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› Module 1: Introduction to Computer Networks › 1.1 What is a Computer Network?
M O D U L E

Module 1: Introduction to Computer Networks

Foundational concepts: definitions, network classifications, topologies, and connecting hardware

1.1 What is a Computer Network?

A Computer Network is a collection of two or more autonomous computing devices (computers, servers, smartphones, routers, switches) interconnected by transmission media to share hardware resources, exchange files, and facilitate communication using standardized protocols.

Core Network Terminology

  • Nodes: Any addressable device attached to the network (host, printer, server, switch, router).
  • Links: The physical or wireless communication channels connecting nodes (twisted-pair copper, fiber-optic cable, Wi-Fi radio waves).
  • Protocol: A formal, agreed-upon set of rules governing the syntax, semantics, and synchronization of data communication (e.g. TCP/IP, HTTP, Ethernet).
  • Bandwidth & Throughput: Bandwidth is the theoretical maximum transmission capacity (e.g. 1 Gbps); throughput is the actual payload transfer rate achieved in practice.

1.2 Types of Networks (PAN, LAN, MAN, WAN)

Networks are primarily classified by their geographical span, which dictates the underlying cabling technology, ownership structure, propagation delay, and transmission error rates.

Figure 1.1: Types of Networks by Geographic Scope PAN Personal Area Network • Range: ~1 to 10 meters Personal devices (Bluetooth, NFC, USB) LAN Local Area Network • Range: Single building/campus Privately owned, high speed (Ethernet, Wi-Fi 802.11) MAN Metropolitan Area • Range: City / Town wide Links multiple LANs (Cable TV, City Fiber) WAN Wide Area Network • Range: Country / Globe Telecom lines, satellites (The Internet) Small Scale (~meters) Increasing Geographic Coverage → Global Scale (Thousands of km)

Figure 1.1: Classification of computer networks arranged by expanding geographical scope: PAN → LAN → MAN → WAN.

1.3 Network Topologies (Bus, Star, Ring, Mesh, Tree)

A Network Topology defines the geometric arrangement of nodes and physical/logical links within a network. The selected topology determines fault tolerance, cabling cost, installation complexity, and maximum throughput.

Figure 1.2: The Five Classic Network Topologies Bus Single backbone Cable break halts all Star Hub Dominant in LANs Single node fault safe Ring Token passing Unidirectional flow Mesh Full redundancy N(N-1)/2 cables Tree Hierarchical stars Campus backbones

Figure 1.2: Comparative architecture of Bus, Star, Ring, Mesh, and Tree network topologies.

Mesh Topology Formula

In a full mesh topology with $N$ nodes, every node has a direct link to all other $N-1$ nodes. Total physical links required is given by:

Number of Links = N × (N - 1) / 2

For example, connecting 6 computers in a full mesh requires $6 imes 5 / 2 = 15$ cables. While fault-tolerant, its cabling cost scales quadratically ($O(N^2)$).

1.4 Networking Devices & Operating Layers

Connecting networks requires specialized hardware operating at distinct layers of the OSI reference model, differing in packet inspection intelligence and routing capability.

Figure 1.3: Key Networking Devices & Their Operating OSI Layers Repeater / Hub Physical Layer (L1) • Regenerates electrical / optical signals. • Hub blindly broadcasts to ALL ports. • Single collision domain (no address awareness) Bridge / Switch Data Link Layer (L2) • Maintains CAM/MAC address lookup table. • Forwards frames to specific target port. • Breaks collision domains per port Router Network Layer (L3) • Routes IP packets between distinct subnets. • Selects optimal path via routing tables. • Breaks broadcast domains completely Gateway All / Application (L4-L7) • Protocol converter between alien systems. • Translates data encodings and communication stacks. • Maximum processing intelligence & payload inspection

Figure 1.3: Connecting devices organized hierarchically by increasing protocol intelligence and operating OSI layer.

MODULE COMPREHENSIVE QUIZ

Module 1 Final Quiz

Test your understanding across all 4 topics of this module with interview-grade questions, tricky edge cases, and code output predictions.

Take Module 1 Final Quiz →
ReadyToGo · Computer Networks Study Guide
Yukti Mascot