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CS A Level Paper 2 > Fundamentals of communication and networking > Flashcards

Fundamentals of communication and networking Flashcards

1
Q

Since the year 2000, hard drive data communication has changed from favouring PATA (Parallel ATA) protocol to SATA (Serial ATA) protocol.

Explain what is meant by the term ‘protocol’. (1 mark)

A

A set of rules OR standards (to allow for data transmission)

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2
Q

Since the year 2000, hard drive data communication has changed from favouring PATA (Parallel ATA) protocol to SATA (Serial ATA) protocol.

Describe the difference in operation between parallel and serial data transmission. (2 marks)

A

In parallel transmission data is sent simultaneously (through a number of wires/lines). (1)

In serial transmission data is sent consecutively/one after another (through a single line). (1)

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3
Q

Since the year 2000, hard drive data communication has changed from favouring PATA (Parallel ATA) protocol to SATA (Serial ATA) protocol.

State disadvantages for using parallel data transmission for peripheral devices (4 marks)

A
  • Interference OR crosstalk from the other wires (1)
  • Data sent simultaneously might arrive at different times OR data skew (1)
  • Parallel data cables more expensive to manufacture (1)
  • The longer distance needed for peripheral devices makes interference OR crosstalk more likely (1)
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4
Q

A computer network lists different values for the baud rate and bit rate of its transmission speeds.

State one other measure of network speed

A

Bandwidth OR latency

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5
Q

A computer network lists different values for the baud rate and bit rate of its transmission speeds.

Explain the impact of bandwidth on the bit rate (2 marks)

A

A wider bandwidth means that each signal can contain more than 1 bit OR can be used to represent more than two possible values (1) meaning that the bit rate can be higher than the baud rate (1)

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6
Q

A peer-to-peer network would remove the need for a server. Explain why this would not be an effective solution for the firm of solicitors (2 marks)

A

Data would not be centralised OR separate copies would be held on each workstation so a workstation may not hold the current/correct version of a file (1)

Changes made on one workstation may not be reflected on the other workstations (1)

(Allow other suitable terms for workstation, e.g. computer, device.)

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7
Q

A cafe currently has a small wired network consisting of two PCs for office work, a modem and a printer. The owner of the cafe is considering the option of adding wireless functionality to the network.

State the name of one piece of hardware that would be reuired to add wireless functionality to the network.

A

Wireless access point

OR

wireless router

OR

wireless network adapter

(Refuse ‘wireless modem’.)

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8
Q

A cafe currently has a small wired network consisting of two PCs for office work, a modem and a printer. The owner of the cafe is considering the option of adding wireless functionality to the network.

Describe benefits to the cafe of adding wireless functionality

A
  • More customers may visit because of access to public WiFi.
  • Computers OR staff can be moved more freely (1) allowing for more flexible working practices (allow any sensible example).
  • Café can charge customers for WiFi increasing profits.
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9
Q

Explain why a wireless network may introduce a new security risk to the network (3 marks)

A
  • Wireless signals are not restricted to the physical building.
  • Data can be received without physical access to the network.
  • Anyone with a wireless network adapter can receive the transmission/data/signal.
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10
Q

Describe methods of securing a wireless network (6 marks)

A

Mark in pairs:

  • Hide the network’s SSID (1) so that only people who know about the network are able to access it. (1)
  • Encrypt the network OR use WPA/WPA2 encryption. (1) Refuse ‘password’ so that unauthorised users cannot understand the signal/data OR data is meaningless to anyone without the key. (1)
  • Use MAC address filtering OR a MAC address whitelist (1) so that only authorised devices are able to access the data. (1)
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11
Q

When a wireless device is ready to send a message, state four steps that the wireless device might carry out as part of CSMA/CA (4 marks)

A
  1. Listen for a current transmission.
  2. Pause (and try again) if a transmission is detected.
  3. Send the message if one is not detected.
  4. If another transmission is detected at the same time the message was sent (1), wait a random amount of time. (1)
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12
Q

Explain one benefit and one drawback of using RTS/CTS (4 marks)

A

Benefits:

In the case of collision, RTS is a small message to resend (1) instead of having to resend the whole message (1) especially on a busy network. (1)

Drawbacks:

Increased latency OR more data needs to be transmitted overall OR delay while performing the RTS/CTS protocol (1) especially on a quiet network (where collisions are less likely). (1)

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13
Q

A student is using file transfer to send data across the internet.

Packet switching is used to transfer the data. Describe what is meant by ‘packet switching’ (4-7 marks)

A
  • Data is split into packets.
  • Each packet is given an (IP) address.
  • Each packet is placed onto the internet via a gateway OR router.
  • Each packet is sent independently.
  • Routers forward the packets until they arrive at their destination.
  • Each router decides on the path for that packet.
  • Packets are reassembled once received.
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14
Q

A student is using file transfer to send data across the internet.

State items of data that are included in a packet (3-7 marks)

A
  • Sender’s IP address
  • Receiver’s IP address
  • Packet number
  • Error checking data OR parity bit(s) OR checksum bit(s)
  • Length
  • Priority
  • Payload OR original data.
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15
Q

Explain the difference between a gateway and a router (2 marks)

A

A gateway is used to allow data to be placed onto/accepted from the internet. (1)

A router is used to forward data across the internet. (1)

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16
Q

State an advantage of using a domain name instead of an IP address to identify the server

A

Easier to remember OR recognise OR provides information to the user (e.g. name of the organisation).

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17
Q

Explain how DNS is used to allow the student to make use of the server’s domain name (5 marks)

A
  • When the user enters a domain name, a DNS lookup occurs.
  • A request is made to the DNS server to find the IP address for a given domain name.
  • DNS server/Domain Name Server holds a table of domain names and corresponding IP addresses.
  • The DNS server responds with the corresponding IP address.
  • The (file transfer) software uses the IP address to establish a connection.
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18
Q

State one situation where a DNS request will not be required when the student enters a domain name

A

The DNS result is stored in the user’s cache (because it was used recently) OR stored on the user’s computer (in the hosts file).

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19
Q

Data can be encrypted using symmetric or asymmetric data encryption.

State the difference between the two principles

A

Symmetric encryption uses the same key to encrypt and decrypt the data OR asymmetric encryption uses different keys to encrypt and decrypt the data

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20
Q

Explain how private-public key encryption can be used to ensure that data can only be decrypted by the receiver ( 3-5 marks)

A
  • A public key is made available to everyone.
  • The data is encrypted using the public key.
  • Because the encryption is asymmetric, no other users can decrypt the message.
  • The authorised receiver of the data holds the private key.
  • The message can only be decrypted using the private key.
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21
Q

Private-public key encryption can also be used to authenticate a message using a digital signature. Describe the principles of operation of a digital signature. ( 5 marks)

A

Any five from: (5) (max. three from either sender/receiver)

Sender

  • The message is hashed (to generate a shorter message digest).
  • The hash OR a message is encrypted using the sender’s private key.
  • The encrypted code is added to the original message.
  • The message is transmitted OR received.

Receiver

  • The public key is publicly available.
  • The encrypted code is decrypted using the public key.
  • The message is hashed.
  • The decrypted code is compared to the hash.
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22
Q

Explain the purpose of a digital certifcate (3 marks)

A

To prove that a user’s public key is authentic (1) by encrypting the public key using the certificate authority’s private key (1) and decrypting it using the certificate authority’s public key. (1)

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23
Q

Describe the principles of operation for virus malware (3 marks)

A
  • Code/program that attaches itself to a file (1)
  • Self-replicating OR copies itself when the file is run (1)
  • Completes some malicious action OR by example. (1)
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24
Q

Describe the principles of operation of a worm malware (3 marks)

A
  • Code that exploits a weakness in the network (as opposed to attaching itself to a file) (1)
  • Software is standalone (1)
  • Replicates automatically OR without having to be run by the user (1)
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25
Q

Describe the principles of operation of trojan malware (3 marks)

A
  • A program that tricks the user into running it OR a program that pretends to do one thing but actually does something else (1)
  • Does not self-replicate (1)
  • Must be loaded/executed by the user in order to function (1)
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26
Q

State the name and the purpose of each of the layers of the TCP/IP stack (8 marks)

A
  • Application: (1) protocol-specific data OR data required by an application OR payload (1)
  • Transport: (1) used to split the data into packets OR packet number OR port number (1)
  • Network OR internet: (1) used to address each packet OR sender’s IP address OR receiver’s IP address (1)
  • Link: (1) used to put the packet onto the transmission medium OR sender’s MAC address OR receiver’s MAC address (1)
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27
Q

Data is transmitted acrsoss a network using the TCP/IP protocol.

Identify which two layers are required in order to open a socket.

A

Transport and network

OR

Transport and internet

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28
Q

Data is transmitted acrsoss a network using the TCP/IP protocol.

State the name of the layer that is used to store the MAC address of the recipient.

A

Link

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29
Q

Data is transmitted acrsoss a network using the TCP/IP protocol.

Describe an advantage of separating the TCP/IP stack into individual layers. (2 marks)

A

So that one layer can be rewritten OR changed OR modified (1)

without affecting the other layers. (1)

30
Q

Other than the port number, state what other information is needed to open a port

A

IP address

(Refuse ‘address’ – not enough.)

31
Q

In order to configure a firewall, the network administrator connects to the server remotely.

Name the most suitable protocol to achieve this.

A

SSH

(Refuse ‘Telnet’ as this is not encrypted.)

32
Q

Describe an advantage of connecting to the server remotely. (2 marks)

A
  • Server may not be in the same location as the administrator (1) so saves on travel time OR having to physically relocate the server. (1)
  • No need for a keyboard and mouse OR input and output devices for the server (1) saving money. (1)
33
Q

the IP address of the modem, 243.16.95.83, is composed of two identifiers. Using a subnet mask of 255.255.255.0 state the

  • network identifier
  • host identifier
A
  • 243.16.95.0 (1) (accept 243.16.95)
  • 0.0.0.83 (1) (accept .83 OR 83)
34
Q

The local area network contains over 1000 devices, but only has access to 245 public IP addresses.

State why network address tranlsation (NAT) is required for workstations to access the internet.

A

When a request is sent from a workstation within the network the return IP address will be non-routable OR private

35
Q

Describe the process of using NAT within a pool of IP addresses

A

A gateway OR router at the edge of the network (1) will provide a return address from the pool of allowable routable IP addresses OR from the 245 available IP addresses (1) so that when the response is received it can be returned to the correct device. (1)

36
Q

Explain the nature and purpose of the websocket protocol. (3 marks)

A

Websocket creates a persistent OR continuous (1) full-duplex OR two-way (1) connection between the web browser and the server. (1)

37
Q

State the meaning of the acronym CRUD

A
  • C – Create
  • R – Retrieve
  • U – Update
  • D – Delete
38
Q

State the name of the four HTTP request methods described by REST and map each one to its relevant CRUD command

A

POST – Create (1)

GET – Retrieve (1)

PUT – Update (1)

DELETE – Delete (1)

39
Q

State the name of two encoding mechanisms for returning the results of a query to a web page (2 marks)

A
  • JSON (1)
  • XML (1)
40
Q

State whether XML or JSON is easier for humans to read and quicker for computers to parse (1 mark)

A

JSON

41
Q

A sensor is to be connected to a data logging computer system that is 3 metres away.

State one advantage and one disadvantage of using parallel transmission. (2 marks)

A

Advantage: Can send more data simultaneously OR can use one line for synchronisation/timing. (1)

Disadvantage: More expensive cable OR crosstalk/interference OR data skew/de-synchronisation of data. (1)

42
Q

A sensor is to be connected to a data logging computer system that is 3 metres away.

A decision is taken to use serial transmission. Explain why asynchronous data transmission must be used and why overhead must be added to the data. (3 marks)

A

Why asynchronous: No common timing signal available. (1)

  • Why extra bits: Any two from: (2)
    • Start and stop bits must be added.
    • Start bit: to synchronise OR wake receiver OR start receiver’s clock.
    • Stop bit: allows start bit to be recognised OR allows message to be processed.
43
Q

Our wireless network is only accessible to corporate staff.

Describe two security strategies that will help prevent visitors from accessing the wireless network. (4-6 marks)

A

Any two from: (4) (mark in pairs)

  • SSID hiding (1) so that visitors will not be able to see the network. (1)
  • MAC address filtering OR MAC address whitelisting (1) so that only authorised devices will be able to connect to the network. (1)
  • WPA OR WPA2 OR encryption (1) so that unauthorised users will be unable to read any of the data that is transmitted. (1)
44
Q

Our network uses DHCP.

Explain the function of using DHCP on the network, why it might be needed and one drawback. (3 marks)

A
  • DHCP dynamically assigns IP addresses to devices on demand. (1)
  • Useful when there are too many devices to configure manually. Rather than configure each device one-by-one you can use a DHCP server to dynamically allocate IP addresses for you (1)
  • Useful when hosts come and go frequenctly e.g. on a wirless LAN in a cafe
  • Drawback is that it can be more difficult to trace an action back to one user/device. (1)
45
Q

An estate agent’s website can be accesses by entereing either 182.93.45.81 or www.barnabyestates.com into a web browser.

State the domain name of the website

A

barnabyestates.com

(Refuse ‘www.barnabyestates.com’)

46
Q

An estate agent’s website can be accesses by entereing either 182.93.45.81 or www.barnabyestates.com into a web browser.

Explain wh it is more common to use the URL for website rather than the IP address (1 mark)

A

Easier to remember than an IP address OR tells the user something about the organisation or nature of the website.

47
Q

An estate agent’s website can be accesses by entereing either 182.93.45.81 or www.barnabyestates.com into a web browser.

A company with the same name, in another country, wishes to use the same URL.

Explain what measures are in place to prevent this. (2 marks)

A

Internet registries manage the sale of domain names (1) so that the same domain name cannot be linked to more than one IP address OR customer. (1)

48
Q

Staff can access a database of existing and previous houses for sale using a webform to perform searches and to update the database.

State which function of CRUD would be used to edit an existing record.

A

Update

49
Q

Staff can access a database of existing and previous houses for sale using a webform to perform searches and to update the database.

To edit an existing record, using REST, what HTTP method would map to an SQL function that would accomplish this?

A

PUT

(Ignore case)

50
Q

Staff can access a database of existing and previous houses for sale using a webform to perform searches and to update the database.

When receiving the result of a query, the data could be encoded using JSON or XML.

Suggest two reasons why JSON may be preferable. (2-4 marks)

A
  • Easier for a person to read.
  • More compact to display.
  • Easier/quicker for computers to parse/read.
  • Easier for computers to generate.
51
Q

Staff can access a database of existing and previous houses for sale using a webform to perform searches and to update the database.

The estate agency is considering replacing its existing thick-client infrastructure with thin-client technology.

Discuss the advantages and disadvantages of replacing the IT infrastructure in terms of hardware requirements. (2 marks)

A

Hardware

The existing thick-client network will be made of standard PCs, each running the majority of tasks locally.

A thin-client network would require a central server (or servers, depending on the scale of the network) with cheaper ‘thin’ or ‘dumb’ terminals, each with very little individual processing power.

The central server may be very expensive and would need to be significantly more powerful than a standard thick-client machine.

Each terminal must be connected to the network at all times or will lose access to the vast majority of its processing capabilities as well as access to data storage.

52
Q

Explain why the logical topology of a network may be different to the physical topology

A

A network can be configured to operate as if it was a different physical topology.

example: a star network can be configured to behave as if it was a bus network.

53
Q

Describe the role of the server in a typical network (3 marks)

A

To manage a centralised resource

By processing requests

And delivering a response

54
Q

State any IP address present in the diagram that is non-routable and explain the significance of this (3 marks)

A
  1. 168.0.2
  2. 168.0.3
  3. 1.1
  4. 168.2.1

any of the above (1)

This is a private IP address (1)

Cannot be addressed directly from outside it’s network (1)

55
Q

State a suitable IP address for (i)

A

any value between 192.168.0.0 and 192.168.0.255 except for 192.168.0.2 or 192.168.0.3

56
Q

State a suitable IP address for (ii)

A

any value between 192.168.0.0 and 192.168.0.255 except for 192.168.0.2 or 192.168.0.3

57
Q

State a suitable IP address for (iii)

A

any value between 192.168.1.0 and 192.168.1.255 except for 192.168.1.1

58
Q

State a suitable IP address for (iv)

A

any value between 192.168.2.0 and 192.168.2.255 except for 192.168.2.1

59
Q

Staff can access a database of existing and previous houses for sale using a webform to perform searches and to update the database.

The estate agency is considering replacing its existing thick-client infrastructure with thin-client technology.

Discuss the advantages and disadvantages of replacing the IT infrastructure in terms of capability. (2 marks)

A

Capability

The existing thick-client network will likely afford staff adequate processing power for the vast majority of office-based tasks and is probably not using its full processing capabilities for the vast majority of the time. A well-designed thin-client network would cope very well with most office-based activities and staff would be unlikely to notice a significant difference in processing capabilities. Graphics-intensive tasks such as producing digital animation, video editing, gaming and detailed image editing is more likely to be problematic, partly due to the requirement for fast data connections and partly due to the remote nature of the server and the latency in waiting for a response to processing requests. It may be wise to maintain a small number of thick clients specifically for any graphics or processor intensive tasks.

60
Q

Staff can access a database of existing and previous houses for sale using a webform to perform searches and to update the database.

The estate agency is considering replacing its existing thick-client infrastructure with thin-client technology.

Discuss the advantages and disadvantages of replacing the IT infrastructure in terms of sustainability. (2 marks)

A

Sustainability

  • thin-client network should be easier to sustain as software updates and the installation of new software only needs to be carried out on the central server.
  • Adding new thin clients will be quicker, easier and cheaper than adding new thick clients to the network.
  • Hardware upgrades to the server are likely to be less frequent, but more expensive when they do occur.
  • Overall the total cost of ownership for a thin-client network may be lower if it is properly specified when first installed and depending on the nature of the tasks and the number of machines that are replaced.
61
Q

List what is provided by a DHCP server

A

IP Address

Subnet Mask

Router/Gateway

62
Q

Describe the 4 steps of DHCP

A
  1. DHCP DISCOVER: The client broadcasts a request for a DHCP server.
  2. DHCP OFFER: DHCP servers on the network offer an address to the client.
  3. DHCP REQUEST: The client broadcasts a request to lease an address from one of the offering DHCP servers.
  4. DHCP ACK (acknowledge): The DHCP server that the client responds to acknowledges the client, assigns it any configured DHCP options, and updates its DHCP database. The client then initializes and binds its TCP/IP protocol stack and can begin network communication.
63
Q

Explain baud rate [1 mark]

A

The baud rate sets the maximum frequeuncy at which signals may change

OR

The number of times a signal in a communications channels changes state

64
Q

Explan what is meant by bit rate [1 mark]

A

The number of bits that are transfered between devices in one second

65
Q

Explain how it is possible for the bit rate to be higher than the baud rate [1 mark]

A

The bit rate is the same as the baud rate when one bit is sent beteen consecutive signal changes.

It is possible to send more than one bit between signal changes if more than two voltage levels are used to encode bits.

66
Q

Decribe two exmaples where using DHCP to configure new client hosts is preferable to manual configuration by other means

A
  • Where hosts come and go frequently an IP address are needed for a limited period .e.g. on a wireless LAN in a cafe
  • Wher an OSP has 16,000 customers but no more than 4000 are ever online at the same time. Rather than needing 16,000 addresses
67
Q

State the valid IP address range for subnet 192.168.1.0/24 and why (3)

A
  1. 168.1.1 -> 192.168.1.254 inclusive
  2. 168.1.0 is not allowed
  3. 168.1.255 is used for broadcasting a message to all IP addresses on a subnet
68
Q

The network uses the CSMA/CA access method with Request to Send/Clear to Send (RTS/CTS)

A computer on the network has data so send to another computer. Explain how the CSMA/CA access metho with RTS/CTS will be used during the transmission [6 marks]

A
  • computer with data to send monitors/listens for (data signal)
  • if (data) signal present/another transmission in progress then continue to wait
  • when no (data) signal present computer sends a Request to Send / RTS A. if no valid points made about RTS/CTS in response then accept that when no data signal is present computer starts to transmit data, but with no marks awarded for RTS/CTS then response is limited to max Level 2
  • two computers could start transmitting simultaneously if they both detect there is no data signal
  • receiver/WAP responds (to RTS) with a Clear to Send / CTS signal A. router
  • RTS/CTS signal blocks any other transmissions from nodes in range
  • if/when CTS received then start to transmit A. by implication as BOD if the student states that the computer will begin to transmit after the receiver sends the CTS
  • if CTS not received continue to wait (until transmission ends)
  • receiver sends acknowledgement / ack after (all) data received
  • after transmitting (the transmitter) waits to receive acknowledgement packet (to confirm data received and not corrupted)
  • if no acknowledgement/ack received (within reasonable time period) then:
    • wait a time period
    • then listen again / retransmit.
  • the acknowledgement/ack also notifies other computers that they can transmit again
  • waiting periods are (often) random A. an example waiting period that is random
  • collisions cannot be detected by transmitter
69
Q

Describe the properties of a peer-to-peer network [5 marks]

A
  • In a peer to peer network all hosts have equal status
  • Each host decides what it shares and who it specifies has access
  • Accounts are managed per machine so each host needs to be individually conifgured
  • There is no centrally controlled storage so files have to be shared to be available elsewhere
  • Each peer acts as a client and a server. if they need information from another peer then they are a client. If they respond the requests then they are acting as a server.
70
Q

Describe the properties of a client-server network [5 marks]

A
  • In a client-server network, most computers are nominated as clients
  • There are other computers on the network that act as servers to provide services specifically to the clients on the network in a centralised manner
  • Clients request services from the servers, for example access to user files provided by a file server or access to email mailboxes from an email server
  • Management of the network can be controlled centrally via the servers as all clients have to authenticate onthe network against information held on the servers
  • Client-server networks are easier to manage centrally but take longer to set up than peer-to-peer networks
71
Q

List 2 examples of peer-to-peer networks [2 marks]

A

BitTorrent; file sharing

Bitcoin; distributed blockchain

CS A Level Paper 2 (8 decks)

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