即時性服務之流量縮減與路徑復原演算法

Abstract

在現今的網際網路中，即時性的服務扮演著很重要的角色。聲音在IP網路上傳送將會取代傳統的電話交換式網路而成為一種趨勢。然而隨著現在語音編碼壓縮技術的進步，因此在傳送的封包承載量便大大的減少，因此若是依舊使用原先網際網路原有的封包檔頭，便會造成很大的檔頭負荷。雖然過去已有很多壓縮及多工的機制出現，但是改善的空間仍然有限，因此在此篇論文中我們會以網路演進的角度，提出一個新的壓縮及多工的機制來克服原有在網路上的問題，並且讓語音可以在較好的路徑上傳送，最後再結合差別式服務的網路，讓我們的機制能夠獲得更好的整合。 而在再更進一步，為了對即時性服務在網路上做更快速的傳輸，因此我們便希望資料流能以交換的方式取代繞徑而在網路上運送，也就是所謂的MPLS(Multi-Protocol Label Switching)。因此我們便設計的一套演算法來針對及時性服務在MPLS網路中，當錯誤發生時的一套處理流程，並以NS2(Network Simulator 2)加以模擬，最後，根據我們的演算法，便可在錯誤發生時，得到最快速且完善的處理。

Nowadays, real-time services play an important part in the Internet. VoIP will become a trend to replace the circuit-switching voice services in PSTN. But end-to-end voice packets transmitting between two IP gateways still have large header overhead, especially we can reduce payload length by new voice compression techniques today. Although there are some header compression and multiplexing schemes, we still can improve them. In the thesis, a novel and evolution way is proposed to run the header compression and multiplexing scheme in a virtual network to overcome the header overhead problem and provide a better path for voice packets. And the mechanism to match in the DiffServ domain is also investigated. Furthermore, for the purpose of fast forwarding the traffic in the Internet, traffic is expected to be transmitted in the MPLS domain. In the thesis, an enhanced algorithm is proposed to deal with the problem that how to solve the path rerouting problem for real-time service. And the final network topology and performance of my algorithm is simulated by MPLS Network Simulator 2. According to the algorithm, the traffic can be fast rerouted to the destination even though the fault is occurred.