代理伺服器被廣泛地採用在各種不同的網路應用當中。透過應用代理伺服器在網際網路上不僅可以有效率地重復利用快取貯存區的資料而且更可有效地改善傳輸品質。然而，當一個行動使用者在行動網路環境下持續地移動、改變其所在位置並且同時地接收多媒體串流服務時，若行動網路使用者一直向同一個代理伺服器取得服務，這樣的情形是相當不合理的。為了解決這個問題，我們提出代理伺服器換手機制並且針對內部領域以及相互領域下的換手提出不同的解決方法。本發明所提出的換手機制使用行動代理人的概念來達到漫遊於不同網路服務提供者的網域之間並且透過會談啟始通訊協定來進行多媒體資料傳輸的溝通。為了使多媒體的傳輸品質更加平滑、順暢，本發明提出的換手機制採用MPEG-4 分層多媒體串流技術。

Proxy servers are widespread to be adopted in network applications. Applying proxies over the Internet not only uses the cached data efficiently but also improves transmission quality effectively. However, if a mobile node (MN) keeps changing its location and getting streaming service simultaneously in a mobile network, it is unreasonable that the MN connects to the same proxy for receiving data all the way. In order to resolve this problem, our previous work has proposed and defined an application-layer proxy handoff. This thesis inherits the proxy handoff concept and extends the original work to handle intra-domain and inter-domain proxy handoff. The proposed mechanism employs the mobile agent concept for the traversal among the domains of different Internet Service Providers (ISPs) and the Session Initiation Protocol (SIP) for the interaction of multimedia streaming. In order to smooth the transition of multimedia streams, the proposed mechanism adopts MPEG-4 layering streaming technique. The comparison with the previous work is also experimented and evaluated in this thesis.

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