LAN/WAN Optimization Techniques Harrell J. Van Norman Presented by Lin Shu-Ping

LAN/WAN Optimization LAN/WAN Optimization TechniquesTechniques

Harrell J. Van NormanHarrell J. Van Norman

Presented by Lin Shu-Ping Presented by Lin Shu-Ping

OutlineOutline

Design Tools as Part of the Total Network Design Tools as Part of the Total Network Engineering ProcessEngineering Process

Network Design Tool UtilizationNetwork Design Tool Utilization

Network Design ToolNetwork Design Tool

Design Tools as Part of the Total Design Tools as Part of the Total Network Engineering ProcessNetwork Engineering Process

NDTs make up only one step in the total nNDTs make up only one step in the total network engineering process.etwork engineering process.

Prior To UsePrior To Use

Requires collecting current traffic measures Requires collecting current traffic measures and forecasting for network growth.and forecasting for network growth.

The precision of any NDT is related to The precision of any NDT is related to correctness of the design criteria upon which correctness of the design criteria upon which analysis is based.analysis is based.

Typical questions asked by NDTTypical questions asked by NDT Message profiles of each applicationsMessage profiles of each applications Protocol characteristicsProtocol characteristics Environment of transmission networkEnvironment of transmission network Traffic ProfilesTraffic Profiles

Prior To UsePrior To Use

When using NDT accurately, defining When using NDT accurately, defining design criteria is crucial.design criteria is crucial.

Integration of NDT into a network Integration of NDT into a network management system is a more credible management system is a more credible approach.approach.

The optimization of the network will be The optimization of the network will be proportional to precision of the design proportional to precision of the design criteria.criteria.

During UseDuring Use

The network engineer postulates with The network engineer postulates with “what if” scenario by changing node “what if” scenario by changing node location.location.

Using NDT involves iterative refinement Using NDT involves iterative refinement generally produced during evaluating of generally produced during evaluating of various network alternatives.various network alternatives.

Subsequent To UseSubsequent To Use

Additional phases of network engineering Additional phases of network engineering include reconfiguration, equipment include reconfiguration, equipment acquisition, verification, installation and acquisition, verification, installation and administrator.administrator.

Iterative improvements are made by Iterative improvements are made by evaluating network costs and performance evaluating network costs and performance against the operational criteria.against the operational criteria.

OutlineOutline





NDT utilization step includesNDT utilization step includes Selecting a design techniqueSelecting a design technique Acquiring a toolAcquiring a tool Developing a modelDeveloping a model Analyzing the modelAnalyzing the model

Design Technique SelectionDesign Technique Selection

Two basic design techniquesTwo basic design techniques Discrete event simulationDiscrete event simulation Analytic heuristic modelingAnalytic heuristic modeling

If network engineer is interested only in If network engineer is interested only in network performance, using simulation.network performance, using simulation.If the network engineer needs circuit cost If the network engineer needs circuit cost and network performance combined, and network performance combined, analytic heuristic is the preferred analytic heuristic is the preferred approach.approach.

Tool AcquisitionTool Acquisition

This step involves acquiring an NDT from This step involves acquiring an NDT from among many suppliers of NDTs.among many suppliers of NDTs.

““You get what you pay for” is generally truYou get what you pay for” is generally true within the NDT market.e within the NDT market.

Model DevelopmentModel Development

Generate a logical model of the network Generate a logical model of the network that requires analysis and design.that requires analysis and design.

The model is based on a set of locations The model is based on a set of locations for data input and termination.for data input and termination.

Model AnalysisModel Analysis

Test model with various inputs and Test model with various inputs and observe the resulting cost and observe the resulting cost and performance outputs.performance outputs.

Developing allowable ranges for Developing allowable ranges for acceptable input parameters assists in acceptable input parameters assists in insuring the model accuracy.insuring the model accuracy.

OutlineOutline





Technical approachTechnical approach Analytic heuristicAnalytic heuristic Discrete event simulationDiscrete event simulation

Design algorithmsDesign algorithms Multipoint line connectionMultipoint line connection Backbone designBackbone design

Topological structuresTopological structures Tree, Ring, Star, StringTree, Ring, Star, String

Technical approachTechnical approach

There is nearly overwhelming number of There is nearly overwhelming number of possibilities in configuring a network.possibilities in configuring a network.

Insuperable amounts of computing times Insuperable amounts of computing times would be required for applying algorithms would be required for applying algorithms to find optimum constrained design.to find optimum constrained design.

It is appropriate to use heuristic It is appropriate to use heuristic techniques or simulation-based techniques or simulation-based approaches.approaches.

HeuristicsHeuristics

Heuristics are chosen approximations of Heuristics are chosen approximations of actual analytic calculations.actual analytic calculations.

Using heuristics is necessary whenever Using heuristics is necessary whenever computational time and resources would computational time and resources would be excessive to provide actual analytic be excessive to provide actual analytic solution.solution.

Heuristics (cont.)Heuristics (cont.)

No NDT can produce totally optimal No NDT can produce totally optimal design due to inaccurate input values.design due to inaccurate input values.

Evidence indicate that good heuristic Evidence indicate that good heuristic algorithms can produce network designs algorithms can produce network designs that are within 5 percent of optimal that are within 5 percent of optimal solution.solution.

SimulationSimulation

Network simulation predicts performance Network simulation predicts performance characteristics.characteristics.

Whenever extremely precise performance Whenever extremely precise performance evaluation is necessary, simulation is the evaluation is necessary, simulation is the preferred technique.preferred technique.

The results of simulation predict how The results of simulation predict how networks will perform under various loads.networks will perform under various loads.

Simulation (cont.)Simulation (cont.)

Simulations overcome deficiencies Simulations overcome deficiencies inherent in entirely analytic heuristic inherent in entirely analytic heuristic algorithm for predicting network reliability.algorithm for predicting network reliability.

Design AlgorithmsDesign Algorithms

When developing a network design, there When developing a network design, there are two basic classes of problemsare two basic classes of problems Developing acceptable line loadingDeveloping acceptable line loading Optimal line configurationsOptimal line configurations

All NDTs address line loading constraints, All NDTs address line loading constraints, with simulation models providing precise ewith simulation models providing precise estimation of end-user response time.stimation of end-user response time.

Design Algorithms (cont.)Design Algorithms (cont.)

Regardless of the method from determininRegardless of the method from determining acceptable lineloading constraints,desigg acceptable lineloading constraints,designing a network configuration is necessary.ning a network configuration is necessary.

Multipoint Line ConnectionMultipoint Line Connection

Multipoint lines reduce total circuit mileage Multipoint lines reduce total circuit mileage costs by enabling multiple users to share costs by enabling multiple users to share circuits.circuits.To minimize the cost of that line involves To minimize the cost of that line involves computing the minimal spanning tree.computing the minimal spanning tree.Minimal spanning tree calculations are Minimal spanning tree calculations are exact optimal algorithms with link-loading exact optimal algorithms with link-loading constraints or unconstrained limits.constraints or unconstrained limits.

Esau-Williams AlgorithmEsau-Williams Algorithm

Start with the simplest type of network Start with the simplest type of network One with a central controller hub connected to One with a central controller hub connected to

each remote terminal by a separate circuit.each remote terminal by a separate circuit. Such network can be accepted when terminal Such network can be accepted when terminal

are very heavily loaded or equipment precludare very heavily loaded or equipment precludes line sharing.es line sharing.

Set aside each fully loaded line, because it Set aside each fully loaded line, because it obviously cannot be multipointed.obviously cannot be multipointed.

Esau-Williams Algorithm (cont.)Esau-Williams Algorithm (cont.)

In each iteration the node with the In each iteration the node with the greatest differential distance from the hub greatest differential distance from the hub to the nearest neighboring node is to the nearest neighboring node is located.located.It reconnects that node to its nearest It reconnects that node to its nearest neighboring node, thereby providing the neighboring node, thereby providing the greatest cost benefits.greatest cost benefits.In this manner, each iteration removes In this manner, each iteration removes one expensive link and replaces it with one expensive link and replaces it with the best alternative link.the best alternative link.

Esau-Williams Algorithm (cont.)Esau-Williams Algorithm (cont.)

Prim AlgorithmPrim Algorithm

Prim’s algorithm functions in the reverse of Prim’s algorithm functions in the reverse of the Esau-Williams algorithm.the Esau-Williams algorithm.It selects the nodes closest to the center thIt selects the nodes closest to the center then connects in those node that are closest en connects in those node that are closest to those already in the network.to those already in the network.Minimizing the maximum costs by means Minimizing the maximum costs by means of the Esau-Williams algorithm yields improf the Esau-Williams algorithm yields improved designs over Prim’s algorithm.oved designs over Prim’s algorithm.

Prim Algorithm (cont.)Prim Algorithm (cont.)

Concentrator PlacementConcentrator Placement

Given potential concentrator Given potential concentrator sites,determine the number and locations sites,determine the number and locations of concentrators and assign each terminal of concentrators and assign each terminal to concentrator.to concentrator.

Add and Drop AlgorithmsAdd and Drop Algorithms

Add and Drop AlgorithmsAdd and Drop Algorithms

Step1:Clustering nearby nodes into COM nodes, Step1:Clustering nearby nodes into COM nodes, thereby reducing the problem in size and thereby reducing the problem in size and converting to a point to point formulation.converting to a point to point formulation.

Step2:Using the add algorithm to partition the Step2:Using the add algorithm to partition the COM nodes with other COM nodes that give the COM nodes with other COM nodes that give the greatest cost benefits by being connected to greatest cost benefits by being connected to generic access facilities instead of resource generic access facilities instead of resource connection point.connection point.

Add and Drop Algorithms (cont.)Add and Drop Algorithms (cont.)

Step3:Local optimization by selecting one Step3:Local optimization by selecting one specific node site for the generic access specific node site for the generic access facility.facility.

Step4:Line layout by replacing all the COM Step4:Line layout by replacing all the COM nodes with the actual nodes.nodes with the actual nodes.

Backbone DesignBackbone Design

In hierarchical network involves two desigIn hierarchical network involves two design problems.n problems. Design of the regional subnetworksDesign of the regional subnetworks Backbone portion of the networkBackbone portion of the network

The cut saturation algorithm is a common The cut saturation algorithm is a common example of backbone design algorithm.example of backbone design algorithm.It iteratively finds the least-cost backbone It iteratively finds the least-cost backbone network for a specified throughput, subject network for a specified throughput, subject to time delay and reliability constraints.to time delay and reliability constraints.

Cut Saturation AlgorithmCut Saturation Algorithm

Cut saturation algorithm consists of five baCut saturation algorithm consists of five basic steps in any one iterationsic steps in any one iteration RoutingRouting Saturated cutset determinationSaturated cutset determination Add-only stepAdd-only step Delete-only operationDelete-only operation Perturbation setpPerturbation setp

Cut Saturation Algorithm (cont.)Cut Saturation Algorithm (cont.)

RoutingRouting setting up at each node along the path a routisetting up at each node along the path a routi

ng table directing messages with a particular ng table directing messages with a particular destination address to appropriate outgoing lidestination address to appropriate outgoing link.nk.

Saturated cutset determinationSaturated cutset determination Links are ordered according to their utilizationLinks are ordered according to their utilization Links are then removed, one at a time, in ordLinks are then removed, one at a time, in ord

er of utilizationer of utilization The minimal set that disconnects the network The minimal set that disconnects the network

is called a saturated cutsetis called a saturated cutset


Add-only stepAdd-only step Adding the least-cost links to the network thAdding the least-cost links to the network th

at will direct traffic from the saturated cutset.at will direct traffic from the saturated cutset. Nodes that are at least two links removed frNodes that are at least two links removed fr

om the cutset are chosen as candidates for om the cutset are chosen as candidates for possible linkages.possible linkages.

Delete-only stepDelete-only step Links from a highly connected topology are Links from a highly connected topology are

eliminated.eliminated. One link at a time is removed at each iteratiOne link at a time is removed at each iterati

on by finding maximum cost link.on by finding maximum cost link.


Perturbation stepPerturbation step Once a desired throughput range has been Once a desired throughput range has been

attained, network links are rearranged by add-attained, network links are rearranged by add-only and delete-only operations to reduce only and delete-only operations to reduce cost.cost.

Add-only and delete-only operations are used Add-only and delete-only operations are used sequentially as long as throughput remains sequentially as long as throughput remains within the bounds.within the bounds.

Routing and Service OptionsRouting and Service Options

Effective design dynamics includeEffective design dynamics include FractionalFractional HublessHubless LEC BridgingLEC Bridging Routing StrategiesRouting Strategies

Routing and Service Options (cont.)Routing and Service Options (cont.)

Three service options Three service options Total serviceTotal service Coordinated serviceCoordinated service Baseline serviceBaseline service


Total serviceTotal service AT&T will design, order, and bill the entire AT&T will design, order, and bill the entire

circuit.circuit. Require the highest degree of dependence Require the highest degree of dependence

upon AT&Tupon AT&T

Coordinated serviceCoordinated service Carrier responsibility for ordering and Carrier responsibility for ordering and

maintaining the circuit as well as a measure of maintaining the circuit as well as a measure of customer control over the networkcustomer control over the network


Baseline serviceBaseline service Taking all responsibilities for their networkTaking all responsibilities for their network Sophisticated diagnostic equipment and Sophisticated diagnostic equipment and

experienced technicians should be on handexperienced technicians should be on hand

Topologies SupportedTopologies Supported

Topology of a network may be Topology of a network may be organized according to two levelorganized according to two level Terminal access network (TAN)Terminal access network (TAN) Backbone-mesh network (BMN)Backbone-mesh network (BMN)

For BMN, satisfactory design are For BMN, satisfactory design are typically star, ring, and hyper-ring.typically star, ring, and hyper-ring.

NDT should support these network NDT should support these network topologies.topologies.

Structures EvaluatedStructures Evaluated

Average number of links per nodeAverage number of links per node A higher link-per-node ration indicates a more A higher link-per-node ration indicates a more

expensive network topologyexpensive network topology

Maximum number of intermediate nodesMaximum number of intermediate nodes The accessibility of any node to any other The accessibility of any node to any other

nodenode A large number of intermediate node results in A large number of intermediate node results in

higher delayhigher delay

Structures Evaluated (cont.)Structures Evaluated (cont.)

Maximum node capacityMaximum node capacity A measure of node vulnerability, defined as tA measure of node vulnerability, defined as t

he maximum number of links that connect to he maximum number of links that connect to a given node.a given node.

Amount of traffic a specific node is required tAmount of traffic a specific node is required to support.o support.

Number of nonredundant routesNumber of nonredundant routes A measure of network reliabilityA measure of network reliability A high number of nonredundant routes pointA high number of nonredundant routes point

s to a network topology with good reliability.s to a network topology with good reliability.

Structures Evaluated (cont.)Structures Evaluated (cont.)

Total interconnect have a high cost and Total interconnect have a high cost and degree of reliabilitydegree of reliability

Tree, star, and string have a low cost and Tree, star, and string have a low cost and degree of reliabilitydegree of reliability

Ring and hyper-ring have relatively low Ring and hyper-ring have relatively low cost combined with high degree of cost combined with high degree of reliability.reliability.

TariffTariff

Tariff are descriptions of telecom Tariff are descriptions of telecom services and prices of those services.services and prices of those services.

Accurate and completer tariff data is Accurate and completer tariff data is essential for bill verification.essential for bill verification.

Telecom companies provide three basic Telecom companies provide three basic types of transmission services: private types of transmission services: private line, switched, and packet services.line, switched, and packet services.

Tariff (cont.)Tariff (cont.)

Three methods of obtaining tariff dataThree methods of obtaining tariff data Getting data directly from tariff database Getting data directly from tariff database

supplier requires the least cost by the NDT supplier requires the least cost by the NDT providerprovider

Obtaining from tariff data supplier and then Obtaining from tariff data supplier and then incorporated into internal database incorporated into internal database structures requires significantly greater structures requires significantly greater effort.effort.

Obtaining tariff data directly from the FCC Obtaining tariff data directly from the FCC or by subscribing to the filing bodies or by subscribing to the filing bodies themselves demands the greatest degree themselves demands the greatest degree of effort and skill by NDT provider.of effort and skill by NDT provider.

Documents

LAN/WAN Optimization Techniques Harrell J. Van Norman Presented by Lin Shu-Ping