+/**
+ * Message from communicator to transport service asking for
+ * transmission of a backchannel message with the given peer @e pid
+ * and communicator.
+ */
+struct GNUNET_TRANSPORT_CommunicatorBackchannel
+{
+ /**
+ * Type will be #GNUNET_MESSAGE_TYPE_TRANSPORT_COMMUNICATOR_BACKCHANNEL
+ */
+ struct GNUNET_MessageHeader header;
+
+ /**
+ * Always zero, for alignment.
+ */
+ uint32_t reserved;
+
+ /**
+ * Target peer.
+ */
+ struct GNUNET_PeerIdentity pid;
+
+ /* Followed by a `struct GNUNET_MessageHeader` with the encapsulated
+ message to the communicator */
+
+ /* Followed by the 0-terminated string specifying the desired
+ communicator at the target (@e pid) peer */
+};
+
+
+/**
+ * Message from transport to communicator passing along a backchannel
+ * message from the given peer @e pid.
+ */
+struct GNUNET_TRANSPORT_CommunicatorBackchannelIncoming
+{
+ /**
+ * Type will be #GNUNET_MESSAGE_TYPE_TRANSPORT_COMMUNICATOR_BACKCHANNEL_INCOMING
+ */
+ struct GNUNET_MessageHeader header;
+
+ /**
+ * Always zero, for alignment.
+ */
+ uint32_t reserved;
+
+ /**
+ * Origin peer.
+ */
+ struct GNUNET_PeerIdentity pid;
+
+ /* Followed by a `struct GNUNET_MessageHeader` with the encapsulated
+ message to the communicator */
+
+};
+