具擴展性及高效能的WAP閘道器系統

Abstract

隨著WAP使用者的增加，帶來WAP閘道器大量的負荷，本篇論文針對此問題，設計且實作一個具擴展性及高效能的WAP閘道器系統(gateway system)，此系統由一個WAP分派器(dispatcher)和多個WAP閘道器所組合而成。WAP分派器負責接收所有進入系統的WAP協定資料單元(PDU)，並為每個WAP session進行負載配置決策。WAP閘道器負責處理WAP用戶端提出的WAP需求，並直接將得到的結果送回WAP用戶端。我們提出一個有效的負載配置方法，稱之為內文知覺需求分配法(Context-Aware Request Distribution, CARD)，主要利用WAP需求的內容及WAP閘道器的負載資訊，選擇適當的WAP閘道器處理該WAP需求。這個方法不但可以節省建立HTTP連線的時間，還可以享有HTTP持續連線的好處。除此之外，我們擴展WDP的功能，使其得以在WAP閘道器系統中，配合內文知覺需求分配法進行WAP連線交遞(connection handoff)。實驗結果顯示，本系統具備良好的擴展性，並能有效降低對使用者的WAP反應時間。

The Wireless Application Protocol (WAP) use has grown continuously and the WAP traffic is increasing. In this thesis, we design a scalable and highly efficient WAP gateway system that consists of one WAP dispatcher and many WAP gateways. The WAP dispatcher accepts all incoming WAP PDUs and makes load allocation decision for each WAP session. The WAP gateways process WAP requests and send response data to the WAP clients. An efficient load allocation mechanism named Context-Aware Request Distribution (CARD) is proposed. It uses the content of the request, in addition to the information about the load on WAP gateways, to determine an appropriate WAP gateway for the request. The CARD not only reduces the time for establishing HTTP connections, but also benefits from the characteristics of the HTTP persistent connections. Besides, a WDP extension that makes WAP connection handoff for CARD in the WAP gateway system is introduced. Simulation results show that our WAP gateway system scales well and reduces the response time.