-#define SPTPS_KEX 0 // Waiting for the first Key EXchange record
-#define SPTPS_SECONDARY_KEX 1 // Ready to receive a secondary Key EXchange record
-#define SPTPS_SIG 2 // Waiting for a SIGnature record
-#define SPTPS_ACK 3 // Waiting for an ACKnowledgement record
+#define SPTPS_KEX 1 // Waiting for the first Key EXchange record
+#define SPTPS_SECONDARY_KEX 2 // Ready to receive a secondary Key EXchange record
+#define SPTPS_SIG 3 // Waiting for a SIGnature record
+#define SPTPS_ACK 4 // Waiting for an ACKnowledgement record
+
+// Overhead for datagrams
+#define SPTPS_DATAGRAM_OVERHEAD 21