|Voice over IP for a corporate network
|TCP/IP (Computer network protocol)
Digital telephone systems
Computer network protocols
Hong Kong Polytechnic University -- Dissertations
Department of Electronic and Information Engineering
|140 leaves : ill. ; 30 cm
|In this dissertation, we studied theoretical aspects of Voice over IP (VoIP); we investigated and evaluated different types of theoretical quality of service (QoS) tools for VoIP. We also tried to integrate various kinds of QoS tools to optimize the VoIP performance in a corporate environment. We found that several tools must be utilized in order to provide an environment that can insure voice quality over a corporate data network. These tools, classification, queuing and network provisioning, should be used in every portion of the network. When applying over the low bandwidths and slow link speeds of a Wide Area Network, several additional QoS tools must also be utilized such as Link Fragmentation and Interleave, Compressed RTP and Voice Activity Detection. By a real world VoIP implementation, designing and building a corporate network for data and voice traffic, we evaluated and finally integrated various types of QoS tools to optimize VoIP performance in a corporate environment. A private VoIP network which can provide high quality of voice as well as data services was finally built, the total one-way end-to-end delay was found to be 65ms in this corporate VoIP network, for some public VoIP networks; the one-way end-to-end delay can vary significantly and frequently be higher than 300ms (ITU max acceptable international call delay), as internet routers forward VoIP packets only by best-effort service model which is mainly based on First-In-First-Out (FIFO). This private VoIP network not only meets the ITU l50ms one-way end-to-end requirements, but also perform nearly 5 times better than some public VoIP networks (by assuming that ISP can constantly provide a maximum 300ms end-to-end delay to meet the minimum ITU requirement) as the total end-to-end delay is only 21.6 percent of those public VoIP networks. Therefore, high quality VoIP has been proven to be flexible in a corporate environment with properly handling of traffic in different parts of the network by suitable QoS techniques.
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