Studies on congestion control mechanisms realizing various end-to-end communication qualities 多様な通信サービス品質を実現する輻輳制御に関する研究
Studies on congestion control mechanisms realizing various end-to-end communication qualities
本タイトル (誤植) : Studies on congestion control mechanisms realizing various end-to-end comunication qualities
九州工業大学博士学位論文(要旨） 学位記番号:情工博甲第202号 学位授与年月日:平成19年3月23日
(Preface)The Internet has become an important infrastructure and continues to expand. With theubiquitousness of the Internet in our daily lives, the amount of data, the number of flows,and the types of applications that coexist on the Internet have been increasing. Originally,people used the Internet to realize connectivity between senders and receivers. Currently,however, connectivity that meets a diverse range of requirements for various applications isdesired. In a well-provisioned network in which the number of users is limited, it is easy torealize connectivity that meets various requirements with no dedicated controls. On the Internet,however, flows that have various requirements coexist and limited network resourcesare shared among those flows. Thus, in order to realize connectivity under these environments,congestion controls are important in the network. The present research, therefore,focuses on the congestion control mechanisms in order to realize end-to-end communicationqualities that are adequate and suitable for the diversity of the network. Three diversities inthe network are considered, i.e., network environments, application types, and the qualityof services required by users. In addition, the problems in the current congestion controlmechanisms are clarified in order to achieve various levels of end-to-end quality of servicein the network and schemes are proposed to solve the problems. The congestion controls inthe network can be classified into two categories from an architectural viewpoint: controlsconducted between end hosts and controls conducted at all nodes along the path, includingintermediate nodes in addition to end hosts. In the following discussion, these two categoriesof congestion control, working between end-to-end hosts and working at all nodes along thepath, are described.Chapter 1 describes the background of the present research and outlines the present approachto target issues.In Chapter 2, the congestion control conducted between end hosts is introduced. TransmissionControl Protocol (TCP) is a representative protocol working between end hosts andhas been adopted as a transport protocol in the network, which can provide a highly reliablenetworking environment for non-real time application flows. However, it is well known thatTCP cannot achieve efficient data transfer in fast long-distance networks. Therefore, varioushigh-speed transport protocols have been proposed to solve this problem, and these protocolswill also be introduced in Chapter 2.In Chapter 3, the congestion control conducted at all nodes along the path is introduced.In Chapter 4, the basic characteristics of a number of existing high-speed transport protocolsare presented, which are obtained in testbed network. In this chapter, I primarilyobserve the throughput characteristics of a single high-speed transport protocol and discussits efficiency and fairness for a Standard TCP flow.In Chapter 5, a number of experimental results are discussed for various scenarios consideringthe future high-speed Internet. High-speed transport protocols were originally developedfor realizing efficient data transfer in fast long-distance networks. Therefore, in thecase of coexisting high-speed transport protocol flows and standard TCP flows, the performanceof the standard TCP flow is affected by high-speed transport protocol flows. On theother hand, on the future Internet, the end-to-end network will be faster. Under these circumstances,I believe that users may be interested in transferring their data using high-speedtransport protocol instead of the current Standard TCP. Therefore, in Chapter 5, an environmentin which high-speed transport protocols are adopted to transfer data by users, andexperimental scenarios are considered.In Chapters 6 and 7, I describe the congestion control mechanisms in which intermediatenodes work in conjunction with end hosts. In Chapter 6, I evaluated the performanceof end-to-end non-real time flows that pass through multiple DiffServ domains. Researchon the quality of service of end-to-end flows achieved by DiffServ technologies focuses primarilyon a single DiffServ domain. However, the actual network environment is a networkof networks, in which multiple DiffServ domains are connected. Therefore, the end-to-endthroughput characteristics of a minimum bandwidth guarantee service flow (AF (AssuredForwarding) service flow) that passes through multiple DiffServ domains in the DiffServframework are investigated. In the AF service, the packets are marked according to serviceclass in their headers based on the measurement at the ingress edge routers, and arethen forwarded to the intermediate nodes. At the border router to another DiffServ domain,the packet arrival rate is measured again and the service classes are re-marked if necessary.I investigate the impact of packet remarking that occurs at edge router on the end-to-endthroughput characteristics of AF flow. In Chapter 7, early packet discarding schemes areproposed in order to improve the delay characteristics of real-time application flows. Somereal-time applications set limits for acceptable network delay. For example, VoIP definesservice classes based on the end-to-end packet delay limit. In these applications, packetsdelayed longer than an acceptable limit are invalidated by their applications when they reachtheir destinations, even though they have successfully arrived at the receiver. These packetsare considered to be useless by the applications and thus impose an excess load on the network.Therefore, an early packet discarding scheme is proposed as a kind of active queuemanagement scheme, in which packets that do not contribute to the quality of real-time applicationsare discarded in advance at intermediate nodes. I evaluate the effectiveness of theproposed schemes via network simulation in Chapter 7.Finally, concluding remarks are presented in Chapter 8.
九州工業大学博士学位論文 学位記番号:情工博甲第202号 学位授与年月日:平成19年3月23日
1 Introduction|2 End-to-end congestion control|3 Controls on intermediate nodes|4 Experiments for High-Speed Transport Protocol of a Single Flow|5 Experiments for High-Speed Transport Protocol of Multiple Flows|6 Quality of Assured Service through Multiple DiffServ Domains|7 Adaptive Early Packet Discarding Scheme to Improve Network Delay Characteristics of Real-Time Flows|8 Concluding Remarks|Bibliography