diff --git a/protocols/osi3/ipv4.yml b/protocols/osi3/ipv4.yml
index 2ecd550..722d53b 100644
--- a/protocols/osi3/ipv4.yml
+++ b/protocols/osi3/ipv4.yml
@@ -66,4 +66,9 @@ protocol:
       length: 4
       optional: yes
     - field: data
-      data: true
\ No newline at end of file
+      data: true
+  nextlayer:
+    - { protocol: tcp, identifier: 6 }
+    - { protocol: udp, identifier: 17 }
+    
+    
\ No newline at end of file
diff --git a/protocols/osi3/ipv6.yml b/protocols/osi3/ipv6.yml
index 6729f65..46b2296 100644
--- a/protocols/osi3/ipv6.yml
+++ b/protocols/osi3/ipv6.yml
@@ -20,6 +20,7 @@ protocol:
     - field: nextheader
       desc: next header identifier (see ipv4 protocol id)
       length: 1
+      nextlayer: yes
     - field: hoplimit
       desc: hop limit
       length: 1
@@ -28,4 +29,74 @@ protocol:
       length: 16
     - field: dstaddress
       desc: destination address
-      length: 16
\ No newline at end of file
+      length: 16
+  nextlayer:
+    - { protocol: hopbyhop, identifier: 0, extension: yes }
+    - { protocol: destoptions, identifier: 60, extension: yes }
+    - { protocol: routing, identifier: 43, extension: yes }
+    - { protocol: fragment, identifier: 44, extension: yes }
+    - { protocol: ipsec_ah, identifier: 51 }
+    - { protocol: ipsec_esp, identifier: 50 }
+    - { protocol: mobility, identifier: 135, extension: yes }
+    - { protocol: tcp, identifier: 6 }
+    - { protocol: udp, identifier: 17 }
+  extensionreferencefield: nextheader
+  extensions:
+    - extension:
+        name: hopbyhop 
+        referenceid: 0
+        fields: &hopbyhop
+          - field: nextheader
+            length: 1
+            nextlayer: yes
+          - field: extlength
+            desc: Header extension lengthin octets
+            length: 1
+          - field: options
+            length: 6
+          - field: options
+            length: 8
+            optional: yes
+            repeatable: yes
+    - extension: 
+        name: destoptions
+        referenceid: 60
+        fields: *hopbyhop
+    - extension:
+        name: routing #is deprecated (see http://en.wikipedia.org/wiki/IPv6_packet)
+        referenceid: 43
+        fields:
+          - field: nextheader
+            length: 1
+            nextlayer: yes
+          - field: extlength
+            length: 1
+          - field: routingtype
+            length: 1
+          - field: segmentsleft
+            length: 1
+          - field: typedata
+            length: 4
+          - field: typedata
+            length: 8
+            optional: yes
+    - extension:
+        name: fragment
+        referenceid: 44
+        fields:
+          - field: nextheader
+            length: 1
+            nextlayer: yes
+          - field: reserved
+            length: 1
+          - field: fragmentoffset
+            bitfield: yes
+            length: 13
+          - field: reserved
+            bitfield: yes
+            length: 2
+          - field: mflag
+            bitfield: yes
+            length: 1
+          - field: identification
+            length: 4
\ No newline at end of file
diff --git a/structure-schema.yml b/structure-schema.yml
index 1631a5b..449c7c5 100644
--- a/structure-schema.yml
+++ b/structure-schema.yml
@@ -54,6 +54,8 @@ mapping:
                 required: yes
               "extension": 
                 type: bool
+      "extensionreferencefield":
+        type: str
       "extensions": 
         type: seq
         sequence: 
@@ -67,7 +69,6 @@ mapping:
                     required: yes
                   "referencedfrom": #referencing field of protocol definition
                     type: str
-                    required: yes
                   "referenceid": #reference id used in protocol definition or extension itself
                     type: int
                     required: yes