NetScope: traffic engineering for IP networks

Managing large IP networks requires an understanding of the current traffic flows, routing policies, and network configuration. However, the state of the art for managing IP networks involves manual configuration of each IP router, and traffic engineering based on limited measurements. The networking industry is sorely lacking in software systems that a large Internet service provider can use to support traffic measurement and network modeling, the underpinnings of effective traffic engineering. This article describes the AT&T Labs NetScope, a unified set of software tools for managing the performance of IP backbone networks. The key idea behind NetScope is to generate global views of the network on the basis of configuration and usage data associated with the individual network elements. Having created an appropriate global view, we are able to infer and visualize the networkwide implications of local changes in traffic, configuration, and control. Using NetScope, a network provider can experiment with changes in network configuration in a simulated environment rather than the operational network. In addition, the tool provides a sound framework for additional modules for network optimization and performance debugging. We demonstrate the capabilities of the tool through an example traffic engineering exercise of locating a heavily loaded link, identifying which traffic demands flow on the link, and changing the configuration of intradomain routing to reduce the congestion     

Providing differentiated services for multi-class traffic in IP/MPLS over WDM networks

Providing differentiated services in IP/MPLS over WDM networks has attracted a lot of recent attention. This article extends the Path Inflation Control (PIC) policy recently proposed by us to provide differentiated services in IP/MPLS over WDM networks with traffic grooming. Three different algorithms are considered for provisioning differentiated services. The simulation results show that, with two of the three algorithms, the network cannot only provide differentiated services when the traffic load is high but also gives significantly lower blocking for the lower priority class traffic and for the overall traffic at low traffic loads.

MPLS advantages for traffic engineering

This article discusses the architectural aspects of MPLS which enable it to address IP traffic management. Specific MPLS architectural features discussed are separation of control and forwarding, the label stack, multiple control planes, and integrated IP and constraint-based routing. The article then discusses how these features address network scalability, simplify network service integration, offer integrated recovery, and simplify network management. Scalability is addressed through integrated routing enabling a natural assignment of traffic to the appropriate traffic engineering tunnels without requiring special mechanisms for loop prevention. Change is greatly reduced. The label stack enables an effective means for local tunnel repair providing fast restoration. Feedback through the routing system permits fast and intelligent reaction to topology changes. Service integration is simplified through a unified QoS paradigm which makes it simple for services to request QoS and have it mapped through to traffic engineering     

TEAM: A traffic engineering automated manager for DiffServ-based MPLS networks

In this article an automated manager called traffic engineering automated manager (TEAM) for DiffServ/MPLS networks is introduced, and its design and implementation details are discussed. TEAM is designed for complete automated management of an Internet domain. TEAM is an adaptive manager that provides the required quality of service to the users and reduces the congestion in the network. The former is achieved by reserving bandwidth resources for the requests and the latter by distributing the load efficiently. These goals are achieved by online measurements of the network state. TEAM is composed of a traffic engineering tool (TET), which adaptively manages the bandwidth and routes in the network, a measurement and performance evaluation tool (MPET), which measures important parameters in the network and inputs them to the TET, and a simulation tool (ST), which may be used by TET to consolidate its decisions. These three tools work in synergy to achieve the desired network operation objectives. The experimental results demonstrate the efficiency of TEAM as a network manager in different and unpredictable traffic conditions at the expense of a limited increase in the computational complexity and costs.     

New preemption policies for DiffServ-aware traffic engineering to minimize rerouting in MPLS networks

The preemption policy currently in use in MPLS-enabled commercial routers selects LSPs for preemption based only on their priority and holding time. This can lead to waste of resources and excessive number of rerouting decisions. In this paper, a new preemption policy is proposed and complemented with an adaptive scheme that aims to minimize rerouting. The new policy combines the three main preemption optimization criteria: number of LSPs to be preempted, priority of the LSPs, and preempted bandwidth. Weights can be configured to stress the desired criteria. The new policy is complemented by an adaptive scheme that selects lower priority LSPs that can afford to have their rate reduced. The selected LSPs will fairly reduce their rate in order to accommodate the new high-priority LSP setup request. Performance comparisons of a nonpreemptive approach, a policy currently in use by commercial routers, and our policies are also investigated.     

Applying saturated cut method for dynamic traffic grooming in IP/MPLS over WDM networks

One of the most important tasks for dynamic traffic grooming in IP/MPLS over WDM networks is to decide when and where to set up new lightpaths to provide bandwidth for the IP/MPLS layer. In this paper, we adapt the conventional saturated cut method to enhance the lightpath establishment capability of various traffic grooming policies proposed earlier. Heuristic modifications are also presented which provide almost the same level of performance with much lower complexity.     

On efficient traffic engineering with DV-based routing protocols in DiffServ-aware IP networks

In this paper, an approach to efficient traffic engineering in the DiffServ-aware network environment is proposed. We focus to distance vector-based routing protocols, considering both modifications of routing protocols needed to support path differentiation and traffic engineering methods relied on adjusting multiple per-link costs to particular network conditions. Further, a method for determining link cost of particular traffic class, as a unique generic function of the single generalized performance metric has been proposed. In order to achieve efficient traffic engineering, possible approximations of generic cost function and mappings of generalized to particular metrics have been proposed. Finally, prerequisites for implementing proposed approach have been discussed in the context of different administrative policies and time scales of their application.     

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。     

An efficient mechanism for dynamic multicast traffic grooming in overlay IP/MPLS over WDM networks

This paper proposes an efficient overlay multicast provisioning (OMP) mechanism for dynamic multicast traffic grooming in overlay IP/MPLS over WDM networks. To facilitate request provisioning, OMP jointly utilizes a data learning (DL) scheme on the IP/MPLS layer for logical link cost estimation, and a lightpath fragmentation (LPF) based method on the WDM layer for improving resource sharing in grooming process. Extensive simulations are carried out to evaluate the performance of OMP mechanism under different traffic loads, with either limited or unlimited port resources. Simulation results demonstrate that OMP significantly outperforms the existing methods. To evaluate the respective influences of the DL scheme and the LPF method on OMP performance, provisioning mechanisms only utilizing either the IP/MPLS layer DL scheme or the WDM layer LPF method are also devised. Comparison results show that both DL and LPF methods help improve OMP blocking performance, and contribution from the DL scheme is more significant when the fixed routing and first-fit wavelength assignment (RWA) strategy is adopted on the WDM layer. Effects of a few other factors, including definition of connection cost to be reported by the WDM layer to the IP/MPLS layer and WDM-layer routing method, on OMP performance are also evaluated.     

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。     

Multisource multicasting in IP/MPLS over WDM networks

Multicasting applications such as multimedia conferencing, online multiplayer interactive games, and distance learning are becoming increasingly popular. With multiprotocol label switching, Internet protocol networks can offer quality of service and traffic engineering capabilities. This article introduces several approaches for multisource multicast sessions in the context of IP over WDM networks and evaluates their performance in terms of blocking probability, time complexity, and memory consumption. Our simulation study shows that among all the approaches, the newly proposed approach, known as one Bidirectional Tree with Just enough bandwidth reserved on each link of the tree, achieves the best overall performance.     

MPLS流量工程及基于约束路由计算的研究

论述了 MPLS 网络的架构及其对流量工程的支持,研究了基于 MPLS 流量工程要解决的几个主要问题：如何把数据包映射为转发等价类等,并对其中最重要的一个——通过 LSP 把流量中继映射到实际网络拓扑,提出了一种约束最短路径优先算法的实现方法。     

一个MPLS流量工程的QoS路由算法

传统Internet中,多媒体流量和实时电子商务应用会引起品质的降低。这可以通过在网络中动态地建立有带宽和延迟保证的路径来解决。讨论了基本算法,如最宽最短路径（WSP）,复杂一些的算法如最小冲突路由（MIRA）或基于剖面的路由。提出了一个新的MPLS网络中的Diff-Serv流的QoS路由算法。这个方法在维持网络效率的同时,有效地传输多媒体流量。     

面向卫星网络的流量工程路由算法

针对卫星网络链路长时延、拓扑时变等特征,将链路传输时延引入并基于MPLS网络中源-目的节点对已知这一先验知识,提出了一种面向卫星网络的MPLS流量工程路由算法。该算法基于卫星网络时变拓扑模型的卫星拓扑快照,定义链路初始权重为链路剩余带宽、传输时延的综合函数,在为当前节点对建路时考虑其余节点对将来建路的可能需求计算链路的关键度,在此基础上通过链路权重的动态调整及延期选用实现流量工程,从而优化卫星网络的链路利用。实验表明,此算法在请求拒绝数、吞吐量、平均跳数及平均时延等方面性能都有较理想的提升。     

RATES: a server for MPLS traffic engineering

It has been suggested that one of the most significant reasons for multiprotocol label switching (MPLS) network deployment is network traffic engineering. The goal of traffic engineering is to make the best use of the network infrastructure, and this is facilitates by the explicit routing feature of MPLS, which allows many of the shortcomings associated with current IP routing schemes to be addressed. This article describes a software system called Routing and Traffic Engineering Server (RATES) developed for MPLS traffic engineering. It also describes some new routing ideas incorporated in RATES for MPLS explicit path selection. The RATES implementation consists of a policy and flow database, a browser-based interface for policy definition and entering resource provisioning requests, and a Common Open Policy Service protocol server-client implementation for communicating paths and resource information to edge routers. RATES also uses the OSPF topology database for dynamically obtaining link state information. RATES can set up bandwidth-guaranteed label-switched (LSPs) between specified ingress-egress pairs. The path selection for LSPs is on a new minimum-interference routing algorithm aimed at making the best use of network infrastructure in an online environment where LSP requests arrive one by one with no a priori information about future requests. Although developed for an MPLS application, the RATES implementation has many similarities in components to an intradomain differentiated services bandwidth broker     

Optimizing IP networks in a hybrid IGP/MPLS environment

In this paper, we consider a traffic engineering (te) approach toip networks in a hybridigp/mpls environment. Thoughigp (Interior Gateway Protocol) routing has proven its scalability and reliability, effective traffic engineering has been difficult to achieve in public IP networks because of the limited functional capabilities of conventionalip technologies.mpls (Multi-Protocol Label Switching) on the one hand enhances the possibility to engineer traffic onip networks by allowing explicit routes. But on the other hand it suffers from the scalability (n-square) problem. Hybridigp/mpls approaches rely onip native routing as much as possible and usempls only if necessary. In this work we propose a novel hybrid traffic engineering method based on genetic algorithms, which can be considered as an offlinete approach to handle long or medium-term traffic variations in the range days, weeks or months. In our approach the maximum number of hops anlsp (Label Switched Path) may take and the number oflsps which are applied solely to improve the routing performance, are treated as constraints due to delay considerations and the complexity of management. We apply our method to the German scientific network (b-win) for which a traffic matrix is available and also to some other networks with a simple demand model. We will show results comparing this hybridigp/mpls routing scenario with the result of pureigp routing and that of a full meshmpls with and without traffic splitting.     

一种基于跳数和时延的MPLS自适应流量工程算法

提出了一种基于跳数和时延的MPLS自适应流量工程算法，该算法根据LSP的跳数和时延来进行流量分配，从而减少由传统路由算法而引起的网络拥塞，优化网络资源的利用。仿真结果表明，该算法简单易行，性能良好。     

跨越不同容量设置DWDM网络的动态IP/DWDM综合路由算法研究

IP/DWDM网络的综合路由中的一个重要的研究问题就是如何对跨越不同DWDM网络的IP路由进行综合路由,特别是当两个DWDM网络的容量设置不同时。本文着重解决的就是如何对从单波长带宽大的网络进入单波长带宽小的网络传输的IP业务的综合路由问题。根据尽量鼓励对波长链路的带宽进行完全使用,以减小波长链路带宽碎片的原则,我们提出了两种解决算法:1 n 算法和 m n算法。仿真结果对两种算法的效率和性能进行了测试。     

基于IP/MPLS网络的动态业务流量矩阵测量模型

IP网络动态业务流量矩阵的测量是业务量工程研究中的一个难点,本文提出了一种面向IP/MPLS骨干网络的基于LSP级的动态业务流量矩阵测量模型。该模型能够获取网络边界处对应于每一条LSP的路径转发信息,并根据每一条LSP上的测量结果,计算得知全网的业务流量矩阵。文中证明该测量模型是可行的,并给出了相关的算法及其性能分析。模型的优点是测量只在网络边界处进行而不涉及网络核心,故引起的网络开销较小。另外模型所需的算法复杂度低,仿真结果显示测量模型是有效的。     

IP network configuration for intradomain traffic engineering

The smooth operation of the Internet depends on the careful configuration of routers in thousands of autonomous systems throughout the world. Configuring routers is extremely complicated because of the diversity of network equipment, the large number of configuration options, and the interaction of configuration parameters across multiple routers. Network operators have limited tools to aid in configuring large backbone networks. Manual configuration of individual routers can introduce errors and inconsistencies with unforeseen consequences for the operational network. In this article we describe how to identify configuration mistakes by parsing and analyzing configuration data extracted from the various routers. We first present an overview of IP networking from the viewpoint of an Internet service provider and describe the kinds of errors that can appear within and across router configuration files. To narrow the scope of the problem, we then focus our attention on the configuration commands that relate to traffic engineering-tuning the intradomain routing protocol to control the flow of traffic through the ISP network. We present a case study of a prototype tool, developed in collaboration with AT&T IP Services, for checking the configuration of the AT&T IP Backbone and providing input to other systems visualization and traffic engineering