diff --git a/IPAConstants.st b/IPAConstants.st
index add1fce..ed52050 100644
--- a/IPAConstants.st
+++ b/IPAConstants.st
@@ -22,6 +22,7 @@ Object subclass: IPAConstants [
     IPAConstants class >> protocolSCCP [ ^ 16rFD ]
     IPAConstants class >> protocolIPA  [ ^ 16rFE ]
     IPAConstants class >> protocolOML  [ ^ 16rFF ]
+    IPAConstants class >> protocolOSMO [ ^ 16rEE ]
 
     IPAConstants class >> msgPing   [ ^ 16r00 ]
     IPAConstants class >> msgPong   [ ^ 16r01 ]
@@ -39,6 +40,11 @@ Object subclass: IPAConstants [
     IPAConstants class >> idtagIpaddr    [ ^ 16r06 ]
     IPAConstants class >> idtagMacaddr   [ ^ 16r07 ]
     IPAConstants class >> idtagUnit      [ ^ 16r08 ]
+
+    "Extensions in Osmocom coming with the OsmoExtension header"
+    IPAConstants class >> osmoCtrl      [ ^ 16r00 ]
+    IPAConstants class >> osmoMgcp      [ ^ 16r01 ]
+    IPAConstants class >> osmoLac       [ ^ 16r02 ]
 ]
 
 CPackedStruct subclass: IPASCCPState [
diff --git a/IPADispatcher.st b/IPADispatcher.st
index fae317c..b8edcd0 100644
--- a/IPADispatcher.st
+++ b/IPADispatcher.st
@@ -1,5 +1,5 @@
 "
- (C) 2010 by Holger Hans Peter Freyther
+ (C) 2010-2011 by Holger Hans Peter Freyther
  All Rights Reserved
 
  This program is free software: you can redistribute it and/or modify
diff --git a/ISUP.st b/ISUP.st
index 5c9d357..49fdbc5 100644
--- a/ISUP.st
+++ b/ISUP.st
@@ -182,6 +182,28 @@ Object subclass: ISUPConstants [
 MSGStructure subclass: ISUPMessage [
     <comment: 'I am the base class for the ISUP messages'>
 
+    ISUPMessage class >> decodeByteStream: aStream [
+        <category: 'parsing'>
+        | col cic type |
+        cic := (aStream next: 2) shortAt: 1.
+        type := (aStream next: 1) at: 1.
+        col := self decodeByteStream: aStream type: type.
+
+        ^ OrderedCollection with: cic with: type with: col.
+    ]
+
+    ISUPMessage class >> encodeCollection: aCollection [
+        | msg type |
+        msg := Osmo.MessageBuffer new.
+        type := aCollection at: 2.
+
+        msg put16: (aCollection at: 1).
+        msg putByte: type.
+
+        msg putByteArray: (self encodeCollection: (aCollection at: 3) type: type).
+        ^ msg
+    ]
+
     parseVariable: aStream with: aClass into: decoded [
         | pos ptr res |
         pos := aStream position.
@@ -203,5 +225,10 @@ MSGStructure subclass: ISUPMessage [
         ptr := aStream next.
         aStream skip: ptr - 1.
     ]
+
+    prepareWrite: aStream [
+        | len |
+        len := self variable size.
+    ]
 ]
 
diff --git a/ISUPTests.st b/ISUPTests.st
index 4e5b1e5..ea02578 100644
--- a/ISUPTests.st
+++ b/ISUPTests.st
@@ -49,6 +49,22 @@ TestCase subclass: ISUPGeneratedTest [
         ].
     ]
 
+    testDecode [
+        | decode struct data |
+        decode := #(16r15 16r00 16r01 16r00 16r00 16r00 16r0A 16r00
+                    16r02 16r0B 16r09 16r04 16r10 16r00 16r19 16r79
+                    16r64 16r64 16r64 16r78 16r0A 16r09 16r02 16r13
+                    16r00 16r79 16r51 16r20 16r01 16r79 16r42 16r00) asByteArray.
+
+        struct := ISUPMessage decodeByteStream: decode readStream.
+        struct inspect.
+
+        data := ISUPMessage encodeCollection: struct.
+        decode printNl.
+        data asByteArray printNl.
+        self assert: data asByteArray = decode.
+    ]
+
     testClassCount [
         self assert: ISUPMessage allSubclasses size = 46.
     ]
diff --git a/MessageBuffer.st b/MessageBuffer.st
index 6b15a4b..d8fa476 100644
--- a/MessageBuffer.st
+++ b/MessageBuffer.st
@@ -46,6 +46,14 @@ Collection subclass: MessageBuffer [
         chunks add: aByteArray.
     ]
 
+    put16: aInt [
+        | data low high |
+        low := (aInt bitAnd: 16rFF).
+        high := (aInt bitShift: -8) bitAnd: 16rFF.
+        data := ByteArray with: low with: high.
+        chunks add: data.
+    ]
+
     putLen16: aInt [
         | data low high |
         low := (aInt bitShift: -8) bitAnd: 16rFF.
diff --git a/MessageStructure.st b/MessageStructure.st
index 231610a..ba494c4 100644
--- a/MessageStructure.st
+++ b/MessageStructure.st
@@ -16,6 +16,13 @@
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 "
 
+Object extend [
+    subclassResponsibility [
+        thisContext backtrace printNl.
+        SystemExceptions.SubclassResponsibility signal
+    ]
+]
+
 "
 The next attempt to generalize the message pattern. We will just describe
 messages that have a type, mandantory and optional parameters. The parameters
@@ -52,6 +59,15 @@ Object subclass: MSGStructure [
         ^ structure decodeByteStream: aStream.
     ]
 
+    MSGStructure class >> encodeCollection: aCollection type: aType [
+        | structure |
+        "This is a generic encoding method that will put the collection
+        onto a MessageBuffer class."
+
+        structure := self findStructure: aType.
+        ^ structure encodeCollection: aCollection.
+    ]
+
     type: aType [
         <category: 'private'>
         type := aType.
@@ -192,12 +208,65 @@ Object subclass: MSGStructure [
             ].
         ].
 
-        aStream atEnd ifFalse: [
-            decoded inspect.
-            ^ self error: 'Stream should be at the end. Unconsumed bytes.'.
+        "TODO: complain about unfetched bytes?"
+        ^ decoded
+    ]
+
+    writeFixed: msg with: clazz from: field [
+        <category: 'encoding'>
+
+        (field isKindOf: clazz) ifFalse: [
+            ^ self error: 'Mandantory information must be %1 but was %2.' % {clazz. field.}.
         ].
 
-        ^ decoded
+        msg nextPutAll: field data.
+    ]
+
+    writeVariable: msg with: clazz from: field [
+        <category: 'encoding'>
+
+        (field isKindOf: clazz) ifFalse: [
+            ^ self error: 'Variable information must be %1 but was %2.' % {clazz. field.}
+        ].
+
+        "TODO: Respect the lengthLength here"
+        msg nextPut: field data size.
+        msg nextPutAll: field data.
+    ]
+
+    prepareWrite: aStream [
+    ]
+
+    encodeCollection: aCollection [
+        | stream msg fixed_done |
+        <category: 'encoding'>
+
+        msg := WriteStream on: (ByteArray new: 3).
+        stream := aCollection readStream.
+        fixed_done := false.
+
+        self fieldsDo: [:type :clazz |
+            type = #fixed ifTrue: [
+                    self writeFixed: msg with: clazz from: stream next.]
+                ifFalse: [
+                    fixed_done ifFalse: [
+                        fixed_done := true.
+                        self prepareWrite: msg.
+                    ].
+                ].
+
+            type = #variable ifTrue: [
+                self writeVariable: msg with: clazz from: stream next.
+            ].
+"
+            type = #optional ifTrue: [
+            ].
+            type = #optionals ifTrue: [
+            ].
+"
+        ].
+
+        ^ msg contents
     ]
 ]