Acknowledgments I would like to thank and express all my gratitude to the following people who have been instrumental in the successful completion of this project. Firstly I would like to thank Mr. Patrick Gaillet, my boss, who is also my teacher, for his monitoring throughout the project. His advices allowed me to work effectively and efficiently. A big thank to him for trusting me to realize this project with a company as prestigious as Swisscom. Thanks to Mr. Michael Kauz, head of the team with which I worked at Swisscom. His help was invaluable to me in order to convince the right people to give me a hand when I needed it. Mr. François Buntschu, of HEIA-FR, for his support and responsiveness during my many requests. Such collaboration would not have been possible without the help of many people who work on different aspects of the mobile core network. Thanks to Mr. Belancic, Thierrens, Gräbner, and Yeddou for their presence and their numerous and valuable tips. A special thank to Mr. Nakai Lucini, a young engineer from Swisscom, who took time to reflect and explain some concepts that were obscure to me. Its availability and responsiveness have been very appreciable. Also thank you to Mr. Leistritz of Syntelio and his team for the time invested in this project. I also wish to thank Mr. Laurent Knoepfli of Ericsson for his clean and precise answers he knew to give me during my many questions. Laurent is undoubtedly THE person to contact in case of questions concerning the IMS. The development of such a service with OpenCloud's API would not have been possible without the help, experience and valuable advices from Mr. Jose Maria Garcia of OpenCloud and Mr. Tonci Ivankovic, an acquaintance met on a specialized forum. Their assistance allowed me to correct, improve and mainly to achieve my goals. All my colleagues from the C10.08 room for the good time and the knowledge sharing throughout all the project. The Hirschmann Stipendium for the funding received through their HES scholarship program to undertake my Master studies.