OSI

Question 1

What are the seven layers of OSI model?

Answer 1

Application, Presentation, Session, Transport, Network, Data Link, Physical

Question 2

What runs in Application Layer?

Answer 2

Network applications for file transfer, web surfing, emails and virtual terminals

Question 3

Protocol for file transfer

Answer 3

FTP

Question 4

Protocol for web surfing

Answer 4

HTTP/S

Question 5

Protocol for emails

Answer 5

SMTP

Question 6

Protocol for virtual terminals

Answer 6

Telnet

Question 7

What is the Presentation Layer responsible for?

Answer 7

Translation, Data Compression, Encryption

Question 8

What is SSL?

Answer 8

Secure Socket Layer

Question 9

What is Session Layer responsible for?

Answer 9

Authentication, Authorization, Session Management

Question 10

What type of data runs in Session Layer?

Answer 10

Data Packets

Question 11

What is Transport Layer responsible for?

Answer 11

Segmentation, Flow Control, Error Control, Connection and Connectionless Transactions

Question 12

What is the difference between UDP and TCP?

Answer 12

UDP does not give feedback, hence is faster than TCP. However, it is less reliable.

Question 13

How can TCP recover lost/corrupted data?

Answer 13

By using the checksum methods to find corrupted data and by checking the sequence number to find lost segments

Question 14

What layers run on the web browser?

Answer 14

Application, Presentation and Session

Question 15

What type of data runs in Transport Layer?

Answer 15

Segments

Question 16

What information does a segment has?

Answer 16

Port number and sequence number

Question 17

What for are port numbers used in a segment?

Answer 17

It helps to direct each segment to the correct application

Question 18

What for are segment numbers used in a segment?

Answer 18

It helps to disassemble segments in the correct order to form the correct message at the receiver

Question 19

What happens in flow control in transport layer?

Answer 19

The amount of data being transmitted is controlled (bandwidth)

Question 20

What happens in error control in transport layer?

Answer 20

Loss and corrupted data are retransmitted by using automatic repeated requests schemes

Question 21

What is checksum?

Answer 21

A group of bits added to each segment by the transport layer to find out the received corrupted segment

Question 22

What protocols run on transport layer?

Answer 22

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

Question 23

Where is UDP used?

Answer 23

Where data loss does not matter. VoIP apps, Video, Music, Games, DNS, TFTP

Question 24

Where is TCP used?

Answer 24

Where full data is necessary. WWW, Emails, FTP

Question 25

What does network layer do?

Answer 25

Transmits data segments from one computer to another in different networks

Question 26

What is Network Layer responsible for?

Answer 26

Logical Addressing (IPv4 & IPv6 + Mask), Routing, Path Determination

Question 27

How are data units called in Network Layer?

Answer 27

Packets

Question 28

How is a IP Packet formed?

Answer 28

Network layer assigns the IP number of source and destination to a segment

Question 29

What is routing?

Answer 29

Method of moving a data packet from source to destination and it is based on the logical IP format of IPv4 or IPv6

Question 30

How does the masking work in Network Layer?

Answer 30

It masks the IP where the numbers masked by 255 represent the network address and the number masked by 0 represents the computer ID inside a local network

Question 31

What is path determination

Answer 31

Is choosing the best possible path for data delivery from source to destination

Question 32

What protocols can determine the best path for data delivery?

Answer 32

OSPF: open shortest path first, BGP: border gateway protocol, IS-IS: intermediate system to intermediate system

Question 33

What are the types of addressing?

Answer 33

Logical addressing (network layer - assigning IPs to segment to form data packets) & Physical addressing (data link layer - MAC addresses are assigned to each segment to form a frame)

Question 34

Where and how is a data frame formed?

Answer 34

At data link layer. MAC1 + MAC2 + IP1 + IP2 + Segment + Tail

Question 35

Where and how is a data packet formed?

Answer 35

At network layer. IP1 + IP2 + Segment

Question 36

What is a MAC address?

Answer 36

A 12-digit alphanumeric number embedded in the network interface card (NIC) of a computer

Question 37

How are data units called in data link layer?

Answer 37

Frame

Question 38

Where is data link layer located and what does it do?

Answer 38

The data link layer is a software embedded int the network card of a computer and provide means to transfer data from one computer to another via local media

Question 39

What are the functions of data link layer?

Answer 39

Access the media (framing) and control how data is placed and received from the media (media access control and error detection)

Question 40

What is CSMA?

Answer 40

Carrier Sense Multiple Access. It controls when the media will be accessed on data link layer to avoid conflicts when multiple computers on the same network send/receive data at the same time

Question 41

What is the tail of each contained of and responsible for?

Answer 41

It contains bit to detect errors in the received frame

Question 42

How does the physical layer work?

Answer 42

it transforms the bits (frames) received from data link layer into signals to transmit over local media (electrical signals - coper cable, light signal - optical fiber, radio signal - wi-fi)