LAN/WAN Optimization
Techniques
Agenda
Current Traffic
 Equipment Inventory and Forecasted
Growth
 Operational Evaluation Criteria
 Network Design Decision Approach

Current Traffic
Loads
 Traffic classes
 Traffic response times
 Transaction types
 Protocol overhead

Loads

Traffic Loads : the volume of data
communication traffic
-data
-data transmission overhead
Loads (cont.)

Traffic Load is generally calculated by
analytically-based NDTs on the following
parameters:
-message definition
-message characteristics
- traffic load is required by NDTs for each
location on the network
Loads (cont.)

NDTs calculate traffic load based on
standard deviations from average values
account for these peaks and valleys in
traffic volume
-peak
-normal
-valley
Traffic classes

Traffic loads should be broken down into
these types of traffic classes for message
prioritizing
-real time
-interactive
-file transfer
Traffic response times

Average transaction response times
RT=I+CPU+O
Traffic response times (cont.)

Polling environments :
I or O =T+W+S
Traffic response times (cont.)

Service times

Transmission time is the time needed to send
the entire message (overhead and text) down
the line
Traffic response times (cont.)

Connection delay is the time needed by the frontend processor to establish a connection with
terminal, including modem turnarounds

Polling delay is attributed to multipoint lines in
which terminals must wait their turn before being
polled by the front-end processor
Traffic response times (cont.)



Arrival rates: number of messages that arrive
at all the terminals on the line
Line utilization (U)
Waiting time (W)
P-K formula:
Transaction types

The most appropriate approach calculates
response time based on the varied mixture of
transaction types that each location supports
Protocol overhead

Control messages are necessary in both
poll and select scenarios to inquire if the
terminal has data to send or is ready to
receive
-polling mode
-select mode
-control message : requires data rates, line
sizes
-protocol overhead
Protocol overhead (cont.)
agenda
Current Traffic
 Equipment Inventory and Forecasted
Growth
 Operational Evaluation Criteria
 Network Design Decision Approach

Equipment Inventory and
Forecasted Growth
Equipment inventory
 Inventory
 forecasting

Equipment inventory
Without an accurate awareness of the
communications network, design and
analysis is impractical
 Equipment inventories and growth
forecasts develop an understanding of the
network that is fundamental to any
engineering process

Inventory
An essential of network design is
identifying communications equipment
 Physical resources
-compatibility
-meet the needs of the network’s users

Inventory (cont.)
Location-in order to identifying communication
equipment types, locations of all devices must be
specified
-equipment types and locations are known, fixed,
unalterable
-equipment types and location possibilities are
known
- equipment locations determination accommodates
an unlimited selection of possibilities
 Types-reference 6.4 communication hardware

forecasting
Network engineers need to consider
forecasted growth when conducting design
exercises
 Forecasting growth is critical during
network design
 Once current and future applications of
data communications have been identified,
engineer must forecast growth trends in
usage over the planning period

Forecasting (cont.)
Forecasting based on trends is the safest
method of determining the future of data
communications traffic demands
-trend lines are independent of business
activity
-outside affects are suspected
-trend lines generally follow business
activity

Forecasting (cont.)
trend lines are not directly dependent on
business activity, survey must be
conducted in an attempt to explain the
independence
 Purpose of surveys is to establish the
aspects of business activity on which the
data communications usage will depend

agenda
Current Traffic
 Equipment Inventory and Forecasted
Growth
 Operational Evaluation Criteria
 Network Design Decision Approach

Operational Evaluation Criteria
Performance
 Availability
 Reliability
 Cost
 security

Performance
Evaluate what performance criteria are
necessary for acceptable operational
characteristics of the network
-response time
-throughput
-utilization
-blocking rate

Availability

Availability
-reliability (MTBF)
-serviceability (MTTR)

Serial-overall system availability
Availability (cont.)

Parallel-overall system availability
Reliability

Mean time between failures
Cost
Line cost –recurring monthly service
charges & nonrecurring one-time
installation costs
 Equipment cost
 Software cost

security

The most effective security measures
involve a variety of barriers of different
types and different places
agenda
Current Traffic
 Equipment Inventory and Forecasted
Growth
 Operational Evaluation Criteria
 Network Design Decision Approach

Network Design Decision Approach
Network design tool utilization
 Cost-performance break-even analysis
 Equipment acquisition

Network design tool utilization

This step involved selection of the most
appropriate design technique, acquisition
of an NDT, development of a network
model, and analysis of the model
--most critical step of the entire network
engineering process
Network design phase
Cost-performance break-even
analysis
This step involved generating and
evaluating alternative network designs
 What-if questions are used to evaluate
various alternative configurations
-proposals for adding / deleting resources
-redesign application to improve the
performance
-modeling different routing strategies

Cost-performance break-even
analysis (cont.)
Each of the various alternative
configurations will have associated costs
and performance levels
 Trade-off between cost/performance

Equipment acquisition
This step involves obtaining the necessary
equipment as specified in the optimal
optimized network design
 Once this step is complete, an optimized
implementable design is available as input
into the next phase: network management
