近幾年來，由於高密度分波多工技術的快速發展，因此在每條光纖鏈結都可以提供更為龐大數量的波長作為傳輸資料的媒介，而且每條波長可以提供的頻寬也都獲得相當大幅度的提升。因此，傳統針對較小頻寬所設計的光通訊解決方法已經無法有效的運用遽增的頻寬以及滿足龐大的使用者需求。光曳帶是近幾年來一個新提出的有效率之解決方法。光曳帶是由光通道衍生而來且具有頻寬共享和有效使用頻寬的優點。之前已經有許多論文在探討光曳帶網路上的路由演算法，然而要在光曳帶網路獲得較好的效能無法僅單靠好的路由演算法就可以達成,還必須配合一個有效率的動態頻寬分配演算法。在這篇碩士論文裡面，我們主要是提出了一個用於光曳帶網路上並能更有效和更精確的分配頻寬之動態頻寬分配演算法，稱為需求以及延遲感知並具備兩次評估審議的動態頻寬分配演算法。 除了動態頻寬分配演算法外，我們也針對光曳帶網路提出了建立新光曳帶以及釋放光曳帶的機制。

為了驗證我們所提出的動態頻寬分配演算法之優勢，我們設計了一個模擬環境來求證。在模擬環境中我們總共使用了四個網路拓墣和四組不同的參數來互相配對組合。根據實驗的結果，可以觀察到我們所提出的方法在阻斷機率和平均封包延遲這兩方面的表現都有著顯著的改善。然而我們的方法在一個週期中需要用到較多的控制封包，但是超出的幅度仍然在一個可以接受的範圍內。尤其在環狀的網路拓墣中會花費較少數量的控制封包但是卻也能達到花費較多控制封包情形下的的改善幅度。

In recent years, because of the rapid advance of Dense WDM, each fiber link can provide hundreds of wavelengths and each wavelength can suffer huger bandwidth than before. The traditional solution of node communication for optical networks can not satisfy the explosive bandwidth and traffic demands anymore owing to the non-efficient allocation for the huge bandwidth. Light trail, a new proposed solution recently, is generalized from the light path and has advantages of bandwidth sharing and efficient bandwidth utilization. There are many researches discuss about the routing algorithm in the light trail networks. However, the better performance of light trail is caused by a good routing algorithm and an efficient dynamic bandwidth allocation scheme. In this thesis, we introduce an efficient dynamic bandwidth allocation scheme with double check mechanism, named Demand and Delay latency-aware with Two-round Evaluation (DDTE), to allocate bandwidth more accurately and efficiently in light trail networks. In addition to the bandwidth allocation scheme, we also propose a setup mechanism and a release scheme for the light trail networks.

For investigating the superiority of DDTE, we develop a simulation by using four topologies with four scenarios and compare DDTE with previously proposed Dual Auction algorithm. We can observe the obvious improvement in both of blocking rate and delay performance through the results of developed simulation. Although the more control packets should be used in DDTE to notify nodes to transmit data in their scheduled duration in one cycle, we can find it still in an acceptable range and the better cost-effective improvement will be achieved in ring-like networks.

[1]. P. Bafna, A. Gumaste, and N. Ghani, “Delay sensitive smoothed round robin (DS2R2) scheduler for light-trail and SLiT networks,” IEEE/OSA OFC 2007, March 2007, pp.1-3.
[2]. G. Chuanxiong, “An O(1) time-complexity packet scheduler for flows in multi-service packet networks, ” ACM Proc. Sigcomm 2001, Vol. 31, Issue 4, pp.211- 222.
[3]. J. Feng, W. He and A. Somani, “Optimal Light-Trail design in WDM optical networks, Intl Conf on Communications, ” IEEE ICC 2004, Vol. 3, June 2004, pp.1699-1703.
[4]. A. Gumaste, “Light-Trail and Light-Frame architectures for optical networks,” Ph.D thesis, Fall 2003, EE UT-Dallas.
[5]. A. Gumaste and I. Chlamtac, “Mesh implementations of Light-trails: A solution to IP centric communication in the optical Domain,” IEEE ICCCN 2003, October 2003, pp.178-183.
[6]. A. Gumaste and I. Chlamtac, “Light-Trails: An optical solution for IP transport, ” OSA Journal on Optical Networking, May 2004, pp.864-891.
[7]. A. Gumaste and I. Chlamtac, “Light-Trails: A novel conceptual framework for conducting optical communications, ” IEEE HPSR 2003, June 2003, pp.251-256.
[8]. A. Gumaste, S. Jain and S. Zheng, “SLiT: Strongly connected Light-trail for dynamic and efficient optical networking, ” IEEE/OSA OFC 2006, March 2006.
[9]. A. Gumaste, G. Kuper and I. Chlamtac, “Optimizing Light-trail Assignment to WDM Networks for Dynamic IP Centric Traffic, ” IEEE LANMAN 2004, April 2004, pp.113-118.
[10]. A. Gumaste and P. Palacharla, “Heuristic and optimal techniques for Light-trail assignment in optical ring WDM networks, ” Computer Communications, Vol.30, March 2007, pp.990-998.
[11]. A. Gumaste and S. Q. Zheng, “Protection and restoration scheme for Light-trail WDM ring networks, ” Optical Network Design and Modeling Conference 2005, February 2005, pp.311-320.
[12]. A. Gumaste and S. Q. Zheng, “Next generation optical storage area networks: The Light-Trails approach, ” IEEE Communications Magazine, Vol. 43, Issue 3, March 2005, pp.72-79.
[13]. A. Gumaste and S. Q. Zheng, “Dual auction (and recourse) opportunistic protocol for Light-Trail network design, ” IEEE Wireless Optical Communications Networks IFIP Conference 2006, April 2006.
[14]. D. Kliazovich, F. Granelli, H. Woesner, and I. Chlamtac, “Bidirectional Light-Trails for synchronous Communications in WDM networks, ” IEEE GLOBECOM 2005, November 2005, pp.1947-1951.
[15]. R. Ramamurthy and B. Mukherjee, “Fixed-alternate routing and wavelength conversion in wavelength-routed optical networks, ” IEEE/ACM Transactions on Networking 2002, Vol. 10, Issue 3, June 2002, pp.351-367.
[16]. A. Saad, K. Elsayed and S. Ahmed, “Enhanced optimal and heuristic solutions of the routing problem in Light-Trail networks, ” Springer Photonic Network Communications, February 2008, pp.7-18.
[17]. Y. Ye , H. Woesner and I. Chlamtac , “Traffic grooming techniques in optical networks, ” IEEE BROADNETS 2006, October 2006, pp.1-9.
[18]. Y. Ye, H. Woesner, R. Grasso, T. Chen, and I. Chlamtac, “Traffic grooming in Light Trail networks, ” IEEE GLOBECOM 2005, Vol. 4, November 2005, pp.1957-1962.
[19]. H. Zang, J. P. Jue, L. Sahasrabuddhe, R. Ramamurthy, and B. Mukherjee, “Dynamic lightpath establishment in wavelength routed WDM networks, ” IEEE Communications Magazine 2001, Vol. 39, Issue 9, September 2001, pp.100-108.
[20]. W. Zhang, G. Xue and K. Thulasiraman, “Dynamic light trail routing and protection issues in WDM optical networks, ” IEEE GLOBECOM 2005, Vol. 4, November 2005, pp.1963-1967.
[21]. http://www.cise.ufl.edu/~fishwick/simpack.html