Ethernet Basics

🤔 What is Ethernet?

Ethernet is the most widely used LAN (Local Area Network) technology for connecting computers and devices in a wired network.

📌 In simple words:

Ethernet is a set of rules and technologies that define how computers communicate over wired networks.

Today, almost every office, college, and home network uses Ethernet in some form.

🧠 Why Ethernet is So Popular

Ethernet became popular because it is:

• ⚡ Fast

• 💰 Cost-effective

• 🔧 Easy to install

• 🔒 Reliable

• 📈 Scalable

🕰️ Brief History of Ethernet

• Developed in the 1970s

• Standardized by IEEE

• Known as IEEE 802.3

📌 Whenever you see 802.3, think of Ethernet.

🧩 Where Ethernet Works in OSI Model

Ethernet mainly works at:

• 🔹 Data Link Layer (MAC sublayer)

• 🔹 Physical Layer

🔗 Basic Components of Ethernet

An Ethernet network consists of:

• 🖥️ End devices (PCs, servers)

• 🔌 Ethernet cables

• 🔀 Switches

• 💳 NIC (Network Interface Card)

• 📜 Ethernet protocols

🔌 Ethernet Cables (Basic Idea)

Most Ethernet networks use:

• Twisted Pair Cables (UTP/STP)

• RJ-45 connectors

📌 Categories:

• Cat5

• Cat5e

• Cat6

• Cat6a

📦 Ethernet Frame Format

🧱 Ethernet Frame Fields

1️⃣ Preamble – Synchronization

2️⃣ Destination MAC Address

3️⃣ Source MAC Address

4️⃣ Type / Length

5️⃣ Data (Payload)

6️⃣ FCS (Frame Check Sequence)

🧠 Why Frame is Important

• Identifies sender & receiver

• Detects errors

• Maintains data integrity

🏷️ MAC Address in Ethernet

🔹 What is a MAC Address?

A MAC (Media Access Control) Address is a unique physical address assigned to every network device.

📌 Format:

• 48-bit address

• Written in hexadecimal

  Example: 00:1A:2B:3C:4D:5E

🧠 Why MAC Address is Important

• Identifies devices uniquely

• Used in LAN communication

• Helps switches forward frames correctly

🔁 Ethernet Communication Types

🔹 1. Unicast

• One sender → one receiver

🔹 2. Broadcast

• One sender → all devices

  Example: ARP request

🔹 3. Multicast

• One sender → group of devices

⚔️ Ethernet & CSMA/CD

Earlier Ethernet used CSMA/CD:

• Carrier Sense

• Multiple Access

• Collision Detection

📌 Used when hubs were common.

👉 Modern Ethernet with switches:

• ❌ No collisions

• ❌ CSMA/CD not required

⚡ Ethernet Speed Standards

🔄 Half Duplex vs Full Duplex Ethernet

📌 Modern Ethernet uses Full Duplex.

🧠 Ethernet vs Wi-Fi

⭐ One-Line Summary

🔹 Ethernet is a widely used wired LAN technology that defines how data is framed, addressed, transmitted, and checked for errors.