【作者】 陈均华；

【导师】 吴春明；

【作者基本信息】 浙江大学 ， 计算机应用技术， 2010， 硕士

【摘要】 多径传输使用多条连接流分割节点和流汇聚节点的路径进行传输。相对于传统的单径传输,多径传输具有充分利用网络资源、减少拥塞、提高传输可靠性和提高网络的安全性等优点,是近几年网络领域的一个研究热点。但是由于每条并行路径的传输延迟存在差别,因此从流分割节点按序发出的包到达流汇聚节点时可能是乱序的;此外,在多条并行的路径上传输数据包存在流量在各条路径间的负载均衡问题:而乱序和路径间的负载不均衡都会给传输速率、服务质量和网络资源的利用率等带来不利影响,因而对保证包有序和实现负载均衡的流量分割算法的研究具有重要的意义。目前多径流量分割算法的研究主要集中在包有序和路径间的负载均衡其中的一个点上,即使有少量的算法是两者都关注到,并且在保证包有序的基础上实现了一定程度的负载均衡,但由于流分割的粒度过于粗糙,其负载均衡性不是很好。本文首先分析了乱序对网络性能带来的不利影响,然后介绍了目前已经提出的几种多径流量分割算法,并分析了它们的优缺点。在此基础上,本文提出了一种新的流量分割算法,其在保证包有序的同时,尽可能细粒度地在路径间分割流从而很好地实现路径间的负载均衡。该算法主要通过构建用作可用路径延迟底线的游标来实现,游标主要取决于两个参数一当前路径传输延迟和相邻包到达流分割节点的时间间隔,它作为选取路径的延时基线来保证包到达的有序性;游标会随着每次选取的路径不同或相邻包到达流分割节点的时间间隔不同而动态地滑动,通过动态滑动游标使得尽可能多的路径可用来传输当前包,从而很好地实现负载均衡。通过对目前已经提出的流量分割算法和基于游标的流量分割算法进行跟踪驱动模拟,仿真结果表明,与已有的保证包有序的流量分割算法相比,本算法使负载更加均衡。更多还原

【Abstract】 Multi-path transmission, using several paths between the diverging point and the converging point, is used to transmit packet. Compare to the traditional single path transmission, multi-path transmission can make the best of network resources, reduce the congestion, improve the transmission reliability and security, etc. Therefore, it is a research hotspot in network field. Because of the delay deference between the parallel paths, the packets reaching the converging point will be out of order while they are sent orderly at the diverging point; in addition, multi-path transmission will present some problems about load balancing among the paths; furthermore, reordering and unbalanced load have adverse effects upon transmission rate, quality of service, the utilization rate of resources, etc. So, it is be of great significance to do some research on traffic splitting algorithm, which can guarantee the order of packets and realize the load balancing.At present, the issue of researching on traffic splitting algorithm mainly focuses on one of the two points, guaranteeing the order of packets and load balancing, although little of them focus on them together, the performance of load balancing is not very good because of the coarse grain of traffic splitting. This paper first analyzes the adverse effects upon the network performance resulted from out of order, and then introduces several traffic splitting algorithms and analyzes their merits and flaws. On this basis, this paper proposes a new traffic splitting algorithm, which can achieve good load balancing by splitting traffic into flow slices as fine-grained as possible. The new algorithm is mainly carried out by constructing a nonius which can be used as a baseline of path latency. The nonius, which is used to guarantee the order of packets, mainly depends on two parameters, the path latency and the interval between two successive packets. The nonius can slide dynamically because of different path or the different interval between two successive packets. By sliding dynamically, the packet can be transmitted among as many paths as possible; as a result, the load balancing can be achieved. Through trace driven simulation of the traffic splitting algorithm based on nonius and other existed traffic splitting algorithms, the simulation results show that the proposed algorithm gains a prominent improvement in load balancing over previous algorithms, while without reordering is guaranteed.更多还原