Chapter 14

Network Design and Implementation

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Network Analysis and Design Aspects of network analysis and design

Understanding the requirements for a communications network Need to decide how detailed the analysis must be Example: just install more capacity than needed to avoid time

consuming estimates of required capacity Investigating alternative ways for implementing the network Selecting the most appropriate alternative to provide the required

capability Similar considerations used for voice and data networks

Usually involves a multi-step process

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Network Implementation

Process of installing a network and making it operational

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Project Approach

Network analysis, design and implementation usually done in multi-phase project

Main objective: Provide network satisfying user requirements at

an appropriate cost May outsource the project

Usually the case for small businesses

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Network Project Steps

1. The request

2. Preliminary investigation and feasibility study

3. Detailed understanding and definition of requirements

4. Investigation of alternatives

5. Network design

6. Selection of vendors and equipment

7. Calculation of costs

8. Documentation of network design and implementation plan

6

Network Project Steps

9. Approval by management

10. Equipment order

11. Preparation for implementation

12. Installation

13. Training

14. System testing

15. Cutover

16. Implementation cleanup and audit

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Preliminary Investigation

A small preliminary project team is formed to examine existing communication system

Determine what improvements are necessary Estimate costs and schedule Creeping commitment of resources

Ramp up project personnel and expenditures as needed

Helps minimize financial risk if project is stopped

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Project Life Cycle

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Definition of Requirements Breakdown requirements by

Geography Traffic loads (peak and average)

Transaction-based network loads are easier to estimate Internet-type environments are more difficult to estimate due

to different traffic types (images, sound, video) Flow pattern

i.e. Star vs. mesh Traffic in star flows through central node Traffic in mesh has more complex pattern

Response time and reliability

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Definition of Requirements

Future growth Completion date Compatibility with old network Costs

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Typical Data Network Traffic Load

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Analysis of Expected Traffic Loads

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Investigate Alternatives

Check availability of different services Public switched vs. private lines Topology type Is packet switching available? Satellite?

14

Network Design

Iterative process Refinements made as project progresses

Translate specs to drawings Simulate the design

Allows “what if” scenarios Simulation model can be difficult to create

Calculate response times Example: Require transmission of 100 million

characters in an 8-hour day with no longer than 1 second response time

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Network Diagram

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Response Time Design Example

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Equipment and Vendor Selection

Evaluate types of equipment available Send out Request

Request for Quotation (RFQ) to vendors of “commodity” products and services.

Request for Proposal (RFP) to vendors of “custom” products and services.

Detail required by vendor in response to RFQ/RFP varies based on application

Evaluate vendor proposals

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Example RFP

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Example Vendor Response to RFP

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Calculate Costs

Examine costs of alternate designs Group costs by

Circuit costs Modem costs Other hardware costs Software costs Personnel costs

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Documentation of Design

Include: Specifications Software and versions Wiring diagrams Equipment list

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Management Approval of Design

Present design and cost/benefit information to management

Design review

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Network Implementation

Equipment Order Make sure equipment specs meet your needs Make purchase contingent on acceptance test

(expensive items) Watch out for lead times

Prepare for Implementation Set up network policies Modify software Track progress

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Network Implementation

Installation Allocate and prepare space Mechanical drawings showing locations Have vendors install and test equipment Make sure equipment interfaces properly

Training Train users, operational and maintenance

personnel

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Network Implementation System Testing

Perform as much testing as possible initially Locate and solve problems

May need to test hardware and software separately Schedule tests when network has minimum load Stress test to find network limits

Workload generator – software that produces network traffic Test component error handling capability

Failure to test error recovery is a major oversight Can the network recover?

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Network Implementation Cutover

High visibility event Typically scheduled for weekend Problems can occur Good idea to have technicians from equipment vendor

companies on hand during cutover Implementation Cleanup and Audit

Make adjustments Revise documentation Audit

Find out if benefits of new network are as expected Interview users and support personnel