diff --git a/src/runtime2/inbox2.rs b/src/runtime2/inbox2.rs
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..d07e95d6839724f9c0b4ae5066a4c42688dc893b 100644
--- a/src/runtime2/inbox2.rs
+++ b/src/runtime2/inbox2.rs
@@ -0,0 +1,64 @@
+use crate::protocol::eval::ValueGroup;
+use crate::runtime2::branch::BranchId;
+use crate::runtime2::ConnectorId;
+use crate::runtime2::port::PortIdLocal;
+
+#[derive(Copy, Clone)]
+pub(crate) struct PortAnnotation {
+    pub port_id: PortIdLocal,
+    pub registered_id: Option<BranchId>,
+    pub expected_firing: Option<bool>,
+}
+
+/// The header added by the synchronization algorithm to all.
+pub(crate) struct SyncHeader {
+    pub sending_component_id: ConnectorId,
+    pub highest_component_id: ConnectorId,
+}
+
+/// The header added to data messages
+pub(crate) struct DataHeader {
+    pub expected_mapping: Vec<PortAnnotation>,
+    pub target_port: PortIdLocal,
+    pub new_mapping: BranchId,
+}
+
+/// A data message is a message that is intended for the receiver's PDL code,
+/// but will also be handled by the consensus algrorithm
+pub(crate) struct DataMessageFancy {
+    pub sync_header: SyncHeader,
+    pub data_header: DataHeader,
+    pub content: ValueGroup,
+}
+
+pub(crate) enum SyncContent {
+
+}
+
+/// A sync message is a message that is intended only for the consensus
+/// algorithm.
+pub(crate) struct SyncMessageFancy {
+    pub sync_header: SyncHeader,
+    pub content: SyncContent,
+}
+
+/// A control message is a message intended for the scheduler that is executing
+/// a component.
+pub(crate) struct ControlMessageFancy {
+    pub id: u32, // generic identifier, used to match request to response
+    pub content: ControlContent,
+}
+
+pub(crate) enum ControlContent {
+    PortPeerChanged(PortIdLocal, ConnectorId),
+    CloseChannel(PortIdLocal),
+    Ack,
+    Ping,
+}
+
+/// Combination of data message and control messages.
+pub(crate) enum MessageFancy {
+    Data(DataMessageFancy),
+    Sync(SyncMessageFancy),
+    Control(ControlMessageFancy),
+}
\ No newline at end of file