代理移动IPv6(PMIPv6)是IETF提出的基于网络的区域移动管理协议,依赖于区域移动锚点(local mobility anchor,简称LMA)和移动接入网关(mobile access gateway,简称MAG)两类移动管理实体实现系统功能.针对PMIPv6网络中的MAG可靠性问题,提出一种基于池的移动接入网关容错方案(MAG fault- tolerant method based on pool,简称MAGFT).方案引入MAG池解决PMIPv6系统中MAG服务不可替代问题,实现对移动节点(mobile node,简称MN)透明的MAG容错.针对PMIPv6系统所部署下层网络的不同,MAGFT分别采用无重叠区部署和有重叠区部署两种模式在PMIPv6域内构建多个MAG池,使得域内各MAG至少归属于一个池.当某MAG失效时,它所在池内的某一有效MAG将快速接管其服务.理论分析和仿真实验结果表明,MAGFT可将容错时间控制在35ms～340ms.当容错时间在120ms以下时,MAGFT可完全避免MAG失效对MN的TCP应用造成的影响;最差情况下,对分别处于WLAN、3G和卫星网络中的MN而言,MAGFT也可在MAG失效发生后的1.1s,1.6s或2.8s内恢复其TCP应用吞吐量.对于UDP应用,MAGFT可在MAG失效发生后2s内将MN的收包率恢复至其稳定值.同时,方案引入的容错开销小,当系统处于较饱和的稳定服务状态时,容错信令开销相比系统基本信令是可忽略的.MAGFT的引入对MN接入延时略有增加,但增值控制在10ms以下.%Proxy Mobile IPv6 (PMIPv6) is the network-based localized mobility management protocol proposed by IETF. The local mobility anchor (LMA) and the mobile access gateway (MAG) are the key entities realizing the system function of PMIPv6. To solve the reliability problem of PMIPv6 MAG, this paper proposes an MAG fault-tolerant method based on pool (MAGFT). MAGFT introduces MAG pool to realize MAG fault-tolerant. Several MAG pools are constructed in an PMIPv6 domain, and each MAG belongs to at least one of the pools. When an MAG fails, a given MAG in the same pool will take over. The results of theoretical analysis and simulation show that the fault-tolerant latency of MAGFT can be restricted within 35ms~340ms. When the fault-tolerant latency is lower than 120ms, MAGFT can avoid the influence of MAG failure on MNs' up-layer TCP applications. In the worst condition, MAGFT can resume an MN's TCP throughput within 1.1s, 1.6s, and 2.8s respectively when the MN resides in WLAN, 3G or satellite network. For the upper applications based on UPD, MAGFT can resume MNs' packet rate within 2s after the occurrence of an MAG failure. At the same time, MAGFT introduces low signaling cost, which can be neglected when compared with the PMIPv6 signaling. MN's access delay introduced by MAGFT is no more than 10ms.
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