diff --git a/library/GTPv1C_CodecPort.ttcn b/library/GTPv1C_CodecPort.ttcn
new file mode 100644
index 0000000..956a674
--- /dev/null
+++ b/library/GTPv1C_CodecPort.ttcn
@@ -0,0 +1,65 @@
+/* dual-faced port sitting on top of IPL4_asp UDP to encode/decode GTPv1C
+ * (C) 2017 Harald Welte <laforge@gnumonks.org>
+ * All rights reserved.
+ *
+ * Released under the terms of GNU General Public License, Version 2 or
+ * (at your option) any later version.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+
+module GTPv1C_CodecPort {
+	import from IPL4asp_PortType all;
+	import from IPL4asp_Types all;
+	import from GTPC_Types all;
+	import from Misc_Helpers all;
+
+	modulepar {
+		SystemUnderTest mp_pl_SystemUnderTest := SGSN;
+	}
+
+	/* identifies a remote peer (sender or receiver) */
+	type record Gtp1cPeer {
+		ConnectionId	connId,
+		HostName	remName,
+		PortNumber	remPort
+	}
+
+	/* Decoded GTP1C (Control Plane), used in send and receive direction */
+	type record Gtp1cUnitdata {
+		Gtp1cPeer		peer,
+		PDU_GTPC	gtpc
+	}
+
+ 	/* Translation port on top of IPL4asp; ASP_Event passed through transparently */
+	type port GTPC_PT message {
+		out	Gtp1cUnitdata;
+		in	Gtp1cUnitdata,
+			ASP_ConnId_ReadyToRelease,
+			ASP_Event;
+	} with { extension "user IPL4asp_PT
+		out(Gtp1cUnitdata -> ASP_SendTo: function(f_enc_Gtp1cUD))
+		in(ASP_RecvFrom -> Gtp1cUnitdata: function(f_dec_Gtp1cUD);
+		   ASP_ConnId_ReadyToRelease -> ASP_ConnId_ReadyToRelease: simple;
+		   ASP_Event -> ASP_Event: simple)" }
+
+	private function f_enc_Gtp1cUD(in Gtp1cUnitdata in_ud, out ASP_SendTo out_ud) {
+		out_ud.connId := in_ud.peer.connId;
+		out_ud.remName := in_ud.peer.remName;
+		out_ud.remPort := in_ud.peer.remPort;
+		out_ud.proto := { udp := {} };
+		out_ud.msg := enc_PDU_GTPC(in_ud.gtpc);
+	} with { extension "prototype(fast)" };
+
+	private function f_dec_Gtp1cUD(in ASP_RecvFrom in_ud, out Gtp1cUnitdata out_ud) {
+		out_ud.peer.connId := in_ud.connId;
+		out_ud.peer.remName := in_ud.remName;
+		out_ud.peer.remPort := in_ud.remPort;
+		out_ud.gtpc := dec_PDU_GTPC(in_ud.msg, pl_SystemUnderTest := mp_pl_SystemUnderTest);
+		if (lengthof(in_ud.msg) != out_ud.gtpc.lengthf + 8) {
+			Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail,
+				log2str("Rx GTPv1-C with field length ", out_ud.gtpc.lengthf, " + 8 != exp ", lengthof(in_ud.msg)));
+		}
+	} with { extension "prototype(fast)" };
+}