Peer-to-Peer(P2P)架構讓社群內的使用者收集分散在網路各處之資源，其中最為風行的P2P系統當屬P2P檔案分享系統。P2P檔案分享系統之架構可分為集中式及分散式，而分散式架構又可細分為結構化及非結構化兩種。採用分散式且非結構化之BitTorrent-like架構，因其可擴張性較佳而廣為風行。在經驗中發現，BitTorrent-like架構在非對稱網路之下雖擁有寬裕的下行頻寬，但是其頻寬使用率卻不高，我們分析其成因如下：(1) Fractional Upward Bandwidth (FUB) 、 (2)Blockage of Acknowledgement (BoA) 與 (3)Long Physical Paths 等。而其中的Blockage of ACK問題，現今尚未有研究學者提出完整解決方案。本研究之目的，即要針對此Blockage of ACK的問題，改良網路協定中的傳輸層 (Transport Layer) 協定以提昇P2P檔案分享系統之效能。我們改用UDP作為傳輸層協定，並在應用層加入自動重建遺失之封包、決定基本傳輸單位大小及決定資料傳送速率等機制，以彌補UDP之缺陷。文中並提供了傳輸協定運作時所需參數的估計法，並且也與其它傳輸協定做效能之比較。實驗結果發現，我們設計的傳輸協定確可改善P2P檔案共享系統的運作效能。 / Peer-to-Peer (P2P) architectures let participants gather resources form network and make participants acquire more computation resources than they could offer. One of the most prominent P2P systems is P2P file sharing system. P2P file sharing system could be classified into to 2 categories: centralized and decentralized model. BitTorrent-like (BT-like) model can be classified as decentralized and unstructured model. BT-like model is quit popular nowadays due to its scalability. Unfortunately, BT-like model has several shortcomings on performance over asymmetric networks, because of some problems, such as Fractional Upward Bandwidth (FUB), Blockage of Acknowledgement (BoA) and long physical paths. No complete solution is available yet to solve the BoA problem. We propose a new UDP-based protocol to alleviate this problem. Since UDP protocol is not able to guarantee the data-integrity nor to determine the proper transmission rate by itself. To offer a complete solution, we have to enhance UDP, to add extra capabilities such as packet loss recovery, segment size determination and data rate determination mechanisms. Experiments show that our proposed protocol has good improvement on performance.

近年來無線網狀網路(Wireless Mesh Networks)備受矚目，無線網狀網路繼承原有的ad hoc networks的特性並提供階層式及多網卡的網路存取架構。在multi-hop networks下，傳輸功率的控制和網路路由的選擇是重要的議題，因為不同的傳輸功率產生不同的網路拓墣連結性和干擾。此外，在不同網路卡間的路由選擇也會產生不同程度的intra/inter-flow 干擾。這些特性對網路效能有密切的影響，過去相關的路由協定設計也大多未同時考量傳輸功率控制與多網路卡的特性。 在這篇論文中，我們提出了跨網路協定層的路由協定，稱作M2iRi2，同時考量傳輸功率的控制並將Intra/Inter-flow的干擾導入到路由路徑的選擇。節點上的網路卡在物理層(Physical layer) 計算目前對潛在可容忍的新增干擾，並將此訊息送到網路層(Network layer)和鄰居節點作交換。透過此資訊的交換，在路由發現時控制路由請求封包的傳輸功率，當路由建立後，封包根據路由表的記載，選擇所對應的路由路徑和傳輸功率。經由NS-2模擬結果顯示，我們所提出的跨網路協定層路由協定可同時兼顧網路的吞吐量和平均點對點的延遲。 / In recent years, WMNs (Wireless Mesh Networks) technologies have received significant attentions. WMNs not only accede to the advantages of ad hoc networks but also provide hierarchical multi-interface architecture. Transmission power control and routing path selections are critical issues in the past researches of multi-hop networks. Variable transmission power levels lead to different network connectivity and interference. Further, routing path selections among different radio interfaces will also produce different intra/inter-flow interference. These features tightly affect the network performance. Most of the related works on routing protocol design do not consider transmission power control and multi-interface environment simultaneously. In this thesis, we proposed a cross-layer routing protocol called M2iRi2 which coordinates transmission power control and intra/inter-flow interference considerations as routing metrics. Each radio interface calculates the potential tolerable added transmission interference in the physical layer. When the route discovery starts, the M2iRi2 will adopt the appropriate power level to evaluate each interface quality along paths. The simulation results demonstrate that our protocol can enhance both network throughput and end-to-end delay.