Adding a new TCP subclass

[Fernando Cela Diaz <fcela@ce.chalmers.se>]

Hi all,

I'm trying to add a new TCP class to NS (a RFC793 TCP with some flags that
allow to switch on and off mechanisms implemented in Tahoe and Reno over
the plain RFC793 TCP, intended just for undergraduate education).

I have written some test code in a file called tcp-rfc793edu.cc and added
a header for it in tcp.h. In the class constructor I have done a test
bind, as in Marc Greiss turorial:

	RFC793eduTcpAgent::RFC793eduTcpAgent() : TcpAgent()
	{
	 bind_bool("add793expbackoff_", &add793expbackoff_);
	...


And I have set the inicialization value for add793expbackoff_ in
ns-default.tcl, as in MG Tutorial:

	  Agent/TCP/RFC793eduTcp set add793expbackoff_ 0


This yields to the following error after compiling and executing:

: invalid command name "Agent/TCP/RFC793eduTcp" 
    while executing "Agent/TCP/RFC793eduTcp set add793expbackoff_ 0" 


If I change that line in ns-default.tcl in this way:

if [TclObject is-class Agent/TCP/RFC793eduTcp] {
        Agent/TCP/RFC793eduTcp set add793expbackoff_ 0
}

Then I get:

warning: no class variable Agent/TCP/RFC793edu::add793expbackoff_

plus a nice core dump, BUT it works, with add793expbackoff_ set to 0.

Can someone help me?

----------

Here you have the header for the class:


class RFC793eduTcpAgent : public virtual TcpAgent {
 public: 
	RFC793eduTcpAgent(); 
	virtual void rtt_backoff(); 
        void reset(); 

 protected: 
        int add793expbackoff_;  /* Add Karn's exp. backoff to rfc793 tcp
*/
};