Computer Networking Fundamentals and OSI Model

Posted on Mar 4, 2026 in Contemporary Music Composition

Purpose of Layered Architecture

  • Divides complex network tasks into layers
  • Easier design and troubleshooting
  • Standardization across vendors
  • Independent development of layers

OSI Model Layers and Functions

  • Physical Layer
    • Transmits raw bits
    • Deals with cables, voltage, and signals
  • Data Link Layer
    • Error detection
    • Framing and MAC addressing
  • Network Layer
    • Logical addressing (IP)
    • Routing of packets
  • Transport Layer
    • End-to-end delivery
    • Error and flow control
  • Session Layer
    • Session establishment and termination
  • Presentation Layer
    • Data encryption and compression
    • Format conversion
  • Application Layer
    • Interface for user applications
    • Examples: HTTP, FTP, SMTP

Q1 (c) Analog to Digital Conversion via PCM

  • Sampling of analog signals
  • Quantization of sampled values
  • Encoding quantized values into binary
  • Produces a digital signal suitable for transmission

Q2 (a) CRC Error Detection

  • Used to detect errors in transmitted data
  • Adds redundancy bits to data

Steps in the CRC Process

  • Choose a generator polynomial
  • Append zero bits to the data
  • Perform binary division
  • Append the remainder to the data
  • The receiver repeats division to check for errors

Q2 (b) Connectionless vs Connection-Oriented Services

Connectionless Service

  • No prior connection setup
  • Faster but unreliable
  • Packets may arrive out of order
  • Example: UDP

Connection-Oriented Service

  • Connection setup required
  • Reliable data transfer
  • Error checking and retransmission
  • Example: TCP

Q2 (c) IPv4 Addressing and Public vs Private IPs

IPv4 Address Format

  • 32-bit address
  • Written as four octets (e.g., 192.168.1.1)

Public IP Address

  • Globally unique
  • Used on the Internet
  • Assigned by an ISP

Private IP Address

  • Used within a local network
  • Not routable on the Internet
  • Examples: 192.168.x.x, 10.x.x.x

Q3 (a) Types of Multiplexing

  • Frequency Division Multiplexing (FDM)
    • Bandwidth divided into frequency bands
    • Used in radio and TV
  • Time Division Multiplexing (TDM)
    • Time divided into slots
    • Each user gets a specific time slot
  • Wavelength Division Multiplexing (WDM)
    • Used in optical fiber
    • Multiple light wavelengths
  • Statistical TDM
    • Dynamic time allocation
    • Better bandwidth utilization

Importance of Multiplexing

  • Efficient use of bandwidth
  • Allows multiple users on the same medium


Q3 (b) Network Congestion Control

  • Congestion occurs when network load exceeds capacity
  • Causes packet loss and delay

Why It Is Needed

  • Prevents network collapse
  • Improves performance

Techniques

  • Traffic Shaping: Controls the data rate
  • Congestion Avoidance: Adjusts the sending rate (e.g., TCP window control)

Q3 (c) Iterative vs Recursive DNS Queries

Iterative Query

  • The client queries multiple DNS servers
  • Each server gives the best possible answer

Recursive Query

  • The DNS server performs all searching
  • The client gets the final answer directly

Q4 (a) Client-Server Advantages over Peer-to-Peer

  • Centralized control
  • Better security
  • Easy data management
  • Scalable architecture
  • Reliable performance

Q4 (c) DHCP Working Mechanism

  • Client sends DHCP Discover
  • Server replies with DHCP Offer
  • Client sends DHCP Request
  • Server sends DHCP Acknowledgment
  • IP address is assigned automatically

Q5 (a) Transmission Impairment and SNR

Transmission Impairment

  • Signal distortion
  • Noise interference
  • Attenuation

Signal-to-Noise Ratio (SNR)

  • Ratio of signal power to noise power
  • Higher SNR = better quality
  • Low SNR causes errors

Q5 (b) Guided Transmission Media

Twisted Pair Cable

  • Cheap and flexible
  • Affected by noise

Coaxial Cable

  • Better noise resistance
  • More expensive

Optical Fiber

  • Very high speed
  • Immune to interference
  • Expensive installation

Q5 (c) Transport Layer Functions

  • Process-to-process communication
  • Port addressing
  • Segmentation and reassembly
  • Flow control
  • Error control