彈性光網路是一種新型態的網路結構，他擁有更小的粒度，相較於波長分波多工光網路，也更能有效率的配置資源。另一方面，現在科技越來越發達，出現了越來越多需要使用到群播來傳輸資料，像是資料備份在多台主機上、大型計算等。所以在彈性光網路上的群播將會是一個需要被討論的問題。
在波長分波多工光網路中，群播已經常常被討論過並且有不少的演算法被提出，其中也提到，每個節點如果都要具備有分光能力將會是一大花費，因為當光網路需要作分光時會需要使用到光電轉換，而每次的光電轉換都會消耗大量的能量，所以要讓每個節點都具備此能力，在現實上是比較難達成的。另一方面，如果要將所有的節點都具有轉換能力，就會需要經過很多的接、收發器，這部分也會造成能量的消耗。因此我們找到了一種方法，是具有稀疏分光能力以及波長轉換能力的結構(虛擬源)，這個方法在波長分波多工光網路也有被提出過，與波長分波多工光網路不同在彈性光網路不已波長作為傳輸單位，所以方法上我們也做了一些修改。
另一部分，因為群播相較於單一傳輸在找尋繞徑與路由配置上更為複雜，所以我們希望有一種方法可以使得在頻譜資源管理上可以更為省時，進而找到使用層化圖的方式來描述頻譜資源使用情況，並且利用此層化圖來找繞徑與頻譜配置的解，縮短搜尋時間以及增加效能。
最後一部分是討論到虛擬源的取法，會影響到傳輸上的資源消耗量，因此如何在有限的資源內選擇分配在最佳的節點上，使的傳輸可以更有效率，將也會是一個非常重要的議題。

Nowadays, there are more and more the cloud-based applications, such as datacenter backup, grid computing, etc. It may rely on optical networks to transmit data. Server may serve many clients at the same time, so server need to pass the same data to different clients. Multicast provision is more important.
To realize the multicast provision, we need more hardware to support, such as splitter and conversion. However, the full splitter is easy to simulate, but the splitter is too expensive to realize. If all nodes are conversion capable, it would use too many transceivers to consume energy. We think of that virtual source node has been use in WDM.
In EON, there are many unicast for RSA algorithm has been proposed. Multicasting request needs more flexible resource management, therefore we use layered-graph model which has been proposed in unicast.
In this thesis we focus on sparse splitting and conversion multicast provisioning schemes for elastic optical network (EON). We use layered-graph, and virtual source (VS) node to solve multicasting problem. We modify the method and combined them. It is an important to select virtual source node, therefore we also proposed select virtual source node method.

[1] Ching-Fang Hsu, et al., “Graph-Model-Based Dynamic Routing and Spectrum Assignment in Elastic Optical Networks,” IEEE J. Opt. Commun. Netw., vol. 8, Issue 7, Jul 2016, pp. 507-520.
[2] G. Zhang, M. De Leenheer, A. Morea and B. Mukherjee, “A survey on OFDM-based elastic core optical networking,” Commun. Surveys Tuts., vol. 15, no. 1, First Quarter 2013, pp. 65-87.
[3] G. Shen and Q. Yang, “From coarse grid to mini-grid to gridless: how much can gridless help contentionless?,” OFC/NFOEC, Mar. 2011, pp. 1-3.
[4] H. Zhang, J.P. Jue, and B. Mukherjee, “A review of routing and wavelength assignment approaches for wavelength-routed optical WDM networks,” IEEE J. Opt. Commun. Netw., vol. 1, no. 1, Jan. 2000, pp. 47-60.
[5] I. Chlamtac, A. Ganz and G. Karmi, “Lightpath communications: an approach to high bandwidth optical WAN's,” IEEE Trans. Commun., vol. 40, no. 7, Jul 1992, pp. 1171-1182.
[6] M. S. Borella, J. P. Jue, D. Banerjee, B. Ramamurthy and B. Mukherjee, “Optical components for WDM lightwave networks,” in Proc. IEEE, vol. 85, no. 8, Aug. 1997, pp. 1274-1307.
[7] M. Jinno, et.al , “Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies,” IEEE Commun. Mag., vol. 47, no. 11, Nov. 2009, pp. 66-73.
[8] M. Jinno, et.al , “Distance-Adaptive Spectrum Resource Allocation in Spectrum-Sliced Elastic Optical Path Network,” IEEE Commun. Mag., vol. 48, no. 8, Aug. 2010, pp. 138-145.
[9] N. Sreenath, N. Krishna Mohan Reddy, G. Mohan, and C. Siva Ram Murthy, “Virtual Source Based Trees: A New Approach for WDM Optical Multicasting,” Proc. of IEEE Workshop on High Performance Switching and Routing, May. 2001.
[10] S. Talebi and G. N. Rouskas, “On distance-adaptive routing and spectrum assignment in mesh elastic optical networks,” IEEE J. Opt. Commun. Netw., vol. 9, no. 5, May 2017, pp. 456-465.
[11] T. Hwang, C. Yang, G. Wu, S. Li and G.Y. Li, "OFDM and its wireless applications: a survey," IEEE/OSA Trans. Veh. Technol., vol. 58, no. 4, May 2009, pp. 1673-1694.
[12] ITU-T Rec. G.694.1, “Spectral grids for WDM applications: DWDM frequency grid,” 2006.
[13] W.Hu and Q.Zeng, “Multicasting optical cross connects employing splitter-and-delivery switch,” IEEE Photon. Technol. Lett., vol. 10, pp.970-972, Jul. 1998.
[14] X. Wan, N. Hua and X. Zheng, “Dynamic Routing and Spectrum Assignment in Spectrum-Flexible Transparent Optical Networks,” IEEE/OSA J. Opt. Commun. Netw., vol. 4, no. 8, Aug. 2012, pp. 603-613.
[15] Xiahe Liu; Long Gong, and Zuqing Zhu, “On the Spectrum-Efficient Overlay Multicast in Elastic Optical Networks Built with Multicast-Incapable Switched,” IEEE communications letters, vol. 17, no. 9, Sep. 2013.
[16] Zuqing Zhu , Xiahe Liu, Yixiang Wang, Wei Lu, Long Gong, and Shui Yu, “Impairment- and Splitting-Aware Clou-Ready Multicast Provisioning in Elastic Optical Network,” IEEE/ACM transctions on networking, vol. 25, no. 2, April. 2007.
[17] Zheyu Fan; Yongcheng Li, Gangxiang Shen, Chun-Kit Calvin Chan, “Distance-Adaptive Spectrum Resource Allocation Using Subtree Scheme for All-Optical Multicasting in Elastic Optical Networks,” Journal of Lightwave Technology , Vol 35, Issue 9, Dec. 2017
[18] P. A. Fishwick, “SimPack: getting started with simulation programming in C and C++,” in Proceedings of the 24th conference on Winter simulation, ACM, Dec. 1972, pp. 154-162.
[19] P. Fishwick, SimPack Toolkit [Online]. Available: http://www. cise.ufl.edu/~fishwick/introsim/node8.html.