Installation of NS2 in Linux Congestion Control in TCP

1. 1
Department of Information Science and Engineering
M S Ramaiah Institute of Technology
(Autonomous Institute, Affiliated to VTU)
Bangalore-560054
NS2 Installation and Congestion control
A presentation submitted to
M S Ramaiah Institute of Technology
An Autonomous Institute, Affiliated to
Visvesvaraya Technological University, Belgaum
in partial fulfillment of 5th Sem Under
DATA COMMUNICATIONS
Submitted by
Suman Raj K(1MS14IS417)
Suneel N P(1MS13IS114)
under the guidance of
Dr. Mydhili K. Nair

2. OVERVIEW
 Installation of NS2
 Recompiling NS2
 Congestion Control

3. LINUX FOR NS2
 Linux
 Use of Linux is recommended
 Fedora (10, 12)
 If DVD Version- no need of additional package installation
 Install all the packages (if default installation selected, then additional
packages have to be installed)
 Ubuntu (9.04, 9.10, 10.04, 10.10)
 Additional packages to be installed, there may be GCC Issues, xgraph and
NAM issues
 Red Hat Enterprise Linux 5 (RHEL5)
 Cent OS is the alternative for RHEL
 Basic commands (ls, chmod, tar, rpm, make, gedit, vi, pwd,
passwd, echo, cd, etc)
 Directory structure and shell prompt
 Path variables setting, Installation of packages and
dependencies

4. INSTALLATION OF NS2
 Download from http://isi.edu/nsnam/ns/ns-
build.html#allinone
 Copy the file under /home/pradeep (if your
username is “abcdef” then home folder will be
/home/abcdef)
 Extract it using “tar zxvf ns-allinone-
2.34.tar.gz”
 “cd ns-allinone-2.34”
 “./install “ (if any errors, please correct it)
 Setting of paths in “.bash_profile” or “.bashrc”

5. BASIC ARCHITECTURE OF NS2

6. DIRECTORY STRUCTURE OF NS2

7. TCLCL
 TCLCL Consists of Six main classes
 Tcl (Methods to access the interpreted hierarchy)
 InstVar (binds member variable in both
hierarchies together
 TclObject (base class of all simulation objects)
 TclClass (maps class of IH to class of CH)
 TclCommand (global access to CH from IH)
 EmbeddedTcl (translates OTCL Script to C++
Code)

8. TCLCL
 Each class have various member functions
that are used to get compiled
 As a case study, lets start how to create a
simple agent.

9. 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);
};

10. 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);
}

11. 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));
}

12. 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);
}

13. SIMPLE AGENT TO TEST
#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

14. 14
CONGESTION CONTROL

15. 15
CONGESTION CONTROL
 When one part of the subnet (e.g. one or
more routers in an area) becomes
overloaded, congestion results.
 Because routers are receiving packets faster
than they can forward them, one of two things
must happen:
 The subnet must prevent additional packets from
entering the congested region until those already
present can be processed.
 The congested routers can discard queued
packets to make room for those that are arriving.

16. 16
FACTORS THAT CAUSE CONGESTION
 Packet arrival rate exceeds the outgoing link
capacity.
 Insufficient memory to store arriving packets
 Bursty traffic
 Slow processor

17. 17
CONGESTION CONTROL VS FLOW CONTROL
 Congestion control is a global issue –
involves every router and host within the
subnet
 Flow control – scope is point-to-point;
involves just sender and receiver.

18. 18
CONGESTION CONTROL, CONT.
 Congestion Control is concerned with
efficiently using a network at high load.
 Techniques for detection and recovery
are:
Warning bit
Choke packets
Load shedding

19. 19
WARNING BIT
 A special bit in the packet header is set by
the router to warn the source when
congestion is detected.
 The bit is copied and piggy-backed on the
ACK and sent to the sender.
 The sender monitors the number of ACK
packets it receives with the warning bit set
and adjusts its transmission rate accordingly.

20. 20
CHOKE PACKETS
 A more direct way of telling the source
to slow down.
 A choke packet is a control packet
generated at a congested node and
transmitted to restrict traffic flow.
 The source, on receiving the choke
packet must reduce its transmission
rate by a certain percentage.
 An example of a choke packet is the
ICMP Source Quench Packet.

21. THANK YOU