對一個網際網路服務， 如多媒體串流(Streaming)和檔案下載(File download)而言， 網路頻寬大小和封包的延遲時間(Delay time)，是影響服務品質(Quality-of-Service)相當重要的參數。Client-Server架構的優點可以減少不必要的傳輸時間延遲(End (source)-to-end propagation delay)，但需要Server端較大的上傳頻寬； 而P2P(Peer to Peer)架構的優點則在於Server端不需要較大的上傳頻寬， 但會造成較長的傳輸時間延遲。因此， 我們將設計一個Hybrid P2P Client-Server傳輸機制， 藉由同儕分群(Peer grouping)的做法，由Original source端決定Connected peers資料傳輸方式，進而將Connected peers分成P2P和Client-Server二個傳輸群組， 並且由Original source動態決定二個群組中各別適當的成員數目與調整分配上傳頻寬，希望能夠在Delay time、伺服器上傳頻寬的限制和系統負載取得一個效能上的平衡點。

For Internet services, e.g., video streaming and file download, network bandwidth and packet delay time are two important parameters that affect Quality-of-Service. The merit of the Client-Server architecture is
able to reduce unnecessary end-to-end propagation delay but larger upload bandwidth is required; the merit of the P2P architecture is to need less upload bandwidth but the longer transmission delay is resulted. In this
paper, we will design a hybrid P2P Client-Server data transmission mechaism, in which the original source is able to determine the method of data transmission of connected peers, and further classify connected peers
into P2P and Client-Server groups. In our experiments, the number of group peers and proper upload bandwidth can be determined to compromise the performance of delay time,upload banwidth at the server side and system loading.