隨著網際網路的快速發展，網路服務與技術也跟著日新月異，使用者對於網路服務品質之需求也日益增長。現今之網路架構所能提供的頻寬是有所限制的，使用者如使用影音串流多媒體服務，需提供足夠的網路頻寬以確保其服務之品質。此舉卻造成絕大部分的頻寬被多媒體服務所佔用，導致其它服務僅能利用剩餘的頻寬，導致服務品質低落或傳輸效能不佳等影響，以至於服務無法符合使用者的期望，且於無線網路環境之情況更是嚴重。因此如何有效分配與管理無線網路頻寬以達到服務品質保證是為當前需解決之課題。

現有的網路流量分析工具，其大多採用系統模擬或以Benchmark的方式進行效能評估，對於現今複雜的網路架構與多元化的服務需求而言，透過模擬方式進行效能評估，其結果之真實性將備受質疑。若能以實體的網路設備進行效能測試，其資料分析的結果將能反映出真實的網路環境狀態、了解真實網路之運作情形，並可在此網路環境下，提出各種方法驗證其效能與實用性。然而市面上所販售之網路設備其內部軟硬體架構係採封閉式建構而成，研究人員無法透過修改底層架構，僅能於上層做應用服務設計與開發。

本研究利用NetFPGA硬體平台及OpenFlow網路虛擬化架構，並延伸至無線環境，建構一完整的開放式虛擬化無線網路環境，於此環境驗證本研究所提出之服務品質保證機制，根據不同服務需求進行頻寬速率之調控。本研究所提出之機制係修改OpenFlow交換機內的Wildcard Table，讀取流入封包之表頭(Header)內的服務類型(Type of Service, ToS)欄位，並將封包置於相對應的輸出佇列，系統根據不同服務之頻寬需求，進行頻寬速率控制，避免頻寬被單一服務佔據之情況產生，使所有服務皆能達到服務品質之保證。本研究所提出之服務品質保證機制針對不同的應用程式進行效能分析，TCP類型(以FTP為例) 實驗結果，封包速率限制以10M、1M與10K為例，平均準確率可達86.6%、99.5%與78.3%；UDP類型(以Video Stream為例)實驗結果，封包速率限制以10M、1M與10K為例，準確率皆可達100%，並可避免壅塞的情況並降低封包遺失率達4.6%、封包延遲之時間降低46.9%。

The demand of design quality of service (QoS) mechanism for internetworking services is very imperious task. This motivation is interrelated with the problem of network bandwidth tendency to be very limited. For instance, multimedia application such as Video Streaming is necessarily to be transmitted in larger committed bandwidth quota, while ocassionaly undesired application flows prone to occupy most of available bandwidth and give some negative effects such as low-quality transmission impacting a low QoS for preferred application. Therefore providing isolation for bandwidth occupancy of each application is the solution that offered in this study. Exploiting Type of Service (ToS) field on the IPv4 header, each service can be identified its traffic behavior, then can be guaranteed by certain level of rate. The rate limiting is the strategy that purposed to obtain desired QoS of end to end application traffic flow.

Due to the sensitiveness of QoS metric, implementing rate limiting QoS design in hardware is considered to more accurate rather than merely perform simulation analysis. Although the commercial network devices such as router and switch are closed for any extension of QoS design and mechanism. Therefore the design is implemented usingOpenFlow System in NetFPGA platform. The modification of wildcard table module inOpenFlow user data path allow each packet is budgeted with a speed level on when it resides on the output queues.

After performing the test-bed implementation of service-based QoS mechanism, the system can isolate the traffic and limit the rate of traffic follow the determined bandwidth budget. The test-bed is also extended to wireless environment for considering QoS guarantee for mobile users. The performance result shows that the rate in the limitation of 10M, 1M and 10K, hits the average accurency of 85.6%, 96.2% and 78.3% for TCP (FTP) case and all hits the accurency of 100% for UDP (Video Stream) case; the percentage of packet loss is lower than without the mechanism 4.6% and the delay time is lower than without the mechanism 46.9%. As the overall the system offers better network utilization and QoS guarantee environment.

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[34]RFC 1122, http://tools.ietf.org/html/rfc1122
[35]RFC 2474, http://tools.ietf.org/html/rfc2474
[36]RFC 3168, http://tools.ietf.org/html/rfc3168
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