Networking Fundamentals

Master the essential concepts that form the foundation of all network communications

OSI Reference Model

The Open Systems Interconnection (OSI) model is a conceptual framework that standardizes network communication into seven distinct layers:

7. Application Layer

Interface for network services (HTTP, FTP, SMTP). Provides services directly to user applications.

6. Presentation Layer

Data translation, encryption, and compression (SSL/TLS, JPEG, MPEG).

5. Session Layer

Manages sessions or connections between computers. Controls dialogues (connections) between applications.

4. Transport Layer

Ensures reliable data transfer between host systems. Handles segmentation, flow control, and error correction.

3. Network Layer

Responsible for logical addressing and routing of data packets.

2. Data Link Layer

Handles physical addressing, error detection and correction, and frame synchronization.

1. Physical Layer

Transmits raw bit stream over physical medium. Defines hardware specifications, cabling, signaling.

1. Physical Layer

Physical connection and bit transmission (Ethernet, USB, Fiber).

Encapsulation Process

Data Encapsulation

Click to show/hide encapsulation details

TCP/IP Protocol Suite

The practical implementation model used in modern networks, consisting of four layers:

TCP/IP Layers
  • 4. Application (HTTP, FTP, DNS)
  • 3. Transport (TCP, UDP)
  • 2. Internet (IP, ICMP)
  • 1. Network Access (Ethernet, Wi-Fi)
TCP vs UDP Comparison
Feature TCP UDP
Connection Connection-oriented Connectionless
Reliability Reliable (ACKs) Unreliable
Speed Slower Faster
Use Cases Web, email, file transfer Video streaming, VoIP

Three-Way Handshake

TCP Three-Way Handshake

SYN → SYN-ACK → ACK establishes a TCP connection

IP Addressing and Subnetting

IPv4 Address Classes
Class Range Default Mask
A 1.0.0.0 - 126.255.255.255 255.0.0.0
B 128.0.0.0 - 191.255.255.255 255.255.0.0
C 192.0.0.0 - 223.255.255.255 255.255.255.0
D (Multicast) 224.0.0.0 - 239.255.255.255 N/A
Private IP Ranges
  • 10.0.0.0/8 (10.0.0.0 - 10.255.255.255)
  • 172.16.0.0/12 (172.16.0.0 - 172.31.255.255)
  • 192.168.0.0/16 (192.168.0.0 - 192.168.255.255)

Subnetting Practice

Enter an IP and subnet mask to calculate:

  • Network Address
  • Broadcast Address
  • Usable Host Range
  • Total Hosts

IPv6 Fundamentals

IPv6 Address Format

2001:0db8:85a3:0000:0000:8a2e:0370:7334

Compressed: 2001:db8:85a3::8a2e:370:7334

IPv6 Address Types
  • Unicast (Global, Link-local)
  • Multicast
  • Anycast

Ethernet Technologies

Ethernet Standards
Standard Speed Cable Type
10BASE-T 10 Mbps Cat3/Cat5 UTP
100BASE-TX 100 Mbps Cat5 UTP
1000BASE-T 1 Gbps Cat5e/Cat6 UTP
10GBASE-T 10 Gbps Cat6a/Cat7 UTP
Ethernet Frame Structure 
| Preamble | Dest MAC | Src MAC | Type/Length | Data | FCS |
|----------|----------|---------|-------------|------|-----|
| 8 bytes  | 6 bytes  | 6 bytes | 2 bytes     | 46-1500 bytes | 4 bytes |

Minimum frame size: 64 bytes
Maximum frame size: 1518 bytes (1522 with VLAN tag)

MAC Address Format

00:1A:2B:3C:4D:5E (Hexadecimal format)

  • First 3 bytes (OUI): Manufacturer ID
  • Last 3 bytes: Device-specific
  • Unicast/Multicast bit: First byte LSB
  • Locally Administered bit: Second byte 2nd bit
Quick Navigation
Key Concepts
CSMA/CD

Carrier Sense Multiple Access with Collision Detection - Ethernet's media access method (mostly obsolete in modern full-duplex networks).

MTU

Maximum Transmission Unit - Largest packet size allowed (1500 bytes standard for Ethernet).

ARP

Address Resolution Protocol - Maps IP addresses to MAC addresses.