date: 2024-03-31
title: DCN-As-1
status: DONE
author:
- AllenYGY
tags:
- DCN
- Assignment
created: 2024-03-31T12:22
updated: 2024-04-10T18:04
publish: TrueDCN-Assignment1
Question I
What is the OSI model?
1. Explain different layers in the OSI model.
There are 7 layers in the in OSI Model
- Physical Layer
- It is concerned with transmitting raw bits over a communication channel.
- Data Link Layer
- It is to transform a raw transmission facility into a line that appears free of undetected transmission errors to the network layer.
- Network Layer
- It controls the operation of the subnet.
- Transport Layer
- It is to accept data from above, split it up into smaller units if need be, pass these to the network layer, and ensure that the pieces all arrive correctly at the other hand.
- Session Layer
- It allows users on different machines to establish sessions between them.
- Presentation Layer
- It is concerned with the syntax and semantics of the information transmitted.
- Application Layer
- It contains a variety of protocols that are commonly needed by users, such as HTTP, Email, etc.
2. Compare the differences between the OSI and TCP/IP models.
There are no Session Layer and Presentation Layer in TCP/IP models
Question II
A company’s computer network is the backbone of its business as it connects all its computers and related devices, allowing staff to work more efficiently across the organization. Suppose a commercial company has about 8000 staff. As a computer officer in the company, you are required to design a computer network for that company. Note that network design involves evaluating and understanding how all the elements of the network link together and how they can be made to run as efficiently as possible. Please answer the following questions.
1. Which network topology will you adopt?
- Star topology will be used in this network
2. What components will be used in the network?
- Central Connection Point (Hub, Switch, or Router)
- Nodes (Computers, Printers, Servers, etc.)
- Cabling
3. Give five important factors when designing a computer network (please give your explanations).
- Cost: This includes the initial setup expenses as well as ongoing maintenance and operation costs. Effective design balances affordability with performance and scalability requirements.
- Stability: A stable network ensures consistent availability and reliability, minimizing downtime and supporting productivity. This involves choosing dependable hardware and implementing redundancy where necessary.
- Scalability: The network should be able to grow and adapt to increased demands without extensive redesigns. This means planning for future expansions in users, devices, and data volumes.
- Performance: Network performance affects data transmission speed and efficiency. A well-designed network minimizes latency and maximizes throughput to provide a smooth user experience.
- Complexity: While some complexity might be necessary for functionality, a simpler network is generally easier to manage and troubleshoot. The goal is to find the optimal balance that meets the network's objectives without unnecessary complication.
Use a figure to illustrate the overall design.
Question III
The CRC method is used to transmit a bit-stream of
1. Show the actual bit string transmitted.
Frame:
Message after 3 zero bits are appended:
Reminder:
2. Suppose the third bit from the left is inverted during the transmission.
Show that this error is detected at the receiver’s end.
Receive Frame:
Receive Data:
Calculate Reminder:
Question IV
1. Sketch the Manchester encoding for the bit-stream: 1001 1000.
Question V
1. Calculate the Hamming Code for the bit-stream: 1101 1010 1010
| Position | Bit | Parity Calculation |
|---|---|---|
| 1 | 1 | - |
| 2 | 0 | - |
| 3 | 1 | 1 + 2 |
| 4 | 0 | - |
| 5 | 1 | 1 + 4 |
| 6 | 0 | 2 + 4 |
| 7 | 1 | 1 + 2 + 4 |
| 8 | 0 | - |
| 9 | 1 | 1 + 8 |
| 10 | 0 | 2 + 8 |
| 11 | 1 | 1 + 2 + 8 |
| 12 | 0 | 4 + 8 |
| 13 | 1 | 1 + 4 + 8 |
| 14 | 0 | 2 + 4 + 8 |
| 15 | 1 | 1 + 2 + 4 + 8 |
| 16 | 0 | - |
| 17 | 0 | 1 + 16 |
1010 1010 1010 1010 0
Question VI
Error correction, and error-detection, and retransmission can be used to tackle error bits in data communication. State two reasons why some applications use error correction instead of error detection and retransmission.
- For some application that need Real-time or Low latency, Delays in processes such as waiting for retransmissions can degrade the quality of service and the user experience.
- In environments where communication channels are inherently noisy or prone to high error rates (e.g., deep space communications, underwater communications), it may not be practical or efficient to retransmit data every time an error is detected.
Question VII
The Internet of Things (IoT) is doing great in many fields and services. Numerous IoT applications can ease our commercial operations. Suppose you are a project leader in a software house, and your team is required to write a proposal about IoT innovation. Please suggest what kind of application you would propose and why.
Proposal:
- A Smart Waste Management System. This system would leverage IoT technology to optimize waste collection and processing in urban areas.
Why:
- A Smart Waste Management System utilizing IoT technology offers a holistic solution to urban waste challenges by enhancing environmental sustainability, reducing operational costs through optimized routes and schedules.