Fine protection of data-paths in multi-layer networks based on the GMPLS paradigm

The telecommunications world is expecting the take off of broadband services, beyond typical telephone, both mobile and fixed, and IPTV. The expectations on huge growth of data traffic will lead the evolution of the network towards the next generation multi-service network. The cornerstone of future network infrastructure will be the possibility of provide carrier grade performance, for those services that require such features. This means to guarantee the QoS performance and the resilience of a circuit-switched network even in a packet-based scenario. Beyond that, key requirements are the capacity of tailoring the QoS to different services, and flexibility, that is the effective utilization of network resources, as well as the ability to react to changes in the traffic demands. This paper addresses the issue of providing adequate levels of protection to data flows in multi-layer networks composed of MPLS and optical layers and based on the GMPLS paradigm. A new approach is proposed allowing for an efficient use of network resources and providing adequate levels of protection, starting from the high standard required for real-time traffic.     

Applying PTF/VTF routing policies in multilayer IP/MPLS-based ASON/GMPLS multi-domain networks

The IP/MPLS-based ASON/GMPLS hybrid network architecture enables the interaction between the IP layer and the optical dense wavelength division multiplexing (DWDM) layer. This architecture makes it possible to transfer huge amounts of traffic data on DWDM networks, while supporting Internet Protocol (IP)-based service applications. Additionally, this architecture provides a unified routing scenario, which allows the dynamic routing in both the IP layer and/or optical layer. Cross- layer routing has been addressed in single domain networks scenarios, where the routing policies Physical Topology First (PTF) and Virtual Topology First (VTP) have been proposed and applied. However, applying cross-layer routing using both routing topology policies PTF and VTF has not been investigated in a multi-domain networks scenario yet. In this study, we address this issue and propose a routing scheme to establish traffic connections in the optical WDM layer and the IP layer, which makes the applicability of PTF and VTF in multilayer multi-domain network feasible.     

基于GMPLS集成动态多层网络故障恢复技术

基于IP/GMPLS over WDM的网络架构下研究多层网络生存性的协调机制,针对基于GMPLS控制平面的生存性协调方案作了详细的论述.主要从故障检测、故障通知和协调控制等几个方面展开详细的分析研究,该方案能减少恢复故障所需的总时间和,以及可对各层生存性技术进行有效的协调控制.     

Label preference schemes in GMPLS controlled networks

The GMPLS assumption that all available labels are equal is reasonable in electronic networks but not always true in WDM optical networks where labels correspond to physical wavelengths. In this paper we present two schemes for collecting the preference for specific labels during GMPLS signaling. For this purpose a new use of the Suggested Label object is proposed, and a novel object called Suggested Vector is introduced. The approach is validated through simulations showing significant wavelength converter usage reduction in a WDM optical network     

IP/MPLS网络与GMPLS网络互联的研究

文章研究了网际协议／多协议标签交换（IP／MPLS）网络升级为通用多协议标签交换（GMPLS）网络的过程中存在的几种演进模型，并重点分析了岛式模型。同时，还分析了MPLS网络和GMPLS网络互联时存在的问题、两种协议问的差异以及解决这些问题所采用的路由、信令和通道计算技术。     

基于GMPLS的多层网络故障恢复框架设计

针对GMPLS控制平面的生存性提出了一种故障恢复机制,以实现多层网络生存性机制之间的迅速协调,通过对方案的分析能减少故障恢复时间的总和,优化网络效率.     

GMPLS and ASON for automatic switched transport networks

In automatic switched transport networks (ASTN), transport services of different granularity can be set up, modified and released on demand, using mechanisms in the control plane. Currently, this novel provisioning paradigm is being standardized under the umbrella of the automatic switched optical network (ASON) and the generalized multiprotocol label switching (GMPLS) framework. This paper gives an overview of the concepts and open issues of ASON and GMPLS at the current stage of their development.     

基于RSVP-TE信令的GMPLS动态性能研究

主要介绍通用多协议标签交换信令性能及测试的相关工作.指出目前急需对多协议标签交换动态性能进行描述,并提出了一组多协议标签交换动态性能参数以期能对网络运营商、设备制造商和应用程序设计者有一定的帮助.最后给出了在现有多协议标签交换光网络平台上的测试结果并对其进行了分析,并讨论了进一步的研究方向.     

一种改进的OBS/GMPLS网络通路建立机制

OBS/GMPLS网络可以很好的实现传统OBS网络不具备的自动发现、流量工程、良好的保护恢复等功能.基于重叠模型的OBS/GMPLS网络架构,针对GMPLS信令执行资源预留时存在的链路资源部分闲置状态,提出了两种改进策略,包括宿结点的上游结点提前回送Resv消息和对BHP消息设置偏置时间以控制BHP的发送.理论分析表明改进方案可以缩短链路的建立时间,提高资源利用率.     

A concurrent two-layer restoration scheme for GMPLS WDM networks

Next generation backbone networks will likely consist of IP routers as well as optical cross connects (OXCs) and will deploy an optical control plane protocol. Generalized Multi Protocol Label Switching (GMPLS) has been proposed as the candidate of choice for the control plane. Optical fibers may carry large volumes of traffic and therefore adequate mechanisms must exist to enable the network to automatically recover from failures of fiber. In mission critical networks survivability becomes very important. We investigate the problem of autonomous recovery in such networks. The literature contains work in this area that investigates the problem of multilayer recovery. Such recovery had only been sequential in the sense that the published work recovers first in the optical domain, assuming the availability of redundant resources, and then proceeds to recover packet label switched paths. We report a recovery procedure for recovering packet label switch paths (packet LSPs) and lambda label switch paths (λLSP) concurrently. We have conducted an OPNET-based simulation study that compares the performance of the concurrent scheme with the previously published sequential two-layer recovery scheme. The study shows that the concurrent two-layer recovery scheme performs as much as forty-four percent faster than the sequential two-layer recovery scheme.     

Service differentiation in IP/MPLS over ASON/GMPLS networks

There is a general agreement that the future infrastructure for broadband communications will consist of Automatically Switched Optical Networks (ASONs) controlled by the Generalized Multi-Protocol Label Switching (GMPLS) control plane. Due to the convergence of most services on the Internet Protocol (IP) layer, ASON/GMPLS networks need to provide transport for a variety of applications having different Quality of Service (QoS) requirements. This implies that the Differentiated Service paradigm, which improves the QoS in pure IP networks, needs to be extended to the new underlying infrastructure. This article proposes and compares three schemes for the service differentiation in IP/MPLS over ASON/GMPLS networks. Simulation results demonstrate that a fair trade-off between QoS and resource utilization is achieved when combining routing policy differentiation (RPD), virtual topology differentiation (VTD), and virtual topology sharing (VTS) techniques. The RPD technique decides on the multilayer routing policy to apply depending on the Class of Service (CoS). The VTD technique transports different CoS over different independent virtual topologies. The VTS technique introduces a certain degree of resource sharing among the different virtual topologies.     

GMPLS网络的近实时拓扑监视服务的性能

提出了一种基于CORBA的网络管理系统模型和一种适用于GMPLS网络的准实时拓扑监视方案。根据LMP的MIB表得到初始化的拓扑信息,并通过分析SNMP的traps更新其拓扑信息。通过检测所提模型的延迟,证明文中所提出的拓扑监视方案可以实现准实时的要求。     

GMPLS网络的路由算法研究与仿真

讨论了基于GMPLS的约束路由机制和约束路由算法,提出了一种适用于智能光网络的CSPF算法.该算法通过考虑SRLG约束和负载平衡因子,能够支持业务的保护与恢复,并在一定程度上均衡业务流量,提高全网资源利用率,从而降低业务阻塞率,通过多次仿真实验验证,该算法是可用的和有效的.     

BGP routing policies in ISP networks

The Internet has quickly evolved into a vast global network owned and operated by thousands of different administrative entities. During this time, it became apparent that vanilla shortest path routing would be insufficient to handle the myriad operational, economic, and political factors involved in routing. ISPs began to modify routing configurations to support routing policies - goals held by the router's owner that controlled which routes were chosen and which routes were propagated to neighbors. BGP, originally a simple path vector protocol, was incrementally modified over time with a number of mechanisms to support policies, adding substantially to the complexity. Much of the mystery in BGP comes not only from the protocol complexity, but also from a lack of understanding of the underlying policies and the problems ISPs face that are addressed by these policies. In this article we shed light on goals operators have and their resulting routing policies, why BGP evolved the way it did, and how common policies are implemented using BGP. We also discuss recent and current work in the field that aims to address problems that arise in applying and supporting routing policies.     

Recovery of the control plane after failures in ASON/GMPLS networks

A reliable control plane plays a crucial role in creating high-level services in the next-generation transport network based on the generalized multiprotocol label switching (GMPLS) or automatically switched optical networks (ASON) model. Approaches to control-plane survivability, based on protection, and restoration mechanisms, are examined. Procedures for the control plane state recovery are discussed, including link and node failure recovery.     

A disjoint path selection scheme with shared risk link groups in GMPLS networks

This letter proposes a disjoint path selection scheme for generalized multi-protocol label switching (GMPLS) networks with shared risk link group (SRLG) constraints. It is called the weighted-SRLG (WSRLG) scheme. It treats the number of SRLG members related to a link as part of the link cost when the k-shortest path algorithm is executed. In WSRLG, a link that has many SRLG members is rarely selected as the shortest path. Simulation results show that WSRLG finds more disjoint paths than the conventional k-shortest path algorithm.     

Improving call admission policies in wireless networks

It is well known that the call admission policy can have a big impact on the performance of a wireless network. However, the nonlinear dependence of new calls and handoff calls makes the search for a better call admission policy – in terms of effective utilization – a difficult task. Many studies on optimal policies have not taken the correct dependence into consideration. As a result, the reported gains in those studies cannot be confirmed in a real network. In this paper we develop a solution to the problem of finding better call admission policies. The technique consists of three components. First, we search for the policy in an approximate reducedcomplexity model. Second, we modify the Linear Programming technique for the inherently nonlinear policysearch problem. Third, we verify the performance of the found policy in the exact, highcomplexity, analytical model. The results shown in the paper clearly demonstrate the effectiveness of the proposed technique.     

Analysis of discarding policies in high-speed networks

Networked applications generate messages that are segmented into smaller, fixed or variable size packets, before they are sent through the network. In high-speed networks, acknowledging individual packets is impractical; so when congestion builds up and packets have to be dropped, entire messages are lost. For a message to be useful, all packets comprising it must arrive successfully at the destination. The problem is therefore which packets to discard so that as many complete messages are delivered, and so that congestion is alleviated or avoided altogether. Selective discarding policies, as a means for congestion avoidance, are studied and compared to nondiscarding policies. The partial message discard policy discards packets of tails of corrupted messages. An improvement to this policy is the early message discard that drops entire messages and not just message tails. A common performance measure of network elements is the effective throughput which measures the utilization of the network links but which ignores the application altogether. We adopt a new performance measure-goodput-which reflects the utilization of the network from the application's point of view and thus better describes network behavior. We develop and analyze a model for systems which employ discarding policies. The analysis shows a remarkable performance improvement when any message-based discarding policy is applied, and that the early message discard policy performs better than the others, especially under high load. We compute the optimal parameter setting for maximum goodput at different input loads, and investigate the performance sensitivity to these parameters