NS2 Simulator for Begin

SungkyunkwanSungkyunkwan UniversityUniversity

Copyright 2000-2006 Networking Laboratory

NS Simulator for beginnersNS Simulator for beginners

Chapter 2. ns Simulator Preliminaries

2007-04-14

Jeonghoon Park

[email protected]

Networking Laboratory 2/24NS Simulator

ContentsContents

� Initialization and termination

� Definition of a network of links and nodes

� Agents and applications

� Scheduling events

� Visualisation: using nam

� Tracing

� Random variables


Initialization and terminationInitialization and termination

� An ns simulation starts with the command

� Creating output files (trace files or nam files)


Initialization and terminationInitialization and termination

� The termination of the program

� At the end of the ns program we should call the procedure “finish”and specify at what time the termination should occur.


Definition of a network of links and Definition of a network of links and nodesnodes

� Definition of a node

� Definition of a link

� In NS, an output queue of a node is implemented as a part of each link whose input is that node.

� Definition of the buffer capacity of the queue related to each link



� Form of a simplex link

� Duplex link is constructed from two parallel simplex links.



� Defining nodes, links and assigning queue size


Agents and applicationsAgents and applications

� FTP over TCP


Agents and applicationsAgents and applications

� CBR over UDP


Scheduling eventsScheduling events

� The Tcl script defines when event should occur.� Format

� Examples

� The scheduler is started when running ns, i.e. through the command $ns run.


VisualisationVisualisation: using : using namnam

� Giving node position (for NAM)


TracingTracing

� Tracing objects in a simplex link

� EnqT registers information concerning a packet that arrives and is queued at the input queue of the link.

� DrpT handles the information concerning the dropped packet.� DeqT registers information at the instant the packet is dequed.� RecvT gives us information about packets that have been received

at the output of the link.


TracingTracing

� Structure of trace files

� Event: event type.� r: receive (at the output of the link)

� +: enqueued

� -: dequeued

� d: dropped

� Time: the time at which the events occurs.

� From node: givens the input node of the link at which the events occurs.

� To node: fives the output node of the link at which the events occurs.

� Pkt id: unique id of the packet


TracingTracing

� Example

� Tracing a subset of events


Random variablesRandom variables

� Seeds and generators� The seed value of 0 results in the generation of a new random

variable each time we run the simulation.

� In contrast, if we use other seeds then each time we run the simulation, the same sequence of random variables that are generated in a simulation will be generated.

� Creating random variables� Creating a new generator

� When actually creating a random variable, we have to define its distribution type and its parameters.








SungkyunkwanSungkyunkwan UniversityUniversity

Copyright 2000-2006 Networking Laboratory

NS Simulator for beginnersNS Simulator for beginners

Chapter 3. How to work with trace files

2007-04-14

Jeonghoon Park

[email protected]


Processing data files with Processing data files with awkawk

� The awk utility allows us to do simple operations on data files.� Averaging the value of a given column, summing or multiplying

term by term between several columns, all data reformatting tastks.

� Examples� Averaging the values in column 4 of a file

� Obtaining the standard deviation of column 4 of a file


Using Using grepgrep

� The grep command allows us to ‘filter’ a file.

� Example� Output traces in ns may contain all types packets that go through

all links and we may be interested only in the data concerning tcppackets that went from node 0 to node 2.

� We may wish to obtain a file containing all lines of tr1.tr begin with the letter r.

� If we wish to make a file of all the lines that begin with “s” and have later “tcp 1020” we should type


Plotting with Plotting with gnuplotgnuplot

� Example

� Produce a curve that is smaller than the default.

� Produce points that are larger than the defaults.

� Tells gnuplot where to put the ‘key’

� Restricts the range of the x axis.

� Superimposes three curves in a single figure

(참고: http://kldp.org/KoreanDoc/html/GnuPlot-KLDP/)


Plotting with Plotting with gnuplotgnuplot

� Example


Plotting with Plotting with xgraphxgraph� Xgraph is a plotting utility that is provided by ns.� Some options in xgraph

� Title: -t “title”� Size: -geometry xsize x ysize� Title for axis: -x “xtitle” –y “ytitle”� Color of text and grid: -v

� Example

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NS2 Simulator for Begin