行動式網際網路通訊協定之無接縫換手機制

近年來，網路技術已日益成熟，各種不同的網路架構如何整合，已成為各方研究的重要課題。由於固接式的網路設備在使用上相當的不方便，為了擺脫線路的限制，讓使用者自由的移動，IETF (Internet Engineering Task Force) 於1996年提出了行動式網際網路通訊協定，致使無線網路設備大幅提昇了機動性。當使用無線網路時，所有的資料封包都是經由本地網路傳送。但由於其涵蓋範圍有限，因此當使用者持續移動時，封包就有可能經由周遭的網路來加以轉送，以達到繼續保持連線的目的。在網路切換的同時，將產生換手的動作。由於現行無線區域網路所採用的IEEE 802.11架構，無法同時存取兩個網路，而在IETF所訂定的通訊協定中，亦不對封包遺失作任何補償，而是交由上層的的通訊協定來加以處理。綜合以上因素，造成封包的延遲與遺失，使得連線品質大幅下降，此為無線網路發展的瓶頸之一。目前針對跨網域的移動問題，已提出的解決方案，多半必須對於整體網路架構進行大幅度的修改，造成實際應用上的困難。本論文提出一個無接縫式的換手機制，利用預先建立資料通道與延遲註冊的方式，只針對代理器以及移動點進行修改，以降低網路架構的變幅，縮短網路中斷的時間，並減少封包的遺失率，進而提升無線網路整體品質。經由網路模擬器NS2 (Network Simulator v2) 的模擬與分析，證實本機制的確可以達成目標。

關鍵字

無線網路；行動式網際網路通訊協定；換手

並列摘要

In recent years, since the network technologies are getting mature gradually, how to integrate various network architectures has become an important research issue. In order to get rid of the inconvenient wire constraint, Internet Engineering Task Force (IETF) proposed the mobile IP protocol in 1996. This protocol enables the mobility of those devices using wireless network. In general, all packets in wireless network are forwarded by home network no matter where the user’s mobile node locates. Because the wireless network has limited coverage, packets might be forwarded by foreign network for keeping uninterrupted connection when user moves around. The handoff procedure occurs while two networks are switching over. Right now, IEEE 802.11 protocol does not allow to access two networks simultaneously and even makes no compensation to lost packets. These bottlenecks obstruct the wireless network for further development and spoil the linking quality. Solutions for these problems were proposed, most of them need to totally remodel the current network architecture and it’s difficult to apply. In this paper, we propose a seamless handoff mechanism which combines pre-tunneling scheme with delayed registration and needs minor revise on both protocols for agent and mobile node. This mechanism can shorten the disconnection interval needed for switch over, reduce the packet loss rate, and improve the service quality of wireless network. We adopted NS2 for simulation and analysis, and proved that the mechanism really works.

並列關鍵字

Wireless network ； Mobile IP ； Handoff

參考文獻

[8] C. E. Perkins, Mobile IP: design principles and practices, Reading, Addison Wesley Longman, 1998

[11] I. Wu, W. Chen, H. Liao, and F. F. Young, “A Seamless Handoff Approach of Mobile IP Protocol for Mobile Wireless Data Networks,” IEEE Transaction on Consumer Electronics, vol. 48, no. 2, 2002, pp. 335-344

[12] H. Matsuoka, T. Yoshimura, and T. Ohya, ”A Robust Method for Soft IP Handover,” IEEE Transaction on Internet Computing, Vol. 7 , 2003, pp.18-24

[15] D. Johnson, C. Perkins and J. Arkko, “Mobility Support in IPv6,” RFC 3775, IETF, 2004

[16] R. Hsieh, Z. G. Zhou, and A. Seneviratne, “S-MIP: A Seamless Handoff Architecture for Mobile IP,” IEEE INFOCOM 2003, vol. 3, 2003, pp. 1774-1784

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行動式網際網路通訊協定之無接縫換手機制

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