Chapter 1 - Introduction to Networking

Question 1

Examples of Application Layer Protocol

Answer 1

HTTP, POP3, SMTP

Question 2

Examples of Transport Layer Protocols

Answer 2

UDP, TCP

Question 3

Examples of Network Layer Protocols

Answer 3

IP, ICMP

Question 4

Examples of Data Link layer protocols

Answer 4

Ethernet, PPP, Wifi (802.11)

Question 5

Define Adjacent-Layer Interaction

Answer 5

• Occurs on one computer between 2 adjacent layers in the TPC/IP model.
• The higher layer requests services from the next lowest layer and this layer provides that data to the next higher layer. (E.g. The HTTP protocol in Application for TCP in Transport to utilise its error recovery services).

Question 6

Define Same-Layer Interaction

Answer 6

Occurs on multiple computers where one computer wants to communicate with the same layer on another computer. They use a protocol from this layer (E.g. TCP headers) to communicate what they want the other computer to do. (E.g. The sender of a packet with a TCP header defines the sequence numbers and the receiver of this packet receives and reacts to these TCP header’s sequence numbers).

Question 7

Define Encapsulation

Answer 7

The process of adding a header in front of data supplied by a higher layer. Each lower layer adds its own header. De-encapsulation is the opposite.

Question 8

What layer uses Bits as its data unit?

Answer 8

Layer 1 (Physical).

Question 9

What layer uses Frames as its data unit?

Answer 9

Layer 2 (Data-Link). Contains the Data-Link header and trailer with encapsulated data.

Question 10

What layer uses Packets as its data unit?

Answer 10

Layer 3 (Network Layer). Contains the Network header with encapsulated data.

Question 11

What layer uses Segments as its data unit?

Answer 11

Layer 4 (Transport Layer). Containts the Transport header with encapsulated data.

Question 12

Label the TCP/IP model in order (top to bottom) and describe what each layer’s focus is.

Answer 12

Layer 5 - Application - Interfaces with user applications
Layer 4 - Transport - Providing end to end communication between hosts and providing services to the application layer.
Layer 3 - Network - Responsible for communication between networks
Layer 2 - Data-Link - Responsible for node-node communication within a network. (e.g. The protocols that define transmission over Ethernet differ from the protocols that define transmission over WLAN).
Layer 1 - Physical - Focuses on the physical aspects of data transmission.

Question 13

Define RFC

Answer 13

Requests for Comment define the specifications for a particular technology.

Question 14

Purpose of the Application Layer

Answer 14

-Provides the protocols and services that an application will use. E.g. Defines how HTTP is used by web browsers to display websites.
-Provides process-process communication.

Question 15

Purpose of the Transport Layer

Answer 15

• Breaks large pieces of data into smaller segments to more easily be sent over the network reducing the likelihood of transmission errors.
• Provides services to the applications layer protocols. E.g. The Error recovery services that TCP provides.
• Provides host-host communication
• Provides layer 4 addressing (ports)

Question 16

Purpose of the Network Layer

Answer 16

• Responsible for ensuring connectivity between 2 different networks.
• Controls anything to do with routing packets across networks. E.g. Provides packets with source and destination IP headers.
• Provides layer 3 address (IPs)

Question 17

Purpose of the Data-Link Layer

Answer 17

• Provides services to the Network layer and controls the delivery of data over a physical link. E.g. Encapsulating packets so that they can be sent to the destination router to be addressed.
• Defines how data is formatted for transmission over a physical connection
• Provides node-node connectivity.
• Detects and sometimes corrects physical layer errors.

Question 18

Purpose of the Physical Layer

Answer 18

-Defines the cabling and energy that flows over said cables. E.g. Properties of electrical signals.
-Does not encapsulate a frame any further.

Question 19

Define Router

Answer 19

Networking devices that connect networks together so that packets can be routed to the correct destination.

Question 20

List all layers of the OSI model from top to bottom

Answer 20

Application
Presentation
Session
Transport
Network
Data Link
Physical

Question 21

Define PDU

Answer 21

A Protocol Data Unit is a unit of data of a specific network model layer encapsulated with that layer’s header and/or Trailer.

Question 22

Define De-encapsulation

Answer 22

As a PDU is passed up the networking model, each layer removes the previous layer’s Header and/or Trailer

Question 23

Define a Networking Model

Answer 23

A set of protocols grouped together into layers that, when followed, allows for communication across a network.

Question 24

Purpose of the Presentation layer

Answer 24

• Translate data from network formats into application formats so that it can be interpreted by the Application layer. (e.g. Encryption of data as it is sent and decryption of data as it is received)

Question 25

Purpose of the Session layer

Answer 25

Controls sessions between communicating hosts. (e.g. Establishes, manages, and terminates connections between the local application (web browser) and the remote application (Youtube))