OSI Model

Question 1

What is the 1st layer of the OSI model?

Answer 1

Physical

PDNTSPA

Question 2

What does the physical layer of the OSI model represent?

Answer 2

The transmission and reception of raw bits of data over physical medium

-Occurs with cable or wirelessly
-Represented by physical topologies

Question 3

What is the 2nd layer of the OSI model?

Answer 3

Data Link

PDNTSPA

Question 4

What does the data link layer of the OSI model represent?

Answer 4

The transfer of data frames between nodes on the same logical segment
–In a segment, all nodes can send traffic to each other using hardware addresses (MAC)
–Layer 2 is also known as the switching layer

Data link moves data in a single segment, not networks

Question 5

What networking devices operates on layer 2?

Answer 5

Switches - Makes forwarding decisions based on layer addresses (MAC)
NICs
Bridges
APs

Question 6

What is the 3rd layer of the OSI model?

Answer 6

Network (a.k.a. the routing layer)

Question 7

What identifying information is the network layer associated with?

Answer 7

IP addresses

Question 8

What networking device operates on layer 3?

Answer 8

Router
–Makes forwarding decisions based on IP addresses
–Forwards packets through routers (hops)

Layer 2, data link, makes decisions with MAC addresses

Question 9

What does the network layer represent?

Answer 9

Taking data packets and sending them to the correct computer
–Forwards information between networks using the destination network layer address (IP)

Question 10

What is the 4th layer of the OSI model?

Answer 10

Transport (a.k.a. the end-to-end layer)

Question 11

What kind of connection identifier does the transport layer work with?

Answer 11

Ports

Question 12

What is the transport layer responsible for?

Answer 12

Making sure the message is received by the destination node with an acknowledgement.

-Also breaks large messages into smaller pieces
-Sends multiple messages at the same time (multiplexing)

Question 13

What is the 5th layer of the OSI model?

Answer 13

Session

Question 14

What is the session layer responsible for?

Answer 14

Establishing and ending active communication sessions between devices
–Start, stop, restart

Question 15

What is a session and what occurs in it?

Answer 15

The exchange of messages, or sequence of
–This is also called a dialog

Question 16

What is the 6th layer of the OSI model?

Answer 16

Presentation

Question 17

What happens in the presentation layer?

Answer 17

Converts information, coding characters and other data into human readable format
– -lh

It is closely related to the application layer

Question 18

What kind of secuirty measure does the presentation layer handle?

Answer 18

Application encryption
-Provides or deines the data format and encryption

Question 19

What is the 7th layer of the OSI model?

Answer 19

Application

Question 20

What does the application layer represent?

Answer 20

What the end user sees and interacts with

Question 21

What protocols is the application layer associated with?

Answer 21

• HTTP (80)
• HTTPS (443)
• FTP (20/21)
• DNS (53)
• POP3 (110)