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Impact of Network Security on Speech Quality Is Far from Being a Closed Chapter Department of Electronics, ……..……..…..…..……..…University of Aveiro Telecommunications and Informatics ……..……..……....……..…2008 ……..VŠB – Technical University of Ostrava Department of Telecommunications ……..2008 Saul IMPACTO DE MECANISMOS DE SEGURANÇA Parada <[email protected]> EM REDES NA TELEFONIA IP IMPACT OF NETWORK SECURITY ON SPEECH QUALITY Department of Electronics, ……..……..…..…..……..…University of Aveiro Telecommunications and Informatics ……..……..……....……..…2008 ……..VŠB – Technical University of Ostrava Department of Telecommunications ……..2008 Saul IMPACTO DE MECANISMOS DE SEGURANÇA Parada <[email protected]> EM REDES NA TELEFONIA IP IMPACT OF NETWORK SECURITY ON SPEECH QUALITY Final report presented to the University of Aveiro in partial fulfillment of the requirements for the degree of Master of Science in Engineering of Electronics and Telecommunications, developed under scientific orientation of Eng. Miroslav Vozňák, PhD., and Eng. António Nogueira, PhD., professors of the Department of Telecommunications in VŠB - Technical University of Ostrava and of the Department of Electronics, Telecommunications and Informatics in University of Aveiro, respectively. This is dedicated to my beloved grandmother Ana Rosa Lopes da Fonseca Parada. the jury president Eng. Aníbal Manuel de Oliveira Duarte, PhD. Full Professor of the Department of Electronics, Telecommunications and Informatics in University of Aveiro examiners committee Eng. Rui Jorge Morais Tomaz Valadas, PhD. Full Professor of the Department of Electrical and Computer Engineering in Instituto Superior Técnico from Technical University of Lisbon Eng. António Manuel Duarte Nogueira, PhD. Assistant Professor of the Department of Electronics, Telecommunications and Informatics in University of Aveiro people involved supervisor Eng. Miroslav Vozňák, PhD. Assistant Professor of the Department of Telecommunications in VŠB - Technical University of Ostrava co-supervisor Eng. António Manuel Duarte Nogueira, PhD. Assistant Professor of the Department of Electronics, Telecommunications and Informatics in University of Aveiro “Whatever you can do or dream you can, begin it. Boldness has genius, power and magic in it.” Johann Wolfgang von Goethe acknowledgments "As we enjoy great advantages from inventions of others, we should be glad of an opportunity to serve others by any invention of ours; and this we should do freely and generously." Benjamin Franklin In the spirit of this dictum, I would like to express my thanks to all who have joyfully contributed to this dissertation with their own "inventions" – be it ideas, technical expertise or feedback, as well as by bearing over with me during this interesting albeit intense time. From VŠB - Technical University of Ostrava, my supervisor Eng. Miroslav Vozňák, PhD., deserves thanks for both professional and practical guidance, as well as all the friendship; to my friend Filip Řezáč for all the precious advices and good moments spent together working. My co-supervisor Eng. António Nogueira, PhD., from University of Aveiro, deserves thanks for all the support, particularly, dealing with the exchange bureaucracy making it possible. Last, I would like to mention the most important persons in my life, my family. To all, my sincerest thanks. keywords VoIP, security, IPsec, TLS, Openswan, OpenVPN, AES, Triple-DES, MOS and R-factor. abstract This dissertation is about the impact of secure network environments on speech quality of IP Telephony. Results of the analysis of voice over different unsecure and secure communication links, such as IPsec and TLS, are presented. The use of secure network environments can affect speech quality. There is also a performance comparison of different cipher algorithms and a description on how the used security mechanisms influence the final MOS and R-factor variables. The presented results are based on numerous experiments which have been performed on a real IP-based network. CONTENTS 1 INTRODUCTION ................................................................................................................... 1 1.1. MOTIVATION ........................................................................................................................ 1 1.2. OBJECTIVES .......................................................................................................................... 1 1.3. DOCUMENT OUTLINE ............................................................................................................. 2 2 STATE-OF-THE-ART .............................................................................................................. 5 2.1. INTRODUCTION ..................................................................................................................... 5 2.2. VOIP TEST AND MONITOR SOLUTIONS ...................................................................................... 5 2.3. SECURITY APPLICATIONS ......................................................................................................... 6 2.4. NETWORK ANALYZERS ............................................................................................................ 8 2.5. CONCLUSIONS ....................................................................................................................... 8 3 OVERVIEW OF VOIP ........................................................................................................... 11 3.1. INTRODUCTION ................................................................................................................... 11 3.2. CONCEPTS .......................................................................................................................... 11 3.3. VOIP IMPLEMENTATION DETAILS ............................................................................................ 12 3.3.1. Call Setup Protocols .............................................................................................. 12 3.3.2. Transport Protocols ............................................................................................... 17 3.4. AUDIO CODECS ................................................................................................................... 22 3.5. VOIP RISKS AND VULNERABILITIES .......................................................................................... 23 4 EVALUATION OF SPEECH QUALITY IN IP TELEPHONY .......................................................... 27 4.1. INTRODUCTION ................................................................................................................... 27 4.2. QOS CONCEPTS................................................................................................................... 27 4.3. TELEPHONY QOS ................................................................................................................. 28 4.4. AUDIO QUALITY MEASUREMENT ............................................................................................ 29 4.5. ITU-T E-MODEL ................................................................................................................. 31 4.6. AUDIO QUALITY EXPECTATIONS .............................................................................................. 33 4.7. BANDWIDTH AND EFFECTIVE BANDWIDTH ................................................................................ 34 4.8. OVERCOME QOS ISSUES ....................................................................................................... 35 5 NETWORK SECURITY TECHNIQUES ..................................................................................... 37 5.1. INTRODUCTION ................................................................................................................... 37 5.2. CRYPTOGRAPHY ................................................................................................................... 38 5.2.1. Symmetric-key Encryption .................................................................................... 39 5.2.2. Public-key Encryption ............................................................................................ 43 5.3. INTERNET PROTOCOL SECURITY .............................................................................................. 44 5.3.1. IPsec Security Protocols ........................................................................................ 45 5.3.2. IPsec Modes .......................................................................................................... 46 5.3.3. The Role of IPsec in VoIP ....................................................................................... 47 5.3.4. IPsec and NAT Incompatibility .............................................................................. 47 5.4. TRANSPORT LAYER SECURITY ................................................................................................. 47 5.4.1. Establishing an Encrypted Communication ........................................................... 48 5.4.2. TLS Handshake Protocol ........................................................................................ 49 5.4.3. TLS Record Protocol .............................................................................................. 50 saulparada i 6 USED TECHNIQUES OF MEASUREMENT .............................................................................. 53 6.1. INTRODUCTION ................................................................................................................... 53 6.2. BANDWIDTH EMULATION .....................................................................................................
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