Title page for 86325017


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Student Number 86325017
Author Sung-Lin Wu(吳松霖)
Author's Email Address No Public.
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Department Computer Science and Information Engineering
Year 1998
Semester 2
Degree Master
Type of Document Master's Thesis
Language zh-TW.Big5 Chinese
Title Two-Layer Dynamic Bandwidth Allocation for Virtual Private Networks
Date of Defense
Page Count 89
Keyword
  • bandwidth allocation
  • call layer
  • temporary state
  • virtual private network
  • VPN layer
  • Abstract The concept of virtual private networks (VPN) is to separate logically several private networks from the public networks by using the technology of tunneling. Besides, security and quality of services (QoS) are supported for VPNs. The bandwidth allocated to VPN tunnels may be wasted for low utilization, and the offered number of users for the system is thus decreased. On the contrary, if the bandwidth of VPN tunnels is less-allocated to increase the utilization, but, the blocking probability will be increased. Therefore, it is important to design a dynamic bandwidth allocation scheme for virtual private networks over public networks. A two-layer dynamic bandwidth allocation scheme is proposed to assign bandwidth for VPNs, where the control architecture is divided in VPN layer and call layer. While a new VPN is created VPN layer control mechanism allocates the predefined low bound bandwidth to the VPN. The bandwidth assigned may be increased only if the assigned bandwidth is not enough. The bandwidth allocation in the call layer is to manage bandwidth already assigned for a VPN. Although the residual bandwidth of the link is less than the low bound, a tunnel with the residual bandwidth is still to be created temporarily, and the tunnel is called to be staying in temporary state. The bandwidth of the tunnel will be increased to the low bound as long as there is released bandwidth. The network will offer more VPNs by introducing the concept of temporary state, and the link utilization is thus improved. Simulation results show blocking probability can be decreased by 11.92% ~41.87%.
    For the call layer bandwidth allocation, there are three schemes for bandwidth increase of tunnels: (1) increase the bandwidth by a call, (2) increase the bandwidth by a step (several calls), and (3) increase the bandwidth by a ratio. There are also three schemes for bandwidth decrease of tunnels: (1) release the bandwidth immediately as long as a call departs, (2) release the bandwidth when the residual bandwidth of the tunnel is larger than a step, and (3) release the bandwidth when the residual bandwidth of the tunnel is larger than a ratio of the current allocated bandwidth of the VPN. It is found that the policy using the third bandwidth increase and the third bandwidth decrease schemes is capable of decreasing the call blocking probability by 25.74% VPN and NPL by 95.51%
    Table of Content 第一章 緒論1
    1.1虛擬私有網路簡介1
    1.2虛擬私有網路之型態3
    1.3相關研究8
    1.4研究動機與目的9
    1.5論文架構11
    第二章 VPN網路之環境12
    2.1網路環境12
    2.2模型與假設13
    2.3VPN架構17
    第三章 雙層式VPN頻寬配置策略20
    3.1VPN層頻寬配置策略20
    3.2呼叫層頻寬配置策略25
    第四章 模擬結果與討論43
    4.1模擬環境說明43
    4.2效能評估指標45
    4.3模擬結果46
    4.3.1具暫態機制之策略的效能比較46
    4.3.2不具暫態機制之策略的效能比較55
    4.3.3有無暫態機制之策略的效能比較62
    4.3.4Two-layer scheme與Static partition scheme之效能比較67
    第五章 結論74
    參考文獻76
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    Advisor
  • Li-Der Chou(周立德)
  • Files No Any Full Text File.
    Date of Submission

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