external Access_Request_Ext sequential :
      identified_by(Code == 1),
      dynamic_size(RecLength) {
         int       Code:           static_size(1);
         int       Identifier:     static_size(1);
         int       RecLength:      static_size(2),
                                   encode_value(udr_size);
         bytearray Authenticator:  static_size(16);
         switched_set( Type ) {
             int Type:           static_size(1);
             int Length:         static_size(1),
                                   encode_value(case_size);
             case(1) {
               ascii User_Name: dynamic_size( Length - 2 );
             };
             case(2) {
               ascii User_Password: dynamic_size( Length - 2 ),
                                   terminated_by(0);
             };
         // ...
         // Further field definitions.
         // ...
         };
};

external Access_Accept_Ext sequential :
      identified_by(Code == 2),
      dynamic_size(RecLength) {
         // ...
         // Further field definitions.
         // ...
};

external Access_Reject_Ext sequential :
      identified_by(Code == 3),
      dynamic_size(RecLength) {
         // ...
         // Further field definitions.
         // ...
};

internal Vendor_Specific_Int {
      int     Type;
      int     Length;
      int     VendorID;
      int     SubAttrID;
      int     VendorLength;
      int     InfoCode;
      string  Data;
};

in_map Access_Request_Map : external(Access_Request_Ext),
                            target_internal(Access_Request_Int) {
      automatic {
          Vendor_Specific_Ext: internal( Vendor_Specific_Int ),
                        target_internal( Vendor_Specific_TI1 );
      };
};

in_map Access_Accept_InMap: external(Access_Accept_Ext),
           target_internal( Access_Accept_Int ) {
      automatic {
          Vendor_Specific_Ext: internal( Vendor_Specific_Int );
      };
};

out_map Access_Accept_Map : external(Access_Accept_Ext), 
                            internal(Access_Accept_Int) {
      automatic;
};

in_map Access_Reject_InMap: external(Access_Reject_Ext),
           target_internal( Access_Reject_Int ) {
      automatic {
          Vendor_Specific_Ext: internal( Vendor_Specific_Int );
      };
};

out_map Access_Reject_Map : external(Access_Reject_Ext), 
                            internal(Access_Reject_Int) {
      automatic;
};

decoder Request_Dec: in_map(Access_Request_Map);

encoder Response_Enc: out_map(Access_Accept_Map),
                      out_map(Access_Reject_Map);