Circuit Switching, Packet Switching (Cambridge (CIE) A Level Computer Science): Flashcards
Exam code: 9618
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- FrontSwitching Methods
Define packetising.
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Define packetising.
Packetising is the process of dividing a large message into smaller, manageable units called packets, each of which can be transmitted individually.
Name the three parts of a packet.
Header, payload and footer (trailer).
Define payload.
The payload is the actual data being sent.
Name four items found in a packet header.
Source IP address, destination IP address, sequence number, protocol, packet length and checksum.
The packet header contains the IP address, showing who sent the packet.
The packet header contains the source IP address, showing who sent the packet.
What is the sequence number in a packet header used for?
To reassemble the packets in the correct order at the destination.
What is the checksum in a packet header used for?
Error checking.
What may a packet footer contain?
Extra error-checking or control information.
How do packets travel across a network?
Independently, and they may travel along different routes through the network.
How is the original message recovered?
The packets are reassembled at the destination using their sequence numbers.
Define packet switching.
Packet switching is a communication method where data is broken into packets and sent across a shared network, with each packet possibly taking a different path and reassembled on arrival.
Define circuit switching.
Circuit switching sets up a dedicated communication path between two devices for the duration of a session.
Circuit switching works like a traditional call.
Circuit switching works like a traditional phone call.
True or False?
Packet switching sends data as a continuous stream.
False.
Packet switching sends data in individual packets. It is circuit switching that sends a continuous stream.
Name three benefits of packet switching.
Efficient use of network bandwidth, more reliable because only lost or corrupted packets need resending, and lower cost because network resources are shared.
Name three drawbacks of packet switching.
Not ideal for real-time applications, packets can arrive out of order and need reassembly, and network congestion may cause packet delay or loss.
Name three benefits of circuit switching.
It is ideal for real-time communication with a steady continuous flow, there are no delays once the circuit is established, and data arrives in order.
Name three drawbacks of circuit switching.
It is less efficient because resources stay reserved when not in use, it has a higher cost due to dedicated lines, and it is less scalable.
True or False?
In circuit switching, resources are freed when the line is idle.
False.
Resources remain reserved even when not in use, which is what makes circuit switching less efficient.
How does data order differ between the two switching methods?
With packet switching, data may arrive out of order and requires reassembly. With circuit switching, data always arrives in order.
Which switching method is more robust to failure, and why?
Packet switching, because packets can be rerouted if a failure occurs. In circuit switching, if the path fails the call is dropped and must be re-established.
Which switching method is more scalable?
Packet switching, which handles large volumes of data and users. Circuit switching needs more physical paths as more users are added.
What is packet switching best used for?
Emails, web pages and file downloads.
What is circuit switching best used for?
Real-time communication, such as voice calls and video conferencing.
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