隨著網際網路發展的日新月異，網路系統在資訊傳遞所扮演的角色越來越顯得重要。但傳統網路架構已經逐漸無法滿足蓬勃發展的網路應用所需要的彈性與適應性。近年來，軟體定義網路(Software-Defined Networking) 概念的提出，被認為是一個解決方案。其特點是將處理網路控制的控制層及封包傳遞的資料層區隔開來，可以讓底層的傳輸設備由控制器統一管理。由於控制器具備了觀察及調整全域網路的能力，網路管理技術如流量控制及服務品質保證策略就能夠對整體網路作出更適切的配置。因此，本研究提出一具優先權差異化之動態封包流路徑切換機制。在盡可能滿足特定的重要封包流傳輸指定頻寬的前提下，策略性地調整網路拓樸中的封包流路徑使整體網路頻寬能夠更充份的被使用。除此之外，在處理新進封包流要求的路徑配置與系統偵測到鏈結超載時，動態進行封包流路徑調整，此機制的路徑遷移演算法會考量路徑頻寬、路徑上封包流總數與鏈結的重複使用率，盡可能的讓封包流能夠享有更多的線路頻寬。實驗顯示，本研究所提出的機制在支援OpenFlow協議的軟體定義網路環境中，能讓指定的高優先權封包流具備傳輸上的服務品質保證能力，並且相對較不易影響到其他非高優先權封包流的傳輸能力。

As the evolvement of network and cloud computing, network system plays an important role in information transferring. Current network architecture has no longer satisfied the flexibility and adaptability which applications need. Software-Defined Networking (SDN), proposed recently, is recognized to be a feasible solution. The crucial concept of Software-Defined Networking is to decouple the data plane and the control plane, and making control plane programmable. The control plane controls transferring devices in data plane. Since controllers have global visibility of network and the ability to adjust current network status, network management technology like flow control and quality guarantee schemes are able to be adopted to make better network resources allocation. Based on above mentioned, the research proposed a dynamic flow-path migration mechanism with priority division in Software-Defined Networking. In the mechanism, the required bandwidth of high priority flows are considered, and guaranteed as much as possible by dynamically migrating flow-paths when needing of requests are unsatisfied. The migration method considers remain bandwidth and number of flows on path, and avoids duplicate flow assignment on single link. The result shows that the dynamic flow-path migration mechanism implemented in OpenFlow environment not only guarantees the required bandwidth of high priority flows, but to some degree avoids interfering normal flows transmissions.

[1]Perlman, Radia. "An algorithm for distributed computation of a spanningtree in an extended LAN." ACM SIGCOMM Computer Communication Review. Vol. 15. No. 4. ACM, 1985.
[2]N. McKeown, et al., “OpenFlow: enabling innovation in campus networks,” ACM SIGCOMM Computer Communication Review, vol.38, no.2, pp.69-74, 2008.
[3](2013). OpenFlow Switch Specication Version 1.3.3 ( Protocol version 0x04 ). Available: https://www.opennetworking.org/images/stories/downloads/sdn-resources/onf-specifications/openflow/openflow-spec-v1.3.3.pdf
[4]N. Mckeown, “How SDN will Shape Networking,” October 2011. [Online]. Available: http://www.youtube.com/watch?v=c9-K5O qYgA
[5]S. Schenker, “The Future of Networking, and the Past of Protocols,” October 2011. [Online]. Available: http://www.youtube.com/watch?v= YHeyuD89n1Y
[6]NetFPGA. Available: http://netfpga.org/site/
[7]OpenvSwitch. Available: http://openvswitch.org/
[8]CPqD OpenFlow Software Switch 1.3. Available:
http://cpqd.github.io/ofsoftswitch13/
[9]HP OpenFlow 1.3 Administrator Guide. Available: http://h10032.www1.hp.com/ctg/Manual/c04495114
[10]N. Gude, T. Koponen, J. Pettit, B. Pfaff, M. Casado, N. McKeown, et al., "NOX: towards an operating system for networks," ACM SIGCOMM Computer Communication Review, vol. 38, pp. 105-110, 2008.
[11]POX. Available: http://www.noxrepo.org/pox/about-pox/
[12]Beacon. Available: https://openflow.stanford.edu/display/Beacon/Home
[13]Floodlight. Available: http://floodlight.openflowhub.org/
[14]Ryu. Available: http://osrg.github.io/ryu/
[15]Open Networking Foundation (ONF). Available: https://www.opennetworking.org/
[16](2015). OpenFlow Switch Specication Version 1.5.1 (Wire Protocol 0x06 ).
Available: https://www.opennetworking.org/images/stories/downloads/sdn-resources/onf-specifications/openflow/openflow-switch-v1.5.1.pdf
[17]OpenFlow Switches Testing on Ryu Controller. Available: https://osrg.github.io/ryu/certification.html#ofs
[18]Koerner, Marc, and Odej Kao. "Multiple service load-balancing with openflow." High Performance Switching and Routing (HPSR), 2012 IEEE 13th International Conference on. IEEE, 2012.
[19]Wang, Richard, Dana Butnariu, and Jennifer Rexford. "OpenFlow-Based Server Load Balancing Gone Wild." Hot-ICE 11 (2011): 12-12.
[20]Bredel, Michael, et al. "Flow-based load balancing in multipathed layer-2 networks using OpenFlow and multipath-TCP." Proceedings of the third workshop on Hot topics in software defined networking. ACM, 2014.
[21]Al-Fares, Mohammad, et al. "Hedera: Dynamic Flow Scheduling for Data Center Networks." NSDI. Vol. 10. 2010.
[22]Curtis, Andrew R., Wonho Kim, and Praveen Yalagandula. "Mahout: Low-overhead datacenter traffic management using end-host-based elephant detection." INFOCOM, 2011 Proceedings IEEE. IEEE, 2011
[23]Lantz, Bob, Brandon Heller, and Nick McKeown. "A network in a laptop: rapid prototyping for software-defined networks." Proceedings of the 9th ACM SIGCOMM Workshop on Hot Topics in Networks. ACM, 2010.
[24]Mininet. Available: http://mininet.org/
[25]Tarjan, Robert. "Depth-first search and linear graph algorithms." SIAM journal on computing 1.2 (1972): 146-160.
[26]Iperf – The network bandwidth measurement tool. Available: https://iperf.fr/
[27]Long, Hui, et al. "LABERIO: Dynamic load-balanced routing in OpenFlow-enabled networks." Advanced Information Networking and Applications (AINA), 2013 IEEE 27th International Conference on. IEEE, 2013
[28]Benson, Theophilus, et al. "CloudNaaS: a cloud networking platform for enterprise applications." Proceedings of the 2nd ACM Symposium on Cloud Computing. ACM, 2011.
[29]Wang, Zheng, and Jon Crowcroft. "Bandwidth-delay based routing algorithms." Global Telecommunications Conference, 1995. GLOBECOM'95., IEEE. Vol. 3. IEEE, 1995.
[30]Mohan, Venkat, YR Janardhan Reddy, and K. Kalpana. "Active and passive network measurements: a survey." International Journal of Computer Science and Information Technologies 2.4 (2011): 1372-1385.
[31]Yassine, Abdulsalam, Hesam Rahimi, and Shervin Shirmohammadi. "Software defined network traffic measurement: Current trends and challenges." IEEE Instrumentation & Measurement Magazine 18.2 (2015): 42-50.
[32]J. Suh, et al., "OpenSample: A low-latency, sampling-based measurement platform for commodity sdn." in International Conference on Distributed Computing Systems, 2014.
[33]sFlow. Available at: http://sflow.org/about/index.php
[34]Ballard, Jeffrey R., et al. "OpenSAFE: Employing a Programmable Network Fabric for Measurement and Monitoring."
[35]Tootoonchian, Amin, Monia Ghobadi, and Yashar Ganjali. "OpenTM: traffic matrix estimator for OpenFlow networks." International Conference on Passive and Active Network Measurement. Springer Berlin Heidelberg, 2010.
[36]S. R. Chowdhury et al., "Payless: A low cost network monitoring framework for software defined networks," in Network Operations and Management Symposium (NOMS), pp.1-9, 2014.
[37]N. L. M. et al., "OpenNetMon: Network monitoring in openflow software-defined networks." in Network Operations and Management Symposium (NOMS), pp1-8, 2014.
[38]Tsai, Pang-Wei, et al. "On the Implementation of Adaptive Flow Measurement in the SDN-enabled Network: A Prototype." Proceedings of the Asia-Pacific Advanced Network 40 (2015): 7-13.
[39]Z. Su, et al., "FlowCover: Low-cost flow monitoring scheme in software defined networks," in Global Communications Conference (GLOBECOM), pp.1956-1961, 2014.
[40]C. Yu, et al., "FlowSense: Monitoring network utilization with zero measurement cost," in Passive and Active Measurement, pp.31-41, 2013.