2021 internet service past paper Flashcards
(7 cards)
Briefly describe the services provided by the top two layers of the internet
protocol stack and give one example of a protocol for each of the top two
layers.
[6 marks
application layer - this layer provides network service for end users such as web browsing an example would be http (hypertext transfer protocol) used for web communication between browser and network
the second layer is the transport layer which enables reliable data transfer between hosts it also ensures error check and flow control, an example protocol would be tcp ( transmission control protocol) which is responsible for delievering data in an accurate and ordered way)
A router has eight interfaces. How many IP addresses does it have? Briefly
explain your answer
each interface would need a unique ip address to communicate with devices on different network . each interface is typically connected to a different network or subnet. a router forwards data between different networks and each interface needs its own ip address to identify itself in the network therefore a router with eight interface will have eight ip address ensuring proper communication between the router and the device on each connected network
Describe two differences between packet-switching networks and circuit
switching networks. Use examples to explain your answer.
packet switching network = data is broken into smaller packets each of which is independentally sent across the network each packet might take a different route to each the destination and they are assembled. and example would be the internet when you send an email or browse the web.
circuit switching network = in circuit switching a path is opened between the sender and receiver during the communication. the path stays open even if no data is transmitted an exmaple could be using a telephone to call someone.
packet switching network may experience variable latency because packets take different route which can lead to a delay when reordering however it is very reliable as if one path fails it can simply can another.
circuit switching networks have a consistent latency are are more predictable as the same path is used throughout the communication.
Consider the protocol TCP (the Transmission Control Protocol).
How can a TCP connection be established? Use an example to explain
your answer.
[3 marks]
A tcp connection uses a three way handshake process which involves these steps :
SYN (synchronise)
the client sends a a syn message to the server to request a connection
SYN-ACK
the server response with a SYN-ACK message to acknowledge the request and offer a connection
ACK
the client replies with an ACK message confirming the connection
an example would be If a user opens a web browser and tries to access a website:
The client (browser) sends a SYN packet to the web server.
The server replies with a SYN-ACK.
The client sends back an ACK.
After this exchange, the TCP connection is fully established, and data transfer (like loading the webpage) can begin.
What is a persistent TCP connection? What is a non-persistent TCP
connection? Explain your answers
persistent tcp = the connection stays open after a request and reponses are completed and exchanges multiple data without having to close an example would be when loading a with many elements such as images and script a persistent connections allows all of them to be transferred over the the same connection improving speed and efficiency
a non persistent connection =the connection closes after each request and response. for every new request a new tcp connection must be established. this increases delays and uses more system resources due to multiple setups
The following are some of the services a transport protocol may provide:
i. A guarantee that data will be delivered within a specified amount of time.
ii. Reliable data transfer.
iii. Confidentiality.
For each of the above, indicate if either UDP or TCP (or both) provides such
a service and explain your answers
Explanation:
Neither TCP (Transmission Control Protocol) nor UDP (User Datagram Protocol) guarantees data delivery within a specific time limit.
TCP focuses on reliable delivery, not timing, and uses mechanisms like acknowledgments and retransmissions which can cause delays.
UDP is faster because it sends data without such checks, but it also lacks any timing or delivery guarantees.
Applications needing strict timing (e.g., voice or video calls) often use UDP with real-time protocols like RTP, but even then, time guarantees are not from UDP itself.
✅ Full explanation gets 4 marks (Identification + Technical reasoning + Example)
ii. Reliable data transfer
Provided by: ✅ TCP only
Explanation:
TCP provides reliable data transfer through several features:
Sequencing: Data is numbered so it arrives in the correct order.
Acknowledgments (ACKs): Receiver confirms receipt of data.
Retransmission: Lost or corrupted packets are resent.
Flow control and error detection further ensure data integrity.
UDP does not guarantee reliability—it sends datagrams without ensuring delivery, ordering, or retransmission. This makes UDP suitable for real-time applications where speed is more important than accuracy (e.g., live streaming).
✅ This section earns 4 marks (Correct answer + technical details + contrast with UDP)
iii. Confidentiality
Provided by: ❌ Neither TCP nor UDP (by default)
Explanation:
Confidentiality means ensuring that data is kept private and secure during transmission.
Neither TCP nor UDP has built-in encryption or confidentiality features.
Instead, encryption is typically handled by higher-layer protocols:
TLS (Transport Layer Security) is used with TCP to form HTTPS, encrypting data between client and server.
UDP-based protocols can also use DTLS (Datagram TLS) to provide similar encryption.
So, confidentiality is not part of TCP or UDP themselves, but rather is layered on top when needed.
✅ This section earns 4 marks (Clear answer + explanation of TLS/DTLS + distinction between layers)
