在網際網路的環境中，開放最短路徑優先協定為最常被應用的協定之一，其隸屬於內部路由通訊協定，該協定的特色在於：以鏈路權重值來決定最短路徑，進而以最短路徑的方式傳送訊務。在該協定當中，訊務工程之主要目的著重在：透過已定義的目標函數式，來提升與最佳化網路的績效表現；其中，我們最常採取最小化「最大鏈路使用率」的目標式，來降低網路壅塞的情形。
本論文主要探討路徑選擇的模式建立，並針對不同的權重設定之方法加以比較。此外，文中我們提出一個啟發式演算法，其藉由最佳化鏈路權重的方式來解決路徑選擇的問題；依據實驗的結果，我們驗證了該演算法確實能達成負載平衡的成效，使網路資源能被有效地利用；我們同時也提出了一套系統化的程序，讓網路能根據最佳的權重設定與訊務配置，來管理與調整目前通訊協定中的權重值。

Open Shortest Path First (OSPF) is the most widely used Interior Gateway Protocol in IP networks. The OSPF protocol directs the Internet traffic along the shortest paths that are defined by the links weight. Traffic engineering is responsible for improving the network performance by optimizing the objective function that we give. The objective function that minimizes the maximal link utilization is usually adopted to avoid the network congestion.
The main concern of this thesis is to formulate the model of OSPF routing, and further evaluate the performance of different approaches. In addition, we propose a heuristic algorithm to solve the routing problems by optimizing OSPF weights. Experimental results indicate that the optimization algorithm could lead to good load balancing, and make efficient utilization of network resources. According to the best weights setting and the traffic allocation, we show how to manage and adjust the OSPF weights in a systematic procedure.

[1] 曾春榮譯，「Cisco網路架構設計指南」，儒林，初版 [2000]。
[2] 張智勝譯，「TCP/IP互連網路」，全華，第四版 [2001]。
[3] 林班侯、林長毅譯，「IP選徑技術」，歐萊禮，初版 [2003]。
[4] Ahuja, R. K., T. L. Magnanti and J. B. Orlin, Network Flows, Prentice Hall, New Jersey (1993).
[5] Leben, J. and J. Martin, TCP/IP networking, Prentice Hall, New Jersey (1994).
[6] Bazaraa, M. S., J. J. Jarvis and H. D. Sherali, Linear Programming and Network Flows, second edition, John Wiley and Sons, New York (1997).
[7] Moy, J., “OSPF Version 2,” Internet Engineering Task Force (IETF), RFC 2328 (1998).
[8] Comer, D. E. and D. L. Stevens, Internetworking with TCP/IP, third edition, Prentice Hall, New Jersey (1999).
[9] Lewis, C., Cisco TCP/IP routing professional reference, McGraw-Hill, New York (2000).
[10] Fortz, B. and M. Thorup, “Internet Traffic Engineering by Optimizing OSPF Weights,” Proceedings of the INFOCOM’2000, 2, 519-528 (2000).
[11] Metz, C., “IP Protection and Restoration,” IEEE Internet Computing, 97-101 (2000).
[12] Ramakrishnan, K. G. and M. A. Roudrigues, “Optimal Routing in Shortest-path Data Networks, ” Lucent Bell Labs Technical Journal, 6, 117-138 (2001).
[13] Bhattacharyya, S., C. Diot, J. Jetcheva and N. Taft, “Pop-Level and Access- Link-Level Traffic Dynamics in a Tier-1 POP,” Proceedings of 1st ACM Sigcomm Internet Measurement Workshop (2001).
[14] Goralski, W. J., Juniper and Cisco routing, John Wiley, Indiana (2002).
[15] Pióro, M., Á. Szentesi, J. Harmatos, A. Jüttner, P. Gajowniczek and S. Kozdrowski, “On Open Shortest Path First Related Optimisation Problems,” Performance Evaluation, 48, Issue 1-4, 201-223 (2002).
[16] Fortz, B. and M.Thorup, “Optimizing OSPF/IS-IS Weights in a Changing World,” IEEE Journal on Selected Areas in Communications, 20, 756-767 (2002).
[17] Villamizar, C., “OSPF Optimized Multipath (OMP),” Internet Engineering Task Force, Internet-Draft (2002).
[18] Fortz, B., J. Rexford and M. Thorup, “Traffic Engineering with Traditional Routing Protocols,” IEEE Communications Magazine, 40, 118-124 (2002).
[19] Kalyanaraman, S., H. T. Kaur, S. Raghunath, J. Akella, H. Nagar and K. Chandrayana, “BANANAS: A New Connectionless Traffic Engineering Framework for the Internet,” Rensselaer Polytechnic Institute Technical Report, 1-14 (2002).
[20] Platt, D., “Improved Utilisation in IP Networks Using Multiple Path Routing”, ICCS2002 8th International Conference on Communication Systems, 1, 617-622 (2002).
[21] Abrahamsson, H., B. Ahlgren, J. Alonso, A. Andersson and P. Kreuger, “A Multi Path Routing Algorithm for IP Networks Based on Flow Optimisation,” Lecture Notes in Computer Science (LNCS), 2511 (2002).
[22] Harris, R., J. Murphy and R. J. Suryasaputra, “A Rapid Hot Spot Remover in OSPF networks,” presented at Australian Telecommunications, Networks and Applications Conference (2003).
[23] Kaur, H. T., Tao Ye, S. Kalyanaraman and K. S. Vastola, “Minimizing Packet Loss by Optimizing OSPF Weights Using Online Simulation,” presented at 11th IEEE/ACM International Symposium on Modeling, Analysis and Simulation of Computer Telecommunications Systems, 79-86 (2003).
[24] Bhattacharyya, S., C. Diot, A. Nucci, B. Schroeder and N. Taft, “IGP Link Weight Assignment for Transient Link Failures,” presented at 18th international Teletraffic Congress (2003).
[25] Diot, C., R. Guérin and A. Sridharan, “Achieving Near-Optimal Traffic Engineering Solutions for Current OSPF/IS-IS Networks,” IEEE INFOCOM 2003, 2, 1167-1177 (2003).