diff --git a/README.md b/README.md
index 8dd72c8..3a4989c 100644
--- a/README.md
+++ b/README.md
@@ -2,11 +2,41 @@
 simple multiplexing
 
 # goals
-1. window size controls all the streams in total.
+1. receive window is shared among the streams.
 2. precise flow control.
 3. precise memory control.
 4. maximized payload.
 5. optimized for high-speed streams.
 
+```
+FRAMETYPE=Data, OPTIONS=(flagSYN, flagACK, flagFIN, flagRST)
++---------------+--------------+------------+--------------+--------------------------------+
+|               |              |            |              |                                |
+| FRAMETYPE(1B) | OPTIONS(1B)  | LENGTH(2B) | STREAMID(4B) | DATA(MAX 64K)                  |
+|               |              |            |              |                                |
++---------------+--------------+------------+--------------+--------------------------------+
+
+FRAMETYPE=WindowUpdate
++---------------+--------------+------------+
+|               |                           |
+| FRAMETYPE(1B) |  WINDOWSIZE(4B)           |
+|               |                           |
++---------------+--------------+------------+
+
+FRAMETYPE=Ping, OPTIONS=(flagSYN, flagACK)
++---------------+--------------+------------+------------+
+|               |              |                         |
+| FRAMETYPE(1B) | OPTIONS(1B)  | PINGID(4B)              |
+|               |              |                         |
++---------------+--------------+------------+------------+
+
+FRAMETYPE=GoAway 
++---------------+---------------+
+|               |               |
+| FRAMETYPE(1B) | ERROR(2B)     |
+|               |               |
++---------------+---------------+
+```
+
 # status
 in-progress
diff --git a/header.go b/header.go
new file mode 100644
index 0000000..4fae8ba
--- /dev/null
+++ b/header.go
@@ -0,0 +1,15 @@
+package smux
+
+const ( // frame types
+	frameData uint8 = iota
+	frameWindowUpdate
+	framePing
+	frameGoAway
+)
+
+const ( // options
+	flagSYN uint16 = 1 << iota
+	flagACK
+	flagFIN
+	flagRST
+)