階層式交換器光纖網路中的通道設置及保護

Abstract

多單位光學交換器(Multi-granularity Optical Cross-Connect)架構是為了提供一個有效節省成本的方式來供應越來越大的網路資料流量的需求。在多單位交換器光纖網路中，數個綁成一束的連續波長形成一個通道(tunnel)並且像一個單獨波長一樣一起做交換。通道路徑上的交換器尺寸可因此而變小並降低成本。這本論文主要在探討多單位光學交換器上的通道配置及保護這兩個問題。 最近提出的容量平衡通道配置法(Capacity-Balanced Static Tunnel Allocation)是用來解決通道配置問題。容量平衡通道配置法選擇流量進出最大的兩個節點並在這兩點之間配置一條通道。然而當為每一個通道選擇一對節點時，容量平衡通道配置法並沒有考慮通道長度的限制。因此，我們提出等長權重通道配置法(Constant Length Weighted Tunnel Allocation,)來改善容量平衡通道配置法的問題。在等長權重通道配置法中，只有符合長度限制的兩節點，才會試著在之間建立通道。我們藉由模擬來驗證等長權重通道配置法的效能並與容量平衡通道配置法做出較。結果顯示等長權重通道配置法的效能比容量平衡通道配置法更好。 在多單位交換器光纖網路的保護方面，我們探討單一線路故障時的保護機制。多單位交換器光纖網路在保護機制方面還未被廣泛研究，因此這篇論文提供一個有效解決單一線路故障發生時的保護機制。我們提出通道式分段保護機制(Tunnel-based Segment Protection)來回復因線路故障所中斷的通訊，在通道式分段保護機制中，配置通道時同時也會考慮保護需求，當我們在網路上配置一個主要通道時，同時也配置一個相對應的備用通道。模擬結果顯示通道式保護機制對多單位交換器光纖網路中的單一線路故障提供一個有效的解決方法。

Multi-granularity Optical Cross-Connect (MG-OXC) has been proposed to provide a cost efficient way to support the increasing number of traffic requests. In the MG-OXC networks, consecutive wavelengths are bundled to form a tunnel and switched as a single unit. Networks resources, including switching fabrics and multiplexers, at the mediate nodes on the route of a tunnel thus can be reduced. This thesis considers the static tunnel allocation problem and the protection problem in MG-OXC networks. For the tunnel allocation problem, a heuristic Capacity-Balanced Static Tunnel Allocation (CB-STA) [1] has been proposed. CB-STA always tries to allocate a tunnel from the node with maximal predicted traffic going out to the node with maximal predicted traffic coming in. However, the length constraint is not considered when selecting node pairs. We propose a heuristic, Constant Length Weighted Tunnel Allocation (CLWTA), to overcome this problem of CB-STA. Only node pairs whose hop distance complies with the length constraint are tried to be allocated tunnels in CLWTA. We examine the performance of the proposed schemes, CLWTA, and make a comparison with CB-STA. The results show that CLWTA outperforms CB-STA in all switching type combinations. For the protection problem, we investigate the protection schemes for the single-link failure in the MG-OXC networks. Since the protection problem has not been studied intensively in MG-OXC networks, this work aims to provide an efficient protection solution. A segment-based protection scheme, called Tunnel-based Segment Protection (TSP) that considers the tunnel allocation with protection requirement in mind is proposed to recover the communications interrupted by a fiber cut. In TSP, a corresponding link-disjoint protection tunnel is always allocated simultaneously with a working tunnel. Simulation results show that TSP provides an efficient protection solution for MG-OXC networks.