diff --git a/library/PCO_Types.ttcn b/library/PCO_Types.ttcn
index 22b475a..0eaa45e 100644
--- a/library/PCO_Types.ttcn
+++ b/library/PCO_Types.ttcn
@@ -48,6 +48,10 @@
 } with { variant "FIELDLENGTH(16)";
 	 variant "BYTEORDER(last)" };
 
+function PCO_P_to_OCT2(PCO_P p) return OCT2 {
+	return int2oct(enum2int(p), 2);
+}
+
 /* RFC 1332 IP Control Protocol options, extensions in RFC 1877 */
 type enumerated IPCP_OPT {
 	IPCP_OPT_IPADDR		(3), /* RFC 1332 3.3 */
@@ -108,15 +112,23 @@
 
 template (value) ProtocolElement ts_PCO_P_DNS_IPv4(template (value) octetstring dns4 := ''O) :=
 	ts_PCO_P_OCTSTR(PCO_P_DNS_IPv4_ADDR, protoIDContents := dns4);
+template (present) ProtocolElement tr_PCO_P_DNS_IPv4(template (present) octetstring dns4 := ?) :=
+	tr_PCO_P_OCTSTR(PCO_P_DNS_IPv4_ADDR, protoIDContents := dns4);
 
 template (value) ProtocolElement ts_PCO_P_DNS_IPv6(template (value) octetstring dns6 := ''O) :=
 	ts_PCO_P_OCTSTR(PCO_P_DNS_IPv6_ADDR, protoIDContents := dns6);
+template (present) ProtocolElement tr_PCO_P_DNS_IPv6(template (present) octetstring dns6 := ?) :=
+	tr_PCO_P_OCTSTR(PCO_P_DNS_IPv6_ADDR, protoIDContents := dns6);
 
 template (value) ProtocolElement ts_PCO_P_PCSCF_IPv4(template (value) octetstring pcscf4 := ''O) :=
 	ts_PCO_P_OCTSTR(PCO_P_PCSCF_IPv4_ADDR, protoIDContents := pcscf4);
+template (present) ProtocolElement tr_PCO_P_PCSCF_IPv4(template (present) octetstring pcscf4 := ?) :=
+	tr_PCO_P_OCTSTR(PCO_P_PCSCF_IPv4_ADDR, protoIDContents := pcscf4);
 
 template (value) ProtocolElement ts_PCO_P_PCSCF_IPv6(template (value) octetstring pcscf6 := ''O) :=
 	ts_PCO_P_OCTSTR(PCO_P_PCSCF_ADDR, protoIDContents := pcscf6);
+template (present) ProtocolElement tr_PCO_P_PCSCF_IPv6(template (present) octetstring pcscf6 := ?) :=
+	tr_PCO_P_OCTSTR(PCO_P_PCSCF_ADDR, protoIDContents := pcscf6);
 
 /* PCO send base template */
 template (value) PCO_DATA ts_PCO(template (value) ProtocolIDList protocols := {}) := {