OSI Model

Question 1

What does OSI stand for?

Answer 1

Open Systems Interconnection model (OSI Model) - how data is moved across a network.

Question 2

What is layer 5 of the OSI model?

Answer 2

Session layer

Question 3

What is layer 2 of the OSI model?

Answer 3

Data Control/Data Link layer (MAC address routing layer).

Question 4

What is layer 6 of the OSI model?

Answer 4

Presentation layer.

Question 5

What is the top layer/layer 7 of the OSI model?

Answer 5

Application Layer.

Question 6

What is the bottom layer/layer 1 of the OSI model?

Answer 6

Physical layer - cabling, connectors, electrical signals - loopback tests, cable tests etc.

Question 7

What are all 7 layers of the OSI model working from the bottom up?

Answer 7

1. Physical
2. Data link control (DLC) - switching layer via MAC address, frames/EUI addresses
3. Network - routers and smart switches - PACKET routing via IP
4. Transport (TCP/UDP IP) - post office layer - gets traffic from one side of network to the other
5. Session - start,stop,restarting sessions - VPN
6. Presentation
7. Application

Question 8

What layer do smart switches exist at?

Answer 8

Layer 3 (because they route packets based on IP)

Question 9

What layer do dumb switches work at of the OSI model?

Answer 9

Layer 2 switches - because they route based on MAC address (good for small networks)

Question 10

If there is a problem with an IP address or subnet mask configuration at what layer of the OSI are you looking?

Answer 10

Layer 3 - network layer encapsulates IP addressing and routing/subnetting.

Question 11

What is the role of the presentation layer (Layer 6)?

Answer 11

The presentation layer makes data human readable, encryption/decryption. Closely linked/tied to the Application layer (7). Presentation preparation layer.

Question 12

When looking at e.g. a webpage what layer of the OSI model are we seeing?

Answer 12

Layer 7 - the application layer is what you see.
HTTPS, pop3, etc protocols operate at this layer.

Question 13

At what level are data PACKETS routed?

Answer 13

Layer 3 - the network layer is where data packets are exchanged.

Question 14

What layer has TCP segments and UDP datagrams?

Answer 14

Layer 4 - Transport Layer has TCP segments and UDP datagrams.

Question 15

At which layer would you find tunnelling and control protocols.

Answer 15

Layer 5 is the session layer where you’d find control protocols and tunnelling protocols.

Question 16

Where would you find SSL/TLS encryption in the OSI model?

Answer 16

Layer 6 - Presentation layer deals with all things encryption/decryption like Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols.