QoS aware traffic grooming and integrated routing on IP over WDM networks

In this article, we consider traffic grooming and integrated routing in IP over WDM networks. The challenges of this problem come from jointly considering traffic grooming, IP routing, and lightpath routing and wavelength assignment (RWA). Due to the high bandwidth of optical fiber, there exists a mismatch between the capacity needed by an IP flow and that provided by a single lightpath. Traffic grooming is therefore used to increase the network utilization by aggregating multiple IP flows in a single lightpath. However, traffic grooming incurs additional delays that might violate Quality-of-Service (QoS) requirements of IP users. In this work, the tradeoff between traffic grooming and IP QoS routing is well-formulated as a mixed integer and linear optimization problem, in which the revenue from successfully provisioning IP paths is to be maximized. Problem constraints include IP QoS, routing, optical RWA, and the WDM network capacity. We propose a novel Lagrangean relaxation (LGR) algorithm to perform constraint relaxation and derive a set of subproblems. The Lagrangean multipliers are used in the proposed algorithm to obtain a solution in consideration of grooming advantage and resource constraints simultaneously. Through numerical experiments and comparisons between the proposed algorithm and a two-phase approach, LGR outperforms the two-phase approach under all experimental cases. In particular, the improvement ratio becomes even more significant when the ratio of IP flow to the wavelength capacity is smaller.     

A next-generation optical regional access network

We describe an optical regional access network which combines electronic IP routing with intelligent networking functionality of the optical WDM layer. The optical WDM layer provides such networking functions as network logical topology reconfiguration, optical flow switching to offload traffic and bypass IP routers, wavelength routing of signals, protection switching and restoration in the optical domain, and flexible network service provisioning by reconfigurable wavelength connectivity. We discuss key enabling technologies for the WDM layer and describe their limitations. The symbiosis of electronic and optical WDM networking functions also allows support for heterogeneous format traffic and will enable efficient gigabit-per-second user access in next-generation Internet networks     

CATZ: Time-Zone-Aware Bandwidth Allocation in Layer 1 VPNs

The layer 1 virtual private network framework has emerged from the need to enable the dynamic coexistence of multiple circuit-switched client networks over a common physical network infrastructure. Such a VPN could be set up for an enterprise with offices across a wide geographical area (e.g., around the world or by a global ISP). Additionally, emerging IP over optical WDM technologies let IP traffic be carried directly over the optical WDM layer. Thus, different VPNs can share a common optical WDM core, and may demand different amounts of bandwidth at different time periods. This type of operation would require dynamic and reconfigurable allocation of bandwidth. This article evaluates the state of the art in layer 1 VPNs in the context of globally deployable optical networks and cost-efficient dynamic bandwidth usage. While exploiting the dynamism of IP traffic in a global network in which the nodes are located in different time zones, we study different bandwidth allocation methods for setting up a worldwide layer 1 VPN. We propose and investigate the characteristics of a cost-efficient bandwidth provisioning and reconfiguration algorithm, called capacity allocation using time zones (CATZ)     

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.     

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.     

Performance analysis of multicast routing and wavelength assignment protocol with dynamic traffic grooming in WDM networks

The need for on‐demand provisioning of wavelength‐routed channels with service‐differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol (IP) network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing (WDM) technologies. Because of the availability of ultra long‐reach transport and all‐optical switching, the deployment of all‐optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video‐on‐demand systems, real‐time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment (RWA). The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call‐blocking probability. The dynamic traffic‐grooming problem in wavelength‐routed networks is generally a two‐layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability. Copyright © 2011 John Wiley & Sons, Ltd.     

On Hierarchical Traffic Grooming in WDM Networks

The traffic grooming problem is of high practical importance in emerging wide-area wavelength division multiplexing (WDM) optical networks, yet it is intractable for any but trivial network topologies. In this work, we present an effective and efficient hierarchical traffic grooming framework for WDM networks of general topology, with the objective of minimizing the total number of electronic ports. At the first level of hierarchy, we decompose the network into clusters and designate one node in each cluster as the hub for grooming traffic. At the second level, the hubs form another cluster for grooming intercluster traffic. We view each (first- or second-level) cluster as a virtual star, and we present an efficient near-optimal algorithm for determining the logical topology of lightpaths to carry the traffic within each cluster. Routing and wavelength assignment is then performed directly on the underlying physical topology. We demonstrate the effectiveness of our approach by applying it to two networks of realistic size, a 32-node, 53-link topology and a 47-node, 96-link network. Comparisons to lower bounds indicate that hierarchical grooming is efficient in its use of the network resources of interest, namely, electronic ports and wavelengths. In addition to scaling to large network sizes, our hierarchical approach also facilitates the control and management of multigranular networks.      

Dynamic provisioning of low-speed unicast/multicast traffic demands in mesh-based WDM optical networks

This paper addresses the problem of dynamically provisioning both low-speed unicast and multicast connection requests in mesh-based wavelength division multiplexing (WDM) optical networks. Several routing/provisioning schemes to dynamically provision both unicast and multicast connection requests are presented. In addition, a constraint-based grooming strategy is devised to utilize the overall network resources as efficiently as possible. Based on this strategy, several different sequential multicast grooming heuristics are first presented. Then, we devise a hybrid grooming approach and combine it with sequential approaches to achieve a grooming scheme that is biased toward serving multicast traffic demands in comparison with all other sequential grooming approaches. To achieve our objective, we decompose the problem into four subproblems: 1) routing problem; 2) light-tree-based logical-topology-design problem; 3) provisioning problem; and 4) traffic-grooming problem. The simulation results of the proposed schemes are compared with each other and with those of conventional nongrooming approaches. To the best of our knowledge, this is the first detailed paper to address and examine the problem of grooming dynamic multicast traffic demands.     

Dynamic grooming in IP over optical networks based on the overlay architecture

This paper defines a formal framework for the definition of dynamic grooming policies in IP over optical networks. The formal framework is then specialized for the Overlay Architecture, where the control plane of the IP (Internet protocol) and optical levels are separated, and no information is shared between the two.We define a family of grooming policies for the Overlay Architecture based on constraints on the number of hops and on the bandwidth sharing degree at the IP level, and we analyze the performances as a function of the grooming parameters in regular and irregular topologies.Results are derived using realistic traffic models that depart from the circuit-like traffic traditionally used in grooming studies.     

Demand assigned capacity management (DACM) in IP over optical (IPO) networks

The demand assigned capacity management (DACM) problem in IP over optical (IPO) network aims at devising efficient bandwidth replenishment schedules from the optical domain conditioned upon traffic evolution processes in the IP domain. A replenishment schedule specifies the location, sizing, and sequencing of link capacity expansions to support the growth of Internet traffic demand in the IP network subject to economic considerations. A major distinction in the approach presented in this paper is the focus of attention on the economics of "excess bandwidth" in the IP domain, which can be viewed as an inventory system that is endowed with fixed and variable costs and depletes with increase in IP traffic demand requiring replenishment from the optical domain. We develop mathematical models to address the DACM problem in IPO networks based on a class of inventory management replenishment methods. We apply the technique to IPO networks that implement capacity adaptive routing in the IP domain and networks without capacity adaptive routing. We analyze the performance characteristics under both scenarios, in terms of minimizing cumulative replenishment cost over an interval of time. For the non-capacity adaptive routing scenario, we consider a shortest path approach in the IP domain, specifically OSPF. For the capacity adaptive scenario, we use an online constraint-based routing scheme. This study represents an application of integrated traffic engineering which concerns collaborative decision making targeted towards network performance improvement that takes into consideration traffic demands, control capabilities, and network assets at different levels in the network hierarchy.     

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     

Logical topology design for IP rerouting: ASONs versus static OTNs

IP-based backbone networks are gradually moving to a network model consisting of high-speed routers that are flexibly interconnected by a mesh of light paths set up by an optical transport network that consists of wavelength division multiplexing (WDM) links and optical cross-connects. In such a model, the generalized MPLS protocol suite could provide the IP centric control plane component that will be used to deliver rapid and dynamic circuit provisioning of end-to-end optical light paths between the routers. This is called an automatic switched optical (transport) network (ASON). An ASON enables reconfiguration of the logical IP topology by setting up and tearing down light paths. This allows to up- or downgrade link capacities during a router failure to the capacities needed by the new routing of the affected traffic. Such survivability against (single) IP router failures is cost-effective, as capacity to the IP layer can be provided flexibly when necessary. We present and investigate a logical topology optimization problem that minimizes the total amount or cost of the needed resources (interfaces, wavelengths, WDM line-systems, amplifiers, etc.) in both the IP and the optical layer. A novel optimization aspect in this problem is the possibility, as a result of the ASON, to reuse the physical resources (like interface cards and WDM line-systems) over the different network states (the failure-free and all the router failure scenarios). We devised a simple optimization strategy to investigate the cost of the ASON approach and compare it with other schemes that survive single router failures.     

Traffic grooming,routing, and wavelength assignment in an optical WDM mesh networks based on clique partitioning

In wavelength routed optical networks, the number of wavelength channels is limited due to several constraints and each wavelength as well as each lightpath support traffic in the Gbps range. On the other hand, the traffic requested by an individual connection is still in the Mbps range. Therefore, to utilize the network resources (such as bandwidth and transceivers) effectively, several low-speed traffic streams have to be efficiently groomed or multiplexed into one or more high-speed lightpaths. The grooming problem of a static demand is considered as an optimization problem. In this work, we have investigated the traffic grooming problem with the objective of maximizing the network throughput for wavelength-routed mesh networks and map this problem to the clique partitioning problem. We have proposed an algorithm to handle general multi-hop static traffic grooming based on the clique partitioning concept. The efficiency of our approach has been established through extensive simulation on different sets of traffic demands with different bandwidth granularities for different network topologies and compared the approach with existing algorithms.     

Optical resources provisioning: multipoint‐to‐point lightpaths mapping in all‐optical networks

In wavelength‐division multiplexing (WDM) optical networks, the bandwidth request of a traffic stream can be much lower than the capacity of a lightpath. Efficiently grooming low‐speed connections onto high‐capacity lightpaths will improve the network throughput and reduce the network cost. In this paper, we propose and evaluate a new concept of traffic aggregation in WDM mesh networks that aims to eliminate both the bandwidth under‐utilization and scalability concerns that are typical in all‐optical wavelength routed networks. This approach relies on the multipoint‐to‐point lightpath concept. In order to assess the efficiency of our proposal, all underlying network costs are compared. To achieve this aim, we devise a new provisioning algorithm to map the multipoint‐to‐point lightpaths in the network. Our results show that the proposed aggregation technique can significantly improve the network throughput while reducing its cost. Copyright © 2005 John Wiley & Sons, Ltd.     

基于层叠模型的动态组播业务疏导算法

流量疏导对于提高波分复用网络的利用率具有重要的意义.文章基于层叠模型的IP over WDM网络结构,研究了动态组播业务疏导问题,给出了两种动态组播业务疏导方法.仿真结果显示,在IP层和光层都计算最短路径来选取最短路径组建组播树的算法能够获得更低的阻塞率.     

Traffic engineering in multigranularity heterogeneous optical WDM mesh networks through dynamic traffic grooming

In this article we investigate the problem of efficiently provisioning connections of different bandwidth granularities in a heterogeneous WDM mesh network through dynamic traffic grooming schemes under traffic engineering principles. Due to the huge amount of traffic a WDM backbone network can support and the large geographic area it can cover, constructing and upgrading such an optical WDM network can be costly. Hence, it is extremely important for network operators to apply traffic engineering strategies to cost-effectively support different bandwidth granularity services using only the appropriate amount of network resources. This requires an optical WDM network to have multigranularity switching capability, and such a network tends to be a multivendor heterogeneous network. However, WDM network heterogeneity increases the difficulty and challenge of efficient traffic provisioning. In this article we present different TE issues that need to be carefully considered in such an optical WDM network, and propose possible solutions and extensions for the generalized multiprotocol label switching optical network control plane. We extend an existing generic graph model to perform efficient traffic grooming and achieve different TE objectives through simple shortest path computation algorithms. We show that our approach is very practical and very suitable for traffic engineering in a heterogeneous multigranularity optical WDM mesh network.     

Cost Comparison of Optical Circuit-Switched and Burst-Switched Networks

This paper examines the economic viability of two technologies—optical circuit-switched (OCS) networks and optical burst-switched (OBS) networks—in the core network. We analyze and dimension OCS network (OCSN) and OBS network (OBSN) architectures for a range of traffic demands given the constraints on the network element capacities. We investigate the effect of traffic grooming for both of these architectures. We evaluate these network architectures for a national core network in Australia in terms of their capital costs and packet-blocking probabilities. We observe that OBSNs with traffic grooming at the optical layer may become more cost effective than OCSNs with traffic grooming at both the IP and optical layers for the same quality of service in terms of blocking probability. The cost advantage of OBSNs over OCSNs grows as the capacity of the core network increases. Hence, among the all-optical networking options that do not involve buffering at the core, OBS appears to be an attractive option especially for high-capacity core networks.      

Investigations on combined XPM and FWM effects on optical pulse propagation in dynamic IP traffic over WDM networks

The influence of IP bursty traffic on combined nonlinear effects of XPM (cross phase modulation) and FWM (four-wave mixing) in IP over WDM networks are investigated and calculated by solving the nonlinear Schrodinger equation (NLSE) using a novel method under two conditions: on–off Poisson distributed IP traffic and self-similar traffic. Different eye diagrams are obtained under various IP traffic types and input optical powers. When the input power of a single channel is larger than 3 dBm, the effect of IP bursty traffic will deteriorate eye diagrams dramatically in a 40-channel WDM network. We also calculate the FWM powers and interchannel power distribution under different IP traffic loads. Based on the interchannel power distribution, we could find out which channels affect the probe channel seriously by the FWM effect. All these numerical results are useful for the Quality-of-Service (QoS) design, traffic grooming, lightpath routing, and wavelength assignment of IP over WDM networks.     

IPoverWDM光网络中基于滑动调度业务模型的节能业务量疏导算法研究(英文)

In this paper,we investigate on the problem of energy-efficient traffic grooming under sliding scheduled traffic model for IP over WDM optical networks,so as to minimize the total energy consumption of the core network.We present a two-layer auxiliary graph model and propose a new energyefficient traffic grooming heuristic named Two-Dimension Green Traffic Grooming(TDGTG) algorithm,which takes both space and time factors into consideration for network energy efficiency.We compare our proposed TDGTG algorithm with the previous traffic grooming algorithms for scheduled traffic model in terms of total energy consumption and blocking probability.The simulation results in three typical carrier topologies show the efficiency of our proposed TDGTD algorithm.     

Algorithms for multicast traffic grooming in WDM mesh networks

Several of the new applications in high-performance networks are of the multicast traffic type. Since such networks employ an optical network infrastructure, and since most of these applications require subwavelength bandwidth, several streams are usually groomed on the same wavelength. This article presents an account of recent advances in the design of optical networks for multicast traffic grooming in WDM mesh networks. The article addresses network design and session provisioning under both static and dynamic multicast traffic. Under static traffic conditions, the objective is to accommodate a given set of multicast traffic demands, while minimizing the implementation cost. Optimal and heuristic solution techniques for mesh network topologies are presented. Under dynamic traffic conditions, techniques for dynamic routing and session provisioning of multicast sessions whose objective is to minimize session blocking probabilities are explained. The article also presents a number of open research issues