CAPF AC 2022 Q10: Science & Technology – Computer & Information Technology
Which one of the following protocols is not an application layer of the TCP/IP model?
- (a) FTP
- (b) HTTP
- (c) DNS
- (d) IP
Answer: (d) IP
Explanation
Layers of the TCP/IP model
How to think: the TCP/IP model has four layers.
The application layer holds the protocols that users and programs deal with.
IP only carries packets from one address to another, so it sits lower down.
| Layer | Job | Protocols |
|---|---|---|
| Application | Services for users and programs | HTTP, FTP, DNS, SMTP, Telnet |
| Transport | End-to-end delivery | TCP, UDP |
| Internet (network) | Addressing and routing of packets | IP, ICMP |
| Network access (link) | Physical sending of data | Ethernet, Wi-Fi |
What each one does: FTP transfers files, HTTP carries web pages and DNS turns names into IP addresses.
Answer: (d) IP.
Why each option is right or wrong
- (a) Incorrect. FTP (File Transfer Protocol) is an application layer protocol.
- (b) Incorrect. HTTP carries web pages and belongs to the application layer.
- (c) Incorrect. DNS resolves names to addresses at the application layer.
- (d) CORRECT. IP works at the internet (network) layer, not the application layer.
Key point
TCP/IP model: application (HTTP, FTP, SMTP, DNS), transport (TCP, UDP), internet (IP, ICMP), network access. The OSI model has seven layers.
Remember
IP = internet layer; HTTP, FTP, DNS = application layer.
Common mistakes
- Marking DNS, thinking a naming system must sit low in the network.
- Mixing up the four-layer TCP/IP model with the seven-layer OSI model.
- Assuming IP is an application because the model is named after it.
Exam tip
Educated guess: FTP, HTTP and DNS are things you use (files, web pages, website names). IP is only an address system working underneath.
Sources
- NCERT Class XII Computer Science — Chapter 10: Computer Networks and Chapter 11: Data Communication (protocols)
- A. S. Tanenbaum, Computer Networks — The TCP/IP Reference Model