Ns is an object-oriented network simulator written in C++ and OTcl that is used to simulate wired and wireless networks. It allows debugging of network protocols and configurations efficiently without physical equipment. Ns simulates network components, traffic models, transport and routing protocols, and physical media. It consists of an event scheduler that handles the simulation by processing events in chronological order.

2. What is ns?
 Object-oriented, discrete event driven network
simulator
 It was normally used in wired & wireless
protocol
 Written in C++ and OTcl

3. ADVANTAGES
1. Debugging of errors makes easy,
2. It is cheap doesnot not require any
equipment,
3. Even an complex scenario can be
tested effiently.

4. ns Architecture
OTcl
Tcl
TclCL
ns-2
Event
Scheduler
Network
Components
C/C++

5. Simulation Network
 Wired Network
◦ Routing: Distance Vector, Link State
◦ Transportation: TCP and UDP
◦ Queuing disciplines: drop-tail
 Wireless
◦ Ad-hoc routing and mobile IP: AODV
◦ Sensor-MAC, WiMAX (new)
◦ Power control in wireless networks

6. NS2 Functionalities
 Traffic models and applications
◦ FTP, CBR
 Transport protocols
◦ Unicast: TCP, UDP
 Routing and queuing
◦ Wired and ad-hoc routing
◦ Queuing protocols: drop-tail, etc
 Physical media
◦ Wired (point-to-point, LANs), wireless (multiple
propagation models), satellite

7. Ns – structure
Types
1. Event Schedular
2. Turn on Tracing
3. Network Topology
4.Transport Connection
5. Generate Traffic
6.Start Simulation

8. Attaching Transport Agents to
Nodes-tcp/udp
TCP :
set src [new Agent/TCP/FullTcp]
set sink [new Agent/TCP/FullTcp]
$ns_ attach-agent $node_(s1) $src
$ns_ attach-agent $node_(k1) $sink
$ns_ connect $src $sink

9. Udp agent
Set udp0 [new Agent/Null]
ns attach-agent $n0 $udp0
set cbr0 [new Application/Traffic/CBR]
$cbr0 attach-agent $udp0
$udp0 set packetSize_ 536 ; #(max=1000)
set null0 [new Agent/Null]
$ns attach-agent $n1 $null0
$ns connect $udp0 $null0

10. PACKETS
It is the collection of data,whether header is
called or not all header files where present in
the stack registers.
Cmn header
Ip header
Tcp header
Rtp header
Trace header
Header
data

11. Trace Analysis
Trace packets on individual link
Tracefile format:

12. NAM
ns has a companion network animator called
nam
hence, has been called the nsnam project

13. Xgraph
One part of the ns-allinone package is 'xgraph', a
plotting program which can be used to create
graphic representations of simulation results.