A Proxy MIPv6 Handover Scheme for Vehicular Ad-hoc Networks

With the rapid growth in the number of mobile devices, such as cellular phones, PDAs and laptops, the need for seamless and ubiquitous Internet connectivity is tangible. Vehicular ad-hoc network (VANET) is a rapidly developing technology, which makes vehicle-to-vehicle and vehicle-to-infrastructure communication feasible. However, when a vehicle travels from one point of attachment to another, handoff delays and provision of seamless connectivity are considered as important issues. Ubiquitous and integrated Internet connectivity can be achieved if on road moving vehicles are connected. However, when vehicle density is small and/or vehicle velocities are different, end users may suffer from a high level of connection failure. IP mobility protocols are designed by Internet Engineering Task Force to provide acceptable levels of continuous Internet connectivity, maintaining mobile node communications as they travel amongst points of attachments. However, the current IP mobility approaches applied on VANET did not resolve the connection failure issues efficiently. Therefore, in this paper a new effective solution is proposed in order to eliminate the large amount of handover latency and eventually high packet loss ratio.     

A Low Cost Route Optimization Scheme for Cluster-Based Proxy MIPv6 Protocol

Proxy Mobile IPv6 (PMIPv6) is a network based mobility protocol which has been designed to relieve the mobile nodes (MNs) from participating in the mobility process and to reduce the long handoff latency of the MIPv6 protocol. However, PMIPv6 incurs a long communication path due to the triangle routing problem, in which, all packets sent by MNs are obligated to pass through the local mobility anchor. Several solutions have been proposed to mitigate this issue. However, they still incur high signaling overhead to recover the Route Optimization (RO) status after handoff. In this paper, we propose a Cluster-Based RO (CBRO) scheme for the clustered architecture of the PMIPv6, in which, the Mobile Access Gateways (MAGs) are grouped into clusters with a distinguished Head MAG (HMAG) for each. In the proposed CBRO, the RO process is relied on the HMAGs to reduce the handoff latency while achieving a fast recovery of the optimized path after handoff. The proposed CBRO is evaluated analytically and compared with the basic PMIP and the current RO schemes. The obtained numerical results have shown that the proposed CBRO outperforms all other schemes in terms of signaling cost required to recover the RO status after handoff and the total cost performance metrics.     

Performance Enhancement of Fast Handover for MIPv6 by Reducing Out-of-Sequence Packets

FMIPv6 can reduce packet loss using a tunnel-based handover mechanism which relies on L2 triggers, such as transmitting a packet from a previous access router (PAR) to a new access router (NAR). However, this mechanism may result in decreasing the performance of TCP due to out-of-sequence packets arriving between the tunneled packets from the Home Agent and PAR, and the directly transmitted packets from the correspondent node (CN). In this paper, we propose a new scheme called EF-MIPv6 that uses a modified snoop protocol to prevent the packet reordering problem. This new scheme can prevent sequence reordering of data packets and improve the performance of TCP using enhanced fast binding update (EF-BU). This approach requires modification of the TCP header to execute the last packet expression from the PAR, include a new polling data packet, and use the modified access point system. Simulation results demonstrate that managing the packet sequence in our proposed scheme greatly increases the overall TCP performance in a Mobile IPv6 and FMIPv6 networks.

基于THMLD的移动多点发送方法的性能分析

Mobile multicast is important for the emerging applications such as mobile video or audio conference and mobile IPTV. Some mobile multicast schemes have been proposed in the past few years, but most of them study the reconstruction ofmulticast delivery tree, and few consider the group membership management for mobile subscribers. In this paper, we propose a new mobile multicast method based on the Two-Hop Multicast Listener Discovery （THMLD） protocol which provides the mobile multicast membership management function by forwarding the traditional MLD messages to its neighboring subnets. To evaluate its performance, we analyze the THMLD and set up the simulation platform to compare it with the several traditional mobile multicast methods. The results show that THMLD can reduce the multicast join time, and the THMLD-based mobile multicast method can reduce the multicast join delay at a cost of increasing additional multicast maintenance cost.     

Explicit Multicast Extension (Xcast+) for Efficient Multicast Packet Delivery

In this letter, we propose a new multicast scheme, named Xcast+, which is an extension of Explicit Multicast (Xcast) for an efficient delivery of multicast packets. The mechanism incorporates the host group model and a new control plane into existing Xcast, and not only does it provide the transparency of traditional multicast schemes to senders and receivers, but it also enhances the routing efficiency in networks. Since intermediate routers do not have to maintain any multicast states, it results in a more efficient and scalable mechanism to deliver multicast packets. Our simulation results show distinct performance improvements of our approach compared to Xcast, particularly as the number of receivers in a subnet increases.     

基于DiffServ的MIPv6安全接入方案

结合DiffServ网络QoS控制与AAA安全机制,文中设计了一种网络区域边界安全的MIPv6接入方案。方案采用AAA认证授权,实现MIPv6转交地址配置和应用层与网络层身份一一映射,为DiffServ区域提供了边界保护;采用应用层与网络层安全协同,减轻了边界路由安全负荷。     

一种移动IPv6地址隐私性解决方法

论文主要介绍了移动IPv6的地址隐私性问题,提出了一种移动IPv6的简单隐私性扩展解决方法,这种方法可以很好地防止窃听者通过家乡地址追踪移动节点,增强了移动IPv6的通信安全性。     

Performance Analysis of Proxy Caching for VOD Services With Heterogeneous Clients

Proxy-caching strategies, especially prefix caching and interval caching, are commonly used in video-on-demand (VOD) systems to improve both the system performance and the playback experience of users. However, because these caching strategies are designed for homogeneous clients, they do not perform well in the real world where clients are heterogeneous (i.e., different available network bandwidths and different sizes of client-side buffers). This paper investigates the problems caused by heterogeneous client-side buffers. We analyze the theoretical performance of these caching strategies, and then, derive cost functions to measure the corresponding performance gains. Based on these analytical results, we develop a caching strategy that employs both prefix caching and interval caching to minimize the input bandwidth of a proxy. The simulation results demonstrate that the bandwidth requirements of a proxy implementing our caching strategy are significantly lower compared to adopting prefix caching or interval caching alone.     

基于AAA的移动IPv6运营架构研究

IPv6网络的发展现状迫切需要一个完整的运营架构来合理分配与管理网络资源。本文提出了一个采用全局惟一的IPv6地址作为身份标志的AAA运营架构,在运营商现有业务平稳过渡的基础上实现融合。该运营模式灵活、兼容性强,对用户透明,可为用户提供实时在线服务,使运营商获得海量日志信息,实现运营商的服务网络的可控、易管。     

SIP和MIPv6的集成在IMS系统中的应用

MIPv6在IP网络层支持移动性,而SIP一直支持VoIP的应用,是IP多媒体子系统（IMS）的信令协议。为了无缝支持在移动领域中的实时多媒体通信,SIP和MIP的集成显得非常重要。本文通过MIPv6、SIP及SIP和MIPv6的集成,显示出SIP和MIPv6的集成对IMS系统性能的优化,说明了该方案可提供有效的路由,并且可减少切换时延。     

移动IPv6中为移动终端动态配置原籍代理

本文从移动IPv6的基本原理和分级管理机制出发，结合移动终端对网络操作的主动性和阶段性，讨论了移动终端不一定必需拥有永久原籍地址，并提出了为移动IPv6终端动态配置原籍代理的新设想，以期消除网络上的大量信令开销。     

Predictive versus Reactive—Analysis of Handover Performance and Its Implications on IPv6 and Multicast Mobility

Handovers in mobile packet networks commonly produce packet loss, delay and jitter, thereby significantly degrading network performance. Mobile IPv6 handover performance is strongly topology dependent and results in inferior service quality in wide area scenarios. To approach seamless mobility in IPv6 networks predictive, reactive and proxy schemes have been proposed for improvement. In this article we analyse and compare handover performance and frequencies for the corresponding protocols, as they are an immediate measure on service quality. Using analytical methods as well as stochastic simulations, we calculate the performance decreases originating from different handover schemes, the expected number of handovers as functions of mobility and proxy ratios, as well as the mean correctness of predictions. In detail we treat the more delicate case of these rates in mobile multicast communication. It is obtained that performance benefits, expected from simple analysis of predictive schemes, do not hold in practice. Reactive and predictive handovers rather admit comparable performance. Hierarchical proxy environments—foremost in regions of high mobility—can significantly reduce the processing of inter–network changes. Reliability of handover predictions is found on average at about 50%.     

具有层间冗余链路的应用层组播及其性能分析

本文讨论了应用层组播环境下拥塞对扩展树性能的影响,提出了使用层间冗余链路来增强扩展树稳定性的方法,并且通过提出的统计链路模型和相关度模型,对该方法进行了理论分析和性能评价.数字仿真结果说明了统计链路模型有效地描述了应用层组播环境中发生的拥塞,即使在高拥塞链路概率的情况下,层间冗余链路的方法也能以较小的网络延迟代价,显著地增强扩展树的稳定性.本文提出的统计链路模型也可用来深入了解应用层组播的动态行为,或者设计相应的拥塞控制算法.     

Study and enhancement on buffer management for smooth handover in MIPv6

For improving Transfer Control Protocol (TCP) performance in mobile environment,smooth handover with buffer management has been proposed to realize seamless handovers. However in our simulation, even if smooth handover in Mobile IPv6 (MIPv6) is implemented, TCP can not always achieve better performance due to packets forwarding burst. Based on the study of buffer management for smooth handover, this paper proposes an enhanced buffer management scheme for smooth handover to improve TCP performance. In this scheme, a packet-pair probing technology is adopted to estimate the available bandwidth of the new path from Previous router (Prtr) to Mobile Node (MN), which will be used by Prtr to control the buffered packets forwarding. The simulation results demonstrate that smooth handover with this scheme can achieve better TCP performance than the original scheme.     

WLAN中基于MIPv6的移动VoIP切换性能仿真分析

移动IP是一个在Internet上基于网络层提供移动性支持功能的要求较高的VoIP业务,切换延迟将直接影响到话音质量,严重时甚至会中断正在进行的会话.文章借助ns2网络模拟器仿真分析了WLAN中基于MIPv6的移动VoIP切换性能.结果表明,MIPv6及其扩展协议的切换性能优劣顺序依次为:F-HMIPv6、FMIPv6、HMIPv6、MIPv6.尤其是F-HMIPv6协议,无论端到端延迟还是切换延迟,都得到了最大的改善.所得结论能为网络切换性能的进一步优化提供重要依据.     

基于网络编码的多播路由算法性能分析

多播传输是目前通信系统中的一项关键技术,可以将相同的信息同时传向多个接收节点。该文提出一种基于网络编码的新的多播路由算法,该算法利用Dijkstra约简网络搜索源节点到各接收节点的路径族。仿真结果表明,该算法在资源消耗和负载均衡方面较传统的多播路由算法有更好的表现,同时性能也更接近基于网络编码的最小费用多播算法。最后,数学分析表明该算法具有较低的计算复杂度。     

点对多点服务的输入/输出排队ATM交换机性能分析

本文分析了一种具有点对多点服务能力的内部无阻塞输入／输出排队ATM交换机在反压控制下的性能指标。在每个输入端口信元的到达具有相同的强度，每个排头信元以一种相同的概率分布函数被复制成多个输往不同的输出端口的排头信元，复制后的排头柜元到达输出端口的概串相同为1/N，且输入、物出缓冲容量均为有限。为保证交换机内部不发生信元丢失，引入了反压机制（Backpressure）。本文利用矩阵几何分析法绘出了数值解，计算机仿真结果表明理论分析是正确的。     

一种代理移动IPv6认证协议

代理移动IPv6为移动节点提供了基于网络的移动性管理方法,移动节点不参与管理移动性信令.为了在移动互联网络中应用代理移动IPv6协议,需要定义安全有效的认证协议.目前还没有见到关于代理移动IPv6认证协议方面的研究,本文提出了一种代理移动IPv6的认证协议,该认证协议可以提供接入认证功能,并可防止重放攻击和密钥暴露.为了分析该认证协议的性能,本文给出了认证费用和认证延迟分析的解析模型,分析了移动性和流量参数对认证费用和认证延迟的影响.研究结果表明提出的代理移动IPv6认证协议安全有效.     

无线网络中移动IPv6的TCP性能的研究

用NS-2网络仿真软件给出了MIPv6的TCP性能分析。通过仿真实验检测了MIN从一个基站移动到另一个基站发生切换时，节点的切换处理对TCP性能的影响。实验结果表明节点的处理时间应该被考虑在仿真的参数设置中。