Design,implementation and experimental evaluation of an end-to-end vertical handover scheme on NCTUns simulator

This paper presents the simulation study of “Host based autonomous Mobile Address Translation” using NCTUns simulator. It is a network layer, end-to-end vertical handover solution, based upon modification of “Mobile IP with address Translation”. Vertical handover approaches generally require new network elements, a new layer in TCP/IP stack, or fixing a protocol at a particular layer. To enhance handover experience, recent approaches focus on reducing signalling, localizing the registration, creating hierarchies, using proxy, preparing handover in advance, predicting target network, or exploiting multicasting and path extension techniques. These approaches, however, demand change in the network infrastructure to support mobility and limit the scope of mobility. Despite end-to-end signalling, the Host based autonomous Mobile Address Translation scheme ensures minimum service disruption and distinctly allows global mobility of the mobile node without requiring any modification in the network. We have simulated the mobility of a multi-interface mobile node in a heterogeneous network environment composed of WiFi (IEEE802.11a, IEEE802.11b) and WiMAX (IEEE802.16e) access networks. Performance of the scheme is evaluated taking into account wide range of end-to-end delays between mobile node and the correspondent node, various speeds of the mobile node and different packet loss rates of the network. Based on our detailed simulation study, it has been observed that this scheme offers reduced service disruption time, packet loss and packet latency. The service disruption time is found to be significantly low (typically in the range of 10 ms) compared to that of Mobile IP (which is in the order of 100 ms); this makes this new scheme perfectly suitable for real time applications. Low service disruption time consequently reduces the packet loss by manyfold and the packet latency remains unaffected during and after handover due to translation of address at the source. The results suggest that this protocol is a viable vertical handover solution due to its simplicity, scalability, low overhead and ready deployability.     

Mobile networking through Mobile IP

Mobile IP is a proposed standard protocol that builds on the Internet Protocol by making mobility transparent to applications and higher level protocols like TCP. Mobile IP (RFC 2002) is a standard proposed by a working group within the Internet Engineering Task Force; it allows the mobile node to use two IP addresses: a fixed home address and a care-of address that changes at each new point of attachment. The article presents the Mobile IP standard in moderate technical detail and points the reader toward a wealth of further information. Is also describes how Mobile IP will change with IP version 6, the product of a major effort within the IETF to engineer an eventual replacement for the current version of IP. Although IPv6 will support mobility to a greater degree than IPv4, it will still need Mobile IP to make mobility transparent to applications and higher level protocols such as TCP. There is a great deal of interest in mobile computing and apparently in Mobile IP as a way to provide for it. A quick Web search for items related to Mobile IP returned over 60,000 hits-impressive even given the notorious lack of selectivity for such procedures. Mobile IP forms the basis either directly or indirectly of many current research efforts and products. The Cellular Digital Packet Data (CDPD), for example, has created a widely deployed communications infrastructure based on a previous draft specification of the protocol. In addition, most major router vendors have developed implementations for Mobile IP     

基于MPLS的层次微移动协议的性能分析*

信息系统的权限管理是保证数据安全的必要条件。在论述了基于角色的权限控制模型的基础上,分析了基于用户-功能的权限控制方法存在的问题,提出了一种基于RBAC的B/S体系结构的信息系统权限控制方法,实现了安全的权限控制,取得了较好的效果。     

SIP在基于TCP应用中的移动性研究

IETF提出的SIP协议以其灵活、容易部署等特性较好地解决了移动节点的全局移动性问题。然而，在利用SIP实现移动TCP应用过程中，频繁的切换过程将会导致TCP连接中断的发生，从而使得各种会话过程和预定业务不能正常进行。本文就此问题提出了一种基于SIP_EYE agent与SIP INFO method实现TCP应用移动性的解决方案。     

宏移动协议和微移动协议中包丢失率的比较

移动IP是支持IP移动性的协议,但是当其用于移动节点驻留在远离归属网络的外地网络时,将会产生严重的注册延迟,从而引起严重的包丢失和通信吞吐量的下降,为了改变这些不足,人们把移动节点的移动方式分为宏移动和微移动,并且提出了很多应用于微移动的移动性管理方案。文章深入研究了宏移动协议(RFC2002)和微移动协议的包丢失率,给出了计算公式,并且对计算结果进行了详细的分析。     

基于位置预查询的因特网移动支持方案

提出一种预查询移动支持方案(mobile Internet protocol_based on location pre-query,简称MIP_Q),以解决家乡网络的流量瓶颈和单点故障问题,从而提高移动通信的效率和可靠性.MIP_Q通过扩展域名服务系统管理和跟踪移动节点的当前位置信息,省去了家乡代理;采用并行切换控制方式,同时避免了MIP(mobile Internet protocol,简称MIP)中的三角路由和隧道路由问题;借助有效的计算方法,分析和比较了MIP_Q与MIP,MIP_LR的平均移动通信成本和切换时延;在实现方面与广泛应用的广域蜂窝移动网络进行了类比.结果表明:MIP_Q在切换效率和新增实体数等方面优于同类方案;MIP_Q可以极大地降低节点的移动通信成本,减小切换时延;MIP_Q具有良好的可行性.最后提出MIP_Q的仿真和实现方案.     

移动式网络中快速认证方法设计与仿真

作为移动IP技术的新的发展方向,移动式网络技术是将节点移动性向网络移动性(NEMO)扩展的关键技术,降低移动式网络在注册和认证过程中的延时,能够提高移动式网络技术的实际应用.提出了新的基于Mobile IP/AAA模型的移动式网络认证方法,研究了AAAL与AAAH之间的距离以及本地切换率对认证延时的影响,并提交了NS2仿真试验结果和安全性分析.该方法能够实现低切换时延,并保证移动式网络注册和切换中的安全性.     

移动支持协议切换性能研究

切换是移动支持协议研究的重要内容,其性能好坏对移动网络的性能和服务质量提供具有至关重要的影响.在合适的网络模型和切换模型的基础上,通过理论分析和数值仿真的方法对各类移动支持协议(包括移动IP与微观移动协议以及不同的微观移动协议)的切换性能进行了深入的研究和比较.结果表明,切换性能受无线网络参数和移动支持协议的路径更新算法两个因素影响;采用微观移动协议时的切换性能好于只使用移动IP时的情形;在所有微观移动协议中,MIP-RR和MMP协议中的路径更新算法切换性能最佳.     

一种新的基于移动IP外地代理分层结构的注册方案

为了在移动网络中运用IP协议,因特网工程任务组(IETF)制定了MobileIP协议。移动IP技术给人们带来极大便利的同时,也造成了许多安全隐患。本文提出一种基于移动IP外地代理分层结构的注册方案,该方案对现有外地代理分层结构的注册方案加以改进,使得移动IP快速切换能力得以提高,减少了注册时延,并提高了移动节点注册过程的安全性。     

一种具有AAA功能的移动IPv6快速切换方案的研究和实现

和目前WCDMA／GPRS、WLAN网络中的移动性相比，移动IPv6是一种网络层移动性解决方案。具有一定的优势。如垂直切换．但是移动IPv6的切换性能和安全性影响了其商业部署，提出了一种将快速切换和AAA结合起来的机制．并在基于网络处理器的接入路由器和Linux主机上实现了该方案．实验表明，该方案具有较小的切换时延．     

基于IP的3G网络间的无缝切换技术

全IP第三代移动通信网络采用移动IP(MIP)技术进行用户移动性管理。而标准移动IP技术在切换时的分组丢失和延迟不能满足移动多媒体这类对延迟敏感的业务。本文分析并比较了MIP为适应无缝切换所作的技术上改进,并分析了如何将这些技术应用于3G移动多媒体通信网络,最后提出了一种在3G移动多媒体通信网络中,基于在PDSN上设置RoutingCache(RC)和PagingCache(PC)以改善切换性能的技术构想。     

移动IP隧道技术在Linux下的实现*

移动IP为移动主机在移动过程中保持其通信不间断提供了实现方法,隧道技术是移动IP的关键技术之一,当通信节点向移动节点发送数据报时,需要使用到隧道技术。介绍了移动IP中隧道技术的基本原理,并给出了一种在Linux系统下的实现方法,对于移动IP相关软件的研究和开发具有一定的借鉴作用。     

一种基于HIP和混合认证的移动管理方案

首先简单而全面地分析了各种移动管理技术,重点讨论了移动IP(MIP)和HIP(Host Identity Protocol)。针对MIP移动管理复杂和HIP认证方法的不足,提出基于HIP实现移动管理,同时基于证书认证和身份认证实现混合认证。这种新颖的移动管理方案在简化会话连接管理、安全关联管理的同时,可以有效地降低认证机制的成本,增强系统的可扩展性和鲁棒性。     

分层移动IP网络的自适应移动性管理

移动IP(mobile IP,MIP)使主机在移动过程中不需改变IP地址便可连续访问Internet,其主要缺点是主机在移动过程中需要频繁地进行绑定更新,产生的信令开销较大。为降低移动IPv6的信令开销,IETF(Internet engineering task force)提出了分层移动IPv6(hierarchical mobile IPv6,HMIPv6)协议。基于HMIPv6,提出了一种自适应的分层移动性管理方案。这种方案采用模糊逻辑,根据移动主机的移动次数及移动性管理代价,动态选取MAP(mobility anchor point)并调整MAP区域所管辖的接入路由器个数。仿真分析表明,所提出的方案的代价优于固定MAP区域的移动性管理方案。     

移动IP的切换特征分析

移动IP是一种简单的、可扩展的全球移动管理方案.从理论上分析了移动IP的切换特征--分组丢失和分组乱序的概率分布.应用这个结果,优化了重叠区域半径.实例表明,模型准确地刻画了移动IP的切换行为.结果对于评价移动IP的切换性能非常有用.     

基于MPLS的微移动性管理

MPLS和移动IP结合（简称移动MPLS）是一种先进的移动性管理技术。将MPLS与微移动管理相结合的技术（简称微移动MPLS）越来越受到广泛关注。该文综合移动性管理策略方面的文献,介绍一种微移动MPLS方案的基本原理,及标签交换路径的建立、切换和路由优化。     

基于多层小区结构的移动IP移动性管理

1.引言为了支持全球的IP网络互通和设备的漫游,IETF提出了IP移动性支持协议——移动IP。其中规定:只要MN移动到另外一个IP子网,它就会获得另外的转交地址,从而启动注册过程,该过程要求MN必须通过FA向HA进行注册,MN的任何移动都必须报告给HA,由HA来维护MN的移动绑定。这种简单的移动性支持方案可以与现有网络兼容,并且只需要在移动代理(包括HA、FA)和MN上根据终端的移动性要求进行改进即可实现移动IP功能。当应用于“宏移动”(macro mobility)时,这是必要的和充分的,而当应用于“微移动”(micro mobility)和“快速移动”(high mobility)的环境时,则存在许多不足,突出表现在以下三点:1.在网络中将引发大量的注册报文的传输从而严重影响网络性能;2.造成较大的     

Improved WWW multimedia transmission performance in HTTP/TCP overATM networks

Transmission control protocol/Internet protocol (TCP/IP) is the de facto standard of the networking world. It dynamically adjusts routing of packets to accommodate failures in channels and allows construction of very large networks with little central management. But IP packets are based on the datagram model and are not really suited to real-time traffic. In order to overcome the drawbacks, a new network technology, ATM, is proposed. ATM provides quality of service (QOS) guarantees for various classes of applications and in-order delivery of packets via connection oriented virtual circuits. Unfortunately, when ATM is to be internetworked with the existing network infrastructure, some special signaling, addressing and routing protocols are needed. IP over ATM is one of the methods proposed by IETF. It allows existing TCP/IP applications to run on ATM end-stations and ATM networks to interconnect with legacy LAN/WAN technologies. But the performance of TCP/IP over ATM leaves something to be desired. Partial packet discard (PPD) and early packet discard (EPD) are two schemes to improve its performance. This paper proposes a “selective packet retransmission” scheme for improving HTTP/TCP performance when transmitting through ATM networks. In selective packet retransmission, we take advantage of the property of humans' perception tolerance for errors to determine whether to retransmit a corrupted TCP segment or not. For lossable data, such as images, when an error occurs because of cell losses, it will not be retransmitted. The simulations show that, for the same buffer size and traffic load, selective packet retransmission performs better than PPD, EPD, and plain TCP over ATM     

OmniCon: a Mobile IP‐based vertical handoff system for wireless LAN and GPRS links

Wi‐Fi based hotspots offer mobile users broadband wireless Internet connectivity in public work spaces and corporate/university campuses. Despite the aggressive deployment of these hotspots in recent years, high‐speed wireless Internet access remains restricted to small geographical areas due to the limited physical coverage of wireless LANs. On the other hand, despite their lower throughput, cellular networks have a significantly wider coverage and are thus much more available. Recognizing that 2.5G or 3G cellular networks can effectively complement wireless LANs, we set out to develop a vertical handoff system that allows mobile users to seamlessly fall back to such cellular networks as the general packet radio service (GPRS) or 3G whenever wireless LAN connectivity is not available. The resulting handoff mechanism allows a network connection of a mobile node to operate over multiple wireless access networks in a way that is transparent to end user applications. In this paper, we present the design, implementation, and evaluation of a fully operational vertical handoff system, called OmniCon, which enables mobile nodes to automatically switch between wireless LAN and GPRS, based on wireless LAN availability, by introducing a simple extension to the existing Mobile IP implementation. We discuss the design issues in the proposed vertical handoff system for heterogeneous networks, including connection setup problems due to network address translation, and the disparity in link characteristics between wireless LANs and GPRS. A detailed performance evaluation study of the OmniCon prototype demonstrates its ability to migrate active network connections between these two wireless technologies with low handoff latency and close to zero packet loss. Copyright © 2006 John Wiley & Sons, Ltd.