Title: LAN/WAN Optimization Techniques
1LAN/WAN Optimization Techniques
- Harrell J. Van Norman
- Presented by Lin Shu-Ping
2Outline
- Design Tools as Part of the Total Network
Engineering Process - Network Design Tool Utilization
- Network Design Tool
3Design Tools as Part of the Total Network
Engineering Process
- NDTs make up only one step in the total network
engineering process.
4Prior 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
5Prior 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.
6During 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.
7Subsequent 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.
8Outline
- Design Tools as Part of the Total Network
Engineering Process - Network Design Tool Utilization
- Network Design Tool
9Network Design Tool Utilization
- NDT utilization step includes
- Selecting a design technique
- Acquiring a tool
- Developing a model
- Analyzing the model
10Design 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.
11Tool 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.
12Model 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.
13Model 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.
14Outline
- Design Tools as Part of the Total Network
Engineering Process - Network Design Tool Utilization
- Network Design Tool
15Network Design Tool
- Technical approach
- Analytic heuristic
- Discrete event simulation
- Design algorithms
- Multipoint line connection
- Backbone design
- Topological structures
- Tree, Ring, Star, String
16Technical 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.
17Heuristics
- 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.
18Heuristics (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.
19Simulation
- 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.
20Simulation (cont.)
- Simulations overcome deficiencies inherent in
entirely analytic heuristic algorithm for
predicting network reliability.
21Design 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.
22Design Algorithms (cont.)
- Regardless of the method from determining
acceptable lineloading constraints,designing a
network configuration is necessary.
23Multipoint 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.
24Esau-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.
25Esau-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.
26Esau-Williams Algorithm (cont.)
27Prim 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.
28Prim Algorithm (cont.)
29Concentrator Placement
- Given potential concentrator sites,determine the
number and locations of concentrators and assign
each terminal to concentrator. - Add and Drop Algorithms
30Add 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.
31Add 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.
32Backbone 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.
33Cut 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
34Cut 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
35Cut 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.
36Cut 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.
37Routing and Service Options
- Effective design dynamics include
- Fractional
- Hubless
- LEC Bridging
- Routing Strategies
38Routing and Service Options (cont.)
- Three service options
- Total service
- Coordinated service
- Baseline service
39Routing 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
40Routing and Service Options (cont.)
- Baseline service
- Taking all responsibilities for their network
- Sophisticated diagnostic equipment and
experienced technicians should be on hand
41Topologies 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.
42Structures 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
43Structures 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.
44Structures 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.
45Tariff
- 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.
46Tariff (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.