Network layer: Links Layer & WiFi

Question 1

What is link layer?

Answer 1

The Link Layer is the part of the network that helps send data between devices on the same network. It makes sure data gets from one device to another correctly.

When you send a file over WiFi, the link layer helps ensure it reaches your friend’s computer without errors.

Question 2

What is Topology?

Answer 2

Topology is how devices are connected in a network. It can be wired (cables) or wireless (WiFi, Bluetooth, etc.).

Example: A star topology means all computers connect to one central switch, like spokes on a wheel.

Question 3

Flow Control

Answer 3

Flow control makes sure that fast computers don’t overload slow ones when sending data. It slows down the sender if the receiver can’t keep up.
📌 Example: A teacher (fast sender) speaking slowly so students (slow receivers) can take notes.

Question 4

Error Detection & Correction

Answer 4

Networks sometimes make mistakes when sending data, like a bad WiFi signal. Error detection finds mistakes, and correction fixes them.

When watching Netflix, if the internet is bad, the video might pause while fixing the missing data.

Question 5

Framing

Answer 5

Framing means breaking data into small packets with labels (like envelopes for mail). This helps in organizing and sending information.

A large email is split into smaller parts, sent separately, and then reassembled at the destination.

Question 6

MAC Address

Answer 6

A MAC (Media Access Control) address is a unique ID for each device on a network. Think of it as a home address for your laptop or phone.

Your laptop’s MAC address helps the WiFi router know which device should receive internet data.

Question 7

ARP (Address Resolution Protocol)

Answer 7

ARP is a protocol that helps find the MAC address of a device when you only know its IP address.

When you type a website name, your computer uses ARP to figure out where to send the request.

Question 8

Ethernet

Answer 8

Ethernet is a wired network technology used to connect devices using cables. It’s faster and more stable than WiFi.

Offices use Ethernet cables to connect computers for faster and more secure internet.

Question 9

Virtual LAN (VLAN)

Answer 9

A VLAN is like a virtual network inside a real network. It separates devices into different groups, even if they are using the same cables.

A company can have one physical network but separate VLANs for HR, IT, and Finance so their data doesn’t mix.

Question 10

Multiple Access Protocols

Answer 10

When many devices share one network channel, they need rules to avoid talking at the same time.

📌 Example: In a Zoom meeting, only one person speaks at a time to avoid confusion.

Question 11

CSMA/CD (Carrier Sense Multiple Access with Collision Detection)

Answer 11

This is used in Ethernet networks to detect collisions when two devices try to send data at the same time.

Two people talking at the same time in a call. If they notice, one person stops and waits.

Question 12

CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)

Answer 12

This is used in WiFi networks to prevent collisions before they happen by waiting and listening before sending.

Question 13

TDMA (Time Division Multiple Access)

Answer 13

Each device gets a time slot to send data so they don’t interfere.
📌 Example: A school schedule where each class has a fixed time slot.

Question 14

FDMA (Frequency Division Multiple Access)

Answer 14

Each device gets a separate frequency to send data, like different radio stations.
📌 Example: FM radio stations use different frequencies so they don’t mix.

Question 15

Hidden Terminal Problem

Answer 15

This happens in WiFi networks when two devices can’t see each other, but both try to send data, causing a collision.
📌 Example: Two people whispering in different corners of a room but accidentally talking over each other.

Question 16

RTS/CTS (Request to Send / Clear to Send)

Answer 16

A system to avoid collisions in WiFi networks by asking for permission before sending data.
📌 Example: Before speaking in a big meeting, you raise your hand and wait for approval.

Question 17

Wireless LAN (WiFi)

Answer 17

A wireless local area network (WLAN) connects devices without cables.
📌 Example: Home WiFi connects your phone, laptop, and smart TV to the internet.

Question 18

WiFi Authentication

Answer 18

WiFi networks need security so only authorized devices can connect. The most common methods are WPA2 or WPA3.
📌 Example: Your home WiFi asks for a password before letting new devices join.

Question 19

ARP Poisoning

Answer 19

A hacking method where someone tricks a network into sending data to the wrong device.
📌 Example: A hacker pretends to be the WiFi router, so your internet traffic goes through them first.

Question 20

Ethernet Frame

Answer 20

An Ethernet frame is a packet of data with extra information like addresses and error checking.
📌 Example: An Amazon package with a shipping label that tells the courier where to send it.

Question 21

Cyclic Redundancy Check (CRC)

Answer 21

A mathematical method to detect errors in transmitted data.
📌 Example: When downloading a file, the computer checks if all parts arrived correctly.

Question 22

Beacon Frames

Answer 22

Beacon frames help WiFi devices find nearby networks and connect to them.
📌 Example: Your phone scans for WiFi and finds a list of networks.

Question 23

Handoff (WiFi Roaming)

Answer 23

When you move between WiFi zones, your device switches between access points to maintain a strong connection.
📌 Example: Walking through an airport, your phone switches between different WiFi routers without disconnecting.

Question 24

Signal-to-Noise Ratio (SNR)

Answer 24

SNR compares the strength of the WiFi signal to background noise. A higher SNR is better.
📌 Example: Listening to music in a quiet room (high SNR) vs. in a noisy café (low SNR).

Question 25

Power Management in WiFi

Answer 25

WiFi devices reduce power use by sleeping when they’re not actively sending or receiving data. 📌 Example: Your phone's WiFi goes into low-power mode when the screen is off.

Question 26

Half-Duplex vs. Full-Duplex

Answer 26

Half-Duplex: Devices can send or receive, but not both at the same time (like a walkie-talkie). Full-Duplex: Devices can send and receive at the same time (like a phone call). 📌 Example: WiFi is usually half-duplex, while an Ethernet cable can be full-duplex.

Question 27

Collision Domain

Answer 27

A collision domain is a part of a network where data collisions can happen when multiple devices try to send data at once. 📌 Example: In an old Ethernet hub, all connected devices share the same collision domain, leading to slow network speeds.

Question 28

Broadcast Domain

Answer 28

A broadcast domain is the part of a network where devices can send broadcast messages that reach all devices. 📌 Example: In a VLAN, only devices inside that VLAN receive broadcast messages, reducing unnecessary network traffic.

Question 29

Spanning Tree Protocol (STP)

Answer 29

STP prevents loops in a network with multiple paths between switches. 📌 Example: Without STP, a message could get stuck in an endless loop, slowing down the entire network.

Question 30

MTU (Maximum Transmission Unit)

Answer 30

MTU is the largest size of a packet that can be sent in one go. If data is too big, it gets split into smaller packets. 📌 Example: Some networks have an MTU of 1500 bytes, so a 2000-byte packet will be split into two smaller packets.

Question 31

Subnetting

Answer 31

Subnetting divides a large network into smaller parts, making it more efficient. 📌 Example: A company with one big network (192.168.1.0/24) might split it into smaller subnets for different departments.

Question 32

QoS (Quality of Service)

Answer 32

QoS prioritizes important network traffic (like video calls) over less important traffic (like file downloads). 📌 Example: Your company prioritizes Zoom meetings over Netflix streaming, so calls don’t lag.

Question 33

WiFi Authentication Types

Answer 33

WEP (Weak, easily hacked) WPA/WPA2 (Stronger, more secure) WPA3 (Latest, most secure) 📌 Example: Your home WiFi probably uses WPA2 or WPA3 to protect against hackers.

Question 34

MAC Filtering

Answer 34

MAC filtering allows only specific devices to connect to a WiFi network. 📌 Example: A company only allows work laptops to access WiFi, blocking personal devices.

Question 35

DHCP (Dynamic Host Configuration Protocol)

Answer 35

DHCP automatically assigns IP addresses to devices in a network. 📌 Example: When you connect to WiFi, your phone gets an IP address without you setting it manually.

Question 36

NAT (Network Address Translation)

Answer 36

NAT allows multiple devices to share one public IP address when connecting to the internet. 📌 Example: At home, all your devices use one public IP, but inside your network, they have different private IPs (192.168.x.x).

Question 37

VPN (Virtual Private Network)

Answer 37

A VPN encrypts your internet traffic and routes it through another location to increase security and privacy. 📌 Example: When using public WiFi, a VPN hides your data from hackers.

Question 38

IPv4 vs. IPv6

Answer 38

IPv4 (e.g., 192.168.1.1) – Older, running out of addresses. IPv6 (e.g., 2001:db8::ff00:42:8329) – Newer, more addresses available. 📌 Example: Websites are slowly switching to IPv6 because IPv4 is running out of addresses.

Question 39

Wireless Channel Interference

Answer 39

If multiple WiFi networks use the same channel, they interfere and slow each other down. 📌 Example: Your WiFi slows down because your neighbor's router uses the same WiFi channel.

Question 40

Wireless Roaming & Handoff

Answer 40

When moving between WiFi zones, your device automatically switches to the strongest access point. 📌 Example: Walking from your living room to your bedroom, your phone switches to the closer WiFi router.

Question 41

2.4 GHz vs. 5 GHz WiFi

Answer 41

2.4 GHz = Slower but longer range (good for walls) 5 GHz = Faster but shorter range (good for speed) 📌 Example: If your WiFi lags, switching from 2.4 GHz to 5 GHz might help.

Question 42

Man-in-the-Middle Attack

Answer 42

A hacker secretly intercepts communication between two devices. 📌 Example: If you connect to fake public WiFi, a hacker could steal your passwords.

Question 43

Wireless Security Attacks

Answer 43

Evil Twin Attack: Fake WiFi that looks like a real one. Deauthentication Attack: Forces you to disconnect so hackers can steal login info. 📌 Example: A hacker sets up "Free Airport WiFi", but it’s actually stealing user data.

Question 44

IPv6 Neighbor Discovery (ND)

Answer 44

IPv6 replaces ARP with Neighbor Discovery Protocol (NDP) to find other devices. 📌 Example: Your IPv6 device automatically discovers other devices on the network.

Question 45

Wireless Mesh Networks

Answer 45

A mesh network is a group of WiFi routers that work together to cover a large area. 📌 Example: Google Nest WiFi uses mesh technology to provide better coverage in big homes.