3.13 Developing the Requirements Specification

The requirements specification and requirements map include the results of the analysis process. The first part of the process is determining any initial conditions for the project. This includes the type of network project, scope of the project, project goals, and political, administrative, and financial forces acting on the project. Part of the initial conditions of the project may be determining whether the network is single-tier or multitier performance. We would also do a rapid, initial evaluation of the problems in the network, if any, and estimate resources and schedule.

Thus, before we gather any requirements for the network, we should have some or all of this information documented. Consider the example of a building network from Chapter 2. The first part of the requirements specification may look like Figure 3.28.

Requirements Specification
Section 1—Initial Conditions
Project Type	Upgrade of building network
Project Scope	Single building, two floors, approximately 150 users
Project Goals	Improve performance to all users, particularly some mission-critical applications, and increase security to Internet
Other Conditions	Financial TBD
Problem Evaluation and Definition		Application performance has been a recurring problem, so management wants to upgrade network and has suggested upgrading interfaces to Fast Ethernet. Some users have GigE interfaces on their workstations.

Figure 3.28: Template for initial conditions.

The second part of the requirements specification includes the gathered and derived requirements for the network. In this example, some requirements were learned in the initial discussion with the customer (management and staff). These requirements are shown in Figure 3.29, using the template from Chapter 2.

Requirements Specification
Section 2—Listing of Requirements
ID/Name	Date	Type	Description	Gathered/	Locations	Status	Priority
1	14Jan03	User	User distribution is 60 engineers, 15 HR and Finance, 30 Manufacturing, 10 Management, 30 Sales/Marketing, 5 Other.	Gathered from Management	TBD	Info	TBD
2	14Jan03	Network	Each area of the building must support Fast Ethernet connections to the backbone.	Gathered from Management	TBD	TBD	TBD
3	14Jan03	Application	Database, Visualization, Manufacturing, and Payroll applications are considered mission-critical for this company. More information needed.	Gathered from Management	TBD	TBD	TBD
4	14Jan03	Application	Payroll application (PAY1) requires 100% uptime (while in operation) between finance and outside payroll company.	Gathered from Management	TBD	TBD	TBD
5	14Jan03	Network	Company must be kept secure from Internet attacks.	Gathered from Management	TBD	TBD	TBD

Figure 3.29: Requirements gathered from initial meeting with customer.

Requirements can't always be gathered from early meetings, though. To get requirements from users, we usually ask them questions about their environment. For this example, a questionnaire was developed and sent to all employees of the company. Figure 3.30 shows an example of such a questionnaire.

List applications that you use	How often? (times per day)	How long each time?
Application 1 -
Application 2 -
Application 3 -
Application 4 -
Application 5 -
List computers or other devices that you use that are connected to network	Network interface	Operating system
Device 1 (Desktop/Laptop) -
Device 2 -
Have you experienced any problems with the network? If so, please give a brief description of each problem
Problems -
What capabilities would you like to see in the network (performance, features)
Performance - Features - Other -
Do you have any issues or problems with security? If so, please give a brief description of each problem.
Security Problems -
Any other suggestions, issues, or comments?
Suggestions/ Issues/ Comments

Figure 3.30: Template for questionnaire.

Of course, not everyone will respond to the questionnaire. Experience has shown that anywhere from 10% to 40% will respond. This depends on how long the questionnaire is, how difficult it is to fill out, and how large the organization is. Also, you will get most of the responses within a few days, but some will trickle in over a longer period (e.g., a few weeks). You can update the requirements a few times based on the results of new responses.

The results of the example questionnaire are shown in Figures 3.31 and 3.32.

Requirements Specification
Section 2—Listing of Requirements
ID/Name	Date	Type	Description	Gathered/Derived	Locations	Status	Priority
6	20Jan03	Application	Inventory application (INV1) for manufacturing requirements not determined at this time.	Gathered from Users (MAN)	TBD	TBD	TBD
7	25Jan03	Device	Engineering users have workstations with GigE NICs.	Gathered from Users (ENG)	TBD	TBD	TBD
8	02Feb03	Application	Other general applications: mail, word processing, internal and external Web access. More information needed.	Gathered from Network Staff	TBD	TBD	TBD

Figure 3.31: Additional requirements gathered from questionnaire.

Requirements Specification
Section 2—Listing of Requirements
ID/ Name	Date	Type	Description	Gathered/Derived	Locations	Status	Priority
9	01Feb03	Application	Database application (DB1) requires a minimum of 150 Kb/s per session.	Gathered from Various Users	TBD	TBD	TBD
10	02Feb03	Network	Company requires a minimum of T1 access to Internet.	Gathered from Network Staff	TBD	TBD	TBD
11	02Feb03	Network	Current network will be completely replaced, so there are no requirements from existing network.	Gathered from Network Staff	N/A	Info	TBD
12	05Feb03	Application	Visualization application (VIS1) for finance requires up to 40 Mb/s capacity and 100-ms round-trip delay.	Derived from Application	TBD	TBD	TBD

Figure 3.32: Additional requirements gathered from meetings with users and staff.

These requirements were refined and added to by meeting with each of the groups (including meetings with management and network staff) in the company.