具備異質平台辨識及效能平衡功能的網頁郵件伺服系統

A Load-Balanced Web-Mail System for Heterogeneous Platforms

張阜民(Fu-Min Chang) ； 沈世文(Shi-Wen Shen) ； 高勝助(Shang-Juh Kao)

《科學與工程技術期刊》 4卷4期 (2008/12) Pp. 45-55

https://doi.org/10.7117/JSET.200812.0045

摘要

隨著上網設備的多樣化，如個人電腦、手機及個人數位助理等，非個人電腦裝置存取電子郵件的情形也愈來愈普遍。不同的硬體平台有其不同的處理及顯示上的限制，但是目前一般提供WebMail服務之電子郵件伺服器，並沒有針對不同的硬體設備提供適當的內容顯示。而隨著多媒體郵件的大量使用，電子郵件伺服器的負載也逐漸增加，如何確保郵件伺服系統有穩定的效能服務，將會是郵件管理者新的挑戰。在本文中，我們提出一個具備異質平台辨識及效能平衡功能的網頁郵件伺服系統。在本系統中，每一個信件讀取的網路連線被導引到硬體辨識模組，此模組利用HTTP(hyper text transfer protocol)表頭的資訊來判斷使用者所使用上網設備的硬體平台種類，並據以給予適當之郵件顯示格式及內容。我們採用RR-DNS(round robin-domain name system)的機制，將郵件依序分配至多個郵件伺服器來處理，同時利用SNMP(simple network management protocol)通訊協定監測郵件伺服器的工作負載，以適時啟動備援主機，使得郵件伺服器能提供穩定的效能服務。爲驗證所提出系統之可行性，我們在台中高農實作一個實驗系統。實驗結果顯示，本系統可以有效、便利的達成異質平台之適用性及伺服器之穩定性，可以提供中小型企業機構建置成本低廉且功能多樣之網頁郵件系統。

關鍵字

網頁郵件伺服系統 ； 異質平台 ； 效能平衡

並列摘要

With a diversity of equipment for surfing the Internet, such as personal computers (PCs), cellular phones and personal digital assistants (PDAs), it is becoming increasingly common to access emails from electronic devices other than PCs. Different hardware platforms have different limitations for handling email. However, mail servers currently offer web-mail services without offering a differentiation in content presentation among the various end devices. Moreover, with heavier use of multimedia content, the load of e-mail servers also increases. How to ensure an efficient use of server systems is also a stringent challenge for email administrators. In this study, we propose a load-balanced web-mail system for heterogeneous end devices. In this proposed system, when a user's mail-access request is received, it is first processed by a hardware-identity module. This module uses the information in the HTTP header of the mail-access request to determine the device type and accordingly provides an appropriate presentation layout for the reader. Round-Robin (RR)-DNS is adopted for sequentially dispatching incoming emails to servers. Meanwhile, Simple Network Management Protocol (SNMP) is used to monitor the workload of each server, so that a timely back-up server can be efficiently started whenever a busy one is detected. Efficient use of back-up servers enables stability. To demonstrate the feasibility of the system, we built a trial system with load simulation at the National Taichung Agricultural Senior High School. The experimental results indicate that the system can successfully distinguish among heterogeneous platforms for various display layouts. Optimum performance of mail servers, in both load balancing and stability, can also be easily achieved. As a result, through this study, we can practically provide a low-cost, yet efficient, web-mail server system for medium-scale enterprises.

並列關鍵字

web mail system ； heterogeneous platforms ； load balancing