【作者】 林容容；

【导师】 丁伟；

【作者基本信息】 东南大学 ， 计算机系统结构， 2006， 硕士

【摘要】 为了评价端到端体系中的网络性能,网络单向延迟等性能参数的测量至关重要。但由于网络中各主机的时钟不同步,使得单向延迟测度值难于准确测量。为此,本论文研究并设计实现了一个分布在网络各主机上的面向单向延迟测量的多主机时钟同步系统,该系统基于环状拓扑模型。即:对在一个逻辑环状拓扑上的各主机的时戳报文数据进行测量和统计,建立时钟同步模型,并利用环状拓扑结构再进一步协同各结点同步。首先,本系统所研究的结点间的同步模型的建立参考了Paxson,Moon和Li Zhang等人提出的时钟同步方法,在此基础上进行改进设计,提出A&V同步方法,为用户提供准确高精度的同步时间戳。其次,基于现有的树型,星型或是P2P网状同步拓扑系统的研究基础,提出环状同步拓扑下的同步系统设计。本系统在结点间的同步模型建立之后,利用逻辑的环状同步拓扑,计算该同步环上的时钟累积误差,对环上各结点的同步模型进行协同修正,以进一步提高同步精度。最后,系统提供动态环状逻辑拓扑的建立、解除及自维护。系统能够以较短的收敛时间自主建立、解除其环状逻辑拓扑。此外,还提供同步拓扑环的自维护能力,即后续结点可以加入已建立的同步环,环上的结点可以主动撤离当前同步环,同步环在同步中若判断环上有失效结点将使该同步结点被动撤离当前同步环。综上所述,本系统可以对在同一逻辑环状拓扑中的若干主机结点进行时钟同步,以此为测量各主机间的网络单向延迟值提供准确的时戳数据。更多还原

【Abstract】 To measure the network performance between end and end, some metrics are really important, such as one-way delay. However, it is difficult to meausre this metric due to the asynchronism among hosts. This dissertation designed and worked out a network clock synchronization which is based on one-way delay measurement and ringed topology. In detail, it collects the time stamp data on hosts which are organize in logically ringed topology, then establishs the clock synchronious model base on the time stamp data, and finially makes all the hosts coorperate with each other to optimize the synchronious model data.Firstly, the research on the establishment of clock synchronous model is based on the present clock synchronous meathod made by Paxson, Moon, Li Zhang and some other person. After some improvement design, this dissertation present A&V synchronous meathod which can provide synchronized time stamps with better precision for the hosts.Secondly, the synchronization based on ringed topology is designed, which is totually different from the present meathod based on the tree, star or P2P model. Benefit from this logically topology, the system can get the inherit synchronous error which can help the host to improve the precision.Thirdly, the synchronous systom provide the dynamic maintenance for its logically topology, such as establishment, dismission, insertion and etc. It means that this system can be established or dismissed by itself within a short time. Another thing to mention is its self-maintenance ability, that is the ability for the other host to join into the established synchronous ring, or for the host which is already in the synchronous ring but who want to leave. In addition, it can passively withdraw the host which cannot be contacted for a long time.All in all, this system can synchronize several hosts in a logically ring topology, and provide the precise time stamp data to measure the one-way delay between hosts.更多还原