2023 internet service past paper Flashcards
(7 cards)
For each of the following layers of the internet protocol stack, describe the
services it provides and give one example of a protocol in that layer:
the application layer = is the top layer of the interent protocol stack it provides network services directly to users and application, such as emails. this layer allows application to communicate over the network. an example would be the http (hyper text transfer protocol)
which is used to access and transfer web pages between browser and web servers
For each of the following layers of the internet protocol stack, describe the
services it provides and give one example of a protocol in that layer:
the network layer
The network layer is responsible for routing data across different networks, ensuring that it reaches the correct destination. It also handles IP addressing and packet forwarding. An example protocol is IP (Internet Protocol), which helps route packets by assigning unique addresses to devices and determining the best path for data to travel.”
Suppose that there are four routers between a source host and a destination
host. A datagram is sent from the source host to the destination host. How
many interfaces will the datagram travel over? Explain your answer.
A datagram sent from a source host to a destination host will travel over ten interfaces in total. Here’s how:
The source host will send the datagram to the first router, crossing its first interface.
The first router receives the datagram and forwards it using its second interface to the next router.
Each of the four routers has two interfaces (one incoming and one outgoing), so the datagram will cross two interfaces per router.
After traveling through the four routers (which contributes eight interfaces), the datagram will reach the destination host via its final interface, making ten interfaces in total.
What is the Transmission Control Protocol (TCP)? What is the User
Datagram Protocol (UDP)? Explain their similarities and differences.
[10 marks]
Transmission Control Protocol (TCP):
Transmission Control Protocol (TCP) is a connection-oriented protocol used in the transport layer. It ensures that data is transferred reliably, in order, and without errors. TCP establishes a connection between the source and destination before sending data, which is done through a 3-way handshake. Once the connection is established, TCP ensures that all data packets are delivered correctly. If any packet is lost or corrupted during transmission, TCP retransmits it.
Key Features of TCP:
Connection-Oriented: Requires a setup before data transmission (3-way handshake).
Reliable: Guarantees data delivery with error detection and retransmission of lost packets.
Ordered: Ensures data is received in the same order it was sent.
Flow Control: Manages data flow to prevent network congestion.
Example of TCP Usage:
TCP is used in applications where reliability is critical, such as web browsing (HTTP/HTTPS), email (SMTP/IMAP), and file transfers (FTP).
User Datagram Protocol (UDP):
User Datagram Protocol (UDP) is a connectionless protocol, meaning it does not establish a connection before sending data. Unlike TCP, UDP does not ensure that data packets are received in order or even at all. UDP is faster because it has lower overhead, as there is no need for connection setup, retransmissions, or acknowledgments. However, this comes at the cost of reliability.
Key Features of UDP:
Connectionless: No setup is required before sending data.
Unreliable: There is no guarantee of delivery, ordering, or error correction.
Faster: Due to its minimal overhead and lack of error checking.
No Flow Control: No mechanisms to prevent congestion.
Example of UDP Usage:
UDP is typically used in real-time applications where speed is crucial and some data loss is acceptable, such as video streaming (YouTube, Netflix), online gaming, and VoIP (Voice over IP).
Similarities Between TCP and UDP:
Transport Layer Protocols: Both TCP and UDP operate at the transport layer of the OSI model.
Data Packetization: Both protocols break data into smaller packets for transmission over the network.
Port Numbers: Both use port numbers to direct data to the correct application on the destination host.
One may require that the data be delivered within a specified amount of
time.
A. Can UDP provide this service? Explain your answer.
No, UDP (User Datagram Protocol) cannot guarantee that data will be delivered within a specified amount of time. Here’s why:
Connectionless Nature: UDP is a connectionless protocol, meaning it does not establish a reliable connection between the sender and receiver.
No Delivery Guarantees: Unlike TCP, UDP does not include mechanisms for acknowledgment, retransmission, or error correction, so packets may be lost or arrive out of order.
No Timing Control: UDP does not ensure timely delivery, as it relies on the underlying network infrastructure, which can introduce delays due to congestion or routing issues.
Best Effort Delivery: While UDP is fast and efficient, it only sends data without checking if it arrives.
Can TCP provide this service? Explain your answer.
Yes, TCP (Transmission Control Protocol) can provide a service where data is delivered within a specified amount of time, but only to a certain extent. Here’s why:
Reliable Delivery: TCP is a connection-oriented protocol, meaning it ensures that data is delivered accurately and in order by using acknowledgments and retransmissions.
Flow Control & Congestion Control: TCP uses mechanisms like flow control and congestion control, which help manage network traffic and prevent excessive delays.
No Guarantee of Precise Timing: While TCP ensures data delivery, it does not guarantee strict timing. Delays can occur due to network congestion or retransmissions, which can slow down the process.
Better for Accuracy, Not Speed: Unlike UDP, which prioritizes speed, TCP prioritizes correctness. If a strict time requirement is necessary (such as for live streaming or real-time gaming), specialized protocols like RTSP (Real-Time Streaming Protocol) or QoS (Quality of Service) mechanisms may be needed.
