← WA Computer Science ATAR Unit 1

Scalability of a network

A scalable network can grow in users, devices and traffic without a major redesign, for example by planning for growth, keeping spare switch ports and having an upgrade path.

Part of: WA Computer Science ATAR Year 11 — Network Communications — Module 86

Understanding Scalability of a network in WA Computer Science ATAR Unit 1

What it does: Buying about 50% more ports than current devices plans for growth, so the network can scale without a redesign. An upgrade path means existing cabling and layout can support faster speeds later, so the network scales without starting again. Planning for growth means allowing for extra users and devices in the future, not just today's needs. Scalability is the core term: a scalable network can be expanded smoothly as demand rises.

Common mistakes: A Python function definition must end with a colon. It should be def spare_ports(ports, used):. The switch is full only when devices >= ports. Using <= would say 'Buy another switch' while spare ports still exist. It should be if devices >= ports:.

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This module's key terms are also in a printable crossword (Modules 315–470) and word search (Modules 100–470).

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Learning
Duo
Which best describes a scalable network?
It can grow in users, devices and traffic without a major redesignIt can never be changed once it is built
Matches
switch_ports = devices # all 24 ports used
↓
Every switch port is already in use, so there are no spare ports. A new device would need extra hardware or a redesign.
Applying
Meanings
Term
scalability
Meaning
A scalable network can grow in users, devices and traffic without a major redesign, for example by planning for growth, keeping spare switch ports and having an upgrade path.
Practice
switch_ports ← 24
Testing
Gaps
spare = ports used
Check Answer
Spots
1def spare_ports(ports, used)
2 return ports - used

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Quick Questions

1. Which best describes a scalable network?
A. It can never be changed once it is built
B. It can grow in users, devices and traffic without a major redesign ✓
Scalability means the network can grow to meet demand without being rebuilt from scratch.
2. A school buys a 48-port switch but only uses 30 ports. What does this help with?
A. Spare ports make the network faster right away
B. Spare ports let new devices be plugged in later ✓
Unused switch ports are spare capacity. They allow growth without buying new equipment straight away.
3. Which choice shows planning for growth?
A. Choosing a switch with more ports than are needed today ✓
B. Buying exactly as many ports as there are devices today
Planning for growth means allowing for extra users and devices in the future, not just today's needs.
4. A company expects to double its staff in two years. Which network design is more scalable?
A. One that can have extra switches and access points added later ✓
B. One that must be completely replaced to add more staff
A scalable design has an upgrade path, so new equipment can be added without a major redesign.
5. What is an upgrade path?
A. A way to add capacity later, such as faster links or more switches ✓
B. A cable that runs between two buildings
An upgrade path is a planned way to expand or improve the network later without starting again.

Match the Pairs

scalability → The ability of a network to grow in users, devices and traffic without a major redesign
spare_ports = 8 → Unused switch ports kept free so new devices can be plugged in as the network grows
Planning for growth: choosing a switch with more ports than are needed today → switch_ports = devices * 1.5
An upgrade path: the network can move to faster links later without replacing everything → upgrade: 1 Gbps -> 10 Gbps
switch_ports = devices # all 24 ports used → Every switch port is already in use, so there are no spare ports. A new device would need extra hardware or a redesign.
design_for = current_users_only → The design ignores future growth. When users and traffic increase, the network will need a major redesign.

Key Term

scalability
A scalable network can grow in users, devices and traffic without a major redesign, for example by planning for growth, keeping spare switch ports and having an upgrade path.

Fill in the Blanks

1. spare = ports - used
Hint: Type the arithmetic operator that works out how many switch ports are still free.
2. if spare == 0: print("Add a switch")
Hint: Type the comparison operator that checks whether the spare ports have run out.
3. future = devices * 2
Hint: Type the operator that plans for growth by doubling the current device count.
4. if devices > ports: ports = ports + 24
Hint: Type the variable name that holds the port capacity being increased by the upgrade.
5. for i in range(5): devices = devices + 1
Hint: Type the function that creates the sequence of numbers for the loop adding new devices.

Spot the Error

Question 1
A def spare_ports(ports, used)
B return ports - used
C print(spare_ports(24, 18))
Line A — A Python function definition must end with a colon. It should be def spare_ports(ports, used):
Question 2
A if devices <= ports:
B print('Buy another switch')
C else:
D print('Spare ports left')
Line A — The switch is full only when devices >= ports. Using <= would say 'Buy another switch' while spare ports still exist. It should be if devices >= ports:
Question 3
A users = 40
B growth = = 0.25
C future = users * (1 + growth)
D print(future)
Line B — Assigning a value to a variable uses a single =. The comparison operator == is wrong here and the line has a syntax error. It should be growth = 0.25
Question 4
A users = 50
B rate = 0.2
C for year in range(3):
D users = users * rate
E print(users)
Line D — Planning for growth means adding growth to the current users, so you multiply by (1 + rate). Multiplying by just rate would shrink the user count. It should be users = users * (1 + rate)
Question 5
A speeds = [1, 10, 40]
B current = speeds(0)
C upgrade = speeds[1]
D print(current, upgrade)
Line B — List items are accessed with square brackets, not round brackets. Round brackets try to call speeds as a function. It should be current = speeds[0]

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