diff --git a/mesh.proto b/mesh.proto
index 7db7c87..e2a1d14 100644
--- a/mesh.proto
+++ b/mesh.proto
@@ -6,6 +6,9 @@ syntax = "proto3";
 
 option java_package = "com.geeksville.mesh";
 option java_outer_classname = "MeshProtos";
+option optimize_for = LITE_RUNTIME;
+
+import "portnums.proto";
 
 /**
 MESH RADIO PROTOCOL
@@ -82,29 +85,12 @@ message Position {
 }
 
 // a data message to forward to an external app (or possibly also be consumed
-// internally in the case of CLEAR_TEXT and CLEAR_READACK
+// internally in the case of CLEAR_TEXT and CLEAR_READACK)
 message Data {
-  enum Type {
-    /// A message sent from a device outside of the mesh, in a form the mesh
-    /// does not understand
-    OPAQUE = 0; // NOTE: This must be 0, because it is documented in
-    // IMeshService.aidl to be so
 
-    /// a simple UTF-8 text message, which even the little micros in the mesh
-    /// can understand and show on their screen eventually in some circumstances
-    /// even signal might send messages in this form (see below)
-    CLEAR_TEXT = 1;
+  // formerly named typ and of type Type
+  PortNum portnum = 1;
 
-    /// a message receive acknowledgement, sent in cleartext - allows radio to
-    /// show user that a message has been read by the recipient, optional
-    CLEAR_READACK = 2;
-
-    /// Apps will eventually be able to register their own handlers for
-    /// particular payload type codes so multiple apps can share the same radio
-    /// (this will replace OPAQUE)
-  }
-
-  Type typ = 1;      // required
   bytes payload = 2; // required
 }
 
diff --git a/portnums.proto b/portnums.proto
new file mode 100644
index 0000000..2ce7f3f
--- /dev/null
+++ b/portnums.proto
@@ -0,0 +1,41 @@
+syntax = "proto3";
+
+/** 
+  For any new 'apps' that run on the device or via sister apps on phones/PCs they should pick and use a
+  unique 'portnum' for their application.
+
+  If you are making a new app using meshtastic, please send in a pull request to add your 'portnum' to this
+  master table.  PortNums should be assigned in the following range:
+
+  0-63   Core Meshtastic use, do not use for third party apps
+  64-127 Registered 3rd party apps, send in a pull request that adds a new entry to portnums.proto to 
+         register your application
+  256-512 Use one of these portnums for your private applications that you don't want to register publically
+
+  All other values are reserved.
+
+  Note: This was formerly a Type enum named 'typ' with the same id #
+  
+  We have change to this 'portnum' based scheme for specifying app handlers for particular payloads.  
+  This change is backwards compatible by treating the legacy OPAQUE/CLEAR_TEXT values identically.
+
+*/
+enum PortNum {
+    /// Deprecated: do not use in new code (formerly called OPAQUE)
+    /// A message sent from a device outside of the mesh, in a form the mesh
+    /// does not understand
+    UNKNOWN_APP = 0; // NOTE: This must be 0, because it is documented in
+    // IMeshService.aidl to be so
+  
+    /// a simple UTF-8 text message, which even the little micros in the mesh
+    /// can understand and show on their screen eventually in some circumstances
+    /// even signal might send messages in this form (see below)
+    /// Formerly called CLEAR_TEXT
+    TEXT_MESSAGE_APP = 1;
+  
+    /// a message receive acknowledgement, sent in cleartext - allows radio to
+    /// show user that a message has been read by the recipient, optional
+    // Note: this concept has been removed for now.  Once READACK is implemented, use the 
+    // new packet type/port number stuff?
+    // CLEAR_READACK = 2;
+  }
\ No newline at end of file