QoS Simulation and Monitoring in a DiffServ network


( Plataforma de Simulação e Monitorização de QoS numa Rede DiffServ )


José Pedro Morais

Departamento de Informática

Universidade do Minho

Braga, Portugal


Keywords: QoS, DiffServ, Monitoring, QoS Metrics



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As more complex and demanding new applications appear, it becomes necessary to give a differentiated treatment to Internet traffic so that an appropriate Quality of Service (QoS) is provided. This work from my master thesis, focusing on QoS in IP networks, proposes an easy-to-use network configuration and monitoring simulator platform based on the Network Simulator (NS). The platform allows the setup and testing of QoS mechanisms usually present in Differentiated Services (DiffServ) networks. The QoS metrics obtained in the simulator application, and provided in the form of tables, graphics and on-line visualization, allow to readjust and correct the setup parameter values of the various QoS mechanisms in order to improve the overall end-to-end performance of a DiffServ network

This work has as the main purpose the construction of an application in which is possible to give values and to test, of a simple and integrated way, the components of a DiffServ network in a perspective end-the-end. The metric results gotten for of QoS, such as the delay in the delivery of packets, maximum size in the queues, the number and ratio of lost packets, Instantaneous Packet Delay Variation (IPDV), among others, are presented in graphical tables and, being these metric ones gotten in the class and flow perspective. Parallel on-line visualization is also possible to present a set of results (after-processing) with the state of the network in one determined instant and its evolution in the time. The creation of an interface of multi-functional configuration allows to choose the multiple normally existing mechanisms in the routers to the different ways of traffic. It is possible to readjust and to correct the values of the diverse mechanisms to obtain an improvement of the global performance of network and to verify if an element of that satisfies the requirements of the traffic and the offered service.

Making use of the tool of simulation NS, a composed model of network for three beginning nodes, three destination nodes and three intermediate nodes was created where two of these had been configured as boundary nodes of the DiffServ domain. The platform allows to set a varied traffic control mechanisms, such as, policies (TB, TSW3CM, srTCM, trTCM), queue managers (Drop, RIO-C, WRED) and schedulers (RR, PQ, WIRR). In the generated traffic the platform supports CBR, Exponential on/off and Pareto on/off. In accordance with the type of traffic, the same is classified as EF, AF and BE, being able its behavior to be analyzed to long of the several nodes that compose the model. It was necessary to proceed to some rectifications in the source code from the simulation NS to be possible the "traceall.out", contend all the results of the simulation, also passed to include code DSCP associated with each packet to allow a class analysis. It was followed creation of a input interface allowing to introduce all the referring values of simulation, the topology and used protocols of network, to the policing to apply to the entrance and exit of the domain, to the management of schedulers and queues to use, total simulation time and type of results to get. After gotten the results, its filtering was made appealing to AWK tool with the purpose to calculate the metric ones of QoS. The generated results also are transmitted to the user through a new interface that is integrant part of the application. In this interface the metric ones of QoS can be analyzed, such as, the loss of packets, the delay end-the-end, the instantaneous variation of delay of the packages, as much in a perspective of flow as of class. Parallel it is possible to analyze the maximum size by queue in the several nodes of the network. It still exists the option of if getting graphs for analysis for flow and class of the metric ones previously related and still to get an analysis detailed through a visualization on-line after-processing.

The main contribution of this work is to create a simulation platform that allow in a simple and integrated way to set traffic control mechanisms usually presented in a DiffServ network. The shown results allow to evaluate these mechanisms and to verify the resultant behavior and the QoS offered to the transmitted traffic. Through an iterative process, these mechanisms could be sharpened by form to prevent eventual imperfections of QoS and to optimize the global performance of the network.  In the developed platform, it is possible to compare different mechanisms of control of normalized traffic and to evaluate the ones that better are adjusted to implement the PHBs, also allowing to identify possible limitations of its functioning.







  • Copy the folder "qos4um" from the “AllInOne” download option inside the path "/root"
  • Copy the file trace.cc (in the folder /root/qos4u/install) to the same folder where the trace.cc from the NS exists. ( because this new file includes the DSCP for each packet )
  • Do the same procedure for the dsred.h file ( because the MAX_CP parameter )
  • To prevent error messages during the NAM simulation go to .../tcl/lib/ns-namsupp.tcl and in function instproc trace-annotate put an "-e" to stay like:

       "v -t[$self now] -e sim_annotations[$self now] $annotationSeq_$str"


     Only after that do the commands "./install" and "make".


  • To initiate the application do: tclsh run.tcl
  • If the application don’t start make sure that you have changed the file ".bash_profile" as it says in the Help from the NS.
  • The QoS application was not tested in ns-2.1b9a or higher.
  • If an error occurred during the application process please contact: antonov@netvisao.pt






            TCL code used to create the application:

                        Interface Data In - Input.tcl

                        NS simulation - Calculat.tcl

                        Interface Data Out - Results.tcl


            Run Code:

                        All modules to run the application - AllinOne.zip



                        CRC2003 ( in Portuguese )




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Communication Group

      Research and Development interests

  • Integrated Network Communication Environments
  • Modelling, Design and Performance Analysis of Communication Protocols
  • Internetworking
  • Networked Information Services
  • Network Management







            José Pedro Morais

            Universidade do Minho

            Campus de Gualtar, Braga





            Main Research Interests

·        Multi-service networks and protocols

·        Image analysis

·        Guide surgery





     ( press each image to zoom it )


Introduction and Network Model



Values and Options Configuration



QoS Results



Linear Graphs



Bar Graphs



OnLine Results




February, 1 – 2004