--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/samples/main-header.cc	Fri Aug 03 17:00:40 2007 +0200
@@ -0,0 +1,123 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+#include "ns3/packet.h"
+#include "ns3/header.h"
+#include <iostream>
+
+using namespace ns3;
+
+/* A sample Header implementation
+ */
+class MyHeader : public Header 
+{
+public:
+  static const char *GetUid (void);
+
+  MyHeader ();
+  virtual ~MyHeader ();
+
+  void SetData (uint16_t data);
+  uint16_t GetData (void) const;
+private:
+  virtual std::string DoGetName (void) const;
+  virtual void PrintTo (std::ostream &os) const;
+  virtual void SerializeTo (Buffer::Iterator start) const;
+  virtual uint32_t DeserializeFrom (Buffer::Iterator start);
+  virtual uint32_t GetSerializedSize (void) const;
+
+  uint16_t m_data;
+};
+
+MyHeader::MyHeader ()
+{
+  // we must provide a public default constructor, 
+  // implicit or explicit, but never private.
+}
+MyHeader::~MyHeader ()
+{}
+
+const char *
+MyHeader::GetUid (void)
+{
+  // This string is used by the internals of the packet
+  // code to keep track of the packet metadata.
+  // You need to make sure that this string is absolutely
+  // unique. The code will detect any duplicate string.
+  return "MyHeader.test.nsnam.org";
+}
+
+std::string 
+MyHeader::DoGetName (void) const
+{
+  // This string is used to identify the type of 
+  // my header by the packet printing routines.
+  return "MYHEADER";
+}
+void 
+MyHeader::PrintTo (std::ostream &os) const
+{
+  // This method is invoked by the packet printing
+  // routines to print the content of my header.
+  os << "data=" << m_data << std::endl;
+}
+uint32_t
+MyHeader::GetSerializedSize (void) const
+{
+  // we reserve 2 bytes for our header.
+  return 2;
+}
+void
+MyHeader::SerializeTo (Buffer::Iterator start) const
+{
+  // we can serialize two bytes at the start of the buffer.
+  // we write them in network byte order.
+  start.WriteHtonU16 (m_data);
+}
+uint32_t
+MyHeader::DeserializeFrom (Buffer::Iterator start)
+{
+  // we can deserialize two bytes from the start of the buffer.
+  // we read them in network byte order and store them
+  // in host byte order.
+  m_data = start.ReadNtohU16 ();
+
+  // we return the number of bytes effectively read.
+  return 2;
+}
+
+void 
+MyHeader::SetData (uint16_t data)
+{
+  m_data = data;
+}
+uint16_t 
+MyHeader::GetData (void) const
+{
+  return m_data;
+}
+
+
+
+int main (int argc, char *argv[])
+{
+  // instantiate a header.
+  MyHeader sourceHeader;
+  sourceHeader.SetData (2);
+
+  // instantiate a packet
+  Packet p;
+  // and store my header into the packet.
+  p.AddHeader (sourceHeader);
+
+  // print the content of my packet on the standard output.
+  p.Print (std::cout);
+
+  // you can now remove the header from the packet:
+  MyHeader destinationHeader;
+  p.RemoveHeader (destinationHeader);
+
+  // and check that the destination and source
+  // headers contain the same values.
+  NS_ASSERT (sourceHeader.GetData () == destinationHeader.GetData ());
+
+  return 0;
+}

--- a/samples/main-packet.cc	Fri Aug 03 14:09:04 2007 +0200
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,118 +0,0 @@
-/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-#include "ns3/packet.h"
-#include "ns3/header.h"
-#include <iostream>
-
-using namespace ns3;
-
-/* A sample Header implementation
- */
-class MyHeader : public Header 
-{
-public:
-  static const char *GetUid (void);
-
-  MyHeader ();
-  virtual ~MyHeader ();
-
-  void SetData (uint16_t data);
-  uint16_t GetData (void) const;
-private:
-  virtual std::string DoGetName (void) const;
-  virtual void PrintTo (std::ostream &os) const;
-  virtual void SerializeTo (Buffer::Iterator start) const;
-  virtual uint32_t DeserializeFrom (Buffer::Iterator start);
-  virtual uint32_t GetSerializedSize (void) const;
-
-  uint16_t m_data;
-};
-
-const char *
-MyHeader::GetUid (void)
-{
-  // make sure the string is really unique.
-  return "MyHeader.test.nsnam.org";
-}
-
-MyHeader::MyHeader ()
-{}
-MyHeader::~MyHeader ()
-{}
-std::string 
-MyHeader::DoGetName (void) const
-{
-  return "MyHeader";
-}
-void 
-MyHeader::PrintTo (std::ostream &os) const
-{
-  os << "MyHeader data=" << m_data << std::endl;
-}
-uint32_t
-MyHeader::GetSerializedSize (void) const
-{
-  return 2;
-}
-void
-MyHeader::SerializeTo (Buffer::Iterator start) const
-{
-  // serialize in head of buffer
-  start.WriteHtonU16 (m_data);
-}
-uint32_t
-MyHeader::DeserializeFrom (Buffer::Iterator start)
-{
-  // deserialize from head of buffer
-  m_data = start.ReadNtohU16 ();
-  return GetSerializedSize ();
-}
-
-void 
-MyHeader::SetData (uint16_t data)
-{
-  m_data = data;
-}
-uint16_t 
-MyHeader::GetData (void) const
-{
-  return m_data;
-}
-
-/* A sample Tag implementation
- */
-class MyTag 
-{
-public:
-  static const char *GetUid (void) {return "MyTag.test.nsnam.org";}
-  void Print (std::ostream &os) const {}
-  uint32_t GetSerializedSize (void) const {return 0;}
-  void Serialize (Buffer::Iterator i) const {}
-  uint32_t Deserialize (Buffer::Iterator i) {return 0;}
-
-  uint16_t m_streamId;
-};
-
-static void
-Receive (Packet p)
-{
-  MyHeader my;
-  p.RemoveHeader (my);
-  std::cout << "received data=" << my.GetData () << std::endl;
-  struct MyTag myTag;
-  p.PeekTag (myTag);
-}
-
-
-int main (int argc, char *argv[])
-{
-  Packet p;
-  MyHeader my;
-  my.SetData (2);
-  std::cout << "send data=2" << std::endl;
-  p.AddHeader (my);
-  struct MyTag myTag;
-  myTag.m_streamId = 5;
-  p.AddTag (myTag);
-  Receive (p);
-  return 0;
-}

--- a/samples/wscript	Fri Aug 03 14:09:04 2007 +0200
+++ b/samples/wscript	Fri Aug 03 17:00:40 2007 +0200
@@ -14,7 +14,7 @@
     obj = create_ns_prog('main-ptr', 'main-ptr.cc')
     #obj = create_ns_prog('main-trace', 'main-trace.cc')
     obj = create_ns_prog('main-simulator', 'main-simulator.cc')
-    obj = create_ns_prog('main-packet', 'main-packet.cc')
+    obj = create_ns_prog('main-header', 'main-header.cc')
     obj = create_ns_prog('main-test', 'main-test.cc')
     obj = create_ns_prog('main-simple', 'main-simple.cc',
                          deps=['node', 'internet-node', 'applications'])

--- a/src/common/header.h	Fri Aug 03 14:09:04 2007 +0200
+++ b/src/common/header.h	Fri Aug 03 17:00:40 2007 +0200
@@ -36,6 +36,29 @@
  *   - ns3::Header::DeserializeFrom
  *   - ns3::Header::GetSerializedSize
  *   - ns3::Header::PrintTo
+ *   - ns3::Header::DoGetName
+ *
+ * Each header must also make sure that:
+ *   - it defines a public default constructor
+ *   - it defines a public static method named GetUid which returns a string.
+ *
+ * The latter should look like the following to ensure that
+ * every header returns a unique string.
+ * \code
+ * class MyHeader : public Header
+ * {
+ * public:
+ *   static const char *GetUid (void);
+ * };
+ *
+ * const char *MyHeader::GetUid (void)
+ * {
+ *   return "MyHeader.unique.prefix";
+ * }
+ * \endcode
+ *
+ * Sample code which shows how to create a new Header, and how to use it, 
+ * is shown in the sample file samples/main-header.cc
  */
 class Header : public Chunk {
 public:

--- a/src/common/packet.h	Fri Aug 03 14:09:04 2007 +0200
+++ b/src/common/packet.h	Fri Aug 03 17:00:40 2007 +0200
@@ -58,21 +58,19 @@
  * were serialized in the byte buffer. The maintenance of metadata is
  * optional and disabled by default. To enable it, you must call
  * Packet::EnableMetadata and this will allow you to get non-empty
- * output from Packet::Print and Packet::PrintDefault.
+ * output from Packet::Print and Packet::Print.
  *
  * Implementing a new type of Header or Trailer for a new protocol is 
  * pretty easy and is a matter of creating a subclass of the ns3::Header 
- * or of the ns3::Trailer base class, and implementing the 4 pure virtual 
+ * or of the ns3::Trailer base class, and implementing the 5 pure virtual 
  * methods defined in either of the two base classes. Users _must_
- * also implement a static public method named GetUid which is
- * expected to return a unique string which uniquely identifies the
- * user's new header or trailer.
- *
- * Sample code which shows how to create a new Header, and how to use it, 
- * is shown in the sample file samples/main-header.cc
+ * also make sure that they class defines a public default constructor and
+ * a public method named GetUid, as documented in the ns3::Header and ns::Trailer
+ * API documentations.
  *
  * Implementing a new type of Tag requires roughly the same amount of
- * work: 
+ * work: users must implement a total of 6 methods which are described in
+ * the ns3::Tags API documentation.
  *
  * The current implementation of the byte buffers and tag list is based
  * on COW (Copy On Write. An introduction to COW can be found in Scott 

--- a/src/common/trailer.h	Fri Aug 03 14:09:04 2007 +0200
+++ b/src/common/trailer.h	Fri Aug 03 17:00:40 2007 +0200
@@ -36,6 +36,26 @@
  *   - ns3::Trailer::DeserializeFrom
  *   - ns3::Trailer::GetSerializedSize
  *   - ns3::Trailer::PrintTo
+ *   - ns3::Trailer::DoGetName
+ *
+ * Each trailer must also make sure that:
+ *   - it defines a public default constructor
+ *   - it defines a public static method named GetUid which returns a string.
+ *
+ * The latter should look like the following to ensure that
+ * every trailer returns a unique string.
+ * \code
+ * class MyTrailer : public Header
+ * {
+ * public:
+ *   static const char *GetUid (void);
+ * };
+ *
+ * const char *MyTrailer::GetUid (void)
+ * {
+ *   return "MyTrailer.unique.prefix";
+ * }
+ * \endcode
  *
  * Note that the SerializeTo and DeserializeFrom methods behave
  * in a way which might seem surprising to users: the input iterator