使用動態非同步傳輸模式動態虛擬路徑樹概念之即時多點傳播

Abstract

多點傳播是一種多點之間由一個資料來源向多個目的地傳送相同資料的傳 輸通訊模式, 而且點對點通訊是多點傳輸中的一個特別的情況.多點傳播 協定的應用包含多團體視訊會議, 電腦支援合作工作, 遠距教學等等.目 前多點傳播發展之技術在於單一來源對相同目地節點群的傳播,亦有些人 開始研究多個目地群的方向. 藉由廣域非同步傳輸模式網路上之即時應 用,一些新的多點傳播研究開始被注意.此篇論文中, 我們提出一個新的在 非同步傳輸模式下多點傳播管理協定. 這個協定的特色是 (1) 動態虛擬 路徑樹的建構, (2) 多點傳播來源的動態轉移, 和 (3) 多數多點傳播來 源. 這個協定主要支援一個即時且大規模多點傳播遠距教學的虛擬教室應 用.首先我們定義一個呼叫組態, 還有一個及時多點傳播協定. 我們的及 時多點傳播協定包含了一些控制訊息, 其功能在於 建立/丟棄 呼叫,開 啟/關閉連接, 增加/丟棄 端點, 新的多點傳播來源的建立和切換等等.最 後對於虛擬路徑樹架構作出簡單的評估, 我們也簡要的討論多點傳播協定 如何應用於可以達成遠距教學目地的虛擬教室系統. Multicast is a multipoint communication mode where a traffic source sends the same data to multiple destinations, and point- to-point communication is a special case of multipoint communi- cation. Applications of multicast protocol include multi-party teleconferencing, CSCW(Computer Supported Cooperative Work), distant teaching, etc. Previous works in this area concentrate on the problem of a single multicast source that always communicates with the same destination group, and some researches focus on multicast to multiple groups. With the emerging real-time applications over broadband ATM (Asynchronous Transfer Mode) networks, new rese- arch problems of multicast need to be addressed. In this thesis, we present a new multicast management pro- tocol over ATM networks. The protocol features (1) dynamic VP (Virtual Path) tree construction, (2) dynamic multicast source migration, and (3) multiple multicast sources. It aims to sup- port the virtual classroom application which requires real-time large-scale multicast for distant teaching. We first define the call model of the protocol, RMP(Real- time Multicast Protocol). Detailed protocol is then described. Our RMP contains the control messages of setup/drop a call , open/close connection, add/drop points, new multicast source setup/switching, etc. At last, a simple evaluation on the VP tree construction is made. we also briefly discuss how multicast protocol applies to the virtual classroom system which achieves the goal of distant teaching.