基于BGP/MPLS的VPN技术及其在CATV宽带数据网络中的应用

介绍基于BGP／MPLS的虚拟专用网的基本原理，并对其主要技术进行较为详细的论述，概括虚拟专用网实现方案的特点并介绍其在CATV宽带数据网络中的应用，最后指出这一技术的应用前景。     

光网中基于MPLS的VPN研究

针对目前互联网中存在的QoS和网络安全等问题,在现有L2 MPLS VPN的基础上,提出了在光网络中实现基于MPLS的VPN的方法.理论结果表明,基于MPLS的VPN网络的路由表减小,路由转发更加高效,从而进一步提高了网络性能.同时,用户通过专用虚拟通道进行数据处理的安全性也得到了保障.     

MPLS-based satellite constellation networks

Nongeostationary satellite constellations with intersatellite links are a challenge for networking due to their continuously changing topology. In order to make maximal use of the network's capacities, special attention has to be paid to routing and traffic engineering. Multiprotocol label switching (MPLS) as underlying protocol is an interesting candidate for this task since it offers many possibilities to exert influence on traffic flows and supports today's dominating Internet protocol traffic very well. This paper describes a general MPLS-based networking concept for satellite networks and discusses different scenarios considering the particularities and constraints of the dynamic topology. Functional elements of MPLS like ingress, egress, or core routers have to be mapped onto the physical entities of the network and prerequisites for traffic engineering are discussed. Routing and rerouting of paths is of key interest since this affects route computation effort and routing performance. Thus, an analytical estimation of routing effort is deduced and numerical and simulation results are presented.     

Hierarchical routing and traffic grooming in IP/MPLS-based ASON/GMPLS multi-domain networks

Routing, connection setup, and path computation are well-known problems in multi-domain networks, which have been largely analyzed in pure IP (packet) networks. In circuit-switched optical multi-domain networks, there remain, however, a number of routing and path computation challenges. Traffic grooming means combining a number of low-speed traffic streams so that the high capacity of each lightpath may be used as efficiently as possible, as path computation implements the core of the grooming function, it is obvious that solutions for the traffic grooming problem in optical multi-domain networks are still not sufficiently investigated. In this study we propose a methodology to address the problems of routing, connection setup, and traffic grooming in optical multi-domain networks, which adapts a two-level hierarchical routing scheme and full-mesh topology abstraction algorithm to improve routing scalability and lower inter-domain blocking probabilities; additionally our proposed methodology adapts a scheme for traffic grooming in DWDM multi-domain networks to improve the resources usage. To test our proposed methodology we propose a detailed IP/MPLS-based ASON/GMPLS multi-domain multilayer test framework.     

Multicast traffic scheduling in single-hop WDM networks with arbitrary tuning latencies

To accommodate the demands of quality of service (QoS) and multicast applications, a multicast QoS traffic-scheduling algorithm with tuning latency consideration in wavelength-division multiplexing star-coupled networks is provided in this paper. To furnish different levels of QoS, two classes of traffic are considered: constant bit rate and available bit rate (ABR). An effective bandwidth-normalization scheme for ABR traffic is also derived. We define the slot scanning problem in the connection-setup process as the maximum assignable slots (MAS) problem. We prove that the optimal solution of the MAS problem can be obtained in polynomial time. Owing to its high-order time complexity, we also propose two heuristics for the MAS problem. The performance of these strategies are evaluated and compared by simulations under different system parameters, such as number of wavelengths, traffic load, and tuning latency.     

在VPN中应用组播的实施方案

组播是适合企业网开展视频服务的一种技术,而现代的企业网经常是由VPN技术进行互联的分散于全球各地的网络。本文分析了现在常用的VPN技术,指出应该如何在各个VPN网络中实施组播的技术及特点,并最后举例说明了在VPN中配置组播的方法。     

基于MPLS技术的IP VPN实现机制（下）

在三层MPLS VPN方式中,由于ISP的PE设备要参与到VPN内部的IP路由选择,因此PE将获知用户VPN内部的IP层面拓扑结构。这对于金融等保密性较强的机构来说,让ISP了解其内部网络结构是不能接受的。他们宁愿采用由运营商的物理或虚电路来组建自己的VPN。另外,由于目前的三层MPLS VPN与三层协议相关(三层网络协议只能为IPv4),不利于网络的扩展。鉴于此,出现了二层MPLS VPN。     

ATM in MPLS-based converged core data networks

Services supported by asynchronous transfer mode account for the majority of data and Internet service revenues generated by carrier networks today. This is based on ATM's ability to support high availability services with quality of service. However, the influences of the Internet and a highly dynamic telecommunications market have raised demands for increased flexibility while controlling costs. Therefore, future carrier networks are likely to continue to be based on established technologies, such as ATM, as well as IP. In many cases, this is achieved through maintaining separate ATM and IP core networks, with the IP network supporting Internet services, while the ATM network continues to support guaranteed services such as private lines, broadband access, and video. In some cases, however, it can be advantageous for a carrier to transport segments of their ATM network over their IP network core; for example, to transport ATM traffic currently carried on leased facilities onto an IP network where the service provider owns the facilities. Developments in IP and MPLS-based traffic engineering and QoS may increase the ability of IP-based networks to support ATM services using MPLS. This article provides an overview of approaches enabling a network based on MPLS that naturally supports IP services to also support ATM services. The drivers and requirements for convergence on an IP/MPLS core network are presented, followed by an overview of the different approaches and associated challenges currently being debated in the standards bodies.     

Mitigating location management traffic via aggregation in multi-hop cellular networks

In high mobility areas such as shopping malls and transportation stations, mobile users tend to move in and out in a bursty fashion, and hence location update (LU) and paging signaling cause substantial traffic burden to the cellular networks, leading to signaling congestion. This poses a great challenge to the system design for wireless cellular systems. Traditional cellular systems cannot cope with this situation very well. However, with the ad hoc operational mode recently introduced into the cellular systems, the added multi-hop relaying via mobile devices provides a new way to mitigate location management traffic. In this paper, based on this new architecture, we propose a novel scheme, called aggregative location management, which aggregates multiple location updates into group location updates. For the scenarios of high capacity transit (HCT) systems, we use this grouping scheme to alleviate the signaling traffic when mobile users in an HCT move into new location areas. For other scenarios with mass arrivals of LU requests, we develop a generic aggregative location management scheme in which LU requests can be first aggregated by designated mobile devices and then are periodically sent to the location registers. Performance evaluation is carried out and shows their significant effectiveness.     

Frame-level traffic splitting for link aggregation in data center networks

Ethernet link aggregation, which provides an easy and cost-effective way to increase both bandwidth and link availability between a pair of devices, is well suited for data center networks. However, all the traffic splitting algorithms used in existing Ethernet link aggregation are flow-level which do not work well owing to the traffic characteristics of data centers. Though frame-level traffic splitting can achieve optimal load balance and the maximum benefits from aggregated capacity, it is generally deprecated in most cases because of frame disordering which can disrupt the operation of many Internet protocols, most notably transmission control protocol (TCP). To address this issue, we first investigate the causes of frame disordering in link aggregation and find that all of them either are no longer true or can be prevented in data centers. Then we present a byte-counter frame-level traffic splitting algorithm which achieves optimal performance while causes no frame disordering. The only requirement is that frames in a flow are the same size which can be easily met in data centers. Simulation results show that the proposed frame-level traffic splitting method could achieve higher throughput and optimal load balance. The average completion time of different sized flows is reduced by 24% on average and by up to 46%.     

组播在MPLS VPN网络中的实现

组播作为一种高效的大数据量传播方式,以其对网络资源的优化利用得到了业界广泛的认可;新兴MPLS VPN 技术以优秀的流量管理、服务质量保证及较高的安全性为传统的纯IP数据网络解决了数据的流量平衡、业务流的服务质量及企业通过公共网互联的安全问题.组播技术与MPLS VPN技术的结合将为运营商提供一个前所未有的多业务发展空间.     

组播在MPLS VPN网络中的实现

组播作为一种高效的大数据量传播方式 ,以其对网络资源的优化利用得到了业界广泛的认可 ;新兴MPLSVPN技术以优秀的流量管理、服务质量保证及较高的安全性为传统的纯IP数据网络解决了数据的流量平衡、业务流的服务质量及企业通过公共网互联的安全问题。组播技术与MPLSVPN技术的结合将为运营商提供一个前所未有的多业务发展空间     

一种基于MPLS的无线接入网微移动方案

将MPLS技术应用到基于IP的无线接入网络是近年越来越受到关注的新课题.本文提出了一种基于MPLS的微移动方案,方案采用在基站进行缓冲的方法降低切换时的分组丢失.最后对方案的性能从算法所产生的网络开销、切换时延与分组丢失几个方面进行了分析和讨论,结果表明本方案适用于高速微蜂窝及微微蜂窝的移动通信环境,并能满足一般的数据及实时业务的需求.     

MPLS VPN组播的研究与仿真

对MPLS VPN特有的组播问题进行了分析和研究,比较了现有各种组播实现方案的优缺点.在此基础上,提出了一种改进的MPLS VPN组播实现方法--组播域显式组播路由法.最后进行了仿真,验证了改进方案的可行性、实用性和优越性.     

组播在MPLS VPN中的一个过渡实现方案

在组播网络中，即使组播用户数量成倍增长，骨干网络中网络带宽也无需增加，在很多多媒体业务中需要网络组播功能。目前由于MPLS VPN网络中很多PE设备尚不支持组播业务，因此在VPN内部署组播业务时遇到了一定的困难。本文讨论一种可以在现有设备条件下，利用DVMRP隧道解决MPLS VPN组播问题的方案。     

MPLS/BGP VPN中组播的实现研究

VPN是利用公共网络资源来实现用户私有网络的一种技术手段,为用户提供可靠、安全的网络服务。然而它是一种针对单播的技术,随着VPN的广泛应用和网络流量的增大,现实要求在VPN上实现组播支持。传统的MPLS VPN组播必须在CE之间配置点到点的隧道,这增加了网络负担和管理成本。文中提出了BGP/MPLS的VPN中组播的一种实现方案MVPN,克服了上述缺点,并对MVPN的各方面进行了综合分析。     

Multicast nonblocking switching networks

This paper considers three-stage switching networks for which nonblocking conditions with point-to-point traffic are given by the well known Clos (1953) theorem, under the assumption of absence of any optimized routing of the connections inside the network. We give the conditions for such a network to be strict-sense nonblocking under multicast traffic, by showing also that previously published papers, although claiming the same result, only provided sufficient conditions.     

在基于MPLS的层次化移动IP网络中支持DiffServ的研究

MPLS支持DiffServ、流量工程,能为网络提供较好的QoS保证,而移动IP(MIP)能为移动设备提供较好的移动性支持。文章探讨了在无线接入网中MPLS和MIP结合实现DiffServ的方案,并给出了一种在基于MPLS的层次化MIP网络结构中支持DiffServ的体系结构,设计了其节点功能模型和关键协议。方案中利用了层次化结构的区域注册和重路由机制,减少了切换时延和网络的信令负荷。     

Reconfiguration of spare capacity for MPLS-based recovery in the Internet backbone networks

This paper introduces a novel approach, called Short Leap Shared Protection with spare capacity Reallocation (SLSP-R), to deal with dynamic reconfiguration of spare capacity for MPLS-based recovery in the Internet backbone networks. SLSP-R is based on the SLSP framework and is designed to quantify the impact of computation complexity on network performance. The basic idea for SLSP-R is to subdivide a lengthy optimization process into several subtasks in order to trade the optimization quality with computation time. For this purpose, we compare three strategies for grouping working paths before an integer programming (InP) formulation is solved, namely, the Most Overlapped, Most Diverse, and Randomly Distributed. Analytical modeling of the problem is provided to show the feasibility of the subgrouping strategy. A numerical experiment as well as simulation-based study are conducted on four networks with different topology to evaluate the SLSP-R algorithm. The design methodology to determine the size of each subset of working paths is verified in the simulation.     

虚拟专网VPN技术

随着Internet的广泛应用，虚拟专用网（VPN）技术越来越受到IT界的关注，本文从VPN的概念开始，介绍了VPN的基本原理，主要技术，业务分类及其在Internet中的应用，最后分析了其发展现状及市场前景。