Packet Switching

Question 1

Give an example of a use of circuit switching

Answer 1

Telephone System in UK

Question 2

What does circuit switching enable?

Answer 2

Enables you to send digital messages across a network by setting up a physical path between the sender and receiver

Question 3

How are circuit switching connections set up?

Answer 3

Using wires or fibre optic cable and is set up prior to transmission of the message

Question 4

Why is circuit switching very inefficient?

Answer 4

Once the connection is made, the line is tied up and no one else can use them, even if no data is passing between them

Question 5

Give another big disadvantage with circuit switching

Answer 5

Difficult to scale up the network to deal with millions of devices

Question 6

What does every connection have to be capable of in circuit switching?

Answer 6

Supporting the maximum bandwidth required

Question 7

What is packet switching an alternative method of?

Answer 7

Sending data across a network

Question 8

What is the difference between packet switching and circuit switching?

Answer 8

Unlike circuit switching where the whole message is sent in one go, with packet switching the message is broken down into smaller parts (data packets) and these parts are sent individually through the network

Question 9

What is each packet give in packet switching?

Answer 9

A ‘packet number’ to identify the order they are in

Question 10

How do packets travel across a network?

Answer 10

By taking the shortest route possible

Question 11

What happens once the individual packets arrive at their destination in packet switching?

Answer 11

They are reassembled back together in the correct order

Question 12

What happens if a packet is missing or corrupted?

Answer 12

The message will instead be sent asking for that particular packet to be resent

Question 13

What are the 2 protocols used in packet switching?

Answer 13

Ethernet

TCP/IP

Question 14

What does each packet contain?

Answer 14

A header which contains 3 important pieces of information

Question 15

What are the 3 pieces of information that the header of a packet contains?

Answer 15

A source or return address to say where the packet originated from
A destination address to tell the packet where it has to go
A sequence number so that the individual data packets can be reassembled in the correct order once they have all safely arrived at their destination

Question 16

What is preamble?

Answer 16

Is data that is attached to the front of a data packet to prime the receiving hardware that a data packet is about to arrive

Question 17

What check is done when a packet is received?

Answer 17

An Error Check

Question 18

What calculation does an error check involve?

Answer 18

‘Check sum number’

Question 19

What is the Internet?

Answer 19

One vast packet switched network consisting of billions of nodes and connections

Question 20

What are 4 advantages with packed switching?

Answer 20

They are robust
They make efficient use of connections
The message is very resilient
Each packet carries its own error correction codes

Question 21

What are 2 disadvantages with packet switching?

Answer 21

The packets travel along random paths, so there is no guarantee that they will arrive within a certain time period (delay called ‘Latency’)
The packets arrive in random order, so they have to be re-assembled