Optimized design of survivable MPLS over optical transport networks

In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks (OTNs) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single-layer survivability, where some recovery mechanism (e.g. protection or restoration) is implemented in a single network layer and multilayer survivability, where recovery is implemented in multiple network layers. The survivable MPLS over OTN design is implemented as a static network optimization problem and incorporates various methods for spare capacity allocation (SCA) to reroute disrupted traffic.The comparative analysis between the single layer and the multilayer survivability shows the influence of the traffic granularity on the survivability cost: for high-bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low-bandwidth LSPs the single-layer survivability is more cost-efficient. For the multilayer survivability we demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9%) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one; however, this is at the increase in the optimization problem complexity. These results are based on a cost model with current technology pricing and were obtained for networks targeted to a nationwide coverage.     

A multilayer solution for path provisioning in new-generation optical/MPLS networks

This paper proposes an offline solution for global path provisioning in new-generation optical networks based on the generalized multiprotocol label switching (GMPLS) paradigm. This solution is based on a multilayer approach, which involves both the optical and the electrical layers and optimizes the network configuration and traffic routing. The proposed global provisioning solution can be easily combined with dynamic routing solutions, providing the network with the possibility of reacting promptly to traffic changes. Data flows are assumed to be structured into label switched paths (LSPs), which represent the connection in a GMPLS-based network, at any hierarchical level. The global provisioning issue is a difficult optimization problem. As a solution, we propose a new heuristic algorithm based on the shortest path computation and a mathematical programming approach, which makes use of the optimization solver CPLEX. A large computational study shows the effectiveness of the former, in terms of quality of the solutions. The advantages of the multilayer provisioning strategy are analyzed in a relevant case study by evaluating the network congestion.     

MPLS网络的生存性技术

目前，网络上的应用越来越多，网络就必须能够在故障发生时保证其连续性和服务质量。因此，网络生存性已经成为互联网中的一个重要问题。另一方面，随着光纤技术的发展，链路传输速率已达数10Gb/s。一条链路的损坏将影响大量的应用,而当前基于IP路由协议的恢复机制至少需要几秒到几分钟的时间，这将导致大量分组的丢失，从而造成严重服务质量问题以及网络性能的下降。网络的生存性是流量工程的重要方面。按照ANSI TIA1.2工作组的定义，网络生存性就是在故障发生的情况下，网络仍能维持服务连续性的能力。以前有关网络生存性的研究主要集…     

Scheduling in overlaid star all-photonic networks with large propagation delays

This paper describes a framework for fixed- length frame scheduling in all-photonic networks with large propagation delays. We introduce the Fair Matching Algorithm a novel scheduling approach that results in weighted max-min fair allocation of extra slots, achieves zero rejection for admissible demands, and minimizes the maximum percentage rejection of any connection. We also propose the Minimum Rejection Algorithm, which minimizes total rejection but treats non-critical connections in a fair manner. Finally, we introduce a feedback control system based on Smith’s principle that reduces the effect of prediction errors and increases the speed of the response to the sudden changes in traffic arrival rates. Simulations performed using OPNET Modeler explore the performance of the scheduling and control algorithms we propose.

Challenges for MPLS in optical network restoration

Previous standards proposals have focused on extending IP-based MPLS protocols to optical networks. These proposals have concentrated on provisioning optical connections. However, a key expectation of the optical network is that it will offer fast restoration capability, competitive in performance to SONET rings. To meet this expectation, there are key features that need to be added to the current proposals to extend MPLS for the optical network. This article discusses some of these key requirements     

MPLS technology in wireless networks

Recently, there has been increasing demand for Multi-protocol label switching (MPLS) technology in most internet service provider networks. The application of MPLS technology in wireless networking is evolving. Therefore, next generation wireless networks are required to have IP mobility solutions with high reliability, low-latency handoffs, and trustworthy security. In this paper, we propose a novel multi-path mobility scheme for fast handoff to achieve these requirements. The scheme is based on MPLS multi-path forwarding and network coding based on modulo-p Galois finite field GF(p = 2 ⁿ ) arithmetic. The simulation results show that our proposed approach scales well to fulfill fast handoff/handover performance while providing security for transmitted data with minor bandwidth overhead.     

宽带综合IP网的MPLS技术及其应用

多协议标记交换（MPLS）技术是综合利用网络第二层交换技术的有效性和第三层IP路由的灵活性等优点而产生的多层交换技术。通过在传统的IP包里加入标记，使路由转发依赖于标记，大大地提高IP包的转发速度，同时可使传统IP网络具有服务质量（QoS）能力。现主要分析MPLS体系结构，指出MPLS的一些应用。     

QoS routing for MPLS networks employing mobile agents

The implementation of new networking technologies, such as multiprotocol label switching and differentiated services, will introduce powerful features to the near-future Internet backbone, making a significant contribution to the overall end-to-end provision of quality of service. However, to achieve such an improvement these technologies require not only effective support from current routing algorithms, but also enhanced capabilities, which are currently being developed. To contribute to this development, a novel and powerful scheme is introduced in this article that provides a means of supporting QoS routing through the use of mobile software agents. Specifically, we describe the use of mobile agents to efficiently realize multipoint-to-point routing trees by means of the Wave paradigm, while satisfying the QoS requirements of the set of traffic streams involved in the process. Both benefits and important issues to be considered when using mobile agent schemes in QoS routing are further stressed     

Service convergence using MPLS multiservice networks

Enterprises are increasingly using virtual private networks to interconnect remote sites. Traditionally, service providers have used ATM core networks to deliver layer 2 services such as frame relay, ATM, or TDM private lines, which enterprise customers have then used to build their corporate network infrastructure. Such services account for the majority of data service revenues today. However, pressure has increased on service providers to combine increased flexibility with reduced costs in the context of a highly dynamic telecommunications market. Service providers also need to generate new revenues from their IP network infrastructure, through new opportunities such as IP VPNs and virtual private LAN services, while simultaneously achieving operational efficiencies through the convergence of all of their services on a common MPLS backbone. New access and metro network technologies, such as Ethernet, are also emerging that can be used to deliver these new services to enterprise customers alongside ATM and frame relay access. This must be achieved while also supporting existing technologies such as ATM, which continue to deliver highly profitable services. This article discusses the technical challenges in meeting the often conflicting requirements of delivering both traditional layer 2 services and new layer 3 services on a converged MPLS network. We show how both network and service interworking are required, and how these must operate at the user, control, and management planes to enable profitable services to be delivered over the new converged network. The different solutions being defined in the standards bodies are described, and the distinct scenarios they address are explained.     

QoS routing granularity in MPLS networks

This study investigates how constraint-based routing decision granularity significantly affects the scalability and blocking performance of QoS routing in an MPLS network. Coarse granularity, such as per-destination, has lower storage and computational overheads but is only suitable for best effort traffic. On the other hand, fine granularity, such as per-flow, provides lower blocking probability for bandwidth requests, but requires a huge number of states and high computational cost. To achieve cost-effective scalability, this study proposes using hybrid granularity schemes. The overflowed cache of the per-pair/flow scheme adds a per-pair cache and a per-flow cache as the routing cache, and performs well in blocking probability. The per-pair/class scheme groups the flows into several paths using routing marks, thus allowing packets to be label-forwarded with a bounded cache     

MPLS网络中DiffServ组播算法

文章提出一种在多协议标签交换(MPLS)网络中边界路由器实现组播和区分服务的算法,该算法利用处于分支点的边界路由器之间的标签交换路径来传输组播数据包,同时引入了信息管理点,用于计算、管理和调整组播树,实现全域的服务质量.描述了算法的具体细节和实现原理,也评价了该算法的可行性和优越性.     

MPLS VPN核心网的邻居保护方案

VPN(虚拟专用网)的安全性是用户首要关注的问题。分析了MPLS(多协议标签交换)VPN的安全保障机制和核心网可能遇到的安全威胁,在此基础上提出了安全改进方案并进行了实验验证。在核心网中,BGP(边界网关协议)邻居间采用MD5(信息摘要算法第五版)鉴权机制,LDP(标签分发协议)邻居间采用GTSM(通用TTL安全机制)。该方案同时考虑了安全性与处理复杂度问题,经验证可以很好地加强MPLS VPN核心网的安全性。     

Distributed schemes for diverse path computation in multidomain MPLS networks

MPLS is currently used by several JSPs to carry some high-value traffic components, such as telephony over IP trunks and VPNs. For this type of traffic, service availability is a critical QoS dimension that needs to be protected from network failures. With MPLS-TE, this can be achieved by means of path protection schemes, where active and backup LSPs are routed along diverse paths. Besides protection, path diversity can be exploited for load balancing, another common means of QoS improvement. In order to preserve other QoS requirements, the paths must meet certain constraints (e.g., bandwidth availability, low load) and/or minimize some metric (e.g., hop count). This requires the ability to establish path diversity in an optimal way. In many cases of practical interest, the QoS traffic has an interdomain scope. This is the case for ToIP and VPN traffic between different carriers, or between different ASs owned by the same carrier, as found, for example, after corporate acquisitions or mergers. Therefore, path diversity is a requirement for interdomain traffic engineering. In this work we address path diversity in a multidomain network, where individual domains are capable of connection-oriented forwarding and endowed with an MPLS-TE control plane. For administrative and/or scalability reasons intradomain routing information is not disseminated externally, so dynamic path computation must be achieved by a distributed scheme based on interdomain collaboration. We briefly describe three alternative schemes recently proposed for interdomain diverse path computation, and quantitatively assess their performance with simulations over real ISP topologies.     

An efficient and flexible MPLS signaling framework for mobile networks

Multiprotocol Label Switching (MPLS) has gained momentum in recent years as an effective tool to provide Quality of Service (QoS) in a variety of networks. This has in turn created active interest in the area of recovery in MPLS based networks. A number of recovery schemes for MPLS domains have been proposed in recent years. However, the current schemes lack support for recovery in dynamic network topologies. In this paper, a new flexible signaling protocol for LSP rerouting in dynamic network environments is introduced. The signaling protocol recovers from node and link failures reactively, taking a local approach to LSP reestablishment. The performance of the signaling protocol is evaluated through simulations. Results indicate that the protocol can effectively and efficiently handle rerouting in dynamic networks with a low protocol signaling overhead as compared to contemporary MPLS rerouting protocols. This would enable the MPLS based IP-QoS support mechanisms to extend to dynamic network topologies. A preliminary version of this work was presented at the 2004 IEEE International Conference on Communications, Paris. Ramprasad Nagarajan has received his B.E. degree in Electronics and Telecommunications from Pune University, India in 1999. He received his M.S. degree in Electrical and Computer Engineering from the Ohio State University, Columbus, OH in 2004. Currently, he is a Wireless Network Engineer in Nortel Networks, specializing in the area of network architecture and design of wireless packet core networks. Ramprasad’s current research interests include the study of wireless network evolution trends, next generation wireless networks, network capacity planning, performance analysis, and optimization. He is a member of the IEEE. Eylem Ekici has received his B.S. and M.S. degrees in Computer Engineering from Bogazici University, Istanbul, Turkey, in 1997 and 1998, respectively. He received his Ph.D. degree in Electrical and Computer Engineering from Georgia Institute of Technology, Atlanta, GA, in 2002. Currently, he is an assistant professor in the Department of Electrical and Computer Engineering of the Ohio State University, Columbus, OH. Dr. Ekici’s current research interests include wireless sensor networks, vehicular communication systems, next generation wireless systems, and space-based networks, with a focus on routing and medium access control protocols, resource management, and analysis of network architectures and protocols. He also conducts research on interfacing of dissimilar networks.     

Edge distributed admission control in MPLS networks

This paper proposes a novel approach for admission control in traffic engineered data networks, which applies at network edges by means of dynamic thresholds evaluated on the basis of network status. The proposed method is described with focus on IP/MPLS networks, but it actually applies as well to a variety of scenarios, such as ATM or generalized MPLS. The proposed solution allows more efficient usage of network resources, especially at medium/high load, and increased robustness of the network.     

A scalable QoS routing model for diffserv over MPLS networks

In this paper, we present a new Quality of Service (QoS) routing model for Differentiated Services (Diffserv) over Multiprotocol Label Switching (MPLS) networks. We use a pre-established multi-path model in which several MPLS label switching paths (LSPs) are established between each ingress-egress router pair in advance. Ingress routers perform per-request admission control and bulk-type resource reservation based on the resource availability on the associated LSPs. We use a utilization-based dynamic load balancing scheme to increase resource utilization across LSPs. The proposed model increases signaling and state scalability in the network core. It also provides hard QoS guarantees and minimizes admission control time. The experimental results verify the achievements of our model under various network topologies and traffic conditions.     

Mobility management support and performance analysis for wireless MPLS networks

Multi‐Protocol Label Switching (MPLS) is deployed in the Internet backbone to support service differentiation and traffic engineering. In recent years, there has been interest in extending the MPLS capability to wireless access networks for mobility management support. In this paper, we present analysis of Micro Mobile MPLS, a new micro‐mobility management scheme which integrates the Mobile IP and MPLS protocols by using two‐level hierarchy architecture. Our proposal supports two protocol variants. First, the fast handoff process, which anticipates the LSP procedure set‐up with neighboring locations where a mobile node (MN) may move to, is provided to reduce service disruption. Second, a new mechanism based on the forwarding chain concept is proposed to track efficiently the host mobility within a domain. This concept can significantly reduce registration update costs and provide low handoff latency. Analytical models are developed and simulations are conducted to justify the benefits of our proposed mechanisms. Copyright © 2006 John Wiley & Sons, Ltd.     

Issues on loop prevention in MPLS networks

In multiprotocol label switching (MPLS) networks, data packets are forwarded through label-switched paths (LSPs) which are set up using a label distribution protocol. Since any label distribution protocol makes use of information obtained from the layer 3 routing protocol, and the routing protocol may not be loop-free, there is a possibility of an LSP forming a loop. This article focuses on MPLS loop prevention by which LSPs are prevented from forming loops. Especially, two loop prevention algorithms that have been proposed to the IETF are simulated to investigate the number of control messages required for setting up or reconfiguring LSPs over an actual routing protocol     

MPLS and traffic engineering in IP networks

Rapid growth and increasing requirements for service quality, reliability, and efficiency have made traffic engineering an essential consideration in the design and operation of large public Internet backbone networks. Internet traffic engineering addresses the issue of performance optimization of operational networks. A paramount objective of Internet traffic engineering is to facilitate the transport of IP traffic through a given network in the most efficient, reliable, and expeditious manner possible. Historically, traffic engineering in the Internet has been hampered by the limited functional capabilities of conventional IP technologies. Recent developments in multiprotocol label switching (MPLS) and differentiated services have opened up new possibilities to address some of the limitations of the conventional technologies. This article discusses the applications of MPLS to traffic engineering in IP networks     

Flow-based load-balancing architecture for the agile all-photonic network

A novel routing architecture that balances incoming Internet flows over the agile all-photonic network (AAPN) is proposed. The architecture is based on the adaptive highest random weight (adaptive HRW) algorithm proposed to design load-balanced Internet routers. Extensive numerical evaluation of static and adaptive variations of the routing architecture is studied, and their effect on the network performance in terms of packet drop and flow remapping is presented. The architecture can be seen as a combination of adaptive core node scheduling and adaptive load balancing at the edge nodes. It is stateless and can compute routes quickly based on the packet flow identifier.