1.1 Understanding the OSI Model

Question 1

What is the purpose of the OSI model?

Answer 1

To standardize and describe how data travels through a network in seven distinct layers.

Question 2

What is the mnemonic for remembering the OSI layers from top to bottom?

Answer 2

“All people seem to need data processing.”
Application, Presentation, Session, Transport, Network, Data Link, Physical

Question 3

Which OSI layer handles IP addressing and routing?

Answer 3

Layer 3 - Network

Question 4

Which OSI layer is responsible for MAC addresses and switching?

Answer 4

Layer 2 - Data Link

Question 5

At which layer does encryption like SSL/TLS take place?

Answer 5

Layer 6 - Presentation

Question 6

What protocols operate at the Transport Layer?

Answer 6

TCP and UDP

Question 7

Which layer is the “post office” of the OSI model and ensures reliable delivery?

Answer 7

Layer 4 - Transport

Question 8

Which layer is responsible for starting and ending sessions between two hosts?

Answer 8

Layer 5 - Session

Question 9

What kind of issues are related to the Physical layer?

Answer 9

Bad cables, signal interference, and broken connectors.

Question 10

DNS operates at which OSI layer?

Answer 10

Layer 7 - Application

Question 11

What OSI layer is responsible for transmitting raw bits over a physical medium?

Answer 11

Layer 1 – Physical

Question 12

What are examples of technologies at the Physical layer?

Answer 12

Cables (copper/fiber), connectors, radio frequencies, electrical signals, hubs, and loopback tests.

Question 13

What OSI layer deals with MAC addresses and framing of data?

Answer 13

Layer 2 – Data Link

Question 14

What protocol is commonly used at the Data Link layer for LANs?

Answer 14

Ethernet

Question 15

What are examples of Layer 2 addresses?

Answer 15

MAC addresses, EUI-48, and EUI-64

Question 16

What devices operate at Layer 2?

Answer 16

Switches and bridges

Question 17

What is the main responsibility of the Network layer?

Answer 17

Logical addressing and routing of packets between networks.

Question 18

What protocols operate at Layer 3?

Answer 18

IP (Internet Protocol), ICMP, IGMP

Question 19

What device operates at the Network layer?

Answer 19

Routers

Question 20

What key addressing method is used at Layer 3?

Answer 20

IP addresses (IPv4/IPv6) and subnet masks

Question 21

What does the Transport layer handle?

Answer 21

Reliable delivery, segmentation, error correction, and flow control.

Question 22

Which protocols operate at Layer 4?

Answer 22

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol)

Question 23

What is the difference between TCP and UDP?

Answer 23

TCP is connection-oriented and reliable; UDP is connectionless and faster but unreliable.

Question 24

What elements are used to track communications at Layer 4?

Answer 24

Port numbers (e.g., TCP 80, UDP 53)

Question 25

What is the role of the Session layer?

Answer 25

Establishing, managing, and terminating sessions between systems.

Question 26

What protocols or technologies may operate at Layer 5?

Answer 26

Control protocols, tunneling protocols

Question 27

What kind of problems are associated with Layer 5?

Answer 27

Session timeouts, reconnect loops, or failed VPN tunneling initiation.

Question 28

What are the responsibilities of the Presentation layer?

Answer 28

Data translation, encryption/decryption, compression, character encoding.

Question 29

What protocols or technologies are associated with Layer 6?

Answer 29

SSL (Secure Sockets Layer), TLS (Transport Layer Security), ASCII, JPEG, MP4

Question 30

At which layer does HTTPS encryption happen?

Answer 30

Layer 6 – Presentation

Question 31

What does the Application layer provide?

Answer 31

Interfaces for end-user applications to access network services.

Question 32

What are examples of protocols at the Application layer?

Answer 32

HTTP, HTTPS, FTP, DNS, POP3, IMAP, SMTP

Question 33

When you're interacting with an email client or browser, which layer are you using?

Answer 33

Layer 7 – Application