軟體定義網路之頻寬保證虛擬交換機

軟體定義網路(Software-defined networking ,SDN)是一個新興的次世代網路架構，SDN是讓網路能夠變得更加靈活的技術，SDN不同於傳統網路架構，將原本分散式(Distributed)的網路改為中央控制(Central control)，網路的管理權交由中央控制器(Controller)對交換機進行設定以決定交換路由。SDN網路可以隨時藉由改變交換機設定以調撥大量的頻寬給最需要通訊的節點，還可進行訊務工程以平衡網路負載與動態網路節能之管理，能更靈活與更彈性的配置網路資源。在本文中，我們將於SDN網路環境中實現一個對於使用者來說，能夠簡易使用的網路設計，設計的目標是將使用者的網路管理功能簡化，使得使用者可以無須對網路做管理，只需要提出所需之頻寬需求，而網路提供者將會提供所需頻寬之保證，同時進行路由的設定，而此設計同時具備與實體交換機相同的特性，因此我們將此設計稱為虛擬交換機(Virtual Switch)。實體交換機的主要特點是，實體交換機是由數個Port組成，每一個Port都有固定的輸入與輸出頻寬，且在未超過Port頻寬的使用情況下，交換機將不會遺棄任何封包。在我們的虛擬交換機設計中，具備與實體交換機同樣的特性，在使用者未超過Port頻寬的情況下，虛擬交換機將不會將任何的封包遺棄。不同的於實體交換機的地方是，用戶可以指定虛擬交換機Port的數目以及虛擬交換機每一個Port的頻寬。為了使網路中的頻寬資源能夠有效的使用，並使得網路中的Flow能夠彈性的分配，在虛擬交換機中Port對Port之間採用多路徑傳輸(bifurcation)的方式，但TCP分流於多條路徑進行傳輸時，會導致封包錯序進而影響TCP的傳輸效率，為避免上述情況發生，因此我們在交換機中設計了一套模組，此模組用以消除虛擬交換機使用多路徑傳輸時造成封包錯序的問題。本文經過實驗證明，我們的虛擬交換機能夠提供用戶選擇其所需的交換機Port數量以及頻寬，且在用戶未超過Port頻寬的使用情況下保證頻寬。使用我們設計實現多路徑傳輸能夠解決封包錯序的問題，且具備分流的高度準確性，相較於其他分流的方法，我們的方法對於TCP吞吐量較高。

關鍵字

虛擬交換機；多路徑；軟體定義網路

並列摘要

Software Defined Networking (SDN) is an emerging technology to enhance flexible control on networks through abstraction of lower-level switch functionality. Recently using SDN to construct datacenter networks has attracted a lot of attention. In this thesis, we propose an approach to realize SDN virtual switches on top of a substrate SDN network. The goal of the design is to mimic the virtual switch like a real switch. A user can specify the number of port and the line rate for each port in the switch. The major feature of the switch is that it is bandwidth guaranteed on each port. We guarantee there is no packet loss for the input traffic if it is within the specified rate of the input port. For any output port, the traffic destined to it won’t get packet loss if the rate of those flows are within the output port speed limitation. In other word, the virtual switch follows the hose model that is used for virtual private network before. To achieve this goal, the virtual switch has to be totally blocking free inside the switch. To enhance the resource utilization on the substrate physical network, multiple paths are used to connect port pairs inside the virtual switch. However, the bifurcating routing would result in packet out-of-order problem for TCP traffic, we applied Multi Path Proxy within the switch to eliminate the packet out-of-order problem caused by the bifurcating routing used in the virtual switch. The experimental results show that our virtual switch can provide user the desired switch Port number and bandwidth. We guarantee user bandwidth if it is within the specified rate. With our approach to multi-path transmission can resolve packet reordering problem, and has a high accuracy of Splitting traffic. Compared to other splitting methods, our method provide a good performance of TCP throughput.

並列關鍵字

Virtual Switch ； Multipath ； Software Defined Networking (SDN)

參考文獻

[1] Pontus Skoldstrom, Kiran Yedavalli, “Network Virtualization and Resource Allocation in OpenFlow-based Wide Area Networks”, in Proc IEEE International Conference on Communications (ICC), 2012.

[5] E. Salvadori, R. D. Corin, A. Broglio, M. Gerola, “Generalizing Virtual Network Topologies in OpenFlow-Based Networks”, in Proc. IEEE GLOBECOM, 2011.

[6] N. Duffield, P. Goyal, A. Greenberg, “A Flexible Model for Resource Management in Virtual Private Networks”, in Proc. ACM SIGCOMM, 1999.

[7] N. Goyal, N. Olver, and B. Shepherd, “The VPN Conjecture is True,” ACM STOC, 2008.

[8] S. Fiorini, G. Oriolo, L. Sanita, D. O. Theis, “The VPN Problem with Concave Costs,” SIAM Journal on Discrete Mathematics, vol. 24, no. 3, pp. 1080-1090, 2010.

國際替代計量

軟體定義網路之頻寬保證虛擬交換機

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