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LAN/WAN Optimization Techniques

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Title: LAN/WAN Optimization Techniques


1
LAN/WAN Optimization Techniques
  • Harrell J. Van Norman
  • Presented by Lin Shu-Ping

2
Outline
  • Design Tools as Part of the Total Network
    Engineering Process
  • Network Design Tool Utilization
  • Network Design Tool

3
Design Tools as Part of the Total Network
Engineering Process
  • NDTs make up only one step in the total network
    engineering process.

4
Prior To Use
  • Requires collecting current traffic measures and
    forecasting for network growth.
  • The precision of any NDT is related to
    correctness of the design criteria upon which
    analysis is based.
  • Typical questions asked by NDT
  • Message profiles of each applications
  • Protocol characteristics
  • Environment of transmission network
  • Traffic Profiles

5
Prior To Use
  • When using NDT accurately, defining design
    criteria is crucial.
  • Integration of NDT into a network management
    system is a more credible approach.
  • The optimization of the network will be
    proportional to precision of the design criteria.

6
During Use
  • The network engineer postulates with what if
    scenario by changing node location.
  • Using NDT involves iterative refinement generally
    produced during evaluating of various network
    alternatives.

7
Subsequent To Use
  • Additional phases of network engineering include
    reconfiguration, equipment acquisition,
    verification, installation and administrator.
  • Iterative improvements are made by evaluating
    network costs and performance against the
    operational criteria.

8
Outline
  • Design Tools as Part of the Total Network
    Engineering Process
  • Network Design Tool Utilization
  • Network Design Tool

9
Network Design Tool Utilization
  • NDT utilization step includes
  • Selecting a design technique
  • Acquiring a tool
  • Developing a model
  • Analyzing the model

10
Design Technique Selection
  • Two basic design techniques
  • Discrete event simulation
  • Analytic heuristic modeling
  • If network engineer is interested only in network
    performance, using simulation.
  • If the network engineer needs circuit cost and
    network performance combined, analytic heuristic
    is the preferred approach.

11
Tool Acquisition
  • This step involves acquiring an NDT from among
    many suppliers of NDTs.
  • You get what you pay for is generally true
    within the NDT market.

12
Model Development
  • Generate a logical model of the network that
    requires analysis and design.
  • The model is based on a set of locations for data
    input and termination.

13
Model Analysis
  • Test model with various inputs and observe the
    resulting cost and performance outputs.
  • Developing allowable ranges for acceptable input
    parameters assists in insuring the model accuracy.

14
Outline
  • Design Tools as Part of the Total Network
    Engineering Process
  • Network Design Tool Utilization
  • Network Design Tool

15
Network Design Tool
  • Technical approach
  • Analytic heuristic
  • Discrete event simulation
  • Design algorithms
  • Multipoint line connection
  • Backbone design
  • Topological structures
  • Tree, Ring, Star, String

16
Technical approach
  • There is nearly overwhelming number of
    possibilities in configuring a network.
  • Insuperable amounts of computing times would be
    required for applying algorithms to find optimum
    constrained design.
  • It is appropriate to use heuristic techniques or
    simulation-based approaches.

17
Heuristics
  • Heuristics are chosen approximations of actual
    analytic calculations.
  • Using heuristics is necessary whenever
    computational time and resources would be
    excessive to provide actual analytic solution.

18
Heuristics (cont.)
  • No NDT can produce totally optimal design due to
    inaccurate input values.
  • Evidence indicate that good heuristic algorithms
    can produce network designs that are within 5
    percent of optimal solution.

19
Simulation
  • Network simulation predicts performance
    characteristics.
  • Whenever extremely precise performance evaluation
    is necessary, simulation is the preferred
    technique.
  • The results of simulation predict how networks
    will perform under various loads.

20
Simulation (cont.)
  • Simulations overcome deficiencies inherent in
    entirely analytic heuristic algorithm for
    predicting network reliability.

21
Design Algorithms
  • When developing a network design, there are two
    basic classes of problems
  • Developing acceptable line loading
  • Optimal line configurations
  • All NDTs address line loading constraints, with
    simulation models providing precise estimation of
    end-user response time.

22
Design Algorithms (cont.)
  • Regardless of the method from determining
    acceptable lineloading constraints,designing a
    network configuration is necessary.

23
Multipoint Line Connection
  • Multipoint lines reduce total circuit mileage
    costs by enabling multiple users to share
    circuits.
  • To minimize the cost of that line involves
    computing the minimal spanning tree.
  • Minimal spanning tree calculations are exact
    optimal algorithms with link-loading constraints
    or unconstrained limits.

24
Esau-Williams Algorithm
  • Start with the simplest type of network
  • One with a central controller hub connected to
    each remote terminal by a separate circuit.
  • Such network can be accepted when terminal are
    very heavily loaded or equipment precludes line
    sharing.
  • Set aside each fully loaded line, because it
    obviously cannot be multipointed.

25
Esau-Williams Algorithm (cont.)
  • In each iteration the node with the greatest
    differential distance from the hub to the nearest
    neighboring node is located.
  • It reconnects that node to its nearest
    neighboring node, thereby providing the greatest
    cost benefits.
  • In this manner, each iteration removes one
    expensive link and replaces it with the best
    alternative link.

26
Esau-Williams Algorithm (cont.)
27
Prim Algorithm
  • Prims algorithm functions in the reverse of the
    Esau-Williams algorithm.
  • It selects the nodes closest to the center then
    connects in those node that are closest to those
    already in the network.
  • Minimizing the maximum costs by means of the
    Esau-Williams algorithm yields improved designs
    over Prims algorithm.

28
Prim Algorithm (cont.)
29
Concentrator Placement
  • Given potential concentrator sites,determine the
    number and locations of concentrators and assign
    each terminal to concentrator.
  • Add and Drop Algorithms

30
Add and Drop Algorithms
  • Step1Clustering nearby nodes into COM nodes,
    thereby reducing the problem in size and
    converting to a point to point formulation.
  • Step2Using the add algorithm to partition the
    COM nodes with other COM nodes that give the
    greatest cost benefits by being connected to
    generic access facilities instead of resource
    connection point.

31
Add and Drop Algorithms (cont.)
  • Step3Local optimization by selecting one
    specific node site for the generic access
    facility.
  • Step4Line layout by replacing all the COM nodes
    with the actual nodes.

32
Backbone Design
  • In hierarchical network involves two design
    problems.
  • Design of the regional subnetworks
  • Backbone portion of the network
  • The cut saturation algorithm is a common example
    of backbone design algorithm.
  • It iteratively finds the least-cost backbone
    network for a specified throughput, subject to
    time delay and reliability constraints.

33
Cut Saturation Algorithm
  • Cut saturation algorithm consists of five basic
    steps in any one iteration
  • Routing
  • Saturated cutset determination
  • Add-only step
  • Delete-only operation
  • Perturbation setp

34
Cut Saturation Algorithm (cont.)
  • Routing
  • setting up at each node along the path a routing
    table directing messages with a particular
    destination address to appropriate outgoing link.
  • Saturated cutset determination
  • Links are ordered according to their utilization
  • Links are then removed, one at a time, in order
    of utilization
  • The minimal set that disconnects the network is
    called a saturated cutset

35
Cut Saturation Algorithm (cont.)
  • Add-only step
  • Adding the least-cost links to the network that
    will direct traffic from the saturated cutset.
  • Nodes that are at least two links removed from
    the cutset are chosen as candidates for possible
    linkages.
  • Delete-only step
  • Links from a highly connected topology are
    eliminated.
  • One link at a time is removed at each iteration
    by finding maximum cost link.

36
Cut Saturation Algorithm (cont.)
  • Perturbation step
  • Once a desired throughput range has been
    attained, network links are rearranged by
    add-only and delete-only operations to reduce
    cost.
  • Add-only and delete-only operations are used
    sequentially as long as throughput remains within
    the bounds.

37
Routing and Service Options
  • Effective design dynamics include
  • Fractional
  • Hubless
  • LEC Bridging
  • Routing Strategies

38
Routing and Service Options (cont.)
  • Three service options
  • Total service
  • Coordinated service
  • Baseline service

39
Routing and Service Options (cont.)
  • Total service
  • ATT will design, order, and bill the entire
    circuit.
  • Require the highest degree of dependence upon
    ATT
  • Coordinated service
  • Carrier responsibility for ordering and
    maintaining the circuit as well as a measure of
    customer control over the network

40
Routing and Service Options (cont.)
  • Baseline service
  • Taking all responsibilities for their network
  • Sophisticated diagnostic equipment and
    experienced technicians should be on hand

41
Topologies Supported
  • Topology of a network may be organized according
    to two level
  • Terminal access network (TAN)
  • Backbone-mesh network (BMN)
  • For BMN, satisfactory design are typically star,
    ring, and hyper-ring.
  • NDT should support these network topologies.

42
Structures Evaluated
  • Average number of links per node
  • A higher link-per-node ration indicates a more
    expensive network topology
  • Maximum number of intermediate nodes
  • The accessibility of any node to any other node
  • A large number of intermediate node results in
    higher delay

43
Structures Evaluated (cont.)
  • Maximum node capacity
  • A measure of node vulnerability, defined as the
    maximum number of links that connect to a given
    node.
  • Amount of traffic a specific node is required to
    support.
  • Number of nonredundant routes
  • A measure of network reliability
  • A high number of nonredundant routes points to a
    network topology with good reliability.

44
Structures Evaluated (cont.)
  • Total interconnect have a high cost and degree of
    reliability
  • Tree, star, and string have a low cost and degree
    of reliability
  • Ring and hyper-ring have relatively low cost
    combined with high degree of reliability.

45
Tariff
  • Tariff are descriptions of telecom services and
    prices of those services.
  • Accurate and completer tariff data is essential
    for bill verification.
  • Telecom companies provide three basic types of
    transmission services private line, switched,
    and packet services.

46
Tariff (cont.)
  • Three methods of obtaining tariff data
  • Getting data directly from tariff database
    supplier requires the least cost by the NDT
    provider
  • Obtaining from tariff data supplier and then
    incorporated into internal database structures
    requires significantly greater effort.
  • Obtaining tariff data directly from the FCC or by
    subscribing to the filing bodies themselves
    demands the greatest degree of effort and skill
    by NDT provider.
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