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2022 - Computer Science A Level AQA > 9 - Fundamentals of Communication and Networking > Flashcards

9 - Fundamentals of Communication and Networking Flashcards

1
Q

Explain how a thin-client network works.

A
  • Most processing is done by a central server
  • The user input is transmitted from the terminal to the server over the network
  • Data needed to produce image is transmitted from server to the terminal over the network
  • Applications are not installed on thin client workstations
  • Operating system is loaded by clients from server at boot
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2
Q

Explain how the use of a thin-client network instead of a traditional rich-client (thick-client) network will affect the selection of the hardware of the system.

A
  • Higher bandwidth network connection required
  • Network must use switch not hub
  • Slower processor and reduced RAM
  • Server must have multiple processors and a lot of RAM
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3
Q

What is Serial Data Transmission?

A

Data bits are sent in a sequence, one after the other, over a single wire from the source to the destination.

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4
Q

What is Parallel Data Transmission?

A

Multiple bits are sent simultaneously over multiple parallel wires from the source to the destination.

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5
Q

What is a problem with Parallel Data Transmission?

A

There is a possibility that data skew may occur as the bits could travel at slightly different speeds over each of the wires.

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6
Q

What are the advantages of serial over parallel data transmission?

A
  • Parallel communication requires more wires and hardware; therefore, serial transmission tends to be cheaper.
  • With parallel communication, there is a risk of data skew over long distances, whereas serial is reliable over much longer distances.
  • Parallel communication carries the risk of crosstalk between wires which results in more chance of errors. This is largely avoided with serial transmission.
  • Serial transmission suffers from little interference at high frequencies, so the serial frequency can be much higher than with parallel transmission. This results in higher net data transfer rates.
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7
Q

What is the bit rate?

What unit is it measured in?

A

The number of bits that are transferred between devices in one second.

It’s measured in bits per second. (Typically megabits or gigabits per second).

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8
Q

What is the baud rate?

What unit is it measured in?

A

Number of signal changes in a communications channel per second.

It’s measured in bauds.

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9
Q

What is the relationship between bit rate and baud rate?

A

bit rate = baud rate × number of bits per signal

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10
Q

What is bandwidth?

What unit is it measured in?

A

A measure of the maximum capacity of a given communication channel.
(Bandwidth and bit rate are directly proportional).

It is measured in hertz.

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11
Q

What is latency?

A

Time delay between the moment an action is initiated and the moment its effect begins.

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12
Q

What is synchronous transmission?

A

Data is transferred at regular intervals which are synchronised by a clock pulse signal.

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13
Q

What is asynchronous transmission?

A

Each byte is sent separately and the receiver and transmitter do not need to be synchronised, as the bytes are sent as soon as they are ready. To control the communication start and stop bits are used.

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14
Q

What is the relationship between bit rate and bandwidth?

A

Bit rate is directly proportional to bandwidth.

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15
Q

Explain how it is possible for the number of bits transmitted per second to be higher than the baud rate.

A

More than one bit is encoded in each signal change

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16
Q

What do start and stop bits do in asynchronous transmission?

A

The start bit is used to synchronise a clock in the receiving device. This means both devices are in step.
Once that has been received, timed periods will be used to receive the remaining bits in the transmission.
A stop bit indicates the end of the data.
The stop bit allows the receiver to identify when the next start bit arrives.

17
Q

What is an advantage of using synchronous transmission over asynchronous transmission?

A

Faster transmission because fewer bits have to be transmitted.

18
Q

What are the differences between a client and a server?

A
  • Client sends requests, server sends responses
  • Server can decide which data is sent, whereas client cannot
  • Servers are usually always on, whereas clients do not need to be
  • Clients are user facing, whereas servers are not
19
Q

Explain why it is common practice for servers to be always running and for clients to be sometimes running?

A
  • Clients should be able to connect at any time to the server
  • The client only needs to be running while the user is accessing the service
  • If the server is shut down, no one will be able to access the service
20
Q

An advantage of peer-to-peer networks over client-server models is that they are cheaper for the founder to run. Explain why this is the case.

A

Servers are more expensive to run because they are more powerful machines, they need more storage space and they need to be always powered on. In p2p, no one is responsible for a server. As more hosts connect to a p2p network, the resource supply increases, whereas when more hosts connect to a single server, the more powerful and expensive the server machines need to be.

21
Q

What are the advantages and disadvantages of thick client computers?

A

Advantages:
• Internet connection not needed to do useful stuff
• Can be used for storage of many files and large files
• More flexible in what can be done (whereas thin are limited to what cloud-based services exist and how they work)

Disadvantages:
• More expensive to buy and maintain
• Sometimes harder to use
• Sometimes less secure because the user is responsible for management of files and programs

22
Q

Explain why a client-server network is likely to be more appropriate than a peer-to-peer network in a situation where a system (for the administration of student courses to be used in an office in a college) must allow users at ten workstations to access and update a central database

A
  • System will be storing confidential data that must be kept securely
  • Administration will be easier
  • Centralised backup
  • Harder for users to change security settings
  • Running database from a server will avoid concurrency issues
  • Running database from server will ensure that it is always available
  • Server may allow more simultaneous connections than a workstation
23
Q

Explain the differences between client-server and peer-to-peer networking

A 
With client-server networking:
• Resources are stored on the server
• Clients access resources from server
• Centralised security management
• Configuration requires greater expertise

With peer-to-peer networking:
• Resources stored on each individual computer
• Any computer can access resources from any other
• Each computer has equal status
• Management of security could be more difficult
• There is no dependence on a server

24
Q

Describe the different parts of the URL http://www.aqa.org.uk/qual/gce/computing_new.php

  • http://
  • www.aqa.org.uk
  • /qual/gce/computing_new.php
A
  • http:// → the protocol used
  • www.aqa.org.uk → address of Aqa’s World Wide Web server
  • /qual/gce/computing_new.php → the path of the resource
25
Q

What is the purpose of a Domain Name Server on the Internet?

A

To resolve domain names into IP addresses

26
Q

What is the Internet?

A

The Internet is a network of interconnected computer networks using a globally unique address space using TCP/IP and supports a range of application protocols.

27
Q

What is the difference between the Internet and an internet?

A

An internet is a collection of networks which are connected together. The Internet describes the specific worldwide internetwork that uses a standard set of Internet protocols for transmitting messages between devices.

28
Q

What is a Domain Name Server?

A

A Domain Name Server is a server that contains domain names and the associated IP addresses.

29
Q

What is an IP address?

A

An Internet Protocol (IP) address is a unique number that identifies devices on a network.

30
Q

What is the link between a domain name and an IP address.

A

A domain name is the string that corresponds to an IP address.

31
Q

What is a protocol?

A

A protocol is a set of agreed signals for data exchange between systems.

32
Q

What is the World Wide Web?

A

A system of interlinked hypertext documents accessed via the Internet using HTTP protocol.

33
Q

Why do people prefer to use a fully qualified domain name (FQDN) rather than an IP address?

A

IP addresses are less memorable

34
Q

Explain what each of these parts of the URL http://www.aqa.org.uk mean

  • http://
  • www
  • uk
A
  • http:// → means Hypertext transfer protocol will be used
  • www → resource is on a web server
  • uk → country the site is registered in
35
Q

Describe how domain names are organised

A

Domain names follow a hierarchy. When forming a domain name, the leaf node appears first, then parents separated by dots. Each top level domain is managed by an internet registry.

36
Q

What is the purpose and function of the domain service, and describe its reliance on the Domain Name Server system

A

The domain service provides a mapping between domain names and IP addresses.
A registrar can help you find an authoritative name server. This name server must always have the most up-to-date record of your server’s IP address. A DNS lookup is used to find the IP address of the host before the web request is sent.

37
Q

Using the Domain Name System we can refer to IP addresses by host name. Explain the role of a Domain Name Server, which makes this possible.

A

Domain name is intercepted by a domain name server. Domain name server looks up domain name in its table and finds the matching IP address. If it can’t find the domain name, contacts another Domain Name Server.

38
Q

Why does a company need to register a domain name with an Internet registry when setting up a website?

A

To ensure the domain name is unique and to allocate a unique IP address to the domain.

39
Q

In what situations will a DNS query not be sent to a remote DNS server?

A
  • The computer already has a copy of the needed IP address
  • The computer has a cache of recent DNS queries
  • The URL typed in already contains an IP address
  • The URL refers to a local resource

2022 - Computer Science A Level AQA (11 decks)

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