一個階層式行動網路下的代理式快速換手機制

Abstract

隨著無線網路與通訊技術迅速的發展，IETF組織提出Mobile IPv6 (MIPv6)協定以支援行動裝置在IPv6網路上的移動管理。然而，支援MIPv6的行動裝置在換手的過程中會遭受很長的換手延遲(handover latency)與封包遺失(packet loss)，對於即時性的多媒體服務，例如VoIP、IPTV等，其換手延遲時間仍無法滿足使用者的需求。雖然IETF組織隨後提出Fast Handover for Mobile IPv6 (FMIPv6)來解決此問題，但是上述兩種標準都需要修改行動裝置的設備，增加了應用普及化的困難度。因此IETF組織也提出了Proxy Mobile IPv6 (PMIPv6)來管理移動網路，由於PMIPv6 是一個以網路為基礎的區域(local)移動管理方法，因此不需要修改到移動網路的設備，但是行動裝置在PMIPv6環境換手的過程仍然會發生換手延遲和封包遺失的狀況。 本論文提出一個快速換手的機制，將階層式網路架構的概念引入PMIPv6網路環境，以解決行動裝置在PMIPv6環境下換手過程中所發生的問題，並且加入額外的緩衝區機制來減少封包遺失並保持封包順序一致。在本篇論文中，我們利用數學解析公式對PMIPv6進行分析，並與其他文獻所提出的方法進行比較。從模擬的結果可以看出，本論文所提出之方法可以有效地減少換手延遲，並且達成無縫隙換手(seamless handover)的服務水準。

The Internet Engineering Task Force (IETF) provides the mobile IPv6 (MIPv6) to support the mobility management of the mobile node (MN). However, MN supporting the MIPv6 suffers from long handover latency and packet loss. For real-time multimedia service such as VoIP and IPTV, the handover latency is not acceptable for service provisioning. Although IETF proposes the Fast Handover for Mobile IPv6 (FMIPv6) to solve the problem, these protocols require modification to the MN and aggravate the difficulty for getting popularity. IETF also provides the Proxy Mobile IPv6 (PMIPv6) to control the mobile networks. The entity of serving network controls the mobility management on behalf of MN without requiring any involvement of MN stack since PMIPv6 is a localized mobility management mechanism. Nevertheless, the MN still suffers from handover latency and packet loss during handover in PMIPv6 domain.

In this thesis, we propose a fast handover mechanism which introduces the idea of hierarchical network architecture into PMIPv6, to solve the problem that the MN encountered during handover in PMIPv6 domain; moreover, we introduce an additional buffering scheme to reduce packet loss and solve packet ordering problem. In this study, we utilize a mathematical formula to analyze the performance of the MN’s handover in the PMIPv6 domain, and compare it with the mechanism in the other literature. The numerical results show that our proposed scheme effectively reduces the handover latency, and fulfills the quality-of-service for seamless handover.