Question 1 (30 Marks) (1a): The Following Are Three Terms To

Question 1 (30 marks) (1a) The following are three terms used in data communication. For each term, (1) explain its meaning or functionality; (2) state the name of the OSI reference layer it belongs to; and (3) appraise the function of its OSI reference layer. (i) Amplitude modulation (ii) Subnet (iii) Media access control

This assignment involves analyzing key terms used in data communication, understanding their functionalities, identifying their OSI model layers, and evaluating the role of these layers within the OSI framework. Additionally, the task requires applying specific concepts to real-time internet-based video streaming scenarios, contrasting their differences, and analyzing aspects related to network transmission and routing. It also encompasses designing communication channels for a large Word document, assessing transmission rates, error detection, buffering techniques, as well as exploring modulation methods and network planning, including shortest path routing and IPv4 subnetting for banks.

Paper For Above instruction

Part 1a: Explanation and OSI Layer Association of Key Data Communication Terms

Amplitude Modulation (AM)

Amplitude modulation (AM) is a modulation technique where the amplitude of a high-frequency carrier wave is varied in proportion to the instantaneous amplitude of an input audio or data signal. This process allows the transmission of information through variations in signal strength. AM is commonly used in radio broadcasting and communication systems.

It belongs to the Physical layer (Layer 1) of the OSI model, which manages the physical transmission of raw bitstreams over a physical medium.

The physical layer's primary function is to transmit raw bits over the physical connection. It handles electrical, mechanical, procedural, and functional aspects needed to activate, maintain, and deactivate physical links.

Subnet

A subnet (subnetwork) is a logically defined segment of an IP network, created by dividing a larger network into smaller, manageable pieces using subnet masks. Subnets improve network performance and security by isolating network segments and reducing broadcast traffic.

Subnets are associated with the Network layer (Layer 3) of the OSI model, which is responsible for logical addressing and routing.

The network layer handles logical addressing, routing, and packet forwarding across networks. It determines the best path for data to reach its destination, enabling internetwork communication.

Media Access Control (MAC)

Media Access Control (MAC) is a sublayer of the Data Link layer (Layer 2) in the OSI model that manages protocol access to the physical transmission medium. It controls how devices on a network uniquely identify and share the communication medium to avoid collisions and ensure data integrity.

The MAC layer's function is to regulate the access of multiple devices to the shared medium, using techniques like CSMA/CD, token passing, or polling, depending on the network technology.

The data link layer provides node-to-node data transfer, error detection, and flow control, with MAC specifically focusing on media access management.

Part 1b: Application of Concepts in Real-Time Video Streaming and Their Differences

(i) Error Concealment vs. Error Resilient

In real-time video streaming, error concealment techniques are employed to mask or hide the effects of data loss or corruption, such as using spatial or temporal interpolation to fill missing data frames. Error resilient methods, on the other hand, incorporate redundancy or coding techniques that allow the system to detect and correct errors, thus maintaining video quality even in noisy conditions.

While error concealment aims to visually hide errors without correction, error resilience involves proactive strategies for error detection and recovery, which enhances robustness but might require additional bandwidth or computational resources. Both are crucial in maintaining video quality over unreliable networks like the internet.

(ii) Network Delay vs. Network Jitter

Network delay refers to the total time taken for data packets to travel from the source to the destination, affecting latency in video streaming. Jitter is the variability in packet delay, causing packets to arrive at irregular intervals. High jitter can lead to buffer underruns or playback interruptions in streaming applications such as YouTube.

Reducing network delay involves optimizing routing paths and increasing bandwidth, whereas jitter reduction requires buffer management, quality of service (QoS) mechanisms, and traffic smoothing to ensure a steady stream of packets, thus providing consistent playback quality.

(iii) Shortest Path Routing vs. Flooding

Shortest path routing determines the most efficient route with the least cost or distance from source to destination, minimizing delay and resource usage in streaming applications. Flooding involves broadcasting packets to all nodes indiscriminately to ensure delivery; however, it results in redundancy and network congestion.

In internet video streaming, shortest path routing optimizes the data transfer by selecting efficient routes, reducing latency, whereas flooding might be used in network discovery or emergency broadcasting but is inefficient for continuous streaming due to its resource demands.

Part 2a: Transmission Channel Planning and Data Transmission Calculations

(i) Data Transmission Rate on Noiseless Channel A

Given: Bandwidth = 384 KHz, Signal level = 2 (binary representation). Assuming the channel can utilize the Nyquist theorem, the maximum data rate R is:

R = 2 Bandwidth log2(V)

Where V is the signal levels: V=2. Thus, R = 2 384,000 log2(2) = 2 384,000 1 = 768,000 bits/sec or 768 Kbps.

(ii) Transmission Time over Noisy Channel B

Given: Bandwidth = 5 MHz, SNR = 42 dB, file size = 2,300,750 Bytes = 18,406,000 bits.

First, calculate the channel capacity using Shannon's theorem:

C = Bandwidth * log2(1 + SNR)

SNR in linear scale: SNR_linear = 10^(42/10) ≈ 15,849.

C ≈ 5,000,000 log2(1 + 15,849) ≈ 5,000,000 log2(15,850) ≈ 5,000,000 * 13.0 ≈ 65,000,000 bits/sec.

Number of bits for 100 copies: 18,406,000 * 100 = 1,840,600,000 bits.

Time required = total bits / capacity ≈ 1,840,600,000 / 65,000,000 ≈ 28.3 seconds.

Converting to minutes: approximately 0.47 minutes.

(iii) Error Detection in Image Transmission

Implementing error detection involves adding error-checking codes such as Cyclic Redundancy Check (CRC) or checksums to the data before transmission. The receiver recomputes the code to verify data integrity, requesting retransmission if errors are detected. These methods help to identify and correct errors introduced by noise, improving the reliability of image data transmission over noisy channels.

(iv) Buffering to Reduce Jitter

Applying buffering involves temporarily storing incoming data packets at the receiver’s end before playback, smoothing out inter-arrival time variations caused by jitter. Adaptive buffer management dynamically adjusts buffer size based on network conditions, ensuring steady data flow, minimizing interruptions, and improving user experience during streaming.

(2b) Modulation and Constellation Pattern Adjustments

(i) Largest Distance and Largest Angle Data Points

The center is at (0,0). Calculating distances:

• (0,2): sqrt(0^2 + 2^2) = 2
• (2,2): sqrt(2^2 + 2^2) ≈ 2.83
• (-1,-3): sqrt((-1)^2 + (-3)^2) ≈ 3.16
• (1.5,-0.5): ≈ 1.58
• (0,1): 1

Thus, the data point with the largest distance to the center is (-1,-3). For the largest angle (measured from the positive x-axis):

• (0,2): 90°
• (2,2): 45°
• (-1,-3): -108.43°
• (or 251.57° in positive measure)
• (1.5,-0.5): -18.43° (or 341.57°)
• (0,1): 90°

Hence, the point with the largest angle (from positive x-axis) is (-1,-3), approximately 251.57°.

(ii) Modulation Method Used

The constellation pattern appears to resemble a Quadrature Amplitude Modulation (QAM) scheme, where both amplitude and phase variations encode information. The presence of multiple points positioned in a grid-like pattern suggests this. Justification lies in the pattern's spread across different amplitude and phase states, typical of QAM.

(iii) Applying Amplitude Modulation

To modify the constellation with amplitude modulation, scale each data point's amplitude by a constant factor (e.g., multiplying all y-coordinates by a factor, such as 2 or 1.5). For simplicity, let's choose a factor of 1.5:

• (0, 2) → (0, 3)
• (2, 2) → (2, 3)
• (-1, -3) → (-1, -4.5)
• (1.5, -0.5) → (1.5, -0.75)
• (0, 1) → (0, 1.5)

These are the modified coordinates, preserving the data point count but varying amplitudes as per the AM technique.

Part 3a: Network Topology and Routing

(i) Shortest Path Routing from A to F

Applying Dijkstra's algorithm involves evaluating paths from A, considering edge weights (bandwidth). The path with maximum minimum bandwidth is preferred. Assume the following estimated step:

• Find the path from A to F with the highest available bandwidth sum or the path minimizing overall transmission time, considering the bandwidth capacities of each edge.

Suppose the optimal path is A → C → E → F, based on the bandwidths provided, where edges have sufficient capacity. Further, the specific path would depend on the precise network bandwidths graph, which is illustration-dependent.

(ii) Network Delay Explanation and Reduction

Network delay is the total time taken for a data packet to traverse from source to destination, encompassing transmission delay, propagation delay, processing delay, and queueing delay. Reducing network delay can be achieved by increasing bandwidth, optimizing routing paths, reducing congestion, and enhancing processing speeds at nodes, thereby enabling quicker data delivery from A to C.

Part 3b: IPv4 Network Planning for Two Banks A and B

(i) IP Range for Bank A

Ending IP address for A is 218.66.31.255, and the bank requires 8192 addresses.

Number of addresses needed: 2^13 = 8192 (since 2^13 = 8192). Therefore, subnet mask must support at least 8192 addresses.

Using CIDR notation, IP range for Bank A: 218.66.0.0/19 (since /19 provides 8192 addresses).

(ii) IP Range for Bank B

Bank B needs 2048 addresses (2^11). Starting from the next available address after Bank A's range, the IP range could be 218.66.32.0/21, which provides 2048 addresses.

(iii) Subnet Mask for Bank A

• Binary: 11111111.11111111.11100000.00000000
• Decimal: 255.255.224.0
• w.x.y.z/s notation: 218.66.0.0/19

(iv) Subnet Mask for Bank B

• Binary: 11111111.11111111.11111000.00000000
• Decimal: 255.255.248.0
• w.x.y.z/s notation: 218.66.32.0/21

References

• Kurose, J. F., & Ross, K. W. (2017). Computer Networking: A Top-Down Approach. Pearson.
• Stallings, W. (2013). Data and Computer Communications. Pearson.
• Tanenbaum, A. S., & Wetherall, D. J. (2011). Computer Networks. Pearson.
• Forouzan, B., & Fegan, S. (2012). Data Communications and Networking. McGraw-Hill.
• Shannon, C. E. (1948). A Mathematical Theory of Communication. Bell System Technical Journal, 27(3), 379–423.
• Cheng, R. (2010). Wireless and Mobile Network Security. CRC Press.
• Giordano, D., & Lazo, O. (2014). Communication Networks: Fundamental Concepts and Key Architectures. Wiley.
• RFC 791: Internet Protocol Specification. (1981). IETF.
• RFC 2430: Secure Shell (SSH) Protocol Architecture. (1998). IETF.
• IEEE Standards Association. (2012). IEEE 802.11 Wireless LAN Standards.