Computer Communications – Data Communications

1. Introduction to Data Communication

• Definition: The process of transmitting digital or analog data between two or more devices via a transmission medium.
  
• Components of a Data Communication System:
  
  • Message: The data to be communicated
    
  • Sender: Device that sends the data
    
  • Receiver: Device that receives the data
    
  • Medium: The physical path (e.g., cables, air)
    
  • Protocol: Set of rules for data exchange
    

2. Characteristics of Effective Data Communication

• Delivery: Data must reach the correct destination.
  
• Accuracy: Data must be delivered correctly.
  
• Timeliness: Data must be delivered in a timely manner.
  
• Jitter: Variation in packet arrival time should be minimal (especially in real-time systems).
  

3. Data Transmission Methods

• Analog vs Digital Transmission
  
  • Analog: Continuous signals (e.g., voice)
    
  • Digital: Discrete signals (e.g., binary 0s and 1s)
    
• Transmission Modes:
  
  • Simplex: One-way communication
    
  • Half-duplex: Both directions, but one at a time
    
  • Full-duplex: Both directions simultaneously
    
• Transmission Media:
  
  • Guided: Twisted pair, coaxial cable, fiber optics
    
  • Unguided: Radio waves, microwaves, infrared
    

4. Communication Protocols

• Definition: Set of rules that govern data communication.
  
• Types:
  
  • TCP/IP (Transmission Control Protocol/Internet Protocol)
    
  • UDP (User Datagram Protocol)
    
  • HTTP, FTP, SMTP, DHCP, DNS
    
• Functions:
  
  • Data formatting
    
  • Addressing
    
  • Routing
    
  • Flow and error control
    

5. Network Topologies

• Bus Topology
  
  • Single backbone cable, easy to implement
    
• Star Topology
  
  • Central hub/switch connects all devices
    
• Ring Topology
  
  • Each device connected to two others
    
• Mesh Topology
  
  • Every device connects to every other
    
• Hybrid Topology
  
  • Combination of two or more topologies
    

6. Error Detection and Correction

• Types of Errors:
  
  • Single-bit errors
    
  • Burst errors
    
• Detection Techniques:
  
  • Parity Check (Even or Odd)
    
  • Checksum
    
  • Cyclic Redundancy Check (CRC)
    
• Correction Techniques:
  
  • Automatic Repeat Request (ARQ)
    
  • Forward Error Correction (FEC)
    

7. OSI and TCP/IP Models

OSI Model (7 Layers)

1. Application – User interface and services (HTTP, FTP)
   
2. Presentation – Data translation and encryption
   
3. Session – Establish and manage sessions
   
4. Transport – Reliable delivery (TCP)
   
5. Network – Routing and addressing (IP)
   
6. Data Link – Error detection, framing (Ethernet)
   
7. Physical – Transmission media and signals
   

TCP/IP Model (4 Layers)

1. Application – HTTP, FTP, DNS
   
2. Transport – TCP, UDP
   
3. Internet – IP, ICMP
   
4. Network Access – Ethernet, Wi-Fi
   

8. Types of Networks

• LAN (Local Area Network)
  
  • Small geographical area (e.g., office, school)
    
• WAN (Wide Area Network)
  
  • Covers large areas (e.g., the internet)
    
• MAN (Metropolitan Area Network)
  
  • Covers a city or large campus
    
• PAN (Personal Area Network)
  
  • Short-range (e.g., Bluetooth)
    

9. Data Communication Devices

• Router – Directs data between networks
  
• Switch – Connects devices within a LAN
  
• Hub – Broadcasts data to all ports (less efficient)
  
• Modem – Converts digital to analog and vice versa
  
• Access Point – Enables wireless connectivity
  

10. Practical Applications in Modern Networking

• Email and Web Browsing
  
• Cloud Computing
  
• VoIP and Video Conferencing
  
• Internet of Things (IoT)
  
• Network Security Protocols
  

11. Preparation for Advanced Topics

• Basics of IP addressing and subnetting
  
• Introduction to network design
  
• Understanding firewalls and network policies
  
• Packet analysis using tools like Wireshark