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S4 ICT: Computer Networks and Internet Protocols (Paper 1 (basics))
Tutor Prep Guide · LAN versus WAN, IPv4 and IPv6 address length, the 8-bit range of each octet, subnet masks and usable hosts, HTTP/HTTPS/FTP/SMTP with their ports, TCP versus UDP, and bandwidth to download time
S4 ICT: Computer Networks and Internet Protocols (Paper 1 (basics))
Paper 1 (basics): ten questions on networks and internet protocols, with answers and notes.
Direct answers Level: S4 ICT; format: IP addresses, subnet masks, usable hosts, ports, TCP and UDP, bandwidth arithmetic.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S4 ICT: Computer Networks and Internet Protocols |
| Level | S4 |
02 Questions (10 items)
- FoundationAn IPv4 address is 32 bits long. How many bytes is that?
- FoundationAn IPv6 address has 128 bits. How many times the 32 bits of IPv4 is that?
- FoundationWhich port does ordinary web traffic (HTTP) use by default?
- IntermediateOne IPv4 octet is 8 bits. What is the largest decimal value it can hold?
- IntermediateWhich port does HTTPS use by default?
- IntermediateHow many usable host addresses does a /24 subnet such as 192.168.1.0/24 provide?
- ChallengeHow many seconds does a 1 GB (take it as 1 000 MB) file need at 100 Mbps?
- ChallengeEach packet is 1 500 bytes. What is the total of ten packets in kB (1 kB as 1 000 bytes)?
- ChallengeFTP transfers files. What is the default port of its control connection?
- Error redoA student writes that an IPv4 octet can be as large as 300. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 4 | One byte is eight bits, so 32 bits is 4 bytes. |
| 2 | 4 | 128 divided by 32 is 4, which is why the IPv6 address space is so much larger. |
| 3 | 80 | HTTP uses port 80 by default; the same page over HTTPS moves to port 443. |
| 4 | 255 | Eight bits give 2 to the power 8, that is 256 combinations, so counting from 0 the largest is 255. |
| 5 | 443 | HTTPS defaults to 443; it adds encryption on top of HTTP and uses a different port. |
| 6 | 254 | A /24 leaves 8 host bits: 2 to the power 8 is 256, less the network and broadcast addresses, which gives 254. |
| 7 | 80 seconds | Multiply 1 000 MB by 8 to get 8 000 Mb, then divide by 100 Mbps, giving 80 seconds. |
| 8 | 15 kB | 1 500 times 10 is 15 000 bytes, and dividing by 1 000 gives 15 kB. |
| 9 | 21 | FTP uses 21 for control and usually 20 for the data connection, and keeping them separate is typical of FTP. |
| 10 | The maximum is 255, because each octet is only 8 bits | Eight bits can only express 0 to 255, so anything from 256 up is invalid; check the bit count whenever you see such a number. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
First ask how many bits the address has and how many host bits remain, then decide between 2 to the power minus two and a plain subtraction; name both the protocol and its port, and convert MB to Mb before dividing by bandwidth.Tutor Registration →
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