Fundamentals of Communication and Networking | AQA A-Level Computer Science (7517)

Fundamentals of Communication and Networking

204 questions
15 subtopics
Paper 2: the written exam
Paper 2

Serial and parallel transmission, networks and their topologies, wireless, the TCP/IP stack, application layer protocols, the client server model and thin-client computing.

Examined on Paper 2.

Sample questions from Fundamentals of Communication and Networking

Answer each one closed book first, then open the answer.

Communication methods

Define parallel transmission.

Show the answer
Parallel transmission sends several bits at the same time, each bit travelling down its own separate wire in a multi-wire link. A group of bits (for example eight) is therefore transmitted simultaneously rather than one after another.
Communication basics

Define latency.

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Latency is the time delay between the moment a signal or data is sent and the moment it arrives or is acted upon at the destination. It is measured in units of time, usually milliseconds.
Network Topology and Types of Networking

What happens to performance on a logical bus as more devices are added, and why?

Show the answer
Performance falls. All the devices share one channel, so the available capacity is divided between them, and as more of them try to transmit the chance of two transmitting at the same time rises. More time is then spent waiting and retransmitting rather than sending useful data.
The Internet and Packet Switching

Define router.

Show the answer
A router is a device that connects networks together and forwards packets between them, choosing the best route for each packet towards its destination using the destination IP address and its routing table. It joins networks that use the same protocol, for example connecting a home or office network to the Internet.
Encryption, Digital Signatures and Certificates

Why can Ali not simply encrypt a confidential message with his own private key?

Show the answer
Because anything encrypted with his private key can be decrypted with his public key, and his public key is available to everyone. That would provide no confidentiality at all. Encrypting with the private key proves who sent the message; encrypting with the recipient's public key is what keeps it secret.
Standard application layer protocols

What is POP3 used for?

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Post Office Protocol version 3 is used by an email client to retrieve messages from a mail server. In its usual mode the client connects, downloads the waiting messages to the user's own device, and the messages are then deleted from the server, so the mail is stored and read locally.
IP Address Structure and Subnet Masking

Apply the subnet mask 255.255.255.0 to the IP address 192.168.10.37. What is the network identifier and what is the host identifier?

Show the answer
The mask 255.255.255.0 is 24 one bits followed by 8 zero bits, so the first three octets are the network part. ANDing gives a network identifier of 192.168.10.0, and the host identifier is 37.
IP Standards and Public and Private Addresses

How many addresses does each standard provide?

Show the answer
Version 4 has 32 bits, giving 2³² addresses, which is about 4.3 billion — 4,294,967,296 exactly, and fewer than that once reserved ranges are taken out. Version 6 has 128 bits, giving 2¹²⁸ addresses, a number vastly larger than the version 4 space and far beyond any foreseeable need.

The 15 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Communication methods	Recall questions on serial against parallel transmission, why serial wins over distance, and synchronous against asynchronous transmission and their overheads.	11
Communication basics	Recall questions on baud rate, bit rate, bandwidth, latency and protocol, and on why the bit rate can exceed the baud rate.	14
Network Topology and Types of Networking	Recall questions on physical star and logical bus topologies and their operation, and on peer-to-peer and client-server networking.	17
Wireless networking	Recall questions on the adapter and the access point, the SSID, why wireless needs encryption when wired does not, and how far hiding the SSID actually protects.	14
The Internet and Packet Switching	Recall questions on the structure of the Internet, how packet switching works, its advantages and the role of a router.	10
Routing, URLs and Domain Names	Recall questions on how a router chooses a route, the parts of a URL and what a fully qualified domain name is.	14
Firewalls, Worms, Trojans and Viruses	Recall questions on firewalls, packet filtering, proxy servers and stateful inspection, how viruses, worms and trojans differ, and how code quality, monitoring and protection address them.	12
Encryption, Digital Signatures and Certificates	Recall questions on symmetric and asymmetric encryption and key exchange, how a digital signature is created and verified, which key does what, and what digital certificates contain and why they are needed.	12
TCP/IP	Recall questions on the four layers and what each does, which addresses change at each hop, sockets and port numbers, and why both MAC and IP addresses are needed.	15
Standard application layer protocols	Recall questions on FTP, HTTP, HTTPS, POP3, SMTP and SSH, which of them expose data to an eavesdropper, and how anonymous FTP access differs.	18
IP Address Structure and Subnet Masking	Recall questions on how an address is structured, why it splits into network and host parts, and how a subnet mask is applied.	12
IP Standards and Public and Private Addresses	Recall questions on the two current standards, the format of each, how many addresses each provides and the private address ranges.	12
DHCP and Network Address Translation	Recall questions on the purpose of DHCP and how it works, what else the server supplies, why addresses are leased, and what NAT does.	17
Client server model	Recall questions on request-response, why Websockets are used and what full-duplex buys you, CRUD, REST, and JSON against XML.	18
Thin- versus thick-client computing	Recall questions on where the processing sits in each model, the hidden costs of cheap client hardware, and which model survives a network failure.	8

Fundamentals of Communication and Networking is 204 of the 1,516 questions in the guide.Get the guide, £9

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.