IP快速恢复机制发展综述

本文分析了影响IP快速恢复的原因,从反应式恢复和主动式恢复两种分类对现有的IP恢复机制方案进行了分析和总结,提出了该方向上尚未解决的问题以及发展趋势.     

对ASON承载IP网的研究(下)

随着业务的发展,IP网逐渐成为统一的多业务分组传送平台,应提供更为严格的可靠性保障机制,其目标不仅是要保障任何情况下的业务连通性,还要保证业务的QoS指标.ASON能快速地提供端到端连接,并能提供多种保护恢复机制,提高网络可靠性.如果采用ASON来承载IP网,则ASON可以为IP网提供保护恢复机制.本文主要探讨ASON承载IP网的需求,研究ASON为IP网提供保护恢复的可行性,从IP网和ASON的保护恢复现状、ASON为IP网提供保护恢复的技术和经济性方面进行详细的分析.     

对ASON承载IP网的研究(上)

随着业务的发展,IP网逐渐成为统一的多业务分组传送平台,应提供更为严格的可靠性保障机制,其目标不仅是要保障任何情况下的业务连通性,还要保证业务的QoS指标.ASON能快速地提供端到端连接,并能提供多种保护恢复机制,提高网络可靠性.如果采用ASON来承载IP网,则ASON可以为IP网提供保护恢复机制.本文主要探讨ASON承载IP网的需求,研究ASON为IP网提供保护恢复的可行性,从IP网和ASON的保护恢复现状、ASON为IP网提供保护恢复的技术和经济性方面进行详细的分析.     

采用多层恢复机制的IP over WDM网络生存性研究

IP over WDM网络是下一代网络的核心,生存性则是保证服务质量(QoS)的关键要素.当网络中出现故障时,选择在IP层还是光层进行保护和恢复是非常重要的课题.文章在论述IP层和光层的保护和恢复机制的基础上,提出了多层联合恢复机制的思想,针对多层联合恢复机制中各层之间如何协调进行了仔细的分析,并提出了自己的见解.     

H．264在互联网抗误码问题中的应用

本文首先简单描述了错误恢复能力在IP视频通信中的重要性和实现途径；然后回顾了传统的抗干扰和恢复方法；最后对H．264中的错误恢复方法及其分层框架进行了分析。     

IP over WDM网络的多层联合恢复策略

由于WDM网络承载着巨大的业务量,其网络可靠性日趋重要.在光层提供生存能力一向具有重要意义,然而由于光层聚集光路径及其粒度较粗的特征,也产生了许多的问题和挑战.MPLS及其扩展MP S的出现,为发展能够协调IP层和光层的联合保护/恢复策略提供了新的方法.鉴于此,文章首先简单介绍了现有MPLS/MP S的恢复机制,然后针对IP over WDM光网络提出了一种联合的二层恢复策略.在这种策略中,光层首先执行恢复动作,如果光层无法恢复所有受损的业务,则上层的IP层接着发起其自身的恢复机制.基于仿真的分析表明,所提出的二层联合恢复策略优于单层的恢复策略;若IP层恢复时具有更好的粒度优势,光层恢复时则具有更高的速度.     

MPLS网络的自愈恢复技术

网络可靠性已经成为IP网的一个重要问题。目前关于IP网可靠性的讨论集中于多协议标记交换(MPLS)的故障恢复机制。在MPLS网络中的任何资源都有可能发生故障,要想提供一个高可用性的网络,网络提供商必须能够预料并且解决这些可能发生的故障。MPLS自愈恢复是MPLS流量工程的一种重要应用特性。自愈恢复能力对于提高MPLS网络的可用性和稳定性具有关键意义。本文首先介绍了MPLS网络的自愈恢复特性,并着重对目前ITU-T、ITEF推荐的几种MPLS故障检测、保护恢复技术进行深入介绍和对比分析。     

基于终端模式的IP网络仿真业务方案

在IP网络中如何解决传统的各种专线业务,正成为影响IP网络统一部署的关键问题。本文在分析各种技术的基础上,提出了一种基于终端模式的专线仿真业务方案,同时对实现仿真业务时必须要解决的技术问题进行了分析,包括时钟的恢复、定时机制,专线仿真业务的维护管理和层次化的OAM思路,通过这些来解决在无连接的IP网络上管理仿真业务。     

IP/WDM网络生存性策略分析

本文在研究网络生存性基本问题的基础上，分析IP层中缩短IP动态路由恢复时间的改进策略和基于MPLS的生存性策略；同时，对不同方案的资源利用率和保护倒换时间进行了比较；最后探讨了多层生存性协调可能遇到的挑战。     

MPLS与业务恢复

本讨论MPLS的快速业务恢复和优化业务恢复能力，首先分析MPLS体系结构中有利于快速业务恢复的属性，如控制与转发分率、统一的转发过程、标签栈等，在此基础上论述MPLS的再选路机制的IP网快速业务恢复和优化业务恢复等方面的应用。最后给出对此问题的看法。     

A survey of packet loss recovery techniques for streaming audio

We survey a number of packet loss recovery techniques for streaming audio applications operating using IP multicast. We begin with a discussion of the loss and delay characteristics of an IP multicast channel, and from this show the need for packet loss recovery. Recovery techniques may be divided into two classes: sender- and receiver-based. We compare and contrast several sender-based recovery schemes: forward error correction (both media-specific and media-independent), interleaving, and retransmission. In addition, a number of error concealment schemes are discussed. We conclude with a series of recommendations for repair schemes to be used based on application requirements and network conditions     

Study on a joint multiple layer restoration scheme for IP over WDM networks

In this article we investigate the problem of a restoration scheme for IP over WDM networks. Network reliability is gaining importance with the huge volume of traffic carried by such networks. Providing survivability at the optical layer is inherently attractive, but raises many questions and challenges, given the characteristic of optical aggregated lightpath and relatively coarse traffic granularity. The emergence of MPLS and its extension, MP/spl lambda/S, opens up new possibilities for developing simple integrated protection/restoration schemes that can be coordinated at both the IP and optical layers . This article first presents an overview of existing MPLS/MP/spl lambda/S recovery mechanisms. Then we propose a joint two-layer recovery scheme for IP-centric WDM-based optical networks where the optical layer takes the recovery actions first, and subsequently the upper IP layer initiates its own recovery mechanism, if the optical layer does not restore all affected services. A simulation-based analysis shows the benefits of the proposed two-layer recovery scheme over single-layer recovery schemes. We demonstrate the advantages of finer granularity in IP layer recovery and the effectiveness in speed on the optical layer. The impact of several network parameters on recovery performance is also studied in the paper.     

多层网络中的生存性

未来传输网络中,不同的网络技术(如IP、SDH和WDM技术)的融合需要不同网络层次之间进行有效地配合,特别是网络生存性领域更是如此。首先对多层网络生存性机制的框架以及在多层网络环境下实现网络生存性的技术进行了概述,同时以IP over WDM为例,说明了这些方法的应用方式。     

IP resilience within an autonomous system: current approaches, challenges, and future directions

Network survivability is gaining increasing attention from the Internet research community. The ubiquity of IP services has fueled increasing interest in ensuring their dependability, by making IP networks more disruption-tolerant. After providing a brief overview of how routing is accomplished in the Internet, this article reviews how the protocols react to failures or changes in network state within an autonomous system. The problems associated with current restoration schemes, with respect to newer and more stringent requirements posed by emerging services such as voice over IP, are identified. We present an overview of the schemes proposed to ameliorate fault recovery and critique their contributions. We also outline future research directions for improving IP resilience.     

IP网络的快速故障恢复

 随着互联网的迅速发展,人类通信对其依赖性日益增强,而IP层故障恢复能力低下,阻碍了互联网性能的提高.近些年来,国际学术界对IP网络快速故障恢复的方案研究异常活跃,提出了加快故障恢复速度的三条途径:(1)加快IP路由收敛;(2)使用主动式故障恢复;(3)提高故障检测的速度与准确性.针对已有解决方案的不足,本文得出,要推动IP网络的快速故障恢复方案的实现,必须做好:(1)故障后的通信负载均衡;(2)互操作测试及路由器体系结构的重新设计.     

An Efficient Rerouting Scheme for MPLS-Based Recovery and Its Performance Evaluation

The path recovery in MPLS is the technique to reroute traffic around a failure or congestion in a LSP. Currently, there are two kinds of model for path recovery: rerouting and protection switching. The existing schemes based on rerouting model have the disadvantage of more difficulty in handling node failures or concurrent node faults. Similarly, the existing schemes based on protection switching model have some difficulty in solving problem such as resource utilization and protection of recovery path. This paper proposes an efficient rerouting scheme to establish a LSP along the least-cost recovery path of all possible alternative paths that can be found on a working path, which is calculated by the upstream LSR that has detected a failure. The proposed scheme can increase resource utilization, establish a recovery path relatively fast, support almost all failure types such as link failures, node failures, failures on both a working path and its recovery path, and concurrent faults. Through simulation, the performance of the proposed scheme is measured and compared with the existing schemes.     

A joint resilience scheme with interlayer backup resource sharing in IP over WDM networks

The survivability of IP over WDM networks gains importance as network traffic keeps growing. Recovery at the lowest layer is fast and scalable. However, it is usually considered to provide poor network utilization. In this article we propose a resilience scheme based on recovery at the lowest layer in which intralayer and interlayer backup resource sharing is utilized to improve the network utilization. By applying interlayer backup resource sharing, we can totally depend on the reserved backup resources for fiber link failures to guarantee 100 percent recovery of IP router failures. In addition, by applying intralayer backup resource sharing, the network utilization improvement of recovery at the lowest layer is much more significant than at the highest layer. Simulations results show that the proposed scheme can efficiently improve network utilization and be even more capacity-efficient than resilience schemes based on recovery at the highest layer.     

Nyberg-Rueppel消息恢复盲签名的一般化和改进

给出Nyberg-Rueppel消息恢复签名方案的一般性盲化方法,由该方法可以得到其3个盲化方案,其中一个就是Camenisch等人的方案,另外两个则是新的。在这两个新的方案中,一个与已有方案效率相当,另一个因无需求逆运算而效率更高。使用填充技术和hash函数,得到在ROM(randomoraclemodel)和GM(genericgroupmodel)模型下抗适应性选择消息伪造的可证明安全的消息恢复盲签名方案。     

IP restoration vs. optical protection: Which one has the least bandwidth requirements?

Survivability in IP-over-WDM networks has already been extensively discussed in a series of studies. While many studies assume an IP restoration scheme and focus on network connectivity in order to ensure proper recovery, few studies deal with optical protection. We investigate this question with the objective of estimating the respective bandwidth requirements of both recovery schemes, subject to single or multiple failures. We also design a mixed recovery scenario where the recovery is taken care at a different layer depending on the type of failures.Results shows that optical protection is by far the most economical recovery scheme in terms of bandwidth requirements.     

基于双向输入型鉴相器锁相环技术的光时钟恢复系统

介绍了一类基于双向输入型鉴相器锁相环技术的时钟恢复系统。分别讨论了基于对称和非对称输入型鉴相器的时钟恢复实现方案,并提出了一种基于对称输入型鉴相器锁相环技术的解复用分离型时钟恢复方案。