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A-Level Computer Science > Fs Of Comms And Networking > Flashcards

Fs Of Comms And Networking Flashcards

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1
Q

What is data transmission?

A

The moving of data from one place to another.

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2
Q

What are the three physical forms in which numbers can be transmitted?

A

Electrical
Magnetic
Electromagnetic

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3
Q

What are the two types of transmission?

A

Serial and Parallel

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4
Q

What are the key factors of serial communication?

A

Sends 1 bit at a time.
Used for communications of over 1 meter.
High transmission rates achieved through USB and network cables.
Easier to regenerate signals.
Cheaper cabling costs.

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5
Q

What are the 3 types of serial transmission?

A

Simplex
Half-duplex
Duplex

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6
Q

What is the simplex method of serial transmission?

A

Allows communication in only one direction. Requires one channel.

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7
Q

What is the half-duplex method of serial transmission?

A

Allows communication in both directions but not at the same time.
Requires single channel that switches direction after transmission completion.

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8
Q

What is the duplex method of serial communication?

A

Allows communication in both directions at the same time. Requires two channels.
Full duplex.

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9
Q

Does serial transmission require synchronous timing?

A

No, serial transmission can be synchronous or asynchronous.

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10
Q

Does parallel transmission require synchronous timing?

A

Yes, general parallel transmission uses synchronous timing.

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11
Q

What is synchronous transmission?

A

Devices send and receive data at the same time.
A mutual system clock is used to time transmission signals meaning no further control information is needed.

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12
Q

What is asynchronous transmission?

A

Transmission is not synchronised between sender and receiver.
Arrival of data cannot be predicted by the receiver.
Additional bits added to data to tell receiver what to do with the data.

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13
Q

What are the additional bits in asynchronous transmission?

A

A start and a stop bit to show where data starts and ends.
A parity bit to check if data has been received correctly.

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14
Q

What is bit rate?

A

Number of bits transmitted per second.
Bit rate = baud rate x bit per baud

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15
Q

What is bandwidth?

A

The useful bit rate, the rate at which information is being transmitted.
Bandwidth discounts bits being “wasted” on handling communications.

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16
Q

What is the baud rate?

A

The number of signal changes per second.

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17
Q

Why is baud rate different to bit rate?

A

One signal change can represent more than one bit of data.

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18
Q

What is the relationship between bit and baud rate?

A

Bit rate is twice the baud rate.
2:1

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19
Q

What is latency?

A

The time between when something is first initiated to when it is first felt.

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20
Q

What are the 3 types of latency? Hint (PTP)

A

Propagation latency
Transmission latency
Processing latency

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21
Q

What is propagation latency?

A

The time taken for a logic gate in a circuit to transmit data.

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22
Q

What is transmission latency?

A

The time taken to pass through an Ethernet or fibre optic cable.

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23
Q

What is processing latency?

A

How many servers are passed through before the signal reaches its destination.

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24
Q

What are protocols?

A

Sets of rules everyone follows when transmitting data to ensure its sent and received correctly.

25
Q

Why is handshaking and protocols needed?

A

Transmission between different types of software and hardware.
Different ways of handling and transmitting data.

26
Q

What is handshaking?

A

The establishing of a connection with a foreign device and setting the rules of communication.

27
Q

What does handshaking allow for?

A

Connecting relatively diverse systems over a communication channel without human intervention.

28
Q

What is a LAN?

A

A set of computers connected over a small geographical area.

29
Q

What is a WAN?

A

A set of LANs connected over a large geographical area.

30
Q

What is a network topology?

A

Describes the way in which devices in a network a connected to one another.

31
Q

What are the 4 types of topology?

A

Bus
Ring
Star
Mesh

32
Q

What are the key points of bus topology?

A

Devices are all connected to a central cable/bus.
Data can travel in both directions.
The main bus standard is known as Ethernet.

33
Q

What are disadvantages to the bus topology?

A

Collisions and traffic when two or more devices try sending data at the same time.
Main cable is a single point of failure.
Less secure as all data travels down one cable.
Less reliable due to dependence on main cable.

34
Q

What are the advantages of the bus topology?

A

Relatively cheap and easy to set up as only one cable.
Easy to add new nodes by removing terminator and branching off main cable.
If a workstation goes down others will continue.

35
Q

What are the key points of the ring topology?

A

No central server or host of the network.
Token passing technique of sending and receiving data.

36
Q

What are the advantages of ring topology?

A

Each node has control over transmission of data and its own node. (No central server)
Very high transmission speeds possible.
Routing between nodes is simple as data usually travels in one direction.
Deterministic performance based on levels of traffic.

37
Q

What are the disadvantages of ring topology?

A

Cabling costs.
Difficult to extend ring.
Dependent on the reliability of the ring repeater.

38
Q

What are the key points of the star topology?

A

Central server; controls flow of data, stores network software, controls user access privileges.
Each node has a dedicated connection to the server.

39
Q

What are the advantages of the star topology?

A

Higher security as each node has a dedicated links to server.
Fast connection speed due to dedicated links.
Easy to add nodes (assuming there is a free port).
No data collisions due to dedicated links.

40
Q

What are the disadvantages to the star topology?

A

Central hub is a single point of failure.
Hardware and software is very expensive.
Installation can be difficult especially across multiple buildings.
Cabling costs are expensive to set up and install.

41
Q

What are the key points of the mesh topology?

A

No central server.
Nodes can communicate directly.
Alternate routes to communicate with each other.

42
Q

What are the advantages of the mesh topology?

A

Nodes can communicate directly with another.
Reduced traffic and collisions as there are multiple comm routes.
There is no single point of failure in the network.

43
Q

What are the disadvantages of the mesh topology?

A

High cabling costs.
Difficult to fully implement additional nodes.

44
Q

What does the physical topology of a network mean?

A

The physical layout of the devices in the network and how they are wired/connected to one another.

45
Q

What does the logical topology of a network mean?

A

How the network operates and how each device communicate with one another.

46
Q

What are some key points about a peer to peer network?

A

Resources stored on each device.
A device can act as both a client and server.
Administration of the network is more difficult.
Each computer has equal status.
Easier to set up.

47
Q

What are some key points about a client server network? (RRAC)

A

Resources are stored on the centralised server.
Works on request and response by the server.
Administration of the network is easier.
More complex setup than P to P.

48
Q

Why might the internet be slower at a public hotspot?

A

More collisions due to more people sending and receiving data.
More clients connecting to one access point.
Connection to the internet might have lower bandwidth.
Speed could be limited per device, throttling.

49
Q

What are some disadvantages to a client server model?

A

Failure due to too many requests at once.
Server location power outage means clients can’t access data.
Slow response time if clients are a long distance from server

50
Q

What are APIs used for?

A

Used to define ways that programs can work together.

51
Q

How do APIs work?

A

Standardised sub routines that are customisable provide an interface between one program and another.

52
Q

What is the Websocket protocol?

A

Provides a full-duplex communications channel over a single TCP channel between a user and a server.
Connection is terminated when client or server decides so.

53
Q

What is a web browser?

A

It allows user to request and retrieve web pages (and other resources) from a webserver

54
Q

Why is Websocket used instead of HTTP in a client server network?

A

Data is exchanged between client and server at a faster rate.

55
Q

What protocol is used for the transfer of data between client and server in a client-server network?

A

Websocket protocol

56
Q

What is a thin-client?

A

Computers with no hard drive.
Low powered CPU and not much memory.

57
Q

How might computer outside a network access a web browser located on a network?

A

Traffic arrives on HTTPS port.
This is forwarded by an external server to the IP address of the web browser.

58
Q

How does NAT work?

A

Network address translation:
- A pool of pubic IP addresses are held at an edge router.
- Packets heading over the internet with private IPs are swapped for public addresses.
- The packet is now routable over the internet.

59
Q

What is the difference between public and private IP addresses?

A

Private addresses can only communicate within their own network (non-routable).
Public addresses are globally unique.
Public addresses are allocated regionally (not be home user/company etc.)
Location cannot be identified by private address.

A-Level Computer Science (17 decks)

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