diff --git a/sys/net/sixlowpan.h b/sys/net/sixlowpan.h
index 679b95998c..f01712fd5b 100644
--- a/sys/net/sixlowpan.h
+++ b/sys/net/sixlowpan.h
@@ -1 +1,5 @@
-// sixlowpan header file
+/* fragmentation defines */
+#define FRAG1_HDR_LEN		32 	// in bit
+#define FRAGN_HDR_LEN		40 	// in bit
+#define FRAG1_DISPATCH		0xC0	// 11000000
+#define FRAGN_DISPATCH		0xE0	// 11100000