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Network Planning and Optimization ToolsGetting the Most out of IP-Centric Networks

Network evolution to new services and the widespreadadoption of IP pose new challenges for networkoperations such as network dimensioning, planning, andengineering.

On the one hand, operators have to rapidly deploy newservices on a converged network, making sure that theQuality of Services (QoS) and Service Level Agreement(SLA) are fulfilled. These data-oriented new servicesgenerate a wide variety of traffic profiles, characterizedby dynamics on a broad time-scale.

To answer the above constraints, carriers have to takeadvantage of new networking technologies. And thesehave to be able to provide their infrastructure with a highlevel of flexibility: a combination of packet-and-circuitswitching, distributed control plane, multilayer networks,carrier-grade packet transport, supporting multipleservices such as IP/MPLS, Ethernet, and legacy.

Carriers need to effectively address the above concernto optimize their CAPEX (through proper equipmentdimensioning) and OPEX (through streamlineddeployment of services, pro-active maintenanceoperations, etc.). In this context, network simulations andoptimization tools adapted to the new challengescould provide valuable support, allowing:

accurate modeling of network behavior;

effective planning of network extensions:evaluate/compare new technologies;accurately identify the portions of thenetwork to extend or upgrade; validate

proposed network evolution beforeimplementation;

support of Quality of Service, fault andService Level Agreement management:predict feasibility/impact of new services orSLAs, validate QOS and restoration policies;

support of network, traffic and policiesengineering: optimization and validation oftraffic engineering strategies to optimize resourceand fulfil SLAs.

As a result of several years of experience in networkdesign, Alcatels research has developed a tool chain for

network dimensioning, real-time simulation and trafficand network engineering optimization. In addition to

being valuable for analyzing and benchmarking forward-looking proposals, these tools can also be used tosupport the tendering process as well as allow Alcatel toprovide its customers with more complete support inengineering and optimizing their networks.

As Ethernet becomes widely deployed in carrier networks,there is a need for network and traffic engineering toolsspecifically tailored to Ethernet networks. COMET is aflexible and easy-to-use traffic engineering tool for MetroEthernet networks. It enables network operators toachieve proper network configuration and efficientresource utilization. COMET implements a complete setof optimization algorithms to assist operators inmanaging bridged Ethernet networks. It can be used tooptimally configure STP parameters, form the actual treeinstances, and map VLANs intelligently into the differentspanning tree instances for load balancing.

The COMET tool also helps optimizing MPLS/GMPLS

networks and consequently facilitates the transition fromconnectionless to connection-oriented networks. Itprovides computation of primary and protection path andoptimal load balancing.

Figure 1: Alcatel COMET VLAN mapping optimization results. Multiplespanning trees help mitigate link over-utilization

Furthermore, COMET provides the ability to performwhat-if analysis, where the network operator can study

different network configurations, analyze the impact ofnetwork failures, or examine network growth.

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Two complementary dimensioning and optimization toolsare used for the design of multilayer networks consistingof IP/MPLS routers and transport equipments. The

Forwarding Adjacency Builder (FAB) focuses onoptimizing topologies, while networks IP enables theconfiguration of network elements and performs detailedcost analysis.

FORWARDING ADJACENCYBUILDER (FAB)

The main purpose of the Forwarding Adjacency Builder(FAB) is to design virtual topologies and dimensionmultilayer resilient networks. From IP/MPLS over SDHoverlay networks to Multi Service Transport Platform-based networks, the FAB supports a variety ofpacket/frame and transport technology integrationmodels. The FAB can both realistically and accurately

estimate bandwidth needs between router pairs. Facedwith the ever increasing traffic volume, network operatorsneed to either upgrade their IP/MPLS infrastructure orintroduce a flexible transport network to offload transittraffic from routers where it is unnecessarily routed atsuch fine granularity. For the latter option, the FAB helpsfinding an optimized virtual topology, i.e. the set ofconnections provided by the transport network andneeded between router pairs. In this way, it achieves aresilient and globally optimized multilayer network. Itaddresses the trade-off between direct switching of biggergranularities (to save costly ports in the upper layers), andmulti-hopping (to increase efficiency of resource filling).

Significant gains in network equipment cost by suchoptimization have been demonstrated on typical real-usecases of customer networks.

NETWORKS IP

Networks IP is a multi-layer planning and dimensioningtool intended for IP/MPLS and subjacent SDH/WDM/OTHtransport layers. The original version is available fromDetecon and is being extended by Alcatels research toinclude support for statistical multiplexing through newalgorithms, algorithms for wavelength assignment, aswell as models of Alcatels products. It supports allplanning steps, from analysis of the current network

status, capacity planning and cost analysis to detailednetwork device configurations. The required capacities ineach network layer can be determined by what-ifanalysis of link or device failures. Its output consists ofdetailed technical system and device configurations (e.g.IP routing tables, but also the number of frames, boards,ports, etc.). With these extensions, the Networks IP toolhas been used for dimensioning studies to optimizeoverall network costs of a real customer IP core network,in terms of different Class of Service (CoS), IP overlaytopologies, and aspects of load sharing and protection.

Figure 2 shows the network layout and the resultingwavelength assignment by networks IP tool of a study on

the influence of lambda conversion in optical transportnetworks.

Figure 2: Wavelength assignment (path coloring) on fibers of thetransport layer for an overlaying IP topology

The Dynamic Flow Simulator (DFS) is a simulation tool

intended for in-depth simulation of packet networksunder realistic traffic conditions, allowing both bandwidthand queue dimensioning. It takes into account thedynamics of the network by simulating the continuousvariations of the traffic at different time-scales on eachlink. Owing to a versatile flow-based model, it copes witha huge scale of dynamics, taking into account thedifferent time-profiles of all the traffic sources, resulting intraffic very close to measured traces. In addition, the DFSsimulates provisioning and restoration of connections viaa distributed control plane, by implementing thesemantics of GMPLS protocols. The DFS tool can be usedfor network performance evaluation or for network

dimensioning, including bandwidth and queuedimensioning. For performance evaluation, the DFSevaluates parameters such as the load distribution insidethe network, the connection blocking probability and therecovery speed. For network dimensioning and planning,the DFS gives the required resources inside each networkelement according to the simulated traffic variations. Itprovides the possibility to use some traffic engineeringrules and to take into account any planning constraintsdue to the node architectures.

Evolution of networks, with their mix of heterogeneoustechnologies (packet, circuit) and multiple layers (IP, SDH,Ethernet, WDM, etc.) requires a new generation ofdimensioning, simulation, and optimization tools. Usingthe latest networking technologies, Alcatels research,with its substantial expertise in network architecture andengineering, has designed a tool chain that bringsvaluable support to network planning and optimization.

This project is partially funded by the European IST and theEUREKA ITEA programs. It represents one of the researchinitiatives underway in Alcatels Research & Innovation labs.

Contact: alcatel.publications@alcatel.com

Transport layerIP layer Wavelength assignment