在移動網路上之互助式多路傳輸機制

Abstract

隨著無線網路的發展，無線裝置亦將具備移動的可能。近幾年來，有相當多的研究在探討移動管理機制(Mobility Management Mechanism)，移動式 IP (Mobile IP)為著名主機移動(Host Mobility)的機制之一，接著亦有行動網路 (Mobile Network) 形式的網路移動 (Network Mobility) 延伸發展，顧名思義移動網路即為整體網路的移動包含了內部所有節點，而其相關機制為NEMO Basic Support Protocol。然而，不論是主機移動或是網路移動，皆須要一個家代理伺服器 (Home Agent，HA) 來幫助追蹤目前位址以及傳遞資料。在主機移動的行動管理中，當行動主機 (Mobile Host) 增加所伴隨的傳輸量變多時，家代理伺服器的負載亦將變重。在網路移動的行動管理中，行動路由器 (Mobile Router，MR) 之中的行動主機越多，則行動路由器所屬的家代理伺服器負載愈重。 以往在解決此問題的方法乃採用固定式的多路 (Multihoming) 機制，意指採用固定式數量的多個家代理伺服器來分擔負載，此種方式不僅沒有彈性，亦無法順應當下的負載改變可承載的總量，且當行動主機越來越多，傳輸量越來越多時，固定數量的家代理伺服器亦將會有不堪負荷的情形產生。然而此一特徵，在網路移動的行動管理中的影響是更加的劇烈，因為在網路移動當中的所有移動主機的資料傳送路徑皆必須經過移動路由器以及移動路由器之家代理伺服器。因此，在這篇論文中我們將針對網路移動之移動管理設計出一個互助式多路機制 (Cooperative Multihoming Scheme) ，透過行動路由器所管理的行動主機數量，來適時的調整運作多路機制的互助家代理伺服器數量，以提供網路移動較具彈性負載平衡多路機制。

With the growth of wireless technology, wireless devices would able to mobile. In recent years, a large amount of effort has been focused on mobility management research; Mobile IP is one of the familiar host mobility protocols. Afterwards, cluster amount of mobile hosts moving together simultaneously as a single moving entity is considered a mobile network. To support this kind of mobility, Network Mobility (NEMO) Basic Support Protocol has been proposed. Network mobility is the extension of host mobility. Both host mobility and network mobility need a home agent (HA) to trace the current location of mobile host and to intercept data packet sent from corresponding node and to tunnel data packet to the current location of mobile host. However, in host mobility when the amount of traffic or the number of mobile host increased, the home agent will bear heavy load and in network mobility when the amount of traffic and the number of mobile host inside mobile network increased, the overhead of home agent would be rose. This kind of overload could result in home agent break down and crash the mechanism. The tradition way to solve the above problem is to use multiple home agents (Multihoming) simultaneously. However, previous Multihoming of mobility management is static approach, which means that number of home agent is pre-configure and permanent. These kinds of Multihoming lack of flexibility and can not accommodate traffic loads when number of connection of mobile host increased. However, in network mobility due to this characteristic the situation will be worse. Therefore, we will purpose an Cooperative Multihoming Scheme. Our approach can adjust the number of home agent cooperative for the network mobility according to the number of mobile hosts inside mobile router and provide a more flexible load balancing way to network mobility.