Layers and Protocols

Question 1

Internet Model

Answer 1

Describes a packet switching network. Means that any communication between devices over the network happens in the form of short packets switched across many intermediate points(routers)

Question 2

Name the 5 Layers of Abstraction

Answer 2

• Hardware Layer
• Data link Layer
• Network Layer
• Transport Layer
• Application Layer

Question 3

Hardware Layer/Physical Layer

Answer 3

Concerned with the actual hardware (cables, plugs, sockets, antennas). Specifies signals transmitted over cables or radio waves

Question 4

Data Link Layer

Answer 4

Defines interface between hardware and software. Specifies how devices within one LAN cab exchange packets

Question 5

Network Layer

Answer 5

Responsible for routing. It is the most important layer for routers. But servers and clients also have network layer software and perform routing

Question 6

Why can servers and clients have a Network layer?

Answer 6

It performs routing if it is connected to more than one network(4G and WiFi)

Question 7

Transport Layer

Answer 7

Established a logical connection between an application sending a message and the receiving app. Performs the main form of virtualisation that makes implementing networked apps much easier

Question 8

Some of the tasks of the Transport Layer

Answer 8

• Breaking up a large message to packets

- Ensures messages are sent correctly, re-sends packets is they have errors

Question 9

Application Layer

Answer 9

The actual application software that a user interacts with

Question 10

What layers does a switch implement?

Answer 10

Hardware and Data-link layers, because its only responsible for communication inside a Local network.

Question 11

Protocol

Answer 11

Formal language that defines how two applications speak to each other.

Question 12

PDU

Answer 12

Protocol Data Unit, the "envelopes" used in message encapsulation
Hardware Layer = 1 bit
Data Link Layer = frame
Network Layer = packet
Transport Layer = segment/datagram
Application Layer = messages

Question 13

Explain message encapsulation

Answer 13

Message in an envelope. the outside of the envelope only contains the sender and receiver addresses. Each layer may add their own information to the outside of the envelope (ex. the transport layer saying packet 13/134). Each layer then adds its own envelopes on top of the original envelope. An and product could be the hardware transmitting a data link layer envelope, inside a network layer envelope, inside a transport layer envelope with PART of the application layer message inside all of that.