601,8 +745,8 @@ void SctpDataChannel::DeliverQueuedReceivedData() {
   }
 }
 
+// RTC_RUN_ON(network_thread_).
 void SctpDataChannel::SendQueuedDataMessages() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
   if (queued_send_data_.Empty()) {
     return;
   }
@@ -619,9 +763,9 @@ void SctpDataChannel::SendQueuedDataMessages() {
   }
 }
 
+// RTC_RUN_ON(network_thread_).
 bool SctpDataChannel::SendDataMessage(const DataBuffer& buffer,
                                       bool queue_if_blocked) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
   SendDataParams send_params;
   if (!controller_) {
     return false;
@@ -641,7 +785,7 @@ bool SctpDataChannel::SendDataMessage(const DataBuffer& buffer,
   send_params.type =
       buffer.binary ? DataMessageType::kBinary : DataMessageType::kText;
 
-  RTCError error = controller_->SendData(id_s_, send_params, buffer.data);
+  RTCError error = controller_->SendData(id_n_, send_params, buffer.data);
 
   if (error.ok()) {
     ++messages_sent_;
@@ -669,8 +813,8 @@ bool SctpDataChannel::SendDataMessage(const DataBuffer& buffer,
   return false;
 }
 
+// RTC_RUN_ON(network_thread_).
 bool SctpDataChannel::QueueSendDataMessage(const DataBuffer& buffer) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
   size_t start_buffered_amount = queued_send_data_.byte_count();
   if (start_buffered_amount + buffer.size() >
       DataChannelInterface::MaxSendQueueSize()) {
@@ -681,8 +825,8 @@ bool SctpDataChannel::QueueSendDataMessage(const DataBuffer& buffer) {
   return true;
 }
 
+// RTC_RUN_ON(network_thread_).
 void SctpDataChannel::SendQueuedControlMessages() {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
   PacketQueue control_packets;
   control_packets.Swap(&queued_control_data_);
 
@@ -692,10 +836,10 @@ void SctpDataChannel::SendQueuedControlMessages() {
   }
 }
 
+// RTC_RUN_ON(network_thread_).
 bool SctpDataChannel::SendControlMessage(const rtc::CopyOnWriteBuffer& buffer) {
-  RTC_DCHECK_RUN_ON(signaling_thread_);
   RTC_DCHECK(connected_to_transport_);
-  RTC_DCHECK(id_s_.HasValue());
+  RTC_DCHECK(id_n_.HasValue());
   RTC_DCHECK(controller_);
 
   bool is_open_message = handshake_state_ == kHandshakeShouldSendOpen;
@@ -708,10 +852,10 @@ bool SctpDataChannel::SendControlMessage(const rtc::CopyOnWriteBuffer& buffer) {
   send_params.ordered = ordered_ || is_open_message;
   send_params.type = DataMessageType::kControl;
 
-  RTCError err = controller_->SendData(id_s_, send_params, buffer);
+  RTCError err = controller_->SendData(id_n_, send_params, buffer);
   if (err.ok()) {
     RTC_DLOG(LS_VERBOSE) << "Sent CONTROL message on channel "
-                         << id_s_.stream_id_int();
+                         << id_n_.stream_id_int();
 
     if (handshake_state_ == kHandshakeShouldSendAck) {
       handshake_state_ = kHandshakeReady;
diff --git a/pc/sctp_data_channel.h b/pc/sctp_data_channel.h
index 588b0cbf63..fcf1ffe6ed 100644
--- a/pc/sctp_data_channel.h
+++ b/pc/sctp_data_channel.h
@@ -192,7 +192,6 @@ class SctpDataChannel : public DataChannelInterface {
 
   // Sets the SCTP sid and adds to transport layer if not set yet. Should only
   // be called once.
-  void SetSctpSid_s(StreamId sid);
   void SetSctpSid_n(StreamId sid);
 
   // The remote side started the closing procedure by resetting its outgoing
@@ -216,10 +215,6 @@ class SctpDataChannel : public DataChannelInterface {
   // stats purposes (see also `GetStats()`).
   int internal_id() const { return internal_id_; }
 
-  StreamId sid_s() const {
-    RTC_DCHECK_RUN_ON(signaling_thread_);
-    return id_s_;
-  }
   StreamId sid_n() const {
     RTC_DCHECK_RUN_ON(network_thread_);
     return id_n_;
@@ -239,6 +234,8 @@ class SctpDataChannel : public DataChannelInterface {
   ~SctpDataChannel() override;
 
  private:
+  class ObserverAdapter;
+
   // The OPEN(_ACK) signaling state.
   enum HandshakeState {
     kHandshakeInit,
@@ -248,21 +245,23 @@ class SctpDataChannel : public DataChannelInterface {
     kHandshakeReady
   };
 
-  void UpdateState();
-  void SetState(DataState state);
+  void UpdateState() RTC_RUN_ON(network_thread_);
+  void SetState(DataState state) RTC_RUN_ON(network_thread_);
 
-  void DeliverQueuedReceivedData();
+  void DeliverQueuedReceivedData() RTC_RUN_ON(network_thread_);
 
-  void SendQueuedDataMessages();
-  bool SendDataMessage(const DataBuffer& buffer, bool queue_if_blocked);
-  bool QueueSendDataMessage(const DataBuffer& buffer);
+  void SendQueuedDataMessages() RTC_RUN_ON(network_thread_);
+  bool SendDataMessage(const DataBuffer& buffer, bool queue_if_blocked)
+      RTC_RUN_ON(network_thread_);
+  bool QueueSendDataMessage(const DataBuffer& buffer)
+      RTC_RUN_ON(network_thread_);
 
-  void SendQueuedControlMessages();
-  bool SendControlMessage(const rtc::CopyOnWriteBuffer& buffer);
+  void SendQueuedControlMessages() RTC_RUN_ON(network_thread_);
+  bool SendControlMessage(const rtc::CopyOnWriteBuffer& buffer)
+      RTC_RUN_ON(network_thread_);
 
   rtc::Thread* const signaling_thread_;
   rtc::Thread* const network_thread_;
-  StreamId id_s_ RTC_GUARDED_BY(signaling_thread_);
   StreamId id_n_ RTC_GUARDED_BY(network_thread_);
   const int internal_id_;
   const std::string label_;
@@ -273,25 +272,26 @@ class SctpDataChannel : public DataChannelInterface {
   const bool negotiated_;
   const bool ordered_;
 
-  DataChannelObserver* observer_ RTC_GUARDED_BY(signaling_thread_) = nullptr;
-  DataState state_ RTC_GUARDED_BY(signaling_thread_) = kConnecting;
-  RTCError error_ RTC_GUARDED_BY(signaling_thread_);
-  uint32_t messages_sent_ RTC_GUARDED_BY(signaling_thread_) = 0;
-  uint64_t bytes_sent_ RTC_GUARDED_BY(signaling_thread_) = 0;
-  uint32_t messages_received_ RTC_GUARDED_BY(signaling_thread_) = 0;
-  uint64_t bytes_received_ RTC_GUARDED_BY(signaling_thread_) = 0;
+  DataChannelObserver* observer_ RTC_GUARDED_BY(network_thread_) = nullptr;
+  std::unique_ptr<ObserverAdapter> observer_adapter_;
+  DataState state_ RTC_GUARDED_BY(network_thread_) = kConnecting;
+  RTCError error_ RTC_GUARDED_BY(network_thread_);
+  uint32_t messages_sent_ RTC_GUARDED_BY(network_thread_) = 0;
+  uint64_t bytes_sent_ RTC_GUARDED_BY(network_thread_) = 0;
+  uint32_t messages_received_ RTC_GUARDED_BY(network_thread_) = 0;
+  uint64_t bytes_received_ RTC_GUARDED_BY(network_thread_) = 0;
   rtc::WeakPtr<SctpDataChannelControllerInterface> controller_
-      RTC_GUARDED_BY(signaling_thread_);
-  HandshakeState handshake_state_ RTC_GUARDED_BY(signaling_thread_) =
+      RTC_GUARDED_BY(network_thread_);
+  HandshakeState handshake_state_ RTC_GUARDED_BY(network_thread_) =
       kHandshakeInit;
-  bool connected_to_transport_ RTC_GUARDED_BY(signaling_thread_) = false;
+  bool connected_to_transport_ RTC_GUARDED_BY(network_thread_) = false;
   // Did we already start the graceful SCTP closing procedure?
-  bool started_closing_procedure_ RTC_GUARDED_BY(signaling_thread_) = false;
+  bool started_closing_procedure_ RTC_GUARDED_BY(network_thread_) = false;
   // Control messages that always have to get sent out before any queued
   // data.
-  PacketQueue queued_control_data_ RTC_GUARDED_BY(signaling_thread_);
-  PacketQueue queued_received_data_ RTC_GUARDED_BY(signaling_thread_);
-  PacketQueue queued_send_data_ RTC_GUARDED_BY(signaling_thread_);
+  PacketQueue queued_control_data_ RTC_GUARDED_BY(network_thread_);
+  PacketQueue queued_received_data_ RTC_GUARDED_BY(network_thread_);
+  PacketQueue queued_send_data_ RTC_GUARDED_BY(network_thread_);
 };
 
 // Downcast a PeerConnectionInterface that points to a proxy object
diff --git a/pc/sdp_offer_answer.cc b/pc/sdp_offer_answer.cc
index c382d611ae..90a6cd2b92 100644
--- a/pc/sdp_offer_answer.cc
+++ b/pc/sdp_offer_answer.cc
@@ -3268,20 +3268,16 @@ void SdpOfferAnswerHandler::AllocateSctpSids() {
     return;
   }
 
-  absl::optional<rtc::SSLRole> role = network_thread()->BlockingCall([this] {
-    RTC_DCHECK_RUN_ON(network_thread());
-    return pc_->GetSctpSslRole_n();
-  });
-
-  if (!role) {
-    role = GuessSslRole();
-  }
-
-  if (role) {
-    // TODO(webrtc:11547): Make this call on the network thread too once
-    // `AllocateSctpSids` has been updated.
-    data_channel_controller()->AllocateSctpSids(*role);
-  }
+  absl::optional<rtc::SSLRole> guessed_role = GuessSslRole();
+  network_thread()->BlockingCall(
+      [&, data_channel_controller = data_channel_controller()] {
+        RTC_DCHECK_RUN_ON(network_thread());
+        absl::optional<rtc::SSLRole> role = pc_->GetSctpSslRole_n();
+        if (!role)
+          role = guessed_role;
+        if (role)
+          data_channel_controller->AllocateSctpSids(*role);
+      });
 }
 
 absl::optional<rtc::SSLRole> SdpOfferAnswerHandler::GuessSslRole() const {
@@ -5117,13 +5113,13 @@ void SdpOfferAnswerHandler::DestroyDataChannelTransport(RTCError error) {
   RTC_DCHECK_RUN_ON(signaling_thread());
   const bool has_sctp = pc_->sctp_mid().has_value();
 
-  if (has_sctp)
-    data_channel_controller()->OnTransportChannelClosed(error);
-
-  context_->network_thread()->BlockingCall([this] {
-    RTC_DCHECK_RUN_ON(context_->network_thread());
-    pc_->TeardownDataChannelTransport_n();
-  });
+  context_->network_thread()->BlockingCall(
+      [&, data_channel_controller = data_channel_controller()] {
+        RTC_DCHECK_RUN_ON(context_->network_thread());
+        if (has_sctp)
+          data_channel_controller->OnTransportChannelClosed(error);
+        pc_->TeardownDataChannelTransport_n();
+      });
 
   if (has_sctp)
     pc_->ResetSctpDataMid();
diff --git a/pc/test/fake_data_channel_controller.h b/pc/test/fake_data_channel_controller.h
index 26ecc31378..d1b41fcf88 100644
--- a/pc/test/fake_data_channel_controller.h
+++ b/pc/test/fake_data_channel_controller.h
@@ -29,23 +29,31 @@ class FakeDataChannelController
         transport_available_(false),
         ready_to_send_(false),
         transport_error_(false) {}
-  virtual ~FakeDataChannelController() {}
+
+  ~FakeDataChannelController() override {
+    network_thread_->BlockingCall([&] {
+      RTC_DCHECK_RUN_ON(network_thread_);
+      weak_factory_.InvalidateWeakPtrs();
+    });
+  }
 
   rtc::WeakPtr<FakeDataChannelController> weak_ptr() {
+    RTC_DCHECK_RUN_ON(network_thread_);
     return weak_factory_.GetWeakPtr();
   }
 
   rtc::scoped_refptr<webrtc::SctpDataChannel> CreateDataChannel(
       absl::string_view label,
       webrtc::InternalDataChannelInit init) {
-    rtc::WeakPtr<FakeDataChannelController> my_weak_ptr = weak_ptr();
-    // Explicitly associate the weak ptr instance with the current thread to
-    // catch early any inappropriate referencing of it on the network thread.
-    RTC_CHECK(my_weak_ptr);
-
     rtc::scoped_refptr<webrtc::SctpDataChannel> channel =
         network_thread_->BlockingCall([&]() {
           RTC_DCHECK_RUN_ON(network_thread_);
+          rtc::WeakPtr<FakeDataChannelController> my_weak_ptr = weak_ptr();
+          // Explicitly associate the weak ptr instance with the current thread
+          // to catch early any inappropriate referencing of it on the network
+          // thread.
+          RTC_CHECK(my_weak_ptr);
+
           rtc::scoped_refptr<webrtc::SctpDataChannel> channel =
               webrtc::SctpDataChannel::Create(
                   std::move(my_weak_ptr), std::string(label),
@@ -54,17 +62,16 @@ class FakeDataChannelController
           if (transport_available_ && channel->sid_n().HasValue()) {
             AddSctpDataStream(channel->sid_n());
           }
+          if (ready_to_send_) {
+            network_thread_->PostTask([channel = channel] {
+              if (channel->state() !=
+                  webrtc::DataChannelInterface::DataState::kClosed) {
+                channel->OnTransportReady();
+              }
+            });
+          }
           return channel;
         });
-    if (ready_to_send_) {
-      signaling_thread_->PostTask(
-          SafeTask(signaling_safety_.flag(), [channel = channel] {
-            if (channel->state() !=
-                webrtc::DataChannelInterface::DataState::kClosed) {
-              channel->OnTransportReady();
-            }
-          }));
-    }
     connected_channels_.insert(channel.get());
     return channel;
   }
@@ -72,6 +79,7 @@ class FakeDataChannelController
   webrtc::RTCError SendData(webrtc::StreamId sid,
                             const webrtc::SendDataParams& params,
                             const rtc::CopyOnWriteBuffer& payload) override {
+    RTC_DCHECK_RUN_ON(network_thread_);
     RTC_CHECK(ready_to_send_);
     RTC_CHECK(transport_available_);
     if (send_blocked_) {
@@ -100,17 +108,14 @@ class FakeDataChannelController
     RTC_DCHECK_RUN_ON(network_thread_);
     RTC_CHECK(sid.HasValue());
     known_stream_ids_.erase(sid);
-    signaling_thread_->PostTask(SafeTask(signaling_safety_.flag(), [this, sid] {
-      // Unlike the real SCTP transport, act like the closing procedure finished
-      // instantly.
-      auto it = absl::c_find_if(connected_channels_, [&](const auto* c) {
-        return c->sid_s() == sid;
-      });
-      // This path mimics the DCC's OnChannelClosed handler since the FDCC
-      // (this class) doesn't have a transport that would do that.
-      if (it != connected_channels_.end())
-        (*it)->OnClosingProcedureComplete();
-    }));
+    // Unlike the real SCTP transport, act like the closing procedure finished
+    // instantly.
+    auto it = absl::c_find_if(connected_channels_,
+                              [&](const auto* c) { return c->sid_n() == sid; });
+    // This path mimics the DCC's OnChannelClosed handler since the FDCC
+    // (this class) doesn't have a transport that would do that.
+    if (it != connected_channels_.end())
+      (*it)->OnClosingProcedureComplete();
   }
 
   void OnChannelStateChanged(
@@ -126,36 +131,40 @@ class FakeDataChannelController
 
   // Set true to emulate the SCTP stream being blocked by congestion control.
   void set_send_blocked(bool blocked) {
-    send_blocked_ = blocked;
-    if (!blocked) {
-      RTC_CHECK(transport_available_);
-      // Make a copy since `connected_channels_` may change while
-      // OnTransportReady is called.
-      auto copy = connected_channels_;
-      for (webrtc::SctpDataChannel* ch : copy) {
-        ch->OnTransportReady();
+    network_thread_->BlockingCall([&]() {
+      send_blocked_ = blocked;
+      if (!blocked) {
+        RTC_CHECK(transport_available_);
+        // Make a copy since `connected_channels_` may change while
+        // OnTransportReady is called.
+        auto copy = connected_channels_;
+        for (webrtc::SctpDataChannel* ch : copy) {
+          ch->OnTransportReady();
+        }
       }
-    }
+    });
   }
 
   // Set true to emulate the transport channel creation, e.g. after
   // setLocalDescription/setRemoteDescription called with data content.
   void set_transport_available(bool available) {
-    transport_available_ = available;
+    network_thread_->BlockingCall([&]() { transport_available_ = available; });
   }
 
   // Set true to emulate the transport OnTransportReady signal when the
   // transport becomes writable for the first time.
   void set_ready_to_send(bool ready) {
     RTC_CHECK(transport_available_);
-    ready_to_send_ = ready;
-    if (ready) {
-      std::set<webrtc::SctpDataChannel*>::iterator it;
-      for (it = connected_channels_.begin(); it != connected_channels_.end();
-           ++it) {
-        (*it)->OnTransportReady();
+    network_thread_->BlockingCall([&]() {
+      ready_to_send_ = ready;
+      if (ready) {
+        std::set<webrtc::SctpDataChannel*>::iterator it;
+        for (it = connected_channels_.begin(); it != connected_channels_.end();
+             ++it) {
+          (*it)->OnTransportReady();
+        }
       }
-    }
+    });
   }
 
   void set_transport_error() { transport_error_ = true; }