The TCP../ns-2/tcp.h represents a simplified TCP sender. It sends data to a TCPSink agent and processes its acknowledgments. It has a separate object associated with it which represents an application's demand. By looking at the TCPAgent../ns-2/tcp.h and TCPSinkAgent../ns-2/tcp-sink.h, we may see how relatively complex agents are constructed. An example from the Tahoe TCP agent TCPAgent is also given to illustrate the use of timers.