在目前所提出的方法裡，主要都在考慮當某一條LSP遇到錯誤時該如何將在該LSP上的資料reroute到backup path上，因為backup 都是在LSP建立時便建立，或當LSP遇到問題時才建立，預先建立雖然能夠減少在reroute時遺失較多的packet，然而網路狀態的一值持續地改變，使得所建立的backup path在需要使用時，可能處於congestion或是斷線的情況而無法提供足夠頻寬以供reroute使用。且設定某條LSP在某條link上遇到錯誤時可以有其他替代路徑，其實也是設定了該路徑上的link發生問題時有哪些替代路徑，因為對所有經過該link的LSP而言都需要有其他替代路徑，且在所找尋的backup path都必定經過一些link，因而本篇研究提出將對LSP設定backup path的方式，改為對topology來設定backup path，也就是當某一條link或LSR發生錯誤時，我們能對找出除此link或LSR的替代路徑，使得因網路錯誤而受影響的LSP能夠有較多的其他替代路徑繼續傳遞資料。我們利用Max-flow Min-cut Theorem來找尋兩個LSR間有哪些link是必須經過的，然後利用shortest augmenting path algorithm來取得bypass tunnel應該設定哪些路徑。在此研究裡我們設定的bypass tunnel是屬於Node protection，也就是我們所建立的bypass tunnel並非只保護的一條link而是針對每一個LSR。模擬結果裡顯示我們的方法在reroute時能達到比使用Pre-Qualify的方式小或是與RSVP相當的packet loss, 在reroute成功部分我們因為提供較多的bypass tunnel可供選擇因而有較高的成功率，不過使得在cost部分比目前方法多。

This paper proposes a new approach to support restoration of Label Switched Paths (LSP) set up in the MPLS network. The proposed scheme tries to establish all possible bypass tunnels according to the maximum bandwidth between two LSR around the protected Label Switched Router (LSR). The proposed scheme uses the idea of the maximum bandwidth between two LSRs and establishes the bypass tunnels passing through the critical links which will affect the maximum bandwidth between two LSRs. All of LSPs affected by a LSR failure or a link failure can choice a bypass tunnel fit its QoS constraints to reroute. This paper also compares the different between the proposed bypass tunnel and link disjoint bypass tunnel. The simulation result show that the proposed approach has better packet loss in rerouting and can allow more affected LSP to reroute compare to RSVP and efficient Pre-Qualify. The proposed bypass tunnels have better performance than link disjoint bypass tunnels.

Chapter 1 Introduction…………………………………………………………1
1.1 Introduction……………………………………………………2
1.2 Motive……………………………………………………………3
1.3 Chapter Introduction…………………………………………4

Chapter 2 MPLS Recovery Mechanism Introduction…………………………5
2.1 Terminology……………………………………………………6
2.2 MPLS Recovery Mechanism Introduction……………………7
2.3 Comparison between these methods…………………………20

Chapter 3 Fast Reroute with Pre-established Bypass Tunnel……………21
3.1 Max-flow Min-cut Theorem……………………………………22
3.2 Node Protection or Link Protection………………………26
3.3 Setup the Bypass Tunnel………………………………………27
3.4 Choose a Bypass Tunnel…………………………………………31

Chapter 4 Simulation………………………………………………………………35
4.1 Simulation Topology………………………………………………36
4.2 ………………………………………………………………………37
4.3 Single Link Fail…………………………………………………40
4.4 Average Link Fail………………………………………………43
4.5 Cost…………………………………………………………………47

Chapter 5 Conclusion and Future Work…………………………………………51
5.1 Conclusion…………………………………………………………52
5.2 Future Work…………………………………………………………53

Appendix A: Max-Flow Min-cut Theorem…………………………………………55

Appendix B: Multi-Protocol Label Switching Architecture…………………59

Reference……………………………………………………………………………71

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