Internet Communication ( 1 )

Question 1

What is circuit switching?

Answer 1

Circuit switching creates a direct link between two endpoints for the duration of the transfer of data.

Question 2

What are some disadvantages to circuit switching?

Answer 2

• Bandwidth is wasted during the periods when no data is being sent
• Can only connect devices that operate at the same transfer rate ( because two devices must transmit and receive data at the same rate )
• Because switches are used to connect and disconnect circuits Electrical interference is produced, may produce corrupt or lost data if the path is already being used to transmit data.

Question 3

What are some advantages of circuit switching?

Answer 3

Exclusive connection between two devices for the duration of the communication, data packets arrive in the same order in which they are sent, making the process of reconstructing the message simpler.

Question 4

How does electrical interference affect circuit switching?

Answer 4

• Because switches are used to connect and disconnect circuits electrical interference is produced, may produce corrupt or lost data if the path is already being used to transmit data.

Question 5

What is packet switching?

Answer 5

• Sending data packets across a network in which other similar communications are happening simultaneously.
• Data that you receive arrives as a series of packets, and leaves as a series of packets

Question 6

What happens to data that is going to be transmitted?

Answer 6

• Data that is to be transmitted across a network is broken down into more manageable chunks called packets.
• Each packet contains: Header, payload, and checksum

Question 7

What does each data packet contain?

Answer 7

• Header
• Payload/Data
• Checksum/Also known as the trailer

Question 8

What is the payload?

Answer 8

The body of data being sent

Question 9

What is the header?

Answer 9

• Part which identifies the source and destination of the packet
Usually contains:
• Sender and recipient IP addresses
• Protocol being used with the packet
• Number of the packet in the sequence being sent
• Hop limit

Question 10

What is the purpose of the checksum?

Answer 10

Contains error checking components that verify data received in the payload has not been corrupted on transfer
• Used to detect transmission errors by creating and attaching a hash total calculated from the data contained in the packets.
• Calculated through adding up the total number of 1s in the transmission, CRC is recalculated for each packet upon retrieval, and matched to help verify the payload data is not changed during transmission of the data
• If the totals differ, the packet is refused due to data corruption, and a new copy is requested.

Question 11

How does the checksum/CRC check verify that data is not altered?

Answer 11

• Creating and attaching a hash total calculated from the data contained in the packets.
• Calculated through adding up the total number of 1s in the transmission, CRC is recalculated for each packet upon retrieval, and matched to help verify the payload data is not changed during transmission of the data
• If the totals differ, the packet is refused due to data corruption, and a new copy is requested.

Question 12

What is an advantage of using data packets?

Answer 12

They increase network efficiency & reliability

Question 13

Where might packet switching be used?

Answer 13

Networks where multiple connections of the same type are occurring simultaneously, and multiple routes to the destination exist

Question 14

What route does a packet take?

Answer 14

Each packet takes the fastest possible route to the destination

Question 15

What does the header contain?

Answer 15

• Sender and recipient IP addresses
• Protocol being used with the packet
• Number of the packet in the sequence being sent
• Hop limit

Question 16

What happens when the packets are received?

Answer 16

Packets are reassembled in the correct order and the data is extracted

Question 17

What does packet switching rely upon?

Answer 17

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

Question 18

What do routers do?

Answer 18

Forward data packets from one network to another

Question 19

How do routers forward data packets?

Answer 19

• Each router stores data about the available routes to the destination node
• Looks up the destination address IP 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 20

What is a hop?

Answer 20

Each transfer between routers