頻寬一直是網路業者急於想解決的問題，光纖網路的高頻寬成為解決網路頻寬之重要方法。但在高頻寬的網路中，即使是在很短暫的時間內，一個鏈路發生故障可能影響大量資料之流失，所以使網路具存活能力(survivability)成為高頻寬網路中不可或缺的因素。光路徑(lightpath)之保護和復原機制(protection/ restoration)是偵測工作路徑上是否有鏈路發生障礙，當故障發生，則將工作路徑切換至備用路徑上，因此保護路徑切換時間(Protection Switching Time)之長短，影響著網路之傳輸品質，在光路徑之選擇時必須加以衡量。很多學術研究，致力於高密度分波多工網路的工作路徑和備用路徑之路徑選擇上，但很少機制是設計在保證保護路徑切換時間上。本論文提出之保證保護路徑機制，是以SLSP(Short Leap Shared Protection)為基礎，以有效的程序尋找剛好能滿足切換時間之備用路徑，除此之外，網路之花費亦加以衡量，讓其不致損耗太多網路資源。由模擬之結果，可以看出在保護路徑切換時間上，都能滿足使用者之需求，所需之花費與共享光路徑保護方式(shared-path protection)不相上下。 It is important to solve the lack of bandwidth for carriers. Optical network can provide high capacity, so it is a key technology to deal with the problem. Survivability is a very important requirement for the deployment of broadband networks because out of service links can affect huge traffic even if it is a very short time. And the data paths of broadband networks, which are critical for traffic engineering, are always necessary to be well protected. The procedure of protection or restoration for a path is initiated when failure is detected within the working path. In order to minimize the influence on transmission quality caused by network failure and to provide a definite time for the recovery from the failure, the protection switching time (PST) should be carefully considered in path design. Several researches have been devoted to construct the protection and restoration schemes of data paths over dense wavelength division multiplexing (DWDM) networks, however, there was rare research on the design of data paths with guaranteed protection switching time. In this paper, the PST-guaranteed scheme, which is based on the concept of short leap shared protection (SLSP), for the arrangement of data paths in DWDM networks is proposed. The proposed scheme provides an efficient procedure to find a just-enough PST-guaranteed backup path for a working path. In addition to selecting the PST-guaranteed path, the network cost is also considered in a heuristic manner. The experimental results demonstrate that the paths arranged by the proposed scheme can fully meet the desired PST and the required cost of the selected path is competitive with which of the shared path scheme.
