Network Simulator 2 (NS2) is a discrete event simulator used for networking research. It models packet-level details and is mainly written in C++ for efficiency and OTcl for flexibility. NS2 can run on Unix systems and Windows using Cygwin. It allows modeling of different network topologies and protocols through a scripting interface. While powerful and popular for research, NS2 also has disadvantages like being complex to model with and time-consuming to use.

1. NETWORK SIMULATOR-2
(FINDING THE NUMBER OF
PACKETS DROPPED)
POOJA.B(IMS13IS074)
NIKITHA.K.N(IMS13IS066)
NIDHI SHETTY(IMS13IS063)
NEHA.M(IMS13IS062)
RASHMI.K(IMS13IS82)

2. NS2
 DISCRETE EVENT SIMULATOR
 PACKET LEVEL
 MAINLY FOR NETWORKING RESEARCH
 THE OBJECT ORIENTED EXTENSION OF
TCL(OTCL)AND C++ USED
 DESIGNED FOR UNIX SYSTEMS BUT RUNS
UNDERWINDOWS CYGWIN ASWELL

3. HISTORY
 In 1996-97,ns version 2(ns-2) was initiated
based on a refactoring by Steve McCanne
 Use ofTcl was replaced by MIT’s Object
Tcl(OTcl),an object oriented dialectTcl
 The core of ns-2 is also written in C++
 Simulation scripts are written in the OTcl
language

4. PLATFORMS REQUIRED TO RUN NS
 Unix and Unix like systems
 Linux(use Fedora or Ubuntu versions)
 Free BSD
 SunOS/Solaris
 Windows 95/98/NT/2000/XP

5. C++ HELPS IN THE FOLLOWING WAY:
 It helps to increase the efficiency of
simulation
 It is used to provide details of the protocols
and their operation
 It is used to reduce packet and event
processing time

6. OTCL HELPS IN THE FOLLOWING
WAY:
 With the help of OTcl we can describe
different network topologies
 It helps us to specify the protocols and their
applications
 It allows fast development
 Tcl is compatible and many platforms and it
is flexible for integration

7. ADVANTAGES
 Cheap
 Complex scenarios can be easily tested
 Results obtained quickly
 Modularity
 Popular
 Supports different protocols and platforms

8. CRITICISM
 Modeling is very complex
 Time consuming task
 No GUI
 One needs to learn scripting language
 Results are not consistent(continuous change
in code)
 Bugs are unreliable

9. BASICS OF TCL PROGRAMMING
 Initialization and termination aspects of
network simulator.
 Defining the network nodes, links, queues
and topology as well
 Defining the agents and their applications
 Network animator(NAM)
 Tracing