diff --git a/src/runtime2/communication.rs b/src/runtime2/communication.rs
index 335f4c6d0864416a0135f0c9522eb433f19f3328..e7b2d674b32c4330a5e07c5cb859aadfa740735e 100644
--- a/src/runtime2/communication.rs
+++ b/src/runtime2/communication.rs
@@ -1,4 +1,5 @@
 use crate::protocol::eval::*;
+use crate::protocol::eval::value::ValueId;
 use super::runtime::*;
 use super::component::*;
 
@@ -31,6 +32,7 @@ pub struct DataMessage {
     pub data_header: MessageDataHeader,
     pub sync_header: MessageSyncHeader,
     pub content: ValueGroup,
+    pub ports: Vec<TransmittedPort>,
 }
 
 #[derive(Debug)]
@@ -61,6 +63,14 @@ pub struct MessageDataHeader {
     pub target_port: PortId,
 }
 
+#[derive(Debug)]
+pub struct TransmittedPort {
+    location: ValueId, // within `content`
+    messages: Vec<DataMessage>, // owned by previous component
+    peer_comp: CompId,
+    peer_port: PortId,
+}
+
 // -----------------------------------------------------------------------------
 // Sync messages
 // -----------------------------------------------------------------------------