Tesis Doctoral. Contribución al Desarrollo de Soluciones Para la Integración de Métodos de Establecimiento de Sesión en Redes 4G

Transcripción

1 UNIVERSIDAD CARLOS III DE MADRID Tesis Doctoral Contribución al Desarrollo de Soluciones Para la Integración de Métodos de Establecimiento de Sesión en Redes 4G (Contribution to Designing Suitable Session Setup Solutions in 4G Networks) Autor: D. Antonio Cuevas Casado Director: Dr. José Ignacio Moreno Novella DEPARTAMENTO INGENIERÍA TELEMÁTICA Leganés, Junio de 2006

2 AGRADECIMIENTOS Son muchas las personas que con sus ánimos, consejos, amistad o cariño, han contribuido a que esta tesis llegara a buen término. Esta tesis es, en parte, también vuestra; recibid mi más cordial agradecimiento. A José Ignacio Moreno, director de esta tesis. Gracias por tu excelente labor como director; por tus consejos, por tu experiencia, por tu constante apoyo y por la confianza que siempre has depositado en mí. Al resto de compañeros del Departamento de Ingeniería Telemática de la Universidad Carlos III de Madrid y a todos los colegas con los que, durante estos cinco años, he tenido el gusto de trabajar. Vuestra ayuda ha sido fundamental. Y, como no, gracias a mi familia y amigos, por contribuir a que esta tesis salga adelante y, sobretodo, por tantas otras cosas. ii

3 ABSTRACT The convergence or, better, migration of the telephone network into the Internet is becoming a reality. It is already common to use, over the Internet, traditional services from the telephone network like voice calls. Besides, features such as mobility are ready to be implemented into the Internet. This converged IP-based communication infrastructure is what is known under the general term of 4G networks. The definition of 4G network is still vague but it is clear that it will be a step beyond the 3G All-IP based networks in the sense that IP will be native in 4G networks while it is an overlay in 3G All-IP ones. The advantages of this migration are clear and, as such, strong research efforts are directed to 4G. In 4G networks the users mobile devices will be like another IP host connected to the Internet. In such a scenario, the network operator infrastructure will be degraded to bit pipes. Because of this and the lack of winning business models, proper session setup and management solutions integrating service and network layers are not yet available. This thesis will tackle this issue. Our aim is to design solutions that place again the network operator in the core of the business value chain. IMS or i-mode business models will be followed. We will concentrate on the orchestration between the different systems, subservices (including transport service) and business entities. But still the Internet model of complete separation between transport and applications will be kept. We will design the session setup interactions between the pillars of 4G networks: QoS, AAA, and SIP proxies infrastructure. Mobility will not be dealt in our thesis, although, as we will see, it could easily be integrated in our framework. Our goal is to propose several approaches for several scenarios, compare and evaluate them (including by the means of simulation) and design the mechanisms for their coexistence. Since some parts of the session setup puzzle are already available we shall analyse them, see what is profitable, identify research opportunities and analyse the optimal way to put all the pieces together. In concrete, we should evaluate session setup protocols and session description languages to see if they fulfil our needs, for instance, we will need to include cost sharing aspects in SDP. Another aspect we will tackle is the design of some aspects of 4G networks relevant to our session setup techniques but not yet available, like the AAA-QoS interaction. The integration and coexistence of the different business models into our 4G framework and session setup solutions will be addressed. This thesis is part of the Communications Technologies Doctorate in the University Carlos III de Madrid. It will apply for a European amendment ( mención Europea ) in the Ph.D. Diploma. Following the rules, part of this thesis is written in English and part in Spanish. iii

4 INDICE 1. Introduction and Objectives Overal objectives Thesis phases Resources employed Document outlook State of the Art Analysis; Research Opportunities Session setup techniques Session setup models IETF s RSVP for QoS enabled transport sessions IETF s SIP and SDP for application sessions H323 and H323 vs. SIP Research efforts Coordination of application and network setup IMS SIP signalling in the IMS Integration of session setup and network setup in IMS Charging aspects in session setup and tear down Authentication and Authorization in SIP registration and session setup _ QoS and policy aspects in session setup and tear down Business model proposed, IMS general conclusions Next Generation Network framework G networks Fundamentals of 4G networks Research projects Session setup aspects in research projects Conclusion. Research opportunities and thesis objectives Análisis del Problema: Dispersión de las Sesiones Diversidad de entidades y de sesiones Interlocutores. Parámetros a negociar Interlocutores -Proveedores de Servicio Proveedor de Red Mediadores en el establecimiento de sesión Modelos de negocio, análisis de requisitos Modelos de negocio, análisis de sus prestaciones Tipos de sevicio y requistios para componer servicios El modelo de negocio Internet El negocio de los operadores móviles. Modelo Walled Garden El modelo Semi-Walled Garden Dueños de puntos de acceso WiFi Propuestas de gestión de los perfiles de usuario Contratos, identidades y perfiles de usuario Perfiles de usuario: el NVUP y contratos con los proveedores de servicio Perfiles de usuario: el SVUP. Coherencia lograda Almacén de los perfiles de usuario Interacción con el proveedor de red. Cohesión de las sesiones Los interlocutores gestionan la petición de servicio de transporte Perfiles y contratos involucrados Negociación, niveles de transporte y aplicación Usuarios y proveedores de servicio iv

5 3.3.3 Uso de mediadores Relación con los modelos de negocio Consideraciones sobre roaming Conclusiones Proposed 4G Architecture & Session Setup Support G Systems involved in session setup Users Profiles and session concept in the 4G systems QoS enabled data transport MMSP AAA Mobilitiy Network Measurement System Systems interactions and their relevance for session setup AAA-security Mobility - AAA+security AAA-QoS MMSP-AAA and MMSP-QoS Architecture of the 4G systems involved in session setup QoS. Proposed designs for setting up QoS sessions QoSBroker as central transport control entity QoSBroker: QoS management and access control Access and Core Networks AN-QoSBroker and AR in session setup Role of the CN-QoSBroker in session setup Interactions with the service providers. Application garden Roaming and local AN-QoSBroker as contact point Summary of QoS system interactions MMSP design AN-MMSP CN-MMSP SIP message routing proposal. MMSP interfaces Roaming Application garden IRTF s AAA and our decentralisation proposal Application garden Conclusion, AAA System interfaces Other systems: Measurements & Mobility AN CN split and WiFi hot spots venue owners Session setup possibilities in the proposed architecture AAA Authorization or distribution of users profiles? Session setup: proposals to orchestrate the interactions between systems Proposals for QoS transport session setup. Propagation of QoS sessions MMSP or Terminal doing the QoS reservation Terminal non inband QoS reservation ways Terminal inband QoS reservation and flow QoS identification Propagation of QoS transport sessions between ANs Propagation of sessions and users profiles Coexistence of the different solutions Co-ordination of transport and application session setup Conclusions Signalling Design Protocols and their ways to identify sessions SIP and SDP s Session id. Cost sharing and preference level COPS and its Handle Diameter and SAML v

6 Diameter aggregation of sessions Distribution of user profiles and single sign-on: SAML Diameter messages employed in this thesis PANA and IPSEC Terminal registration. SAML and QoS registration Setup and propagation of transport sessions Application and transport sessions, MMSP scenario Non-MMSP assisted scenarios: user and VASP Conclusions Validación Escenarios / Implementación Validación del simulador Pruebas individuales Pruebas generales Pruebas Tasa de llamadas soportada por el sistema Respuesta ante un pico de llamadas Heterogeneidad en las capacidades. Cuellos de botella Momento de realización de la reserva de QoS Conclusión Conclusions and Future Work Research avenues and forecast for our proposal Referencias vi

7 INDICE ABREVIADO 1. Introduction and Objectives Overal objectives Thesis phases Resources employed Document outlook State of the Art Analysis; Research Opportunities Session setup techniques IMS G networks Conclusion. Research opportunities and thesis objectives Análisis del Problema: Dispersión de las Sesiones Diversidad de entidades y de sesiones Modelos de negocio, análisis de requisitos Interacción con el proveedor de red. Cohesión de las sesiones Conclusiones Proposed 4G Architecture & Session Setup Support G Systems involved in session setup Architecture of the 4G systems involved in session setup Session setup possibilities in the proposed architecture Conclusions Signalling Design Protocols and their ways to identify sessions Terminal registration. SAML and QoS registration Setup and propagation of transport sessions Application and transport sessions, MMSP scenario Non-MMSP assisted scenarios: user and VASP Conclusions Validación Escenarios / Implementación Validación del simulador Pruebas Conclusión Conclusions and Future Work Research avenues and forecast for our proposal Referencias vii

8 INDICE DE FIGURAS Figure 1: Possible signalling protocol modes Figure 2: Yes/No signalling Single Configuration Figure 3: Low granularity signalling SLA like signalling Figure 4: Fine granularity signalling Parameter level signalling Figure 5 SIP Basic Call Setup Figure 6 SIP signalling proposed in RFC 3312 to coordinate application and network setup Figure 7 IMS architecture Figure 8 IMS session setup, interaction with AAA (Accounting) Figure 9 IMS session release, interaction with AAA (Accounting) Figure 10 IMS session setup, interaction with QoS Figure 11 IMS session tear down, interaction with QoS Figure 12 ETSI-TISPAN NGN Architecture Figure 13 A QoS enabled interface in a router Figure 14 an example of QoSBroker functionality, MSC Figure 15 Diameter Protocols organisation Figure 16 Gross' architecture for inter-domain QoS and AAA enabled SIP communications Figure 17 escenario: sesiones desde el punto de vista de los usuarios Figure 18 Clasificación propuesta de los parámetros negociados en el establecimiento de sesión Figure 19 escenario: sesiones desde el punto de vista de un proveedor de servicio Figure 20 escenario: sesiones desde el punto de vista del proveedor de red Figure 21 escenario: sesiones desde el punto de vista del mediador Figure 22 VAS en el mercado de las telecomunicaciones Figure 23 Business relations in the internet business model Figure 24 Business relations in the walled garden business model Figure 25 business relations in the semi walled garden business model Figure 26 sessions handled by the QoS system Figure 27 sessions handled by the MMSP Figure 28 AAA system interactions Figure 29 sessions handled by the AAA system Figure 30 AAA-QoS proposed interaction Figure 31 Hierarchical network topology Figure 32 Triggers in the AN-QoSBroker to setup a QoS enabled transport session Figure 33 Triggers in the AN-QoSBroker to tear down a QoS enabled transport session Figure 34 QoS system interactions Figure 35 MMSP interactions. Dashed, intra domain communication; solid inter domain Figure 36 AAA system interactions Figure 37 MMSP driven transport QoS session setup. Setup is propagated by the AN-QoSBrokers_ Figure 38 MMSP driven transport QoS session setup. Setup is propagated by MMSPs Figure 39 Registration processes Figure 40 MIP registration Figure 41 AAA registration and assertion "push to AN-AA Figure 42 Transport service registration. Explicit QoS request Figure 43 QoS session setup. Explicit request sent by terminal. 1 st AN Figure 44 QoS session setup. Explicit request sent by terminal. 2 nd AN Figure 45 Implicit QoS request and AAA-QoS interaction Figure 46 Session setup. AAA, MMSP and QoS interworking. Caller side Figure 47 Session setup. AAA, MMSP and QoS interworking. Callee side Figure 48 Session setup in a non-mmsp supported VASP scenario Figure 49 Session setup in a non-mmsp supported VASP scenario. Terminal setting QoS sessions Figure 50 Escenario de simulación. Un AN (izquierda), un CN y la Internet (derecha) Figure 51 Cálculo del tiempo de procesamiento en cada nodo Figure 52 escenario ns2 para pruebas de validación Figure 53 Mensajes impresos por los distintos nodos al hacer una llamada. Nótese como la llamada se considera establecida cuando el llamado recibe el ACK, evento que sucede antes de que el AN- QoSBroker reciba el mensaje RPT Figure 54 Trazas ns realizadas en los terminales (llamante y llamado) junto con la interpretación de los mensajes y el análisis hecho por nuestra herramienta (tiempo de inicio y duración del establecimiento de la llamada) viii

9 Figure 55 Trazas ns realizadas en los AN-AA (en este caso el mismo para llamante y llamado) junto con la interpretación de los mensajes y el análisis hecho por nuestra herramienta (tiempos de recepción y envío del mensaje) Figure 56 Enlaces CN-Internet atravesados para el caso Figure 57 Enlaces CN-Internet atravesados para el caso Figure 58 Enlaces CN-Internet atravesados para el caso Figure 59 tiempo de procesamiento en el CN-AAA Figure 60 Tiempo de establecimiento de llamada. Condiciones de saturación. MMSP Figure 61 Tiempo de procesamiento en un AN-AA. Condiciones de saturación. Estrategia MMSP _ Figure 62 Tiempo de procesamiento de los mensajes en un AN-MMSP. Condiciones de saturación. Estrategia MMSP Figure 63 Tiempo de procesamiento de los mensajes en un AN-MMSP. Condiciones de saturación. Estrategia MN Figure 64 Tiempo de establecimiento de llamada. Estrategia MMSP" Figure 65 Tiempo de establecimiento de llamada. Estrategia MMSP" (2) Figure 66 Tiempo de establecimiento de llamada. Estrategia MN Figure 67 Tiempo de procesamiento de los mensajes en el AN-MMSP. Estrategia MMSP Figure 68 Establecimiento de llamada (extracto). Pico de llamadas. Estrategia MMSP" Figure 69 Tiempo de establecimiento de llamada. Pico de llamadas. Estrategia MMSP" Figure 70 Tiempo de establecimiento de llamada (extracto). Pico de llamadas. Estrategia MN" Figure 71 Tiempo de procesamiento en el AN-MMSP. Pico de llamadas. Estrategia MMSP Figure 72 Tiempo de procesamiento de los mensajes en el AN-MMSP. Estrategia MN Figure 73 Tiempo de procesamiento en el CN-AAA. Pico de llamadas. Estrategia MN Figure 74 Establecimiento de llamada. 4 colas en el AN-MMSP. Estrategia MMSP Figure 75 Tiempo de procesamiento de los mensajes en el AN-MMSP. Pico de llamadas y 4 colas en el AN-MMSP. Estrategia MMSP ix

10 INDICE DE TABLAS Table 1 The SIP messages (or methods) Table 2 Some of the SIP responses (status codes) Table 3 Perfil de usuario con un proveedor de red (NVUP) Table 4 Perfil de usuario con un proveedor de contenidos Table 5 Perfil de usuario con un proveedor de espacio de archivo Table 6 contratos involucrados cuando los interlocutores hacen la reserva de red Table 7 Niveles de la negociación, cuando los interlocutores hacen la reserva de red Table 8 Reparto de costos de la sesión cuando los interlocutores hacen la reserva de QoS Table 9 Reparto de costos de la sesión cuando los interlocutores hacen la reserva de QoS Table 10 contratos involucrados cuando un interlocutor es proveedor de servicios Table 11 Niveles de la negociación, cuando un interlocutor es proveedor de servicios Table 12 contratos involucrados cuando un mediador asiste a los interlocutores Table 13 Niveles de la negociación cuando un mediador asiste a los interlocutores Table 14 Reparto de costos de la sesión cuando un mediador asiste a los interlocutores Table 15 Ways to orchestrate MMSP, QoSBroker and AAA interactions Table 16 Ways to orchestrate MMSP, QoSBroker and AAA interactions with the AAA being the sole network contact point Table 17 Session aggregation in the AAA server Table 18 Diameter Messages Table 19 Casos de llamada en función de la situación Table 20 Simplificación de los casos de simulación Table 21 Casos simulados en nuestro escenario Table 22 Mensajes procesados por un CN-MMSP en los distintos escenarios Table 23 Casos simulados en nuestro escenario, retardo introducido por los enlaces CN-Internet cuando el tiempo de propagación es 400 ms Table 24 Nº de mensajes gestionados por cada nodo. 128 llamadas en el escenario Table 25 velocidad de procesamiento en los nodos para soportar 64 llamadas/s Table 26 Tiempo de establecimiento de llamada bajo condiciones de mínima carga Table 27 Tiempo de establecimiento de llamada con carga máxima antes de tener saturación Table 28 Velocidad de proceso de las 4 colas del AN-MMSP Table 29 tiempos medios de establecimiento de llamada en condiciones estables x

11 GLOSARIO A4C, AAAC, AAAAC, AAA AD AN AN-AA(A) AN-QoSBroker AN-QoSB AR CCF CID CMS CN CN-AAA COPS CN-QoSBroker CN-QoSB CR CSCF (P-CSCF, S- CSCSF, I-CSCF) DiffServ DSCP ER FHO HD IMS IntServ MMSP(P) MSC MT, MN nar AAA Authentication, Authorisation, Accounting (AAA), Auditing and Charging Administrative Domain Access Network Access Network Accounting and Authorization Server Access Network Quality of Service Broker Access Router Charge Collection Function Charge Identifier Central Monitoring System Core Network Core Network Authentication, Authorisation, Accounting Server, or AAA- Server Common Open Policy Signalling Core Network Quality of Service Broker Core Router Call Service Control Function. Proxy, Server, Interrogating Differentiated Services Differentiated Services Code Point Edge Router Fast Handover Home Domain IP Multimedia Subsystem Integrated Services Multimedia Service Provision Platform Message Sequence Chart Mobile Terminal, Mobile Node New Access Router xi

12 NME NVUP oar PBNMS PDF PDP PEP PHB QoS RSVP RTMS RTP/RTCP SDP SIP SLA SNMP SP SVUP TSpec UA (SIP-UA) VAS(P) Network Monitoring Entity Network View of User Profile Old Access Router Policy-Based Network Management System Policy Decision Function Policy Decision Point Policy Enforcement Point Per Hop Behaviour Quality of Service Resource Reservation Protocol Real Time Monitoring System Real Time (Control) Protocol Session Description Protocol Session Initiation Protocol Service Level Agreement Simple Network Management Protocol Service Provider Service View of User Profile Traffic Specification SIP User Agent Value Added Service (Provider) xii

13 1. Introduction and Objectives It is foreseeable that in the future the circuit switched telephone fixed or mobile- networks will converge, or, better, migrate, into the Internet packet switched network. Currently, we can already use, over the internet, the applications that were normally employed in the telephone networks. For instance the Deutsche Telekom cellular clients in Germany can connect to the internet and since recently they can use the Skype application to do their voice calls via the internet and not via the cellular telephone network [SPI02]. Vinton Cerf s, one of the fathers of today s Internet, in a statement on a recent interview for the Spanish Journal El Mundo [MUN05], supported this view. Due to its relevance, we translate the following excerpt: Interviewer: Do you believe that VoIP will replace the telephony we are used to? Do you believe that every information transmission will use the Internet? Vinton Cerf: It has no sense to keep two different networks if there is enough capacity and quality to merge them. Even more, network operators such as NTT are already driving its efforts to this convergence. NTT offers Freedom of Mobile Multimedia Access (FOMA) [FOMA], it was the first 3G service worldwide. FOMA supports a connection to the Internet via cellular phones. Over this connection, the users can enjoy the classical telephone network services like voice calls. NTT forecasts [SCH02] that by 2010, the biggest revenue will come from Internet based services and no longer from cellular network ones. We believe that two are the motivations that are driving this change. First it will spare costs to the network operators since, instead of managing two different networks, they will need to handle one single network. Second, it will increase revenue since, due to the open characteristic of the Internet, it is very easy to build more and better services upon it and to offer them to the users who will then expend more money. But this convergence is full of challenges. First, the services offered today in mobile and fixed telephone networks should be moved -with the same or better performance- to the Internet. This is far from being simple due to the very different technical natures of the telephone and the Internet networks. On the other hand, business-related aspects pose also serious constraints to this convergence. For instance, although the above mentioned

14 A. Cuevas Tesis Doctoral openness of the Internet is positively seen as a source for increased revenue, networks operators fear to loose their central role in the provision of services, particularly in telephony or SMS services. If care is not taken the network operators may become mere bit pipes. Many approaches and ideas, sometimes quite different but, nevertheless, valid exist to make this migration come true. This exciting and hot research area is known under the generic term of 4 th Generation networks. There is not yet a clear concept of what a 4G (4 th Generation) network will be; but, broadly speaking, we can say it will be an IPv6 Internet like network [COM05] with extra features; some, such as mobility, coming from today s telephone networks. Also any access technology wired or wireless- will allow the user to connect to these 4G networks [WIR04]. Research projects in 4G networks concentrate on several aspects such as providing QoS, mobility and fast handovers, AAA (Authentication, Authorization, Accounting), etc. in IP based 4G networks; All these aspects are hard to provide in IP based networks since they were not designed for this. Until 4G networks are ready, an intermediate system, known as UMTS (Universal Mobile Telecommunication Service) or 3G (3 rd generation) has been developed and is already under commercial use. One of the topics still to be properly handled in 4G networks is the question of session setup. When two or more users want to establish a session between themselves (for instance to begin a voice call) they need, among others, to agree on the quality and on who will pay. It is true that available solutions partially cover these aspects. Among them is the SIP (Session Initiation Protocol) [RFC3261] which is widely used. With SIP, two users can agree on the codecs they will employ and that will determine the quality (e.g. in voice or video) they will experience during their session. Depending on the codecs chosen the users will require from the network different transport capabilities. If SIP is used to negotiate the setup of sessions at application level, there are also protocols to setup sessions at data transport level, for instance RSVP [RFC2205]. But there is not yet a clear way to integrate both into a common framework taking into account issues such as users profiles or tariffs and with characteristics like single sing-on. These shortcomings arise certainly from the fact that we need to negotiate at two different levels: service and transport and that the business entities offering the service and the transport may be different. This is a key issue in the development of 4G networks and, in the session setup aspect, it is of special relevance. This integration between service and transport in session setup is, among others, one of the key points the network operators have to achieve being in the core of the value chain of the telecommunications business. However, we can not go back to classical telephone network model, where transport and service are combined. It is just the opposite, we must go to an Internet like model where transport and service are separated and we have to define the correct interaction between them. We think that decisions and solutions in this field must be available as soon as possible, since this migration is already happening, sometimes out of the control of the network operator. For its good insight into this problem we translate and comment an article that appeared in the Spanish journal Cinco Días [CDI05]. The article begins with a quotation from Niklas Zennstrom, founder of Skype: paying for telephone calls is history. Further on, the importance of Skype, a company that developed a program to do voice calls over the internet, is highlighted: Ebay bought it paying about millions euros. The article also analyses the market in the USA and Europe. Last year Internet telephony accounted for 232 million dollars revenue in the USA and this

15 Introduction and Objectives revenue should increase till millions in In Europe, it is estimated that Internet telephony has diminished by 25% the revenues of traditional telephone network operators 1.1 Overal objectives The objective of this thesis is to contribute to design suitable session setup solutions in 4G networks integrating both application and network layer aspects and services. Integrating those aspects in session setup implies, actually, to integrate the applications and the network transport services. Our challenge is that the Internet model of complete separation between transport and applications will be kept. Our solutions will position the network operator in the core of business chain, thus giving an answer to the urgent needs just presented. First let s define the concept of session. The encyclopaedia Britannica defines a session, among others, as a meeting or period devoted to a particular activity. This same encyclopaedia defines a service as useful labor that does not produce a tangible commodity. We can thus term as services, voice calls, , web browsing, etc. We will say that a session is the instantiation of a particular service. The session setup includes all the means so that the service can be instantiated. A service can be formed of different subservices (like a video call, it can be formed of the audio and video services). Likewise, sessions can be composed of several subsessions. In telecommunications, sessions can cover many aspects and mainly in pervasive environments. In this thesis we will focus on application (actual services ) and transport (the telecommunication service that exchanges the information between the different parties participating in a session). Besides, this thesis will concentrate on session setup aspects and the orchestration between the different systems, subservices and business entities. It will not focus on other aspects such as session mobility. Neither will we analyse deeply multiparty calls. However our design will allow to integrate these aspects in similar ways as they are integrated today. As the framework of our thesis is 4G networks we need to analyse the different approaches to 4G networks and propose or choose a 4G architecture where we will apply our design. To orchestrate the different entities participating in the session setup, several aspects need to be covered. Those include signalling, handling of user profiles, division of tasks and functionality, etc. All this will be done in our proposed 4G framework. The interaction between application and network layer implies an interaction between service and network providers so it is important to study the different possible business models between users, network providers and service providers. We need to define how these business models can be provided in the proposed architecture and the technical requirements (such as messages exchanged between the elements) to support them. If we focus again on session setup, our goal is to propose several approaches, compare and evaluate them (including by the means of simulation). We aim to obtain a solution where the session setup between users is assisted by proxies. Those proxies either pertain to the network operator or have a business agreement with it. That way the

16 A. Cuevas Tesis Doctoral network operator will keep playing a fundamental role in the provisioning of services (besides being a mere bit pipe). This issue is fundamental for 4G networks to become a reality. The reason is that the network operators will be the key driver in the movement to 4G networks and they will favour such a change only if they keep the central role in the provisioning of services, as we propose in our model. Our goal is challenging since users could employ (e.g. to establish voice calls between them) peer to peer communications or applications assisted by proxies with no relation with the network provider. In those scenarios the network operator is just a bit transporter. If the network provider aims to offer added value services to its costumers it must entice them to use its service infrastructure and not the applications servers widespread in the Internet. The advantages that can be offered to the users can be twofold, either cost saving (paying less) or having better quality (e.g. more valuable services or best video quality). To reach so, our design must be open enough to offer any kind of service, it must offer them with the best quality and yet it must be simple enough to require few managing cost from the operator. To achieve such requirements may be a difficult task and may need a clever design, evaluation and comparison as it will be done in this thesis, focussing on the session setup aspects. As we have stated, the objective of this thesis is to contribute to design suitable session setup solutions in 4G networks. They will encompass interaction between users, network providers and services providers. Several approaches will be proposed, analysed, evaluated and compared. The main milestones of this thesis could be: Analysis and enhancement of the existing session setup protocols. We will focus mainly on SIP and H323. We will also tackle SDP (and SDPng) [RFC3264] [OTT05], which is a session description language, to evaluate how well are they suited to describe session-setup-negotiation related aspects. Others approaches will be also evaluated. This point can be divided into two sub-objectives: Analysis and Enhancement of the Session Description Languages: We will examine the parameters they can describe, focussing on QoS and pricing aspects. If they lack information on some of these facets we will propose ourselves the needed information. We will also analyse the capabilities of session setup protocols to coordinate the session setup with network setup: session setup at application level must be paired with setup at network level, otherwise, for instance, the participants may have agreed on the session and be ready to communicate, but the network may not be ready yet to accommodate their data. The extensions to SIP [RFC3312] to allow preconditions will be analysed. They are focused on QoS and we will see the possible ways to extend them to other aspects such as AAA. Special care must be taken in scenarios were caller and callee have very different profiles. Analysis of 3GPP s IMS: Integration of application service and network layers session setup. We will see how the IMS model proposes a way to integrate SIP services into a telecommunications operator infrastructure. We will parallel it to possible 4G solutions. First we will examine the business model(s) considered which are of special interest since they put the network operator in the core of the service provisioning. We will check if these business models can accommodate to the 4G open networks. Then we will tackle technical aspects. We will analyse the different architectural elements,

17 Introduction and Objectives see if they may fit with 4G networks or they are too specific to 3G ones. We will see the processes defined (registration, session setup, ) and the messages exchanged, paying special attention if they follow the existing protocols (SIP, COPS, DIAMETER). We will analyse if these processes could be exported to 4G scenarios. Finally we will see aspects not sufficiently covered in the IMS and that will need to be addressed in 4G networks. Analysis of 4G networks and proposed framework: First, we will find the common points of the different approaches to 4G networks to try to give a definition of what a 4G network is and we will also present our own view. Once this is done, we will focus on key aspects that are present in 4G networks like mobility, QoS and AAA and how they are intended to be solved, we will also give our view and see the degree the different approaches match with existing IETF solutions. Based on this, we will propose the framework architecture that will be considered in this thesis. We will focus on aspects such as QoS, AAA, service providers, session setup proxies, etc. Discussion and integration of different business models. Several business models will be analysed, focusing on the model proposed by the 3GPP. Within the 3GPP model we will concentrate in the IMS framework. However other business models will also be considered. Those may target different business scenarios or applications. Our goal is to integrate all the business models in a coherent 4G framework. Proposals for session setup in 4G networks: based on the IMS analysis previously done, we will design session setups solutions for our 4G network design. We will analyse existing 4G solutions and will propose new ones. We don t aim to provide one single solution, but to offer several choices and compare them. Aspects such as the number of messages to be sent in the access network (radio, ADSL, ), possible bottlenecks, time to establish a session in each approach, network and processing load introduced, their response to congestion situations (like massive number of calls trying to be established), how there are suited to deal with user mobility or with multiparty calls, etc. will be analysed. As we will see next, an important tool to do so is simulation. As a result, a complete characterization of the different approaches will be given and network operators will have the criteria to choose the one that best fits their needs. Evaluation and validation: We stress again that besides proposing several solutions we will analyse their pros and their cons under different scenarios and situations. One of the means to do so will be simulation. Simulation will be of much value since the two other approaches (mathematical model and measurements in a prototype test bed) to evaluate a proposal are difficult to do. Concerning the mathematical model, it would be too costly because a lot of interactions would need to be considered. Respect to the prototype test-bed two are the issues that make this approach difficult, first, as it is obvious, the test bed must be implemented, which is costly. Second, to evaluate scalability and performance issues, several users (from dozens to hundreds) will need to be present in the test bed to emulate the conditions (million of users) that will appear in public 4G networks. 1.2 Thesis phases To achieve the mentioned objectives the next steps will be followed

18 A. Cuevas Tesis Doctoral First the existing session setup protocols will be studied and special care will be taken to the extensions they may support to negotiate QoS or handle AAA aspects. IETFs QoS architectures focusing on the processes needed to request QoS (even if they are not defined by the IETF)- and AAA and mobility solutions will be analysed. Next we will focus on the IMS solution that integrates some of the mentioned aspects under a 3GPP architecture and we will see which aspects are not covered by it. The step beyond IMS is 4G networks, which shall integrate many aspects under their architecture. We will study the different approaches, find their weak and strong points and propose our own 4G architecture. At this point, we should have defined our framework and within it we will try to contribute to find solutions for session setup in 4G networks. Those solutions will be built upon our framework but should not be tied to it and be, whenever possible, applicable to other approaches. Major work will be done in this step, since we will propose several solutions and evaluate and compare them. Finally, to help to evaluate and compare our proposals we will use simulation tools. We first have to build a simulation model and see whether, despite the simplifications done, if the model is still valid to compare and evaluate our approaches. Once the simulation model is built we will test it to see if it was correctly implemented. Finally we will do the required tests over it, extract results and analyse them. 1.3 Resources employed This thesis is mainly a study and a contribution to find proper solutions for session setup in 4G networks. It is not the objective to implement the proposed solutions (only a few limited aspects). The solutions will, nevertheless, be evaluated and compared using simulation tools. State of the art documents were gathered thanks to the Carlos III University s and Telematic s department library services. Online access to several magazines was also available and used. We help ourselves with simulation tools building the simulation model- to accomplish this task. To do so, we required simulation tools and computers to run the simulation in. As we will detail, ns2 was the most suited simulation tool, it is freely available and was our choice. We run the simulations in a Linux based Pentium-4 PC. For the prototype implementation of some of the aspects defined an IPv6 network with at least two mobile nodes, one access router and some servers such as SIP proxy or AAA server will be needed. Finally, for UML modelling Telelogic Tau was used. Offimatic tools such as Microsoft Word were also made available by the Telematics Department

19 Introduction and Objectives 1.4 Document outlook Chapter 2 will summarize the work carried out in the research fields related to this thesis. Emphasis will be made in the 3GPP-defined IMS framework integrates some of these research results under a coherent umbrella and achieves a business model that places the network operator in the core of the business value chain which, as we have seen, one of the driving objectives of this thesis. However IMS must be extended to 4G and as we will see in this chapter there are still many gaps and shortcomings. Those shortcomings bring the research opportunities to this thesis and justify the objectives presented in the introduction. Chapter 3 will analyze the problems derived from today s Internet business model. We will focus on the split of subsessions between the different entities. The future business models, along with their advantages will be presented. Their requirements for session setup will be analyzed. The ways to correlate the different subsessions will be presented, focusing on users profiles, contracts, business relationship with the users and different negotiation levels (application and transport). This will be the key point to understand the session setup signaling design described in chapter 5. Chapter 4 proposes the design of the 4G architecture where our session setup solutions are developed. The endpoints of the signalling, nodes and systems, are identified and their role is described. Several design solutions are presented and evaluated. Since different scenarios have to be supported in the same architecture, different proposals have to coexist and some systems and nodes need to play different functionalities. The ways to orchestrate the various systems is presented. Chapter 5 describes in a straight forward way the signalling and the protocols. Chapter 3 and 4 have provided already the basis to understand our solutions and chapter 5 gives the level of detail necessary to understand completely our design. Different proposals will also be presented and evaluate. Signalling will be the basis for the overall evaluation done in chapter 6. Chapter 6 will deal with the simulation based evaluation of the several proposed, all integrated in a complete session setup framework. This evaluation will be quantitative and pretends to identify issues such as scalability and bottlenecks. Finally, the conclusion gathers the main results and contributions of this thesis. The way the objectives presented in this introduction are fulfilled will be detailed. The research areas still open or resulting from this thesis will be explained. This thesis is part of the Communications Technologies Doctorate in Universidad Carlos III de Madrid. It will apply for a European amendment ( mención Europea ) in the Ph.D. Diploma. Following the rules, part of this thesis is written in English and part in Spanish

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