diff --git a/src/internet-node/udp-impl.h b/src/internet-node/udp-impl.h
index 3cccb0f31..7981335da 100644
--- a/src/internet-node/udp-impl.h
+++ b/src/internet-node/udp-impl.h
@@ -28,12 +28,26 @@ namespace ns3 {
 
 class UdpL4Protocol;
 
+/**
+ * \brief Object to create UDP socket instances 
+ *
+ * This class implements the API for UDP sockets.
+ * It is a socket factory (deriving from class SocketFactory) and can
+ * also hold global variables used to initialize newly created sockets, 
+ * such as values that are set through the sysctl or proc interfaces in Linux.
+ */
 class UdpImpl : public Udp
 {
 public:
   UdpImpl (Ptr<UdpL4Protocol> udp);
   virtual ~UdpImpl ();
 
+  /**
+   * \return smart pointer to Socket
+   * 
+   * Implements a method to create a UdpImpl-based socket and return
+   * a base class smart pointer to the socket.
+   */
   virtual Ptr<Socket> CreateSocket (void);
 
 protected:
diff --git a/src/node/socket-factory.h b/src/node/socket-factory.h
index 09b8c9cda..ae999adf3 100644
--- a/src/node/socket-factory.h
+++ b/src/node/socket-factory.h
@@ -28,6 +28,22 @@ namespace ns3 {
 
 class Socket;
 
+/**
+ * \brief Object to create transport layer instances that provide a 
+ * socket API to applications.
+ *
+ * This base class defines the API for creating sockets.  
+ * The socket factory also can hold the global variables used to
+ * initialize newly created sockets, such as values that are
+ * set through the sysctl or proc interfaces in Linux.
+
+ * If you want to write a new transport protocol accessible through
+ * sockets, you need to subclass this factory class, implement CreateSocket, 
+ * instantiate the object, and aggregate it to the node.  
+ * 
+ * \see Udp
+ * \see UdpImpl
+ */
 class SocketFactory : public Object
 {
 public:
@@ -35,6 +51,11 @@ public:
 
   SocketFactory ();
 
+  /**
+   * \return smart pointer to Socket
+   * 
+   * Base class method for creating socket instances.
+   */
   virtual Ptr<Socket> CreateSocket (void) = 0;
 };
 
diff --git a/src/node/udp.h b/src/node/udp.h
index 408d77caf..d67dce768 100644
--- a/src/node/udp.h
+++ b/src/node/udp.h
@@ -27,6 +27,19 @@ namespace ns3 {
 
 class Socket;
 
+/**
+ * \brief API to create UDP socket instances 
+ *
+ * This abstract class defines the API for UDP sockets.
+ * This class also can hold the global default variables used to
+ * initialize newly created sockets, such as values that are
+ * set through the sysctl or proc interfaces in Linux.
+
+ * All UDP implementations must provide an implementation of CreateSocket
+ * below.
+ * 
+ * \see UdpImpl
+ */
 class Udp : public SocketFactory
 {
 public:
@@ -34,6 +47,12 @@ public:
 
   Udp ();
 
+  /**
+   * \return smart pointer to Socket
+   * 
+   * API for creating socket instances; must be implemented by UDP 
+   * implementations..
+   */
   virtual Ptr<Socket> CreateSocket (void) = 0;
 };