Internet Communication

Question 1

What does circuit switching do?

Answer 1

• Creates a direct link between two devices for the duration of the communication.
• Involves creating a communication connection between two endpoints for the duration of a phone call or transfer of data.

Question 2

Why was packet switching developed?

Answer 2

Allow simultaneous data transfer along the same channel.

Question 3

What are some disadvantages of circuit switching?

Answer 3

• Bandwidth is wasted during the periods when no data is being sent.
• Two devices must transmit and receive data at the same rate, so circuit switched networks can only connect computers or devices that operate at the same transfer rate.
• Switches are used to connect and disconnect the circuits, electrical interference is produced, may produce corrupt or lost data if the path is being used to transmit data.

Question 4

What are some advantages to using circuit switching?

Answer 4

Exclusive connection between two devices for the duration of the communication, data segments arrive in the same order that they are sent, simplifying the process of reconstructing the message at the recipient end.

Question 5

What is packet switching?

Answer 5

A method of communicating packets of data across a network on which other similar communications are happening simultaneously.

Question 6

What happens to data that is to be transmitted across a network?

Answer 6

Data is broken into equal sized chunks called data packets, and assembled again at the receiving end.

Question 7

Why is splitting data into data packets better?

Answer 7

Increases network efficiency and reliability.

Question 8

What does each packet contain?

Answer 8

• Header
• Payload containing the body of data being sent.
Some data packets may contain a trailer section with:
Either:
• Checksum
Or
• Cyclical Redundancy Check

Question 9

What path do packets take?

Answer 9

• Sent across networks that have multiple connections with multiple routes through to a destination.
• Each packet takes the fastest available route

Question 10

What happens to data packets once received?

Answer 10

Packets are re ordered by the receiving node

Question 11

What are routers used for?

Answer 11

Connect at least two networks, commonly two LANS or WANS.

Question 12

What do routers do?

Answer 12

Forward data packets from one network to another.

Question 13

What does the router store?

Answer 13

• Each router stores data about the available routes to the destination node.
• Looks up the destination IP address in its routing table to find the best router to forward the packet to.
• Routers continue to forward the packet until it reaches its destination node

Question 14

What is a hop?

Answer 14

Each transfer between routers.

Question 15

What is a data packet?

Answer 15

A segment of data that needs to be sent, often referred to as the payload.

Question 16

Why are packets kept small?

Answer 16

To ensure that individual packets do not take excessive time to transfer preventing other packets from moving.

Question 17

What does the packet header contain?

Answer 17

• Packet header contains the recipient’s address so that it can be directed appropriately across the network.
• Sender’s and recipient’s IP addresses.
• The protocol being used with this type of packet
• Number of the packet in the sequence being sent.
• Time to live/Hop limit, after which the data packet expires.

Question 18

What does the packet trailer contain?

Answer 18

• Error checking components that verify the data received in the payload has not been corrupted on transfer
• Techniques such as check-sums of cyclical redundancy checks are used to check the data by the receiving host.
• The same checksum is recalculated at the destination end.
• If they do not match, the data become corrupted and is refused and a a new copy is requested to be sent again.

Question 19

How do check-sums work?

Answer 19

• Techniques such as check-sums of cyclical redundancy checks are used to check the data by the receiving host.
• The same checksum is recalculated at the destination end.
• If they do not match, the data become corrupted and is refused and a a new copy is requested to be sent again.
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• Creates and attaches a hash total calculated from the data contained in the packets
• This hash total commonly involves adding up the total number of 1s in the transmission.
• The CRC checksum is recalculated for each packet upon receipt and matched to help verify that the payload data has not changed during transmission.
• If the CRC totals differ, the packet is refused with the suspected data corruption and a new copy is requested from the sender.

Question 20

What does packet switching rely on?

Answer 20

• Ability of packets to be sent from sender to recipient along entirely separate routes from each other.

Question 21

What happens when packets are sent?

Answer 21

• At the moment that a packet leaves the sender’s computer, the fastest or least congested route is taken to the recipient’s computer, the can easily be re assembled in the correct order at the receiving end and any packets that don’t make it can be requested again.