# NS2 Simulation

Today, many kinds of network simulators are available on market. Most of the computer networking projects are developed with the help of network simulators like Ns2, Ns3 etc,. Our organization offers simulation related projects for the engineering students and Phd scholars also. Both computer science and Electronic students are using Ns2 simulation for their final year projects. Our development team has good knowledge in all type of latest simulation tools. Our experts are having deep knowledge in Ns2 simulation concepts. Specifically, in past 7 years we are hiring the faculty who are reputed number of students in network simulation related fields.

## Why Ns2 simulation?

• The real-systems are not available which is complex/costly or dangerous (eg: space simulations, flight simulations)
• The design alternatives (eg: different system configurations) are evaluated quickly.
• The complex functions for which closed form formulas or numerical techniques not available are evaluated.

• Ns2 simulation is cheaper in sometimes.
• Sometimes it find bugs (in design) in advance manner.
• Generality: over analytic/numerical techniques it gives more generality.
• Detail: At arbitrary level system details can be simulated.

### Objective of Ns2 simulation

• Performance.
• Direct Measurement.
•  Reactive.
•   The behavior/characteristics is affected when the user/system is disturbed.
•   The simulation can be done only on completed running systems.
•   Predictive

Analytical Methods: The model is available and is computationally efficient when it useful.

Most systems are complex and require highly complex mathematical models,Usually only steady state can be modeled in Ns2 simulation.

NS2 Simulation

Ns2 simulation can give more detail than analytical modeling

The large design space is explored. It is very useful in that time.

The dynamic behavior can be studied.

Programmatic representation of system entities

Algorithmically, we know how bits and pieces of the system work

• Mathematically, we know possible for some bits

Implement these algorithms and let them interact

Two main types of simulation

Discrete event

Using random number generators are used in discrete points in time

Continuous time

Continuously, State changes can occur across time

Packages

The number of packages is used in Ns2 simulation. E.g. OPNET (commercial), NS-2 (open source), OMNeT++

Levels of detail

E.g. packet level, flow level

Evaluation spectrum

• Numerical models
• Simulation
• Emulation
• Prototype
• Operational system

Programming a simulation

• Simulated Time: The simulated time is kept by the internal (to simulation program) variable.
• System “state”: The variables maintained by simulation program is defined as system “state”.

e.g., may track number (possibly order) of packets in queue, current value of retransmission timer

• Events: The system changes state when points in time
• Every event has associated with event time

e.g., the arrival of packet to queue, departure from queue precisely at these points in time that simulation must take action (change state and may cause new future events).

• An external environment causes the model for time between events (probabilistic).

Structure of Ns2 simulation

A list of future events are maintained and updated by the simulation programs: event list

Need:

Well defined set of events are maintained.

For every event: The simulated system actions, the updating of event list

Basics of using Ns2 simulation

The Network topology, load, output files in Tcl Script are defined in Ns2 simulation.

Internally, C++ classes based on the tcl scripts are instantiated by Ns2 simulation

We can get the output is in form of trace files

In every year we are updates the new titles with new technology on network simulation which is used for B.E, B.Tech, M.E, M.Tech students and Phd scholars.