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利用可變速率方法賦予網路電話壅塞控制能力 / Congestion Control Enabled VoIP by Flexible Bit-rate

近年來,一個具有壅塞控制機制的傳輸協議DCCP被提出,期能取代UDP成為不可靠傳輸的主流協議。我們以NS-2網路模擬器和實際網路進行實驗,發現DCCP無法與其他傳輸協議公平分享頻寬,因此現行DCCP的設計,尚無法完全取代UDP。此外,目前DCCP以調整封包間隔的方式進行壅塞控制,也不適用於講求時效性的網路服務。
本研究首先以實驗證明,當網路情況不佳時,DCCP無法與其他傳輸協議公平的分享頻寬;當使用DCCP傳輸越洋長距離網路電話,如遇頻寬不足時,會因頻寬競爭力較弱而無法維持通話品質。本研究提出可變速率方法(Flexible Bit-rate)調整時效性網路服務的封包大小來進行壅塞控制,在維持一定服務品質之前提下,促進網路的和諧。我們在一個實際網路的實驗環境中評估以UDP、DCCP及可變速率三種方式傳輸網路電話封包的效能,結果顯示透過可變速率方法,能有效降低網路電話的封包遺失率,維持通話品質。 / With congestion-control ability, Datagram Congestion Control Protocol (DCCP) is expected to replace UDP as a mainstream unreliable transport protocol. But our study found that DCCP is not able to get a fair share of bandwidth under the competition of others transport protocols no matter in NS-2 simulation or real world networking environments. Furthermore, any congestion control protocol that postpones the transmission of packets may not be adequate to support time-sensitive network services.
To maintain the quality of time-sensitive network services as well as to be TCP-friendly when facing network bandwidth fluctuation, we propose a Flexible Bit-rate congestion control mechanism for VoIP to adjust their data rate. Our experiments show that Flexible Bit-rate congestion control method could effectively reduce the packet loss rate and to maintain VoIP quality as compared with UDP and DCCP. Furthermore, it can have a much better bandwidth efficiency and adjust better to network fluctuation.

Identiferoai:union.ndltd.org:CHENGCHI/G0977530141
Creators丁諭祺, Ting, Yu Chi
Publisher國立政治大學
Source SetsNational Chengchi University Libraries
Language中文
Detected LanguageEnglish
Typetext
RightsCopyright © nccu library on behalf of the copyright holders

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