Ch 12: Networking | Exam Fusion Prep

Computer Network / कंप्यूटर नेटवर्क

A network is a collection of interconnected devices — computers, mobiles, servers, printers, etc. — linked by wired or wireless communication paths to share data, resources and services.
Key elements: Nodes • Links/Transmission Media • Protocols • Resources.
Nodes include computers, laptops, smartphones, printers and special devices such as servers.
Transmission media can be wired (twisted pair, coaxial, optical fiber) or wireless (Wi‑Fi, Bluetooth, satellite, infrared).
Protocols listed early in the chapter include TCP/IP, HTTP/HTTPS and SMTP/IMAP.

Source visual: a basic network with Internet, firewall, wireless router and endpoint devices

Source visual: key components of a computer network

Source visual: guided and unguided transmission media

Network Hardware at a Glance

Router

Connects different networks such as LAN ↔ Internet.

Switch

Connects multiple devices within a LAN.

Hub

Basic multi-device connector; broadcasts traffic.

Access Point

Provides wireless connectivity.

Firewall

Monitors/controls traffic for security.

Source visual: hardware components in a network

Source visual: common network device types

History of Computer Networks / इतिहास

1950sMainframe + terminal based early networking

1969ARPANET; four universities; source notes first message “LO”

1970sTCP/IP by Vint Cerf & Bob Kahn; source notes 1973 international link

1980sEthernet expansion; DNS (1983); WWW (1989)

1990sPublic/commercial Internet; websites, email, e-commerce; Wi‑Fi (1997)

2000s–PresentBroadband, 4G/5G, cloud, IoT, social media, AI

Source visual: TCP/IP pioneers shown in the PDF

Source visual: Tim Berners-Lee image in the PDF

Source visual: DNS server concept

Source visual: networking / Internet development timeline graphic

Source visual: 5G-enabled IoT / modern network concepts

Source-bound

Dates, labels and historical claims here follow the supplied PDF; no outside verification or correction has been mixed into this chapter.

Classification of Networks / नेटवर्क का वर्गीकरण

The chapter lists classification by geographical area, topology, ownership and transmission medium.
The detailed source material in this chapter primarily expands geographical-area classification and topology classification.

Type	Full Form	Coverage	Technology / Devices	Source Example
PAN	Personal Area Network	~10 m	Bluetooth, Infrared, USB	Phone ↔ headset / smartwatch
LAN	Local Area Network	Few km	Ethernet, Wi‑Fi	School, office, computer lab
CAN	Campus Area Network	Campus / premises	Multiple LANs	University departments
MAN	Metropolitan Area Network	10–50 km	Fiber, microwave, leased lines	City Wi‑Fi, cable TV, bank branches
WAN	Wide Area Network	1000s km	Routers, modems, satellites	Internet, IRCTC, ATM networks
SAN	Storage Area Network	Storage-centric	High-speed server-storage links	Data center / bank storage

PAN & LAN

PAN — Personal Area Network

Range: source says up to ~10 m.
Devices: laptop, smartphone, smartwatch, Bluetooth printer/headset.
Tech: Bluetooth, IR, USB.
Pros: easy setup, personal use, few/no cables.
Limits: limited range and number of devices.

LAN — Local Area Network

Coverage: school, office, building; source says up to a few km.
Tech: Ethernet, Wi‑Fi.
Pros: high speed, easy management/security, low error rate.
Limit: limited coverage and initial setup cost.

Source visual: Local Area Network

Source visual: LAN with switch/router connections

CAN, MAN, WAN & SAN

CAN

Connects multiple LANs in a campus, industrial area or organization premises. Advantage: efficient inter-department communication and centralized resources.

MAN

City/metropolitan network; source gives 10–50 km. Uses fiber, microwave or leased lines. Examples: city Wi‑Fi, cable TV, bank branches.

WAN

Country/continent scale; source says 1000s km. Routers/modems/satellites. Internet = source’s largest WAN example.

SAN

High-speed server-to-storage network. Examples: data centers, banks, cloud storage backends.

Source visual: Campus Area Network

Source visual: Metropolitan Area Network

Source visual: Wide Area Network

Source visual: Storage Area Network

⚠ EXAM TRAP

PAN ≠ LAN ≠ CAN ≠ MAN ≠ WAN ≠ SAN. Remember the progression: Personal → Local → Campus → Metropolitan → Wide; SAN is storage-oriented rather than simply “next larger area”.

Topology / टोपोलॉजी

Network topology is the arrangement/layout of computers, cables and components and how nodes/links are organized.
Physical topology: actual physical connections of devices and cables.
Logical topology: how data flows among network devices.
Six common types listed: Bus, Star, Ring, Mesh, Tree, Hybrid.

Source visual: common network topologies

Core Topology Terms

Node

Any connected device that can send/receive data.

Link

Communication path between two nodes; wired or wireless.

Backbone

Main central cable/channel carrying most traffic.

Segment

Part of a network separated by switches/routers.

Path

Sequence of links/nodes from source to destination.

Hop

One movement from one node to the next.

Redundancy

Multiple paths so another route can be used if one fails.

Collision

Signals overlap when multiple devices send simultaneously on same medium.

Token

Small control frame passed around a Ring network.

Fault Tolerance

Network keeps working even when components fail.

Scalability

Ease of adding nodes/links without harming performance.

Node Degree

Number of direct connections a node has.

Performance Terms

Throughput

Successfully transmitted data per unit time; source measures in Mbps.

Latency

Delay between sending and receiving data; source notes satellite networks can have high latency.

Bandwidth

Maximum data transfer capacity, commonly Mbps/Gbps.

Efficiency

Useful data transmission ÷ total transmission.

Source visual: throughput formula

Data Flow

Simplex

One-way only.
Example: Keyboard → computer/monitor in source examples.

Half Duplex

Both directions, but one at a time.
Example: Walkie-talkie.

Full Duplex

Both directions simultaneously.
Example: Telephone.

Bus Topology / बस टोपोलॉजी

All nodes connect to one central Bus/Backbone cable.
Data placed on the bus travels in both directions; each node checks the destination address.
Terminators at both ends prevent signal reflection; drop lines connect nodes to the bus.
Source examples: early Ethernet 10Base2/10Base5, small coaxial-cable office networks.

Advantages

Easy installation • less cable than star • suitable for small networks • easy node expansion.

Disadvantages

Main cable failure stops network • troubleshooting difficult • limited length/nodes • collisions/reflection • heavy-load slowdown.

Source visual: Bus topology with terminators

Ring Topology / रिंग टोपोलॉजी

Each node connects to exactly two others, forming a closed loop.
Data moves around the ring to destination; source discusses Token Passing for access control.
Only the node holding the token can transmit; after sending it releases/passes the token.
Types: Single Ring (one direction) and Dual Ring (two rings / bidirectional).
Source examples: IBM Token Ring and FDDI.

Source visual: Ring topology and token passing

Source visual: Single Ring vs Dual Ring

Advantages

Orderly communication • no collisions in token access • equal access • token absence can help fault identification.

Disadvantages

One node failure may disrupt network • adding/removing nodes difficult • troubleshooting/maintenance complex.

Star Topology / स्टार टोपोलॉजी

Every node connects to a central hub, switch or router; nodes are not directly connected to each other.
Source examples: Ethernet LANs, Wi‑Fi router home networks, office switch networks.

Advantages

Easy install/manage • one node failure does not affect others • easy troubleshooting • dedicated cable gives good performance • scalable.

Disadvantages

Central hub failure stops network • more cable than bus • higher installation cost • hub can bottleneck under heavy load.

Mesh Topology / मेश टोपोलॉजी

Nodes are connected directly or through multiple paths; alternate routes provide redundancy and fault tolerance.
Types: Full Mesh and Partial Mesh.
Source applications: military communication, Internet backbone routers, mission-critical control systems.

Full Mesh connections: n(n − 1) / 2

Source visual: Full Mesh vs Partial Mesh

Source visual: full-mesh connection formula with 5-node example

Advantages

High reliability/redundancy • one-link failure does not affect others • high traffic support • high security • alternate paths.

Disadvantages

Very expensive • many cables/ports • complex install/maintenance • not suitable for small networks.

Tree & Hybrid Topology

Tree

The source lists Tree Topology as hierarchical in comparison tables and describes it as scalable with moderate reliability/cost. A full standalone Tree explanation is not present in the supplied chapter pages, so no extra details are added here.

Hybrid

Combination of two or more topologies such as Bus, Star, Ring, Mesh or Tree. Used when different departments/sub-networks use different layouts and are joined via hub/router/backbone.

Source visual: Hybrid topology combining Star, Ring and Bus

Hybrid — Source Pros & Cons

Pros: highly flexible/scalable, combines strengths, reliable, suitable for large/complex networks, easy to add nodes/topologies.
Cons: expensive, complex design/maintenance, advanced management, difficult troubleshooting, more hardware.

Topology Comparison

Feature	Tree	Star	Bus	Ring	Mesh
Structure	Hierarchical	Central hub	Single line	Circular	Fully connected
Reliability	Moderate	Medium	Low	Medium	High
Cost	Medium	Medium	Low	Medium	Very high
Scalability	High	Medium	Low	Low	Difficult
Fault Tolerance	Good	Medium	Poor	Poor	Excellent

Source table

This comparison follows the PDF’s table wording. It is reproduced as source material rather than normalized with outside networking references.

Network Protocol / नेटवर्क प्रोटोकॉल

A network protocol is a set of rules/conventions that determines how data is transmitted and received between computers.
Purpose: reliable communication; definition of data format, timing, error checking and compression.
Main source categories: Communication, Security, Management, Routing.

HTTP vs HTTPS

HTTP

Layer: Application
Port: 80
Transfers web pages/resources between browser and server. Source notes plain-text/no encryption.

HTTPS

Layer: Application
Port: 443
Secure HTTP using SSL/TLS; source describes certificate verification and encrypted connection.

HTTPURL → Browser request → Server → HTTP response → Browser display

HTTPSURL → Port 443 → SSL certificate → CA verification → Encrypted connection → Secure data

⚠ QUICK DIFFERENCE

HTTP = 80, no encryption • HTTPS = 443, SSL/TLS encryption + lock indicator according to the source.

Application & Common Protocols

Protocol	Category	Layer	Port	Main Function
HTTP	Communication	Application	80	Web data transfer
HTTPS	Security	Application	443	Secure web transfer (SSL/TLS)
FTP	Communication	Application	20, 21	File transfer
SMTP	Communication	Application	25 (source also notes 587 secure)	Send email
POP3	Communication	Application	110	Receive/download email
IMAP	Communication	Application	143	Manage mail on server
DNS	Communication	Application	53	Domain name → IP address
DHCP	Communication	Application	67, 68	Automatic IP assignment
TELNET	Communication	Application	23	Remote command-line access; source marks insecure
SSH	Security	Application	22	Secure remote login
SNMP	Management	Application	161	Monitor network devices
ICMP	Management	Network	—	Diagnostics/error reporting; ping
RIP	Routing	Network	520	Path selection by hop count
OSPF	Routing	Network	89	Link-state best path
BGP	Routing	Network	179	Routes between networks / ISPs

Security, Transport & Network Protocols

SSL/TLS

Source: Application layer; HTTPS security on port 443; encrypts browser-server data.

SSH

Application layer, port 22; secure encrypted remote login.

IPSec

Network layer; secures IP packets; source example: VPN.

TCP

Transport layer; reliable, connection-oriented, ordered; retransmits lost packets.

UDP

Transport layer; fast, connectionless, no delivery/order guarantee; streaming/gaming/VoIP.

IP

Network layer; logical addressing and routing of packets.

ARP

Data Link layer; maps local-network IP addresses to MAC addresses.

ICMP

Network layer; diagnostics and error/control messages; ping example.

RARP

Source summary: reverse mapping MAC → IP; booting diskless systems.

Other Protocol Families in Source

Network Access / Data Link

Ethernet — LAN wiring/signalingPPP — Point-to-PointHDLC — WAN error-free transferFrame Relay — WAN transferATM — fixed-size cells

Routing

RIP — hop countOSPF — link-stateBGP — between ISPsIGRP / EIGRP — source labels Cisco proprietary

Layered Network Architecture

Networking is divided into functional layers; each layer performs specific tasks, serves the layer above and receives services from the layer below.
Purpose: simplify design/troubleshooting, promote interoperability, modular upgrades and clear interfaces.
Main models listed: OSI (7 layers) and TCP/IP (4 or 5 layers).

Source visual: seven layers of OSI

Source visual: OSI vs TCP/IP mapping

OSI — 7 Layers

Layer	Name	Main Function in Source	Examples
7	Application	Network services directly to end-user applications	HTTP, FTP, SMTP, DNS, Telnet
6	Presentation	Translation, formatting, encryption/decryption, compression	SSL/TLS, JPEG, MPEG, ASCII, Unicode
5	Session	Establish, maintain, terminate sessions; synchronization/dialog control	NetBIOS, RPC
4	Transport	End-to-end delivery, segmentation/reassembly, flow/error control	TCP, UDP
3	Network	Logical addressing, packet routing/forwarding, path selection	Router, IP, ICMP, OSPF, RIP
2	Data Link	Frames, error detection/correction, flow control, MAC addressing	Switch, Bridge, Ethernet, ARP
1	Physical	Raw bits, media, cables/connectors, voltage/signal timing	Cables, fiber, hubs, repeaters

Source visual: OSI data units / layer responsibilities

OSI Working Example — Sending Email

7 ApplicationEmail sent using SMTP

6 PresentationMessage encrypted/formatted

5 SessionSession created

4 TransportMessage segmented (TCP)

3 NetworkIP routing

2 Data LinkFrames + MAC addresses

1 PhysicalBits over cable/wireless

At Receiver

The source notes that the process is reversed — bottom to top.

OSI Pros & Cons

Advantages

Standardized model • easy understanding/troubleshooting • modular design • vendor interoperability.

Disadvantages

Theoretical model • duplicated functions across layers • implementation described as more complex/slower than simpler TCP/IP model.

Network Devices / नेटवर्क उपकरण

Hardware components that connect systems and help with data communication, routing, filtering, security and traffic control.

Source Category	OSI Layer	Examples
Layer 1 Devices	Physical	Hub, Repeater, Modem
Layer 2 Devices	Data Link	Switch, Bridge
Layer 3 Devices	Network	Router, Gateway

Source visual: common types of network devices

Source visual: Hub broadcasting to connected devices

Device Functions — Detailed

Router — Layer 3

Connects LAN/WAN/Internet; finds best path; source says it can assign IP via DHCP and provide firewall-based security.

Switch — Layer 2

Connects LAN devices; uses MAC addresses; forwards to intended device; reduces congestion; can support VLANs.

Hub — Layer 1

Broadcasts to all ports; no filtering/intelligence; source notes congestion/collision and lower security.

Modem

Modulator-Demodulator; source describes digital ↔ analog conversion for telephone/cable communication; DSL/cable/fiber types.

Access Point

Connects wireless devices to a wired network using Wi‑Fi; extends wireless coverage.

Repeater

Regenerates/strengthens weak signals to extend distance and coverage.

Bridge — Layer 2

Connects network segments and filters traffic using MAC addresses.

Gateway

Connects networks using different protocols; acts as protocol translator.

Firewall

Monitors and controls incoming/outgoing traffic using security rules.

⚠ HUB vs SWITCH vs ROUTER

Hub: Layer 1, broadcasts • Switch: Layer 2, MAC-based forwarding • Router: Layer 3, routes between networks using logical/IP addressing.

Firewall / फ़ायरवॉल

Firewall = hardware or software that monitors and controls incoming/outgoing network traffic using security rules.
Acts as a barrier between trusted internal networks and untrusted external networks such as the Internet.
Functions listed: traffic filtering • attack protection • access control • monitoring/logging • network segmentation.

Source visual: firewall between a secure private LAN and external network

Types of Firewall

Packet Filtering

Checks source/destination IP, ports, protocols; fast but limited security.

Stateful Inspection

Tracks active connection state/context; more security than basic packet filtering.

Proxy Firewall

Application-level intermediary; high security but slower performance.

Circuit-Level Gateway

Session-layer; checks TCP handshakes/connection legitimacy, not packet contents.

NGFW

Traditional filtering + intrusion prevention, deep packet inspection, application awareness.

Hardware Firewall

Physical device between network and gateway; common in organizations.

Software Firewall

Installed on individual computers/servers to protect specific devices.

Cloud Firewall

Cloud-hosted scalable/flexible firewall service.

Proxy Server / प्रॉक्सी सर्वर

Intermediary between a client and the Internet: client sends request to proxy → proxy checks rules → forwards to destination → receives response → returns it to client.
Source purposes: security, usage control, privacy and performance through caching.
If cached content exists, proxy may return it directly without contacting destination server.

Source visual: Proxy Server between device and Internet

1Client request

2Proxy checks filter/auth/logging rules

3Allowed request forwarded

4Destination responds

5Proxy returns response / cache

Types of Proxy Servers

Forward Proxy

Between client and Internet; organization controls/monitors access; can hide client IP.

Reverse Proxy

In front of web servers; handles client requests; load balancing, security, caching.

Transparent Proxy

Does not hide client IP; used for content filtering/caching without user configuration.

Anonymous Proxy

Hides client IP; moderate privacy.

High-Anonymity / Elite

Highest privacy in source description; completely hides client IP.

SOCKS Proxy

Lower-level than HTTP proxy; can handle varied traffic such as email, file transfers and torrents.

Network Addressing System / नेटवर्क एड्रेसिंग

Structured method for uniquely identifying devices so packets reach the correct destination.
Each packet contains source and destination addresses.
Source distinguishes: routers use logical addresses across networks; switches rely on physical addresses within a local network.

Types of Network Addresses

IP Address

Logical address. IPv4: 32-bit, e.g. 192.168.1.1. IPv6: 128-bit, e.g. 2001:0db8::1. Can be static or DHCP-assigned dynamic.

MAC Address

Physical NIC address assigned by manufacturer. Source: 48-bit hexadecimal, e.g. 00:1A:2B:3C:4D:5E.

Port Address

Identifies a process/service. Range 0–65535: well-known 0–1023, registered 1024–49151, dynamic 49152–65535.

Broadcast Address

Sends to all devices in a network. Source example: IPv4 subnet’s last address, e.g. 192.168.1.255.

Multicast Address

Sends to selected group. Source IPv4 range: 224.0.0.0–239.255.255.255.

Network Address

Identifies the entire network. Example: in 192.168.1.0/24, 192.168.1.0 is the network address.

Addressing + Protocol Recall

DHCP

Automatically assigns IP addresses when devices join a network.

ARP

Maps local-network IP addresses to MAC addresses.

Chapter Boundary

This source chapter ends with network addressing. The next PDF page begins Cyber Security.

Ultra-Fast Revision

Basics

Nodes • Links • Protocols • Resources

Area Types

PAN • LAN • CAN • MAN • WAN • SAN

Topologies

Bus • Star • Ring • Mesh • Tree • Hybrid

Performance

Throughput • Latency • Bandwidth • Reliability • Efficiency

Protocols

HTTP/S • FTP • SMTP • POP3 • IMAP • DNS • DHCP

Transport

TCP = reliable/order
UDP = fast/connectionless

OSI

Application → Presentation → Session → Transport → Network → Data Link → Physical

Devices

Router • Switch • Hub • Modem • AP • Repeater • Bridge • Gateway

Security

Firewall • Proxy • SSH • SSL/TLS • IPSec

Addresses

IP • MAC • Port • Broadcast • Multicast • Network

Exam Traps

Bus uses one backbone; terminators are at both ends.
Ring uses a closed loop; Token Passing controls access in the source.
Star depends on a central hub/switch/router — central-device failure is critical.
Full Mesh links = n(n−1)/2.
HTTP 80 vs HTTPS 443; HTTPS uses SSL/TLS in the source.
FTP 21 control / 20 data according to the PDF.
SMTP 25, POP3 110, IMAP 143, DNS 53, SSH 22, SNMP 161.
RIP = hop count • OSPF = link-state • BGP = Internet/ISP routing.
Hub = Layer 1 • Switch = Layer 2 • Router = Layer 3.
IPv4 = 32-bit • IPv6 = 128-bit • MAC = 48-bit in the source.

Source Picture Gallery

Network overview visual

Sender–Medium–Receiver / protocol visual

DNS concept

Hybrid topology

OSI layers

Network devices

Firewall

Proxy server

Source fidelity

This HTML is based on the supplied PDF’s Chapter 12 material. Source values and terminology were organized into mind-map format; no web verification or outside corrections were mixed in.