Distributed Ip Multimedia Services, Network Architecture And Key Technologies

In recent years, the Internet has been rapidly developed and widely used with rich applications. P2P technology is one of the main driving force for the sustainable development of the Internet for its high scalability, robustness and fault tolerance by using distributed scheme. On the other hand, P2P technology brings great challenges on network management and security. Telecommuni-cation networks could provide secure and reliable services with quality of ser-vices (QoS) guarantee.These networks could be controlled and managed. But they are difficult to accept new or outside services and to provide variable-rate multimedia services. IP Multimedia Subsystem (IMS) is an all-IP based multi-service converged networks. It aims to converge telecommunications networks and the Internet. However, IMS is a complicated architecture and it is expen-sive to configure, manage and operate a IMS network. Furthermore, it probably encounters the problems of single point bottleneck and single point failure be-cause of concentrated elements.Therefore, it is a meaningful but challenging research topic to design an open, scalable and reliable, operable and manageable network for delivering IP-based multimedia services. This dissertation studies the architecture of dis-tributed IP multimedia service network and related key technologies by com-plementing the advantages of P2P technology and telecommunication technol-ogy.The work in the dissertation can be summarized as follows:In flat distributed hash table (DHT) overlays, all participating peers are considered having the same functionality, while they are heterogeneous ac-tually. The DHT scheme without any knowledge about underlying physical topology could cause a serious topology mismatching between the P2P overlay network and the underlying physical network. The above two facts degrade the lookup performance and the throughput of DHT systems. To avoid these problem, we present a new distributed hierarchical network architecture named S-P2PSIP for IP multimedia services, in which powerful peers with high CPU computation, memory and bandwidth form the top-level overlay network, while weak peers participate the local overlay. In S-P2PSIP, a node's identity (ID) is generated based on the hierarchical IPv6 address prefix, which makes the over-lay topology match the underlying physical topology. We define a unified ser-vice interface to support different DHT algorithms and different applications. It is easy to create a new service or support a existing service.The churn and Network Address Translation (NAT) are two main facts that degrade lookup performance in DHT systems and may cause high latency. We analytically study the lookup performance of the existing lookup strategies and analyse their advantages and disadvantages. According to the characteristics of a distributed network, we introduce acknowledgement (ACK) with retrans-mission into the lookup process. Once the lookup times out, the measures will be taken timely. Thus, ACK schemes make DHT systems more robust to sys-tem churn. We investigate how end-to-end ACK and hop-by-hop ACK used in TCP/IP network work in DHT lookup strategies. Furthermore, we propose a new ACK scheme in which the ACK messages are delivered to the source node. Then evaluating models are presented to analysis their lookup latencies and message overheads. Since NAT will result in non-transitive connectivity, we analysis the impact of NAT on the performance to make better choices for different environments.To provide the appropriate services automatically for different users or different identities of a user at different time, we presents a mapping between user public user identities and private user identity. Each public user identity has a customized list of services in the network. Then We present the user reg-istration process and session establishment flow in S-P2PSIP. We evaluate the availability of hierarchical distributed services network by performing simula-tion. Finally, this dissertation investigates the realization scheme of service based on S-P2PSIP. We present two realization schemes of Instant Messaging (IM) for different scenarios:paging mode and session mode. Presence service often comes together with IM. We realize presence service by using common interface of DHT to publish and subscribe presence information. For real-time streaming media services, a key service in NGN networks, we design trans-mission schemes based on layered random linear network code and inter-layer hierarchical random linear network code to provide the partial decidability for low-bandwidth peers then guarantee the continuous decoding.