CompTIA Network + Lesson 1

Question 1

What does OSI stand for?

Answer 1

Open Systems Interconnection

Question 2

Explain what the OSI model is

Answer 2

The OSI model breaks down the data communication process into discrete layers.

It is not a standard or specification, but it serves as a functional guideline for designing network protocols, software, and appliances. It’s also used for troubleshooting networks

Question 3

How many layers are there to the OSI model?

Answer 3

7

Question 4

List all of the layers in the OSI model

Answer 4

Application
Presentation
Session
Transport
Network
Data Link
Physical

Question 5

What is a network protocol and what are their two principal functions?

Answer 5

A network protocol is a set of rules for exchanging data in a structured format. Its two principal functions are Addressing and Encapsulation.

Addressing describes where data messages should go.

Encapsulation describes how data messages should be packaged for transmission.

Question 6

What is Addressing in terms of the function of a network protocol?

Answer 6

Addressing describes where data messages should go. At each layer there are different mechanisms for identifying nodes, and rules for how they can send and receive messages.

Question 7

What is Encapsulation in terms of the function of a network protocol?

Answer 7

Encapsulation describes how data messages should be packaged for transmission. Encapsulation is like an envelope for a letter, with the distinction that each layer requires its own envelope. At each layer, the protocol adds fields in a header to whatever data (payload) it receives from an application or other protocol.

Question 8

How do nodes communicate with each other?

Answer 8

At each layer, for two nodes to communicate they must be running running the same protocol. The protocol running at each layer communicates with its equivalent layer on the other node. This communication between nodes at the same layer is described as a same layer interaction.

Question 9

What is a same layer interaction?

Answer 9

When two nodes running the same protocol communicate with each other. The protocol running at each layer communicates with its equivalent layer on the other node.

Question 10

What is adjacent layer interaction?

Answer 10

To transmit or receive a communication, on each node, each layer provides services for the layer above and uses the services of the layer below.

Question 11

What does PDU stand for and what does it do?

Answer 11

Protocol Data Unit - A PDU is a chunk of data that is formed from the sending node adding a header to the data payload at each layer as it travels down the stack.