Internet multimedia services are a crucial application provided by the current Internet and the evolving IP-based Next Generation Network (NGN) that unifies the telecommunication and the IP platforms. Internet multimedia services are established through a signaling phase, during which several key Internet protocols are involved, such as the Next Step In Signaling (NSIS) protocol for Quality of Service (QoS) support, the Domain Name System (DNS) and E.164 NUmber Mapping (ENUM) protocol for identity and location mapping, the Session Initiation Protocol (SIP) for session creation and management. This thesis studies the scalability, robustness and security aspects of these protocols with the goal of making sure that they can properly meet the ever growing demand for next generation Internet multimedia service signaling.;We start with a comprehensive Internet routing measurement and go on to investigate the interaction between NSIS QoS signaling and network route changes. Network route changes may cause an application data flow to diverge from its original forwarding path where QoS has been arranged. We provide insights on how NSIS could better detect routing dynamics to avoid disrupting the application-perceived QoS. We also look at NSIS operating over IP tunnels. IP tunneling masks NSIS QoS signaling inside the tunnel, resulting in "NSIS-blind" segments in the end-to-end path. We propose a mechanism that extends the NSIS QoS signaling into the tunnels to solve this problem. Next, we focus on ENUM. Built on DNS technology, ENUM enables Internet-based services to be addressed by conventional telephone numbers, and therefore bridges traditional and next generation telecommunication applications. Our work on ENUM provides the first comprehensive evaluation of whether typical name server implementations used as ENUM can meet the unique ENUM requirements that distinguish it from traditional DNS usage We compare open source and commercial servers. Through server instrumentation, we provide insights on the ENUM scalability performance bottlenecks and improvements of popular open source ENUM servers.;SIP is a core signaling protocol of the NGNs. Our work on SIP is divided into two broad areas: one on security, the other on scalability and robustness. Running SIP over Transport Layer Security (TLS) provides a standard way to secure SIP signaling. However, the deployment of SIP-over-TLS has been lagging due to lack of understanding about the performance overheads that the added security mechanism could incur. We present the first systematic experimental study to reveal the impact of TLS on SIP server performance. We use profiling tools to illustrate the difference in various SIP operation modes. Our complete set of tests also allows us to construct a measurement-parameterized cost model which helps operators in their capacity planning when adopting SIP-over-TLS.;Our study on SIP server scalability and robustness focuses on server overload management. We propose a taxonomy of SIP server overload based on whether the proxy server or the registrar server is overloaded. For most of the general proxy server overload scenarios, we propose new feedback-based overload control algorithms, including both application-level feedback for SIP running over UDP, and transport-level feedback for SIP running over TCP. For a set of common scenarios with predictable overload time and scope (e.g., TV viewer-voting shows), we introduce filter-based solution which could prevent sessions that will potentially cause overload from entering the network in the first place. The last scenario we examine is SIP registrar server overload, also known as avalanche restart, for which we present a new solution based on server-assisted client backoff.
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