Internet Technology, Protocols & IoT
Complete Revision Notes · TCP/IP · OSI Model · Protocols · Port Numbers · IoT
1. Internet Technology Overview
The Internet is a global network of interconnected computer networks that communicate using the TCP/IP protocol suite. It allows billions of devices — computers, smartphones, servers, IoT devices — to exchange information across the world.
Major Internet Services
World Wide Web (WWW)
Email
File Transfer (FTP/SFTP)
Remote Login (SSH/Telnet)
Cloud Computing
Video Streaming
Online Banking
Voice over IP (VoIP)
Social Media
IoT Communication
Exam Point: Internet is the infrastructure; WWW is just one service running on it.
2. Internet vs World Wide Web
A classic trap in competitive exams — know the difference!
Internet
- Network of networks
- Uses TCP/IP
- Provides Email, FTP, DNS, SSH
- Infrastructure
World Wide Web (WWW)
- Collection of web pages
- Uses HTTP/HTTPS
- Only Websites
- Service running on Internet
Memory Trick: The Internet is the highway; the WWW is just one type of vehicle driving on it.
User
|
↓
Browser
|
↓
ISP
|
↓
Internet Backbone
|
↓
DNS Server
|
↓
Web Server
|
↓
Website
3. TCP/IP Model (Most Important)
+--------------------------------+
| Application Layer |
| HTTP HTTPS FTP SMTP DNS DHCP |
| POP3 IMAP SSH Telnet MQTT |
+--------------------------------+
| Transport Layer |
| TCP UDP |
+--------------------------------+
| Internet Layer |
| IP ICMP ARP IGMP |
+--------------------------------+
| Network Access Layer |
| Ethernet Wi-Fi PPP |
+--------------------------------+
| Layer | Main Protocols | Devices |
|---|---|---|
| Application | HTTP, HTTPS, FTP, SMTP, DNS, DHCP, MQTT, SSH | Gateway |
| Transport | TCP, UDP | Host |
| Internet | IP, ICMP, ARP | Router |
| Network Access | Ethernet, Wi-Fi, PPP | Switch, NIC |
Exam Trick: TCP/IP = 4 Layers | OSI = 7 Layers
4. OSI Model (7 Layers)
Mnemonic (Top to Bottom): All People Seem To Need Data Processing
(Application, Presentation, Session, Transport, Network, Data Link, Physical)
Bottom to Top: Please Do Not Throw Sausage Pizza Away
(Application, Presentation, Session, Transport, Network, Data Link, Physical)
Bottom to Top: Please Do Not Throw Sausage Pizza Away
| Layer | Devices | Example Protocols |
|---|---|---|
| Application (Layer 7) | Gateway | HTTP |
| Presentation (Layer 6) | Gateway | SSL |
| Session (Layer 5) | Gateway | NetBIOS |
| Transport (Layer 4) | Host | TCP, UDP |
| Network (Layer 3) | Router | IP |
| Data Link (Layer 2) | Switch | Ethernet |
| Physical (Layer 1) | Hub | Cable |
5. Network Devices & Their Layers
| Device | Layer | Function |
|---|---|---|
| Hub / Repeater | Layer 1 (Physical) | Regenerates signals / Broadcast |
| Bridge / Switch | Layer 2 (Data Link) | Filters & forwards via MAC addresses |
| Router | Layer 3 (Network) | Routes packets via IP addresses |
| Gateway | All Layers (1–7) | Translates between different protocols |
| Modem | Layer 1 (Physical) | Modulates/Demodulates signals |
Favourite Exam Question:
Router → Layer 3 | Switch → Layer 2 | Hub → Layer 1 | Gateway → All Layers
Router → Layer 3 | Switch → Layer 2 | Hub → Layer 1 | Gateway → All Layers
6. Addressing: IP & MAC
IP Address (Logical Address)
- IPv4: 32 Bits, Four Octets — e.g.,
192.168.1.20 - IPv6: 128 Bits — e.g.,
2001:db8::10
MAC Address (Physical Address)
- 48 Bits (6 Hex Pairs)
- Assigned by Manufacturer
- Unique for every device
- Example:
00:1A:2B:3C:4D:5E
Key Addressing Services
DNS — Port 53
- Domain Name System
- Converts
google.com→142.xxx.xxx.xxx - Uses TCP + UDP
DHCP — Ports 67/68
- Dynamic Host Configuration Protocol
- Automatically provides IP, Gateway, DNS
- Uses UDP
7. TCP vs UDP
TCP Three-Way Handshake:
Client Server
| |
|------ SYN (Seq=X) ------------> |
| |
|<--- SYN-ACK (Seq=Y, Ack=X+1) ---|
| |
|------ ACK (Ack=Y+1) -----------> |
| |
Connection Established
| Feature | TCP | UDP |
|---|---|---|
| Connection Type | Connection-oriented (Handshake) | Connectionless (Fire & forget) |
| Reliability | Guaranteed delivery (ACKs) | No guarantee |
| Speed | Slower (overhead) | Faster (minimal overhead) |
| Header Size | Large (~30 bytes) | Small (8 bytes) |
| Use Cases | HTTP, HTTPS, FTP, SMTP | Video Streaming, VoIP, Gaming, DNS |
8. Essential Protocols & Port Numbers
Memorizing port numbers is a high-yield strategy for competitive exams.
| Protocol | Full Form | Port(s) | Use Case |
|---|---|---|---|
| FTP | File Transfer Protocol | 20 (Data), 21 (Control) | Upload/Download files |
| SSH | Secure Shell | 22 | Encrypted remote login |
| Telnet | Teletype Network | 23 | Unencrypted remote login |
| SMTP | Simple Mail Transfer Protocol | 25 | Send Emails |
| DNS | Domain Name System | 53 | Name Resolution |
| DHCP | Dynamic Host Config Protocol | 67, 68 | Automatic IP Configuration |
| HTTP | Hypertext Transfer Protocol | 80 | Unencrypted web traffic |
| POP3 | Post Office Protocol v3 | 110 | Receive Email (downloads & deletes) |
| NTP | Network Time Protocol | 123 | Time Synchronization |
| IMAP | Internet Message Access Protocol | 143 | Receive Email (syncs across devices) |
| SNMP | Simple Network Management Protocol | 161 | Network Monitoring |
| HTTPS | HTTP Secure (SSL/TLS) | 443 | Encrypted web traffic |
Quick Port Cheat-Sheet:
HTTP: 80 | HTTPS: 443 | FTP: 20,21 | SSH: 22 | Telnet: 23
SMTP: 25 | POP3: 110 | IMAP: 143 | DNS: 53 | DHCP: 67,68
HTTP: 80 | HTTPS: 443 | FTP: 20,21 | SSH: 22 | Telnet: 23
SMTP: 25 | POP3: 110 | IMAP: 143 | DNS: 53 | DHCP: 67,68
9. Internet of Things (IoT)
IoT connects physical devices to the Internet for monitoring and automation.
IoT Examples
Smart Home
Smart TV
Smart Watch
Smart Agriculture
Smart City
Smart Parking
Industrial Automation
Healthcare Monitoring
IoT Architecture:
Sensors
|
↓
Controller
|
↓
Gateway
|
↓
Internet
|
↓
Cloud
|
↓
Mobile App
|
↓
User
IoT Communication Protocols
MQTT
Pub/Sub over TCP
Lightweight Messaging
CoAP
RESTful over UDP
Low Power Devices
AMQP
Enterprise Messaging
Robust Queuing
MQTT-SN
Sensor Networks
Low Power
IoT Advantages
- Automation
- Remote Monitoring
- Better Decision Making
- Energy Saving
- Increased Productivity
IoT Challenges
- Security
- Privacy
- Power Consumption
- Scalability
- Compatibility
- Cost
IoT Core Basics: MQTT = Pub/Sub over TCP | CoAP = RESTful over UDP
10. Quick Revision (5-Minute Recap)
InternetNetwork of Networks
WWWService of Internet
TCP/IP4 Layers
OSI7 Layers
IPv432 Bits
IPv6128 Bits
MAC48 Bits
RouterLayer 3
SwitchLayer 2
HubLayer 1
GatewayAll Layers
TCPReliable
UDPFast
HTTPPort 80
HTTPSPort 443
FTPPorts 20,21
SSHPort 22
TelnetPort 23
SMTPPort 25
DNSPort 53
DHCPPorts 67,68
POP3Port 110
IMAPPort 143
SNMPPort 161
NTPPort 123
DNSDomain → IP
DHCPAutomatic IP
HTTPSSSL/TLS
MQTTIoT Messaging
CoAPLow Power IoT
1-Minute Ultra Revision:
Internet = Network of Networks | WWW = Web Pages | TCP/IP = 4 Layers | OSI = 7 Layers
IPv4 = 32 Bits | IPv6 = 128 Bits | MAC = 48 Bits | Router = L3, Switch = L2, Hub = L1
TCP = Reliable | UDP = Fast | HTTP = 80 | HTTPS = 443 | FTP = 20/21 | SSH = 22
SMTP = 25 | DNS = 53 | DHCP = 67/68 | POP3 = 110 | IMAP = 143 | MQTT = IoT
Internet = Network of Networks | WWW = Web Pages | TCP/IP = 4 Layers | OSI = 7 Layers
IPv4 = 32 Bits | IPv6 = 128 Bits | MAC = 48 Bits | Router = L3, Switch = L2, Hub = L1
TCP = Reliable | UDP = Fast | HTTP = 80 | HTTPS = 443 | FTP = 20/21 | SSH = 22
SMTP = 25 | DNS = 53 | DHCP = 67/68 | POP3 = 110 | IMAP = 143 | MQTT = IoT
35 Interactive MCQs
Results
0 / 35
Excellent!
0 Correct
0 Wrong
0 Unanswered
Click 'Retry' above to try again