diff --git a/muxer/mplex/constants.py b/muxer/mplex/constants.py
new file mode 100644
index 00000000..dc3e6137
--- /dev/null
+++ b/muxer/mplex/constants.py
@@ -0,0 +1,6 @@
+HEADER_TAGS = {
+    "NEW_STREAM": 0,
+    "MESSAGE": 2,
+    "CLOSE": 4,
+    "RESET": 6
+}
\ No newline at end of file