Full in a year
A charity builds its office system with 24 ports on one switch. Twenty are used on day one. A year later, new staff, a printer and two meeting rooms fill the rest.
Growth is not a surprise. A good build leaves room for it, and keeps the same security rules when the new parts are added.
By the end of this lesson
Note
I can plan spare capacity for growth and check that a build meets what its users asked for.
Key words
| Word | What it means |
|---|---|
| Scalability | room for a system to grow without a rebuild |
| Capacity | how much a system can hold or carry, such as ports or addresses |
| User need | something a user has asked a system to do for them |
| Acceptance test | a check, done with the users, that the system does what they asked |
| Availability | how much of the time a system works when people need it |
| Network | computers and devices joined together so they can share data |
| Firewall | a device or program that blocks some messages and lets others through |
The cells students fill in are left blank in this preview.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
This is practice
Important
The real Task 4a has its own user needs and its own network file. Here the firm is invented. Practise the planning, then apply it to the real brief and say how your build meets each need.
Worked example: capacity and spare
| Thing | Total | Used on day one | Spare | Growth each year | Full in |
|---|---|---|---|---|---|
| Switch ports | 24 | 20 | 4 | 3 | 2 years |
| Staff addresses (/26) | 62 | 30 | 32 | 8 | 4 years |
| Cable runs to the comms room | 30 | 24 | 6 | 2 | 3 years |
| Internet speed in use | 100 | 40 | 60 | 15 | 4 years |
The cells students fill in are left blank in this preview.
Growing must not weaken security
When you add a new group, give it its own subnet. Give it its own firewall rules, with default deny. Give its people roles with the least access.
Do not "just plug it in" to the staff network. The new part follows the same rules as the old parts, from the first day.
Worked example: adding a group safely
| Step | What to do | Security reason |
|---|---|---|
| 1 | Choose a free subnet from the spare block | No clash with an existing range |
| 2 | Add its gateway and routes | The new group can reach only what it should |
| 3 | Add firewall rules after default deny | Nothing is open by accident |
| 4 | Create a group and give the least access | People see only what their role needs |
| 5 | Test allowed and blocked cases | Proof the new part follows the rules |
| 6 | Update the diagram, the address table and the build log | The documents stay true |
The cells students fill in are left blank in this preview.