FlowTrace： measuring round-trip time and tracing path in software-defined networking with low communication overhead  

作　　者：Shuo WANG Jiao ZHANG Tao HUANG Jiang LIU Yun-jie LIU F. Richard YU 

机构地区：[1]State Key Laboratory of Networking and Switching Technology,Beijing University of Posts and Telecommunications, Beijing 100876, China [2]Science and Technology on Information Transmission and Dissemination in Communication Networks Laboratory, Shijiazhuang 050081, China [3]Beijing Advanced Innovation Center for Future Internet Technology,Beijing University of Technology, Beijing 100124, China [4]Department of Systems and Computer Engineering, Carleton University, Ottawa, ON KIS 5B6, Canada

出　　处：《Frontiers of Information Technology & Electronic Engineering》2017年第2期206-219,共14页信息与电子工程前沿（英文版）

基　　金：Project supported by the National High-Tech R&D Program(863)of China(No.2015AA016101);the National Basic Research Program(973)of China(No.2012CB315801-1);the Beijing Nova Program,China(No.Z151100000315078);the National Natural Science Foundation of China(No.61302089)

摘　　要：：In today＇s networks, load balancing and priority queues in switches are used to support various quality-of-service （QoS） features and provide preferential treatment to certain types of traffic. Traditionally, network operators use ‘traceroute＇ and ‘ping＇ to troubleshoot load balancing and QoS problems. However, these tools are not supported by the common OpenFlow-based switches in software-defined networking （SDN）. In addition, traceroute and ping have potential problems. Because load balancing mechanisms balance flows to different paths, it is impossible for these tools to send a single type of probe packet to find the forwarding paths of flows and measure latencies. Therefore, tracing flows＇ real forwarding paths is needed before measuring their latencies, and path tracing and latency measurement should be jointly considered. To this end, FlowTrace is proposed to find arbitrary flow paths and measure flow latencies in OpenFlow networks. FlowTrace collects all flow entries and calculates flow paths according to the collected flow entries. However, polling flow entries from switches will induce high overhead in the control plane of SDN. Therefore, a passive flow table collecting method with zero control plane overhead is proposed to address this problem. After finding flows＇ real forwarding paths, FlowTrace uses a new measurement method to measure the latencies of different flows. Results of experiments conducted in Mininet indicate that FlowTrace can correctly find flow paths and accurately measure the latencies of flows in different priority classes.为了针对不同的应用和流量提供服务质量保障和差异化服务,负载均衡和多优先级队列技术被广泛地应用于网络中。在传统网络中,网络管理员经常使用"traceroute"和"ping"工具来检测负载均衡机制或者服务质量策略是否正常工作。然而,由于这些工具并不被现有的OpenFlow交换机所支持,所以还不能够应用于软件定义网络中。此外,traceroute和ping依靠主动发送探测包来探测路径。然而,当负载均衡机制把探测包和所需追踪流的数据包均衡到不同路径时,这些工具将无法探测出流的真实转发路径,更无法测量出真实的路径时延。因此,为了准确的测量链路时延,测量工具必须能够提前找出数据包的真实转发路径。基于此发现,我们提出了一套新的软件定义网络中的流追踪机制"FlowTrace",利用它来追踪任意流量的转发路径以及测量数据流所经历的链路时延。该工具通过收集交换机的流表来计算流的转发路径。然而,如果直接从交换机中查询流表会产生很大的数据平面流量,从而带来巨大的开销。因此,我们提出了一种被动的零开销的流表收集方法来解决该问题。在获得流的真实转发路径后,我们提出了一种新的测量方法来测量不同流的网络时延。最后,实验结果显示我们设计的方法可以准确的找出流的真实转发路径并测量出不同种类流所经历的时延。

关 键 词：Software-defined networking Network monitoring TRACEROUTE 

分 类 号：TF393[冶金工程—冶金机械及自动化]