13 Step Approach to Network Design. 2 13 Steps A Systems Approach 8Conduct a feasibility Study 8Prepare a plan 8Understand the current system 8Design.

13 Step Approach to Network Design

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13 Steps A Systems Approach Conduct a feasibility Study Prepare a plan Understand the current

system Design the network Identify the Geographic

scope Analyze the Messages

Calculate Traffic / Circuit Loading

Develop A control Matrix Determine Network

configuration Software Considerations Hardware Considerations Network Costs Sell and Implement Network

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1 : Conduct A feasibility Study Purpose : Make a go /no go network decision. Do we

proceed with designing a new network or come up with another solution?

What do we do at this Stage? :Define the problem, and put it in writing.

Deliverable upon completion: Statement of Objectives Feasibility report and/or Oral presentation to Management

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Analyze Needs Assessment Factors

Increased volume of inputs/outputs Inadequate data processing Obsolete Hardware/ Software Unsatisfactory Movement of data Inadequate file structures (database) Inadequate interfacing between application systems

and other staff

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Needs Assessment Factors Continued

Documentation not available in a timely manner Unreliability of current system Inability to maintain current system Inadequate security/privacy Decreasing productivity Inadequate training Future growth that requires new methods

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Needs Assessment Factors Continued

Competition that forces change Negative effect of the old system on morale New network viewed as positive investment Inadequate floor space for personnel files Avoidance of future costs Need for more timely access to information for

improved decision making

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Needs Assessment Factors Continued Increasing flow of information or paperwork Need to expand capacity of business functions Need to increase level of service quality or

performance Need for new methods and better exchange of

information in conducting international operations Reduction of inventories Need for a paperless office Desire to take advantage of future technology

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Feasibility Study

After our problem is defined

1: the scope, boundaries are established

2: preliminary magnitudes of cost identified

3: preliminary geographical study

4: identify areas of business to be affected

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2: Prepare a Plan Consider

1: Technical Feasibility

2: Operational Feasibility

3: Economic Feasibility

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Prepare a Plan STEP 1 : Split Purpose and objectives into three groups of

goals

1: Major Goals : reason that network is being built

2: Intermediate Goals : other gains the system can make while serving its major purpose

3: Minor Goals : future enhancements (wish list)

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Prepare a Plan

Step 2: Identify Sources of Information and the types of information that need to be collected

Step 3: Develop some evaluation criteria

This aids in doing a post – implementation evaluation. Was our design a success?

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Evaluation Criteria Time Cost Quality Capacity Efficiency Productivity Accuracy

Flexibility Reliability Acceptance Controls Documentation Training System Life

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3: Understand the Current System Objective: to gain complete understanding of current

operations and any system that is functioning

Understanding of : sequence of operations, processing times, work volumes, current communication systems, existing costs, user management needs/complaints.

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Understand the Current System Gather Information Identify application that the network is used for Identify proposed future applications Learn about industry (check what competitors are doing) Legal requirements? Who will be affected? Try to understand company politics Describe and identify each input/ process / output cycle Identify file formats

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Understand The Current System Deliverable: Detailed Description of Existing System

Should include: design ideas, notes on whether forms or interfaces are adequate, who was helpful, who hindered investigation, impressions, DFD’s etc.

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4: Design The Network At this Stage do not propose solutions just state precisely the

requirements such as What to do

Need to transmit 50 characters per minute plus overhead.

As opposed to

9600 bps modem is required.

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Step 4: Design the new network requirements

Assemble a list of functions to be performed by the proposed network

DFD’s would be helpful at this stage Review of organizations short term and long term

plans

Future changes expected etc.

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Map out, plan , arrange the parts to satisfy objectives.

Leave actual hardware and software considerations for later

Design The Network

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5: Identify Geographic Scope A data Communication Network has four levels of

geographic scope

1: International (worldwide)2: Country (within boundaries and laws of a single

country)3: City4: Local facility

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Identify Geographic Scope Start internationally and

work your way down At International and

Country Level all you require is a map Illustrate interconnection

points etc.

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Identify Geographic Scope

At City Level we can consider two things

State map showing interconnections between cities Map showing interconnected local facilities.

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Identify Geographic Scope Local Facility Level

Blueprints or drawings of building floor layouts are used

1: Terminal Locations are identified

2: Telephone equipment rooms and location of communication circuits are identified

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Conclusion step 5

Deliverables at the end of this stage All maps developed

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6 : Analyze The Messages Can be done in combination with previous Step or post

step (calculate traffic/circuit loading)

Identify each message type that will be transmitted or received

Identify each message field and average number of characters per field (consider peak or extreme situations)

In report include description of message and example

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Analyze The MessagesConsider peak periods of the day/ month / financial year

Find out size of each message

Determine on average how many messages are sent of each type per day as well as originator of messages

Use of monitors/analyzers may be helpful

Deliverable: Network Link Traffic Table

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7 Calculate Traffic / Circuit LoadingCalculate circuit capacities required at each link on our geographic and location maps

Convert characters to bits

Examine alternative links possibly to improve speed etc.

If links cannot support traffic then make adjustments as needed. Consider time zones etc.

Consider Growth factor

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8: Develop Control Matrix

Considers

1: Who uses what?

2: What type of access do they or should they have?

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Develop Control MatrixMust protect data from threats such as Errors and omissions Message loss or change Disasters Breaches of privacy, security/theft Unreliability Incorrect recovery Poor error handling Lack of validation

For now just state threats and components, our solutions will be developed in next step

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9: Determine network configurations

Configuring our network to achieve our goalsGenerally this step is performed with next twoConsider Minimum circuit mileage between stations, nodes Adequate circuit capacity for future needs Reliability Efficient software/protocols Reasonable cost Acceptance by users