diff --git a/example-data/nfv.xml b/example-data/nfv.xml
index a956b2b51ebb5f5c36cab9095f918b8eefc8bded..43e532fbe77905df6070f5ba5ba34a28d8085f82 100644
--- a/example-data/nfv.xml
+++ b/example-data/nfv.xml
@@ -11,15 +11,15 @@
       <name>Firewall VDU</name>
       <int-cpd>
         <id>inside</id>
-        <layer-protocol>Ethernet</layer-protocol>
+        <layer-protocol>ethernet</layer-protocol>
       </int-cpd>
       <int-cpd>
         <id>management</id>
-        <layer-protocol>Ethernet</layer-protocol>
+        <layer-protocol>ethernet</layer-protocol>
       </int-cpd>
       <int-cpd>
         <id>outside</id>
-        <layer-protocol>Ethernet</layer-protocol>
+        <layer-protocol>ethernet</layer-protocol>
       </int-cpd>
       <virtual-compute-desc>asa-vcd</virtual-compute-desc>
       <virtual-storage-desc>asa-vsd</virtual-storage-desc>
@@ -52,7 +52,7 @@
 	<vdu-id>firewall</vdu-id>
 	<cpd>inside</cpd>
       </int-cpd>
-      <layer-protocol>Ethernet</layer-protocol>
+      <layer-protocol>ethernet</layer-protocol>
     </ext-cpd>
     <ext-cpd>
       <id>management</id>
@@ -60,7 +60,7 @@
 	<vdu-id>firewall</vdu-id>
 	<cpd>management</cpd>
       </int-cpd>
-      <layer-protocol>Ethernet</layer-protocol>
+      <layer-protocol>ethernet</layer-protocol>
     </ext-cpd>
     <ext-cpd>
       <id>outside</id>
@@ -68,7 +68,7 @@
 	<vdu-id>firewall</vdu-id>
 	<cpd>outside</cpd>
       </int-cpd>
-      <layer-protocol>Ethernet</layer-protocol>
+      <layer-protocol>ethernet</layer-protocol>
     </ext-cpd>
     <df>
       <id>normal</id>
@@ -106,15 +106,15 @@
       <name>Router VDU</name>
       <int-cpd>
         <id>left</id>
-        <layer-protocol>Ethernet</layer-protocol>
+        <layer-protocol>ethernet</layer-protocol>
       </int-cpd>
       <int-cpd>
         <id>management</id>
-        <layer-protocol>Ethernet</layer-protocol>
+        <layer-protocol>ethernet</layer-protocol>
       </int-cpd>
       <int-cpd>
         <id>right</id>
-        <layer-protocol>Ethernet</layer-protocol>
+        <layer-protocol>ethernet</layer-protocol>
       </int-cpd>
       <virtual-compute-desc>csr-vcd</virtual-compute-desc>
       <virtual-storage-desc>csr-vsd</virtual-storage-desc>
@@ -147,7 +147,7 @@
 	<vdu-id>router</vdu-id>
 	<cpd>left</cpd>
       </int-cpd>
-      <layer-protocol>Ethernet</layer-protocol>
+      <layer-protocol>ethernet</layer-protocol>
     </ext-cpd>
     <ext-cpd>
       <id>management</id>
@@ -155,7 +155,7 @@
 	<vdu-id>router</vdu-id>
 	<cpd>management</cpd>
       </int-cpd>
-      <layer-protocol>Ethernet</layer-protocol>
+      <layer-protocol>ethernet</layer-protocol>
     </ext-cpd>
     <ext-cpd>
       <id>right</id>
@@ -163,7 +163,7 @@
 	<vdu-id>router</vdu-id>
 	<cpd>right</cpd>
       </int-cpd>
-      <layer-protocol>Ethernet</layer-protocol>
+      <layer-protocol>ethernet</layer-protocol>
     </ext-cpd>
     <df>
       <id>normal</id>
@@ -243,7 +243,7 @@
       <id>fw2dpi</id>
       <connectivity-type>
         <layer-protocol>
-	  <protocol>Ethernet</protocol>
+	  <protocol>ethernet</protocol>
 	</layer-protocol>
       </connectivity-type>
       <df>
@@ -258,7 +258,7 @@
       <id>mgmt</id>
       <connectivity-type>
         <layer-protocol>
-	  <protocol>IPv4</protocol>
+	  <protocol>ipv4</protocol>
 	</layer-protocol>
       </connectivity-type>
       <df>
@@ -273,7 +273,7 @@
       <id>r2fw</id>
       <connectivity-type>
         <layer-protocol>
-	  <protocol>Ethernet</protocol>
+	  <protocol>ethernet</protocol>
 	</layer-protocol>
       </connectivity-type>
       <df>
@@ -498,7 +498,7 @@
       <id>r2fw</id>
       <connectivity-type>
         <layer-protocol>
-	  <protocol>IPv4</protocol>
+	  <protocol>ipv4</protocol>
 	</layer-protocol>
       </connectivity-type>
       <df>
@@ -570,7 +570,7 @@
     <version>1.0</version>
     <ext-cpd>
       <id>outside</id>
-      <layer-protocol>Ethernet</layer-protocol>
+      <layer-protocol>ethernet</layer-protocol>
     </ext-cpd>
   </pnfd>
 </nfv>
diff --git a/src/yang/etsi-nfv-common.yang b/src/yang/etsi-nfv-common.yang
index 23092426674b924167c950a593d8e903b548d710..410e2a390e8333d0d61c8094420ed27f5192c3e0 100644
--- a/src/yang/etsi-nfv-common.yang
+++ b/src/yang/etsi-nfv-common.yang
@@ -20,22 +20,22 @@ submodule etsi-nfv-common {
    */
   identity layer-protocol {
   }
-  identity Ethernet {
+  identity ethernet {
     base layer-protocol;
   }
-  identity MPLS {
+  identity mpls {
     base layer-protocol;
   }
-  identity ODU2 {
+  identity odu2 {
     base layer-protocol;
   }
-  identity IPv4 {
+  identity ipv4 {
     base layer-protocol;
   }
-  identity IPv6 {
+  identity ipv6 {
     base layer-protocol;
   }
-  identity Pseudo-Wire {
+  identity pseudo-wire {
     base layer-protocol;
   }
 
@@ -392,7 +392,7 @@ submodule etsi-nfv-common {
     }
 
     leaf-list layer-protocol {
-      default Ethernet;
+      default ethernet;
       type identityref {
         base layer-protocol;
       }