This document discusses OTCL/C++ linkages and provides an example of creating a simple agent class in C++ and exposing it to OTCL. It shows the C++ code for the TSPAgent class with public, private and protected variables and functions. It then shows how to define a TclClass for TSPAgent and register it. The example demonstrates how to instantiate a TSPAgent object from OTCL and call its member functions. The document also briefly describes two case studies on multimedia over UDP and provides information on where to modify different aspects of the NS-2 network simulator code.

1. OTCL/C++ Linkages
T S Pradeep Kumar
http://www.pradeepkumar.org
http://www.nsnam.com
pradeepkumarts@gmail.com

4. TCLCL Classes

5. Simple Agent
class TSPAgent : public Agent {
public:
TSPAgent();
protected:
int command(int argc, const char*const* argv);
private:
int tsp_var1;
double tsp_var2;
void TSPPrivFunc(void);
};

6. Simple Agent
static class TSPAgentClass : public TclClass {
public:
TSPAgentClass() : TclClass("Agent/TSPAgentOtcl") {}
TclObject* create(int, const char*const*) {
return(new TSPAgent());
}
} class_tsp_agent;
TSPAgent::TSPAgent() : Agent(PT_UDP) {
bind("tsp_var1_otcl", &tsp_var1);
bind("tsp_var2_otcl", &tsp_var2);
}

7. Simple Agent
int TSPAgent::command(int argc, const char*const*
argv) {
if(argc == 2) {
if(strcmp(argv[1], "call-tsp-priv-func") == 0) {
TSPPrivFunc();
return(TCL_OK);
}
}
return(Agent::command(argc, argv));
}

8. Simple Agent
void TSPAgent::TSPPrivFunc(void) {
Tcl& tcl = Tcl::instance();
tcl.eval("puts "Message From TSPPrivFunc"");
tcl.evalf("puts " tsp_var1 = %d"", tsp_var1);
tcl.evalf("puts " tsp_var2 = %f"", tsp_var2);
}

9. Creation of a Simple Agent
#name it as .tcl file
# Create TSPAgent
set myagent [new Agent/TSPAgentOtcl]
# Set configurable parameters of TSPAgent
$myagent set tsp_var1_otcl 2
$myagent set tsp_var2_otcl 3.14
# Give a command to TSPAgent
$myagent call-tsp-priv-fun

10. Case study – 2 – Multimedia over udp
• to build a multimedia application that runs
over a UDP connection,
• five rate media scaling
• by changing encoding and transmission policy
pairs associated with scale parameter values.

11. Case study – 2 – Multimedia over udp
• Based on 5 rate
– 0 0.3mb
– 1 0.6mb
– 2 0.9mb
– 3 1.2mb
– 4 1.5mb
– Packetsize 1000
– Random false

12. Case study – 2 – Multimedia over udp
ÒWhen connection established, Sender/receiver
agree on 5 different sets of encoding and
transmission policy pairs.
ÒSender sends with scale 0 but changes the
transmission rates according to the value that the
receiver notifies.
ÒThe receiver is responsible for monitoring the
network congestion and determine the scale
factor. If congestion, then the receiver reduces the
scale factor.

13. Where to modify
• ~ns-2.34 is the folder where all the cc modules
are located
Topic Where to modify
Routing Protocol
(AODV, DSDV, DSR)
~ns-2.34/aodv/aodv.cc, aodv_rtable.cc, etc
Mobile Node (Energy, Propagation,
Antenna)
~ns-2.34/mobile/*.cc and *.h
TCP (Vegas, Reno, New Reno, etc) ~ns-2.34/tcp/ *.cc
New packet, agent to be added ~ns-2.34/common/packet.h, agent.h
Wireless Physical layer or MAC Layer
modification
~ns-2.34/mac/*.cc

14. Where to modify
Topic Where to modify
MPLS ~ns-2.34/mpls
Adding a new Queue ~ns-2.34/queue/*.cc and *.h
Adding a new application ~ns-2.34/apps/app.h
Sensors ~ns-2.34/sensor-net (still to be developed)
Examples (more than 100) ~ns-2.34/tcl/ex/
What not lot more in NS2