Network Simulator-2

Prepared byDeeksha poornashri-1MS13IS141Greeshma R J-1MS13IS142Shakunthala B V-1MS14IS412Shantha-1MS14IS413

INTRODUCTION

Network simulator (Ns)• Ns is a discrete event simulator that is used by

networking research to simulate wired, wireless and satellite networks.

• Ns allows for the simulation of various protocols, applications, routing, queue types etc.

• A graphical front end has been developed for use with Ns known as network animator.

Network simulator version 2(Ns-2)

• In 1996-97, ns version 2(ns-2) was initiated based on a refactoring by Steve McCanne.

• Use of Tcl was replaced by object Tcl, an object oriented dialect of Tcl.

• The core of ns-2 is also written a C++, but the C++ simulation objects are linked to shadow objects in oTcl and variables can be linked between both language realms.

• Simulation scripts are written in the oTcl language an extension of the Tcl scripting language.

Congestion• Congestion, in the context of network, refers

to a network state where a node or link carries so much data that it may deteriorate network service quality, resulting in queing delay frame or data packet loss and the blocking of new connections.

• Congestion occurs when bandwidth is insufficient and network data traffic exceeds capacity

Congestion has been described as a fundamental effect of limited network resources, especially router processing time and link througput.Avoiding network congestion and collapse requires two major components:

a. Routers capable of re-ordering or dropping data packets when received rates reach critical levels.

b. Flow control mechanisms that respond appropriately when data flow rates reach critical level.