Transcript LAN/WAN Optimization Techniques

LAN/WAN Optimization
Techniques
Harrell J. Van Norman
Presented by Lin Shu-Ping
Outline
Design Tools as Part of the Total Network
Engineering Process
Network Design Tool Utilization
Network Design Tool
Design Tools as Part of the Total
Network Engineering Process
NDTs make up only one step in the total
network engineering process.
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
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Message profiles of each applications
Protocol characteristics
Environment of transmission network
Traffic Profiles
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.
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.
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.
Outline
Design Tools as Part of the Total Network
Engineering Process
Network Design Tool Utilization
Network Design Tool
Network Design Tool Utilization
NDT utilization step includes
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Selecting a design technique
Acquiring a tool
Developing a model
Analyzing the model
Design Technique Selection
Two basic design techniques
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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.
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.
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.
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.
Outline
Design Tools as Part of the Total Network
Engineering Process
Network Design Tool Utilization
Network Design Tool
Network Design Tool
Technical approach
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Analytic heuristic
Discrete event simulation
Design algorithms
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Multipoint line connection
Backbone design
Topological structures
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Tree, Ring, Star, String
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.
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.
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.
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.
Simulation (cont.)
Simulations overcome deficiencies
inherent in entirely analytic heuristic
algorithm for predicting network reliability.
Design Algorithms
When developing a network design, there
are two basic classes of problems
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Developing acceptable line loading
Optimal line configurations
All NDTs address line loading constraints,
with simulation models providing precise
estimation of end-user response time.
Design Algorithms (cont.)
Regardless of the method from
determining acceptable lineloading
constraints,designing a network
configuration is necessary.
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.
Esau-Williams Algorithm
Start with the simplest type of network
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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.
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.
Esau-Williams Algorithm (cont.)
Prim Algorithm
Prim’s 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 Prim’s algorithm.
Prim Algorithm (cont.)
Concentrator Placement
Given potential concentrator
sites,determine the number and locations
of concentrators and assign each terminal
to concentrator.
Add and Drop Algorithms
Add and Drop Algorithms
Step1:Clustering nearby nodes into COM nodes,
thereby reducing the problem in size and
converting to a point to point formulation.
Step2:Using 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.
Add and Drop Algorithms (cont.)
Step3:Local optimization by selecting one
specific node site for the generic access
facility.
Step4:Line layout by replacing all the COM
nodes with the actual nodes.
Backbone Design
In hierarchical network involves two
design problems.
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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
Cut Saturation Algorithm
Cut saturation algorithm consists of five
basic steps in any one iteration
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Routing
Saturated cutset determination
Add-only step
Delete-only operation
Perturbation setp
Cut Saturation Algorithm (cont.)
Routing
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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
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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
Cut Saturation Algorithm (cont.)
Add-only step
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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
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Links from a highly connected topology are
eliminated.
One link at a time is removed at each
iteration by finding maximum cost link.
Cut Saturation Algorithm (cont.)
Perturbation step
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Once a desired throughput range has been
attained, network links are rearranged by addonly and delete-only operations to reduce cost.
Add-only and delete-only operations are used
sequentially as long as throughput remains
within the bounds.
Routing and Service Options
Effective design dynamics include
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Fractional
Hubless
LEC Bridging
Routing Strategies
Routing and Service Options (cont.)
Three service options
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Total service
Coordinated service
Baseline service
Routing and Service Options (cont.)
Total service
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AT&T will design, order, and bill the entire
circuit.
Require the highest degree of dependence
upon AT&T
Coordinated service
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Carrier responsibility for ordering and
maintaining the circuit as well as a measure of
customer control over the network
Routing and Service Options (cont.)
Baseline service
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Taking all responsibilities for their network
Sophisticated diagnostic equipment and
experienced technicians should be on hand
Topologies Supported
Topology of a network may be
organized according to two level
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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.
Structures Evaluated
Average number of links per node
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A higher link-per-node ration indicates a more
expensive network topology
Maximum number of intermediate nodes
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The accessibility of any node to any other
node
A large number of intermediate node results in
higher delay
Structures Evaluated (cont.)
Maximum node capacity
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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
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A measure of network reliability
A high number of nonredundant routes
points to a network topology with good
reliability.
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.
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.
Tariff (cont.)
Three methods of obtaining tariff data
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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.