無線網路環境下MSN即時訊息不斷網機制設計

近年來，即時通訊已成為一個滿足多種需求的前瞻性整合通訊方式。由於微軟的大力推廣，MSN即時通訊軟體已成為台灣最普及的即時通訊工具之一，且因為微軟的作業系統可使用在智慧型手機上，我們亦可在智慧型手機上使用MSN即時通訊軟體。MSN即時通訊被普遍地應用在筆記型電腦和智慧型手機之上，當MSN即時通訊使用在3G / 3.5G或是無線區域網路等無線網路環境，其網路的不穩定性將是一個我們所要面臨的大問題。使用在不穩定的無線網路環境下，高封包遺失率將導致MSN即時通訊系統出現非預期的服務中斷，這將是一個我們所要克服的大問題。以傳統的MSN即時通訊系統為架構，我們設計了一個改良式的系統架構，系統稱之為SEA-WIM。SEA-WIM的設計目標是加強系統對於封包遺失率的容忍程度。這個新的系統架構，將原本MSN即時通訊中的客戶端和伺服器端的TCP連線切成三段，其中兩段維持TCP協定，而另一段則使用我們自己設計的通訊協定，ptou。ptou是一個以UDP為基礎，並加進一些TCP特性的協定。因為我們的目的為加強系統對於封包遺失率的容忍程度，我們只關心TCP當中的重傳機制，並且在此協定中加入了最大重傳次數，傳送逾時以及傳輸序號等參數。此外，”合法監聽”這個概念首先使用在傳統的公眾電話網路，在合乎法律層面的需求之下，包括電子郵件系統等其他的通訊方式皆加入了這項能力，既然即時通訊系統已成為一項重要的通訊工具，我們也把合法監聽的這項功能加入了我們的系統設計。在使用MSN即時通訊工具時，有許多不必要的封包在使用者端和伺服器端傳送，在我們的系統架構底下，可藉由過濾掉非必要性的封包，減少封包傳送與接收的方式，對於行動裝置達到省電的功能。

關鍵字

即時通訊；不斷網；無線網路

並列摘要

In the recently years, IM (Instant Messaging) has become promising integrated tools for various communication needs. With the help of Windows Mobile, MSN IM is now also available in many smart phones, and MSN has been one of the most popular IMs in Taiwan. Since MSN IM can be used in the mobile system, unstable wireless network environments, such as WLAN, 3G or 3.5G, may become a new problem for the operation of IM application. Obviously, the high ratio of packet losses in an unstable wireless environment would lead to unexpected interrupts of IM services. We design a modified IM system based on the conventional IM architecture, which is called as the Service Enhancement Agent for Wireless IM (SEA-WIM). The goal of SEA-WIM is to improve the tolerant capacity of high packet loss rate. We split any TCP connection between the MSN IM client and the MSN IM server into three connections, two of them are used as TCP and the other is ptou. Ptou is a TCP-like protocol, it is based on UDP but is added some TCP features. Because we want to improve the tolerant capacity of packet loss rate, we only concern about the retransmission mechanism, which includes the sequence number, timeout and maximum retransmission number. Meanwhile, it is more and more important for telecommunication providers to provide the lawful interception. For the judiciary needs, the lawful interception mechanism has been developed in many communication networks in the past decades, for examples, in e-mail services or circuit switch telephone systems. Since IM has become of the most communication methods, the SEA-WIM architecture also provides the ability of lawful interception. Because there are many unnecessary packets transmitted between the MSN IM client and MSN IM servers, the mobile device will consume much power in transmitting and receiving these packets. By filtering these unnecessary packets in a third network device, the SEA-WIM system can also reduce the power consuming.

並列關鍵字

Instant Messaging ； Wireless networks ； Connection-Sustainable

參考文獻

[1] “Transmission Control protocol,” RFC 793, 1981

[6] J. Ishac, M. Allman, “On the performance of TCP spoofing in satellite networks,”MILCOM 2001, IEEE

[10] Y. Tian, K. Xu, N. Ansari, “TCP in Wireless Environments: Problems and Solutions,” IEEE Communications Magazine, volume 43, no. 3, pp 27-32, 2005

[11] F. Lefevre, G. Vivier, “Understanding TCP's behavior over wireless links,” Communications and Vehicular Technology, 2000. SCVT-200. pp.123-130, Oct. 2000

[14] “Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations,” IETF RFC 3135, last modified on 27 June 2001

國際替代計量

無線網路環境下MSN即時訊息不斷網機制設計

全文下載

主題瀏覽