Lecture: Basic Concepts of Networking

Introduction

• Course: Ethical Hacking
• Today's Lecture: Basic Concepts of Networking
• Topics: Types of computer networks, circuit switching vs packet switching, virtual circuits

Computer Networks Overview

• Definition: Communication system connecting computing devices
• Purpose:
  • Enable communication between devices
  • Connect various gadgets and equipment to networks (e.g., home security systems)
  • Improve connectivity, resource sharing (cloud computing), and social networking

Types of Computer Networks

Local Area Networks (LAN)

• Characteristics:
  • Connect hosts in small geographical areas (same room, building, or campus)
  • Typically use Ethernet standards (e.g., 10 Mbps, 100 Gbps)
  • Fast and relatively cheaper in the long run
• Speed: Typical speeds up to 100 Gbps or more

Wide Area Networks (WAN)

• Characteristics:
  • Connect devices across large geographical areas (cities, countries, continents)
  • Traditionally slower than LAN
  • More expensive due to service provider renting
• Cost: Hefty rental fees compared to owning local LAN infrastructure

Data Communication Techniques

Circuit Switching

• Concept: Establish a dedicated path before communication
• Characteristics:
  • Fixed sequence of intermediate nodes and links
  • Logical channels provide guaranteed bandwidth (e.g., 64 kbps)
• Steps:
  1. Connection Establishment
  2. Data Transfer
  3. Connection Termination
• Drawbacks:
  • Inefficient for bursty computer data
  • Initial delay due to connection establishment

Packet Switching

• Concept: No dedicated resource, all links are shared
• Characteristics:
  • Message broken into smaller packets with headers
  • Packets transmitted separately
  • Uses store-and-forward method
• Routing:
  • Intermediate nodes buffer packets and forward when the link is free
  • Each packet routed independently using routing tables
• Advantages:
  • Better link utilization
  • Suitable for bursty data traffic
  • Easier data rate conversion using buffering
  • Allows packet prioritization

Packet Transmission Models

Virtual Circuits

• Definition: Similar to circuit switching but with shared links; paths are established and followed for packets
• Process:
  1. Route establishment with virtual circuit number
  2. Packets contain virtual circuit number in the header
  3. Intermediate nodes use routing tables for forwarding
• Drawbacks:
  • Static; no dynamic routing
  • Not adaptive to changing network conditions
• Usage: Rarely used in the internet

Datagram Approach (Covered in Next Lecture)

Conclusion

• Next Lecture: Datagram approach and additional networking issues