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Measurement and Modelling of Internet Traffic Over 2.5 and 3G Cellular Core Networks

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Measurement and Modelling of Internet Traffic Over 2.5 and 3G Cellular Core Networks DISSERTATION Measurement and Modelling of Internet Traffic over 2.5 and 3G Cellular Core Networks ausgef¨uhrt zum Zwecke der Erlangung des akademischen Grades eines Doktors der technischen Wissenschaften eingereicht an der Technischen Universit¨at Wien Fakult¨at f¨ur Elektrotechnik und Informationstechnik von DI Philipp Svoboda Wanriglgasse 1/5 A-1160 Wien Osterreich¨ geboren am 25. M¨arz 1978 in Wien Matrikelnummer: 9825199 Wien, im November 2008 Begutachter: Univ. Prof. Dr. Markus Rupp Institut f¨ur Nachrichtentechnik und Hochfrequenztechnik Technische Universit¨at Wien Osterreich¨ Univ. Prof. Dr. Andreas Kassler Computer Science Department Karlstadt University Sweden Abstract HE task of modeling data traffic in networks is as old as the first commercial telephony systems. TIn the recent past in mobile telephone networks the focus has moved from voice to packet- switched services. The new cellular mobile networks of the third generation (UMTS) and the evolved second generation (GPRS) offer the subscriber the possibility of staying online everywhere and at any time. The design and dimensioning is well known for circuit switched voice systems, but not for mobile packet-switched systems. The terms user expectation, grade of service and so on need to be defined. To find these parameters it is important to have an accurate traffic model that delivers good traffic estimates. In this thesis we carried out measurements in a live 3G core network of an Austrian operator, in order to find appropriate models that can serve as a solid basis for traffic simulations. A requirement for this work was a measurement system, which is able to capture and decode network traffic on various interfaces of the mobile core network. Such a system was established within the METAWIN system. Our results are based on this setup. The work can be split into three parts. First, we studied the service usage on a per user and session base separately for UMTS and GPRS. This analysis revealed that the service usage for UMTS and GPRS is gradually becoming more and more similar and that the main application in terms of transfered bytes is HTTP. Nevertheless, the main application in terms of handsets is WAP. As seen in many network measurements a small fraction of the subscribers generates the majority of the traffic. In a second step we derived traffic models at flow level for UDP/TCP, HTTP, WAP 1.x and WAP 2.0. The TCP and HTTP flows follow a heavy-tailed behavior as expected from wireline measurements. However, UDP and WAP flows showed no heavy-tail effects. Many properties of the mobile flows follow the same distributions as in wireline networks. Third, we designed several source level traffic models. These models allow a better understanding of the user interaction and network settings. In the case of HTTP and FTP we updated the parameters of existing models in order to meet our requirements. The mobile Internet access features high RTTs, so we modified existing e-mail models to reproduce traffic at a better granularity. In order to provide models for upcoming applications we designed three models for online games and a push to talk implementation. i ii Kurzfassung ER Wunsch nach einem Modell f¨ur den durch die Benutzer erzeugten Verkehr reicht zur¨uck Dbis zu den Anf¨angen der kommerziellen Telefonie. Die Einf¨uhrung der dritten Generation der Mobilfunktechnik (UMTS) beziehungsweise die Weiterentwicklung der zweiten Generation haben den Schwerpunkt der angebotenen Dienste von Sprache zu paketvermittelten Diensten verschoben. Im Gegensatz zu Sprachdiensten, wo seit Jahrzehnten bew¨ahrte Modelle verwendet werden, gibt es f¨ur paketvermittelte Dienste keine Verkehrsmodelle, welche auf ein mobiles Szenario zugeschnitten w¨aren. In dieser Arbeit haben wir die Messungen aus einem im operativen Betrieb befindlichen Mobil- funktnetz der dritten Generation herangezogen, um den Verkehr zu analysieren und in Folge passende Modelle zu entwerfen. Die Basis unserer Arbeit bildet das METAWIN System. Dieses erlaubt es, auf verschiedenen Schnittstellen des Mobilfunktnetzes Paketdaten aufzuzeichnen und dann je Benutzer und Sitzung auszuwerten. Wir haben die Arbeit in drei Bereiche gegliedert. Der erste Bereich befasst sich mit der Analyse des Benutzerverhaltens bezogen auf die verwendeten Dienste in UMTS und GPRS. Es hat sich gezeigt, dass die Hauptanwendung, bezogen auf das erzeugte Volumen, in beiden Netzen HTTP ist. Setzt man hingegen die Anzahl der involvierten Endger¨ate als Massstab f¨ur die Wichtigkeit eines Dienstes, so sind die verschiedenen Versionen von WAP am wichtigsten. Ahnlich¨ wie es sich in fr¨uheren Messungen an Festnetzkunden gezeigt hat, erzeugt ein kleiner Anteil der Kunden den Großteil der anfallenden Verkehrslasten. In einem weiteren Schritt haben wir Verkehrsmodelle auf Basis von Dienstfl¨ussen erstellt. Wir haben dabei eine Auswahl der wichtigsten Dienste herausgegriffen: TCP/UDP, HTTP und WAP. Die Verteilungen f¨ur HTTP und TCP zeigen, ¨ahnlich wie im Festnetz, eine sogenannte heavy tail Eigenschaft, w¨ahrend die anderen Dienste diese Eigenschaft nicht haben. Die Eigenschaften von UMTS und GPRS unterscheiden sich kaum, offenkundig reagieren diese Eigenschaften nicht auf die unterschiedlichen physikalischen Netzwerkparameter. In dritten und letzten Schritt haben wir f¨ur einige der Topdienste separate Verkehrmodelle ent- worfen. Im Falle von HTTP und FTP haben wir die Parameter von existierenden Modellen an unsere Daten angepasst. F¨ur den Maildienst haben wir gezeigt, dass man im Falle eines Internet- zugangs mit hohen Latenzzeiten den Authentifizierungsvorgang detailiert nachbilden muss, um eine hohe Genauigkeit zu erhalten. Die drei Modelle f¨ur Dienste, aus dem Bereich der Onlinespiele dienen als Grundlage f¨ur zuk¨unftige Dienste die mit steigender Leistungf¨ahigkeit der Funkschnittstelle ¨uber kurz oder lang auch Einzug in der mobilen Welt finden werden. Ein Modell f¨ur Push to Talk Dienste rundet die Analyse ab. iii iv Acknowledgements “The shortest distance between two points is under construction” N. Altito I would like to thank some of the persons without whose support this work would not have been possible. First of all, Univ. Prof. Dr. Markus Rupp, whose support and encouragement helped me through the difficult times which such a thesis has. Second, Dr. Fabio Ricciato for the opportunity to work in the METAWIN research group at the ftw. in Vienna. Third, Univ. Prof. Dr. Andreas Kassler, whose support and review helped me to improve and polish my work. I am also very grateful for the many fruitful discussions I had with the METAWIN staff which helped me greatly in succeeding in my work. In this context I thank mobilkom austria AG for technical and financial support of this work1 and the Kapsch Carrier Com as the second industrial partner in the METAWIN project. I would also like to express my thanks to my fellow colleagues of the Mobilfunk Gruppe at the Institute of Communications and Radio-Frequency Engineering in Vienna, Austria for an inspiring working environment and for many helpful comments and inputs. I would like to thank my father Alfred, my mother Gabriele and my brother Markus for supporting me in my work and providing me with a pleasant and stable background. Finally, I thank all my friends for their patience and the relaxing times we had. Vienna, November 2008 Philipp Svoboda Phone: (+43 1) 58801-38968 e-mail: [email protected] 1The views expressed in this thesis are those of author and do not necessarily reflect the views within mobilkom austria AG. v vi Contents 1 Introduction 1 1.1 Motivation ...................................... .... 3 1.2 OutlineandContributions. ......... 5 2 Theoretical Background 11 2.1 TheInternet:Acrashcourse . ........ 13 2.1.1 TheInternetProtocolSuite . ....... 13 2.1.2 The Application Layer: Internet Services . ........... 16 2.2 TrafficEngineering ................................ ...... 17 2.2.1 IntroductiontoTrafficEngineering . ......... 18 2.2.2 TrafficModels ................................... 19 2.3 Summary ......................................... 26 3 Measurement Setup and Introduction to 3G Core Networks 27 3.1 The Evolution of Mobile Core Networks . .......... 29 3.2 Introduction to the 3G Packet Switched Core Network . .............. 30 3.2.1 SystemArchitecture . ..... 31 3.2.2 BearerSpeedinUMTS ............................. 33 3.2.3 BearerSpeedinGPRSandEDGE . 34 3.3 ADataSessionina3GNetwork . ...... 35 3.4 TheMeasurementSetup............................. ...... 36 3.4.1 METAWIN ...................................... 36 3.4.2 Tracesfromalive3GCoreNetwork . ...... 40 3.5 Summary ......................................... 42 4 User Related Composition of GPRS/UMTS Traffic 43 4.1 Daily Usage Profile for UMTS and GPRS . ....... 45 4.2 VolumeandUserPopulation . ....... 47 4.2.1 Volumes and User Population in GPRS and UMTS . ....... 47 4.2.2 FractionofVolumeperService . ....... 48 4.2.3 ServiceMixDiurnalProfile . ...... 50 4.2.4 Grouping Subscribers per Service Access . ........... 52 4.2.5 FilteringinthePortAnalysis . ........ 53 4.3 AnalysisofthePDP-ContextActivity . .......... 54 4.3.1 Per-UserActivity............................... 54 4.3.2 Distribution of PDP-Context Duration . ......... 55 4.3.3 TheVolumeofaPDP-Context . 58 4.3.4 TotalNumbersperGroups . 60 4.4 Detecting and Filtering of Malicious Traffic . ............. 60 4.5 Summary ......................................... 62 vii 5 Application Flow Patterns 65 5.1 IntroductiontoFlowAnalysis. .......... 67 5.1.1 TheFlow ....................................... 68 5.1.2 ProtocolShares...............................
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