Η μεγάλη εξάπλωση των δικτύων που βασίζονται στο Internet Protocol (IP) , έδωσε την ευκαιρία για χρήση του Διαδικτύου για μετάδοση φωνής , μέσω της τεχνολογίας Voice over IP(VoIP) , έναντι των παραδοσιακών δημοσίων τηλεφωνικών δικτύων (PSTN) . Το Session Initiation Protocol είναι το πρωτόκολλο σηματοδοσίας , που χρησιμοποιείται για τον έλεγχο συνόδων πολυμέσων , όπως κλήσεις φωνής ή βιντεοκλήσεις στα δίκτυα IP . Η χρησιμοποίηση του πρωτοκόλλου σε φορητές συσκευές , όπου η διαχείριση πόρων παίζει σπουδαίο ρόλο , δίνει το ερέθισμα για τη δημιουργία ειδικού υλικού που θα αποφορτίζει τον επεξεργαστή της συσκευής από τους απαιτητικούς ελέγχους που χρειάζονται για την δημιουργία μιας συνόδου . Στα πλαίσια της παρούσας διπλωματικής εργασίας παρουσιάζεται ένα σύστημα , υλοποιημένο σε FPGA , που προσομοιώνει έναν χρήστη SIP , κι έχει τη δυνατότητα να λαμβάνει , να επεξεργάζεται και να απαντά σε μηνύματα για την δημιουργία μια συνόδου . Στα κεφάλαια που ακολουθούν παρουσιάζεται η δομή του πρωτοκόλλου και τα χαρακτηριστικά του συστήματος που υλοποιήθηκε . Αρχικά παρουσιάζονται οι βασικές αρχές του πρωτοκόλλου και τα δομικά στοιχεία του . Έπειτα αναλύεται η δομή ενός SIP μηνύματος κι εξηγούνται οι λόγοι που κάνουν την αποθήκευσή του απαιτητική εργασία για την CPU . Έπειτα αναλύεται η βασική διαδικασία δημιουργίας συνόδου χρησιμοποιώντας ένα παράδειγμα . Το επόμενο μέρος αφιερώνεται στην αναλυτική περιγραφή του συστήματος που υλοποιήθηκε και την διαδικασία ελέγχου της ορθής λειτουργίας του . Τέλος παρουσιάζονται τα αποτελέσματα και συμπεράσματα της εργασίας . / The wide spread of networks based on Internet Protocol (IP), gave the opportunity for using the Internet for voice transmission , through Voice over IP (VoIP) technology, over traditional public telephone networks (PSTN). The Session Initiation Protocol is a signaling protocol , used to control multimedia sessions such as voice calls or video calls in IP networks. The use of this protocol in mobile devices , where resources management is very important ,is giving the stimulus for the creation of special hardware that offloads the CPU of demanding controls needed to create a session . As part of this thesis ,a system implemented on FPGA, which simulates a SIP user, and has the ability to receive, process and respond to messages to create a session , is presented. The following chapters present the structure of the protocol and the characteristics of the implemented system . Originally presented the basic principles of the Protocol and its structural elements . Thereafter the structure of a SIP message is analyzed , and the reasons that make storing a demanding work for the CPU , are explained. Then the basic process of creating a session is analyzed , using an example . The next part is devoted to a detailed description of the implemented system and the process of verifying the proper operation. Finally are presented the results and conclusions of the work .

Magistrinio darbo tikslas yra ištirti SIP protokolo panaudojimo galimybes mobiliems prietaisams skirtuose internetinės telefonijos sprendimuose ir parengti tokio bendravimo modelį. Atlikto darbo pagrindinis rezultatas yra reikalingos literatūros apžvalga ir analizė bei eksperimentinio IP telefonijos modelio realizacija mobiliose operacinėse sistemose. Pirmame skyriuje trumpai pateikiamas įvadas apie tradicinės telefonijos evoliuciją į balso perdavimą per interneto tinklus. Taip pat, kad palaipsniui IP telefonija vis labiau realizuojama į mobilius prietaisus. Tolimesniame skyriuje, norint argumentuoti IP telefonijos augimą, aprašomas atliktas rinkos tyrimas ir jo išvados apie esamą padėtį IP telefonijos srityje. Trečiame skyriuje pateikiama informacija apie apžvelgtą literatūrą: SIP protokolo struktūrą ir savybes, įkraunamas aplikacijas į mobiliuosius terminalus bei jų palyginimas. Sekančiame skyriuje pateikiama atlikto eksperimentinio modelio realizacija: reikalavimų specifikacija, reikalavimai įrangai, pasirinktų priemonių veikimo demonstravimas mobiliose aplinkose. Penktame skyriuje parašyti pagrindiniai rezultatai ir gautos išvados, o paskutiniame – nurodomi darbe naudoti literatūros šaltiniai. / The goal of this Master Thesis is to research practice possibilities of SIP protocol in voice over IP solutions for mobile devices and to formulate such communication model. The main result of accomplished work is review and analysis of needful literature and implementation of experimental IP telephony model in mobile operating systems. In the first section is introduced the preface about traditional telephony development to a voice transfer over internet networks. Also, that IP telephony is more and more actualized to mobile devices. To prove the growth of IP telephony was done a market research and was made the conclusions about existing position in VoIP sphere. That information can be found in the next chapter. The third chapter is about reviewed literature: the structure and features of SIP protocol, applications which can be installed into mobile terminals and their comparison. In the next section of the Master Thesis is given realization of experimental model: specifications, request for hardware, demonstration of chosen software tools in mobile systems. The main results and obtained conclusions are written in the fifth chapter, literature list – in the last one.

Telephony plays a fundamental role in our society. It enables remote parties to interact and express themselves over great distances. The telephone as a means of communicating has become part of every day life. Organisations and industry are now looking at Voice over IP (VoIP) technologies. They want to take advantage of new and previously unavailable voice services. Various interested parties are seeking to leverage the emerging VoIP technology for more flexible and efficient communication between staff, clients and partners. <o>VoIP is a recent innovation enabled by Next Generation Network (NGN). It provides and enables means of communication over a digital network, specifically the Internet. VoIP is gaining wide spread adoption and will ultimately replace traditional telephony. The result of this trend is a ubiquitous, global and digital communication infrastructure. VoIP, however, still faces many challenges. It is not yet as reliable and dependable as the current Public Switched Telephone Network (PSTN). The employed communication protocols are immature with many security flaws and weaknesses. Session Initiation Protocol (SIP), a popular VoIP protocol does not sufficiently protect a users privacy. A user’s information is neither encrypted nor secured when calling a remote party. There is a lack of control over the information included in the SIP messages. Our specific concern is that private and sensitive information is exchanged over the public internet. This dissertation concerns itself with the communication path chosen by SIP when establishing a session with a remote party. In SIP, VoIP calls are established over unknown and untrusted intermediaries to reach the desired party. We analyse the SIP headers to determine the information leakage at each chosen intermediary. Our concerns for possible breach of privacy when using SIP were confirmed by the findings. A user’s privacy can be compromised through the extraction of explicit private details reflected in SIP headers. It is further possible to profile the user and determine communication habits from implicit time, location and device information. Our research proposes enhancements to SIP. Each intermediary must digitally sign over the SIP headers ensuring the communication path was not be altered. These signatures are added sequentially creating a chain of certified intermediaries. Our enhancements to SIP do not seek to encrypt the headers, but to use these intermediary signatures to reduce the risk of information leakage. We created a model of our proposed enhancements for attaching signatures at each intermediary. The model also provides a means of identifying unknown or malicious intermediaries prior to establishing a SIP session. Finally, the model was specified in Z notation. The Z specification language was well suited to accurately and precisely represent our model. This formal notation was adopted to specify the types, states and model behaviour. The specification was validated using the Z type-checker ZTC. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Computer Science / unrestricted

In the first part of my master's thesis the network architecture of IMS (IP Multimedia Subsystem) is presented. The database of subscribers HSS (Home Subscriber Server) and SLF (Subscription Locator Function), as well as a SIP CSCF servers (Call Session Control Functions) process a SIP signalization and an AS application server performing services, etc. I focus on the registration of subscribers in the IMS network with a list of transmitted messages and description of each interface that is used in this network. The most important interfaces, which I described here, are Gm, Mw, Cx, Dx and Sh. Then I focused on security in IMS problems, which are divided into categories of access security and network security. After that is the implementation of IMS network in an open source Open IMS Core System considered under the Linux operating system. Here is the problem description from the actual system installation, through the configuration of all necessary elements of the network to the communication party itself. The communication analysis in the initial registration process and in subsequent communications is described. Finally I created laboratory exercises with a focus on the Open IMS Core System, where students learn about architecture and principle of networks based on IMS technology operation, with individual elements necessary for the operation of the network and their configuration. Students also test simple captured traffic analysis.

A arquitetura IP Multimedia Subsystem, proposta pelo consórcio 3rd Generation Partnership Project como base para o suporte à convergência entre telefonia móvel e a Internet, define uma série de elementos arquiteturais, entre os quais, o componente Call Session Control Function e o protocolo Session Initiation Protocol. Session Initiation Protocol é um protocolo da camada de aplicação utilizado para estabelecer, modificar e terminar sessões multimídia entre dispositivos. Em redes baseadas na arquitetura IP Multimedia Subsystem, o Session Initiation Protocol é o responsável pela comunicação entre dispositivos e a rede, e entre os componentes responsáveis pelo gerenciamento de sessão. Nos últimos anos, estudos detectaram degradação de desempenho em redes baseadas na arquitetura IP Multimedia Subsystem em função das características centralizadas do Session Initiation Protocol e dos componentes de gerenciamento de sessão. Este trabalho apresenta uma arquitetura distribuída para redes baseadas em IP Multimedia Subsystem, tendo como fundamento o paradigma de computação paralela baseado em espaço de tuplas onde os servidores são organizados em uma rede P2P, com objetivo de prover uma infraestrutura escalável e tolerante a falhas. A validação da arquitetura em termos de desempenho e escalabilidade se deu através de modelagem formal e simulação com Redes de Petri Coloridas. / The IP Multimedia Subsystem architecture, proposed by the 3rd Generation Partnership Project consortium as basis to support the convergence between mobile networks and the Internet, defines a set of architectural elements, among them, the Call Session Control Function and the Session Initiation Protocol. The Session Initiation Protocol is an application layer protocol used to establish, modify and terminate sessions between devices. On the IP multimedia subsystem based network, the Session Initiation Protocol play a key role on the communication between devices and the network, and between session management components. In the last years, studies have detected a performance bottleneck on IP multimedia subsystem networks due to centralized characteristic of the Session Initiation Protocol and in Session Control components. This work shows a distributed architecture for IP Multimedia Subsystem networks based on the tuple space paradigm, and the servers structured in a P2P network, aiming to achieve a scalable and fault-tolerant infrastructure. The validation of the architecture on the performance and scalability took place through the Coloured Petri Net formal modeling and simulation.

A arquitetura IP Multimedia Subsystem, proposta pelo consórcio 3rd Generation Partnership Project como base para o suporte à convergência entre telefonia móvel e a Internet, define uma série de elementos arquiteturais, entre os quais, o componente Call Session Control Function e o protocolo Session Initiation Protocol. Session Initiation Protocol é um protocolo da camada de aplicação utilizado para estabelecer, modificar e terminar sessões multimídia entre dispositivos. Em redes baseadas na arquitetura IP Multimedia Subsystem, o Session Initiation Protocol é o responsável pela comunicação entre dispositivos e a rede, e entre os componentes responsáveis pelo gerenciamento de sessão. Nos últimos anos, estudos detectaram degradação de desempenho em redes baseadas na arquitetura IP Multimedia Subsystem em função das características centralizadas do Session Initiation Protocol e dos componentes de gerenciamento de sessão. Este trabalho apresenta uma arquitetura distribuída para redes baseadas em IP Multimedia Subsystem, tendo como fundamento o paradigma de computação paralela baseado em espaço de tuplas onde os servidores são organizados em uma rede P2P, com objetivo de prover uma infraestrutura escalável e tolerante a falhas. A validação da arquitetura em termos de desempenho e escalabilidade se deu através de modelagem formal e simulação com Redes de Petri Coloridas. / The IP Multimedia Subsystem architecture, proposed by the 3rd Generation Partnership Project consortium as basis to support the convergence between mobile networks and the Internet, defines a set of architectural elements, among them, the Call Session Control Function and the Session Initiation Protocol. The Session Initiation Protocol is an application layer protocol used to establish, modify and terminate sessions between devices. On the IP multimedia subsystem based network, the Session Initiation Protocol play a key role on the communication between devices and the network, and between session management components. In the last years, studies have detected a performance bottleneck on IP multimedia subsystem networks due to centralized characteristic of the Session Initiation Protocol and in Session Control components. This work shows a distributed architecture for IP Multimedia Subsystem networks based on the tuple space paradigm, and the servers structured in a P2P network, aiming to achieve a scalable and fault-tolerant infrastructure. The validation of the architecture on the performance and scalability took place through the Coloured Petri Net formal modeling and simulation.