隨著網際網路技術的成長與普及，上網的人數激增，網頁服務（web service）儼然成為最為廣泛使用的應用平台。單一網頁伺服器架構已經不能滿足如此龐大的使用者需求，叢集式網頁伺服器的架構成為另一個更好的解決方案。本實驗室之前也已完成了一個 Content-aware 的叢集式網頁伺服器前端分配器，提供 Layer 7 的負載平衡機制，並且設計了一個完整的管理系統，可供系統管理者透過網頁介面組態整個叢集式伺服器系統。然而在不斷發展的網頁技術中，各網站開始提供具備 session 概念的服務型態，使用者與伺服器之間的各個要求是具有相關性的，本論文針對一類型的服務加以分析討論，並根據實際網站的運作模式，整理此類型服務的模型，並在我們的系統上建立一個 session-aware 的管理機制，透過管理系統的特性，提出系統容錯與提供服務品質保證的策略，以提高系統的可靠性與效能。最後在我們的測試中，我們可以看出在系統上做造成的額外負擔，仍在使用者可以接受的範圍之內。

The rapidly increasing expansion and popularity of the Internet makes more and more users accept web service type. The web server with single server architecture is no longer satisfying a large number of user requests. The web cluster architecture becomes another batter solution. In our previous work, our laboratory has implemented a prototype of layer7 web switch, which provides content-aware land balancing. We also designed and implemented a management system to provide a easy way for system configuration. With the increasing of web technologies, most of web sites supply “session-aware” service type. The session is that clients and servers that wish to exchange state information to place HTTP requests and responses within a lager context. In this paper, we propose a session-aware management in the web cluster. Base on our management system, we design a fault tolerance and QoS policy with session to improve performance and reliability of our web cluster system.

1 緒論
1.1 研究動機
1.2 研究目標
1.3 內容編排
2 相關研究討論
2.1叢集式伺服器
2.2 Content-aware 繞送
2.3 相關研究
3 問題定義與分析
3.1 Session
3.2 HTTP 中的 Session
3.2.1 隱藏表格欄位 （Hidden Fields）
3.2.2 URL 重寫
3.2.3 Cookies
3.3 現行網站分析
3.4 Shopping Cart 模型之使用者狀態轉換
3.5 叢集式架構下的 session
3.6 本章摘要
4系統設計與實作
4.1 系統架構
4.2 Session的管理機制
4.3 Session 搬移的程序
4.4 Session-based 容錯（Fault Tolerance）
4.4.1 Fault model
4.4.2 使用 primary backup 方式實作系統容錯功能
4.5 Session-based 的服務品質
4.5.1 服務品質的保證
4.5.2 session-based QoS policy
4.5.3 session-aware 的 QoS 策略
5效能評估
5.1 測試環境
5.2 搬移session 之系統負擔
5.3 容錯功能之效能評估
5.4 QoS 之效能評估
6 未來展望與結論
7 參考文獻

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