一個以多屬性權重設定為基礎的代理伺服器置換機制

Abstract

隨著網際網路的蓬勃發展，網路已成為很多人生活的一部份。雖然上網人口逐年成指數性的成長，但網路資源與頻寬並沒有明顯的增加，使得網路壅塞的情形愈來愈嚴重。因此，如何能提昇存取效率，縮短使用者的回應時間，是現今各種網路技術一致的目標。利用代理伺服器來加快傳輸效率是目前常見的一種方法。要使得快取伺服器的效能提高，就必須將平常不會使用到的物件置換掉，以便留下多餘的空間來儲存經常存取的物件。 本篇將提供一個代理伺服器的置換策略－以多屬性權重設定為基礎的預測模式。觀察代理伺服器中歷史日誌檔的各屬性與記錄筆數的關係，群集相關屬性值以期能利用關聯規則產生較高支持度的規則，將『交易完成時間』、『檔案大小』及『瀏覽路徑層次數』等三屬性依內容範圍值，分配權重大小，並結合使用者的行為分類，『以搜尋為目的』、『漫遊於網站之間的使用者』、『專注於同一網站探索的使用者』，依置換的優先順序來計算網頁關聯的權重，使得快取伺服器在置換時，能夠輕易地依照權重值的大小選擇適合的物件，並有效地減少使用者的等待時間。最後經由模擬的結果顯示，本研究的確有助於快取伺服器命中率的增加，同時也沒有增加網路的流量。

World Wide Web (WWW) grows up rapidly in recent years. The network communication has become a part of daily life for many people. Although the population of the internet access increases year by year, the resource and bandwidth of the internet do not raise correspondingly. These reason leads to a serious network-congestion problem. Therefore, how to improve the efficiency of data accessing and reduce the querying response time have become critical issues. Caching at proxy servers is one of the methods to increase the transmission efficiency. To improve the efficiency of the proxy server, we need to replace the less-using objects so that we have enough space to store the frequently- accessing objects. This thesis proposes a replacing policy for the caching mechanism of proxy server - using weighted multi-attribute settings. Observing the relation between the various attributes and the record numbers in the log files of proxy server, we group related attribute values to generate high-supporting rules by using association rule. Then, we set weight according to ‘the finishing time of the transaction’, ’the size of the file’ and ’the depth of the browsing path’. In addition, the user behavior - ‘aiming at searching’, ‘roaming among different web sites’ and ‘surfing only at one web site’ are also considered to calculate the web-weight for the priority of the replacement. Therefore, the proxy server can replace an object simply by its weight. Thus, we can reduce waiting time. The result of the simulation shows that the method proposed in this thesis does increase the hit rate of proxy server and the traffic flow in the internet decreases in the meantime.