---
title: "Tasks done at OSI layers (set 2)"
subject: "Computer Networks and Security"
chapter: 1
key: "semester_7/computer_networks_and_security:osi-layer-task-mapping-2"
source: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/osi-layer-task-mapping-2
site: BCT Engineering
---

# Tasks done at OSI layers (set 2)

Computer Networks and Security · Chapter 1: Introduction to Computer Network

- Asked in: 2069 Chaitra, 2 marks
- Video: [What is OSI Model?](https://www.youtube.com/watch?v=Ilk7UXzV_Qc) — RealPars
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/osi-layer-task-mapping-2
- Whole chapter: https://www.bctengineer.com/md/semester_7/computer_networks_and_security/chapter-1

## Question

Mention in which level of the layer of the OSI reference model the following tasks are done: i) Timing and voltage of received signal ii) Encryption and decryption of data iii) Data framing iv) Point-to-point connection of socket.

## Short answer

Timing and voltage of a received signal belong to the physical layer, encryption and decryption to the presentation layer, data framing to the data link layer, and point-to-point socket connection to the transport layer.

## Answer

| Task | OSI layer |
|---|---|
| i) Timing and voltage of received signal | **Physical layer** |
| ii) Encryption and decryption of data | **Presentation layer** |
| iii) Data framing | **Data link layer** |
| iv) Point-to-point connection of socket | **Transport layer** (port and socket address) |

The physical layer defines bit duration and voltage levels. The data link layer groups bits into frames. Sockets (IP address plus port number) identify end-to-end process connections at the transport layer.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Timing and voltage of the received signal are handled at which layer?
   A. Data link
   B. Physical
   C. Network
   D. Presentation
   Answer: B. The physical layer defines bit duration and voltage levels. (Key point: Timing and voltage)

2. Data framing is done at which layer?
   A. Physical layer
   B. Network layer
   C. Data link layer
   D. Transport layer
   Answer: C. The data link layer groups bits into frames. (Key point: Data framing)

3. A socket (IP address plus port number) identifies connections at which layer?
   A. Transport layer
   B. Network layer
   C. Session layer
   D. Data link layer
   Answer: A. Port numbers and sockets belong to the transport layer. (Key point: Socket layer)

## Related in Computer Networks and Security

- [Tasks done at OSI layers (set 1)](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aosi-layer-task-mapping-1) — Computer Networks and Security, chapter 1
- [Explain OSI model and its layers](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aosi-model-layers) — Computer Networks and Security, chapter 1, asked 2×
- [Data link layer framing](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aframing-mechanisms) — Computer Networks and Security, chapter 3, asked 3×