CP7101-Design and Management of Computer Networks

1. CP7101-Design and Management
of Computer Networks
Requirements Analysis:
Process
Dr.G.Geetha
Professor /CSE
Jerusalem College of Engineering

2. • Gathering and Listing Requirements
• Developing Service Metrics
• Characterizing Behavior
• Developing RMA Requirements
• Developing delay Requirements
• Developing capacity Requirements
• Developing supplemental performance
Requirements
• Requirements mapping
• Developing the requirements specification

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.”

11. 4.Taking Performance
Measurements
Measuring Performance Using
• a Test bed
• on the Existing Network

12. 5.Tracking and Managing
Requirements
• Paragraph form
• Tabular Form

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.