本文首先对区分服务（DiffServ）结构中的边缘路由器和核心路由器机制进行了系统的分类研究，分析并比较了各种机制。接着，对区分服务结构中TCP的性能问题进行了研究，总结了国内外对这一问题的仿真、解析模型分析和实验研究的成果。找出了关键的问题所在,并根据我们的研究成果提出了一些区分服务结构本身的改进建议。

本文推导出了SDH/ATM双向自愈环在链路失效、节点失效及链路节点混合失效三种模型情况下的网络生存性函数，从导出的网络生存性函数可以方便地求出生存率的均值、最坏生存率、百分比生存率及零生存率等单个生存性测度. 同时对导出的生存性函数结果进行了分析，结果表明本文的分析方法符合实际情况，是切实可行的，为分析和设计高生存性通信网络提出了统一的可实现的方法。

As an extensive study of Internet QoS, a framework for emerging Internet QoS strategies is presented. Inte-grated service (Intserv/RSVP), Differentiated service (Diffserv), MPLS, and QoS routing, are overviewed. The key issues and relationship of these QoS architectures are discussed. Some algorithms in IP QoS implementation and unsolved problems are also studied in this paper. Furthermore, a new strategies of incorporating Intserv with Diff-serv to archive end2to2end QoS is proposed. It is also discussed why MPLS and QoS routing are introduced into this framework, how they differ from and relate to other schemes and where they fit into the Diffserv architecture. The timescales of different QoS strategies are also studied and some proposals for QoS routing deployment are given.

IEEE 802.11 Medium Access Control(MAC) is proposed to support asynchronous and time bounded delivery of radio data packets in infrastructure and ad hoc networks. The basis of the IEEE 802.11 WLAN MAC protocol is Distributed Coordination Function(DCF), which is a Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) with binary slotted exponential back-off scheme. Since IEEE 802.11 MAC has its own characteristics that are different from other wireless MAC protocols, the performance of reliable transport protocol over 802.11 needs further study. This paper proposes a scheme named DCF+, which is compatible with DCF, to enhance the performance of reliable transport protocol over WLAN. To analyze the performance of DCF and DCF+, this paper also introduces an analytical model to compute the saturated throughput of WLAN. Comparing with other models, this model is shown to be able to predict the behaviors of 802.11 more accurately. Moreover, DCF+ is able to improve the performance of TCP over WLAN, which is verified by modeling and elaborate simulation results.