Providing end-to-end quality of service guarantee for IP services.

摘要

In this dissertation, we address two major issues pertaining to providing end-to-end Quality of Service (QoS) guarantee over the Internet: (1) Per-flow based end-to-end QoS guarantee between a pair of edge nodes in a backbone network. This study is based on the Differentiated Services (DiffServ) architecture. (2) QoS guarantee in an access network, i.e. from the user end to the backbone. In particular, this research is focused on the Asymmetric Digital Subscribe Loop (ADSL) technology, which has the greatest potential to become the dominate broadband access technology.; In the backbone network arena, a connection-oriented DiffServ model is proposed. Unlike the traditional approach, which suffers from an intrinsic conflict between maximizing resource utilization and achieving a high service assurance, our approach provides end-to-end QoS assurance for each class of service (CoS) and high resource utilization simultaneously. This is achieved by developing a series of techniques including (a) a path pinning mechanism for assured service allowing aggregated bandwidth reservation for assured service at each intermediate router in the forwarding path; (b) a packet marking strategy; (c) a dropping policy; (d) an adaptive dropping-threshold calculation method for queue management based on aggregated reserved bandwidth and real-time traffic measurement. Furthermore, a series of measures is taken based on the developed connection-oriented DiffServ to provide per-flow-based QoS assurance. Simulation study is carried out to test the effectiveness of these measures.; In the study of the access network based on ADSL technology, steps are taken towards a complete solution to provide QoS guarantee. They are: (1) Transmission Control Protocol (TCP) performance analysis and bit loading scheme over the ADSL network, (2) Resource provisioning algorithm.; First, the performance of TCP sessions over ADSL loops is analyzed based on the simulations. The simulation results show that there is a threshold for the signal-to-noise ratio (SNR) gap or bit error rate (BER) above which TCP throughput drops quickly. This threshold takes its value in a wide range depending on the TCP Round Trip Time (RTT) as well as different noises. This suggests that it would be insufficient to set a fixed target BER at, e.g., 10−7, when calculating the number of bits to be loaded in each subchannels. Instead, the bit loading should take TCP performance into account. Finally, a dynamic bit loading scheme is proposed, which jointly optimizes the channel bit rate and TCP throughput performance.; Second, the resource provisioning issues for multiple services over ADSL are studied. Based on the TCP performance analysis, we propose a resource provisioning architecture, which enables three CoSs, i.e., constant bit rate (CBR) type of service for voice application, variable bit rate (VBR) type of service for assured data service, and best-effort service respectively. Finally, a case study is given which demonstrates how the architecture can be used to enforce Service Level Agreement (SLA) between a customer and a service provider.