3. Gathering and Listing Requirements
1.Determining Initial Conditions
2.Setting Customer Expectations
3.Working with Users
4.Taking Performance Measurements
5.Tracking and Managing Requirements
6.Mapping Location Information
4. 1.Determining Initial Conditions
• Initial conditions consist of the type of
network project, the scope of the architecture
and design, initial architecture/design goals,
and any outside forces acting on the network.
5. Type of Network Project
• New network
• Modification of an existing network
• Analysis of network problems
• Outsourcing
• Consolidation
• Upgrade
6. Scope of Network Project
• Network size
• Number of sites
• Distance between sites
7. Initial Architecture/Design Goals
• Upgrade technology/vendor
• Improve performance to part or all of network
• Support new users, applications, or devices
• Solve perceived problems within system
• Increase security
• Support a new capability in system
8. Multi-tier Vs Single-tier
• Multi-tier performance networks typically have one
or a few applications, users/groups, and/or devices
whose performance requirements are significantly
greater than other performance requirements for
that network.
• Single-tier performance networks do not have a
distinctive set of applications, users, or hosts that
have significantly greater performance requirements
for that network;
9. 2.Setting Customer Expectations
This consists of
• a rapid, initial evaluation of the problem, and
• estimating resources and schedule
Problem statements are descriptions of each of
the problems being addressed by your
network project
10. 3.Working with Users
• Developing a survey to email, FAX, or mail to users
• following up on the survey with one-on-one
telephone calls or conference calls
• Following up calls with face-to-face meetings with
selected individuals or groups
• Whiteboard sessions to elicit ideas from users
• Spending time with users while they work to better
understand what they do and how they do it
• While gathering requirements, look for warning
signals, also known as “red flags.”
13. 6.Mapping Location Information
• note (when possible) the locations of servers
and specialized devices, andwhere specific
applications are being used.
14. Developing Service Metrics
• Performance thresholds and limits and
performance characteristics are measured in
the system with service metrics.
• Measurement Tools
• ping, pathchar, TCPdump, traceroute
15. Characterizing Behavior
• Means representing how users and
applications use the network, in order to
develop and understand their requirements
• User behavior
• Application behavior
• Network behavior
16. Measuring Uptime
• Where
• Uptime Measured Everywhere
• Uptime Measured Selectively
• How
lack of connectivity or as a loss rate (biterror
rate, cell, frame, or packet loss rates).
17. Developing Delay Requirements
• Interaction delay (INTD) is an estimate of how long a
user is willing to wait for a response from the system
during an interactive session.
• Human response time (HRT) is an estimate of the
time threshold at which users begin to perceive
delay in the system.
• Network propagation delay is an estimate of how
long it takes for a signal to cross a physical medium
or link
18. End-to-End and Round-Trip Delays
• End-to-end and round-trip delays are
composed of many sources of delay, including
propagation, queuing, transmission, I/O,
switching, and processing.
19. Delay Variation
• to use 1% to 2% of the end-to-end delay as
the delay variation.
20. Developing Capacity Requirements
• Estimating Data Rates
• Peak data rate (PDR)
• Sustained data rate (SDR)
• Minimum data rate(mdr)
• Combinations of these
• These data rates may be measured at one or more
layers in the network (e.g., physical, data-link,
network, transport, or session).
21. Developing Supplemental Performance
Requirements
• Operational suitability is a measure of how well our
network design can be configured, monitored, and
adjusted by the customer’s operators.
• Supportability is a measure of how well the
customer can keep the system performing, as
designed, over the entire life of the system.
• Confidence is a measure of the ability of the network
to deliver data without error or loss at the required
throughput.
22. Environment-specific thresholds
and limits
• Environment-specific thresholds and limits are
an acknowledgment that each network is
unique, and that the requirements of users,
applications, and devices are specific to the
environment that they are in.