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Computer Science Cards Rewrite > Networks > Flashcards

Networks Flashcards

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1
Q

What is a network

I

A

A group of 2 or more devices that can communicate

Connected by physical or wireless connections

If cable breaks then only one device is affected

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2
Q

What is a LAN

A

A network that connects devices that are within a small geographical area

E.g. an office, school etc.

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3
Q

What is a WAN

A

A network that connects geographically remote devices and LANs

E.g. Internet

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4
Q

What are the benefits of networking

A

Sharing devices e.g. printers and scanners

Accessing Internet

Accessing shared data and software (from a server)

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5
Q

What is a server

A

A server is similar to a pc but is usually left on at all times

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6
Q

What is a disadvantage of devices on networks

A

Without good security they could be vulnerable to unauthorised access (hacking), viruses etc.

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7
Q

What are topologies

A

Arrangements of devices for a network

Each device that is connected is called a node

All different topologies have their advantages and disadvantages

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8
Q

What would larger networks contain

A

Many servers carrying out different roles including file and software sharing.

They also authenticate users who wish to login and dealing with access rights (files that the user is allowed to access)

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9
Q

What would smaller peer-to-peer (e.g. home) networks contain

A

May not have a server

Will instead have a PC on the network that may have files that other devices access

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10
Q

Describe a STAR network

A

Each device has its own cable linking to a device called a switch or router

Creates a star shape

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11
Q

Advantages of a STAR network

A

Faster speeds are possible

No collision of data packets (wire is only used by 2 devices using full-duplex)

If cable breaks then only one device is affected

Easier to extend/add new stations

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12
Q

Disadvantages of STAR network

A

More cabling required so more expensive

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13
Q

Describe a BUS network

A

each device shares a cable

Therefore the more devices added the greater the liklihood of collision, therefore slower

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14
Q

Disadvantages of a BUS network

A

The more devices added, the greater the liklihood of collision, therefore slower

If the cable breaks then all devices lose connection

All data is broadcast so security can be compromised

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15
Q

Advantages of a BUS network

A

Less cabling required so cheaper to install

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16
Q

Describe a RING network

A

Packet of data is sent from device to device in one direction

Circular shaped

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17
Q

What are the advantages of a RING network

A

No collisions

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18
Q

What are the disadvantages of a RING network

A

If cable breaks then network fails

Difficult to extend / add new stations

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19
Q

What is a packet

A

Data to be transmitted across a modern network is separated into blocks of data called packets

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20
Q

What are the contents of the packet

A

The data to be sent (payload)

Specifying the type of packet (e.g. whether using TCP/IP or UDP protocol)

Source address (IP address of where being sent from)

Destination address (IP address of computer data being sent to)

Packet sequence number (if data is split into a number of packets, first packet would have sequence number 1, then 2 etc.

A checksum

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21
Q

What is a checksum

A

A calculation/formula that is applied to data in a packet

The computer receiving the data can apply the same formula and if result differs from the checksum then the data has been corrupted/damaged

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22
Q

What does a network consist of

A

It consists of links between nodes (network routers or switches)

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23
Q

What does a packet switched network do

A

Data to be sent is split into packets and passed from node to node until it reaches the destination

Multiple routes can be used (if one route is busy a packet can be sent a different way)

At the destination the packet sequence number is used to put the data packets back in order

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24
Q

Advantages of packet switched networks

A

Less likely to be affected by network failure: if one line fails there are usually other routes

Better security: data is less likely to be intercepted because packets are sent down multiple routes and are likely to be interleaved with other packets

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25
Q

What is handshaking

A

The exchange of signals between devices to establish their readiness to communicate

I.e.

One device says: “are you ready to receive data?”
Other device when ready says: “yes I am”
And then communication can begin

If the connection has not been established, the operating system must time out the transfer and display an error message

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26
Q

What is the hardware required for a wireless network connection

A

A wireless router

Wireless network card (or wireless adapter) for each device

Although infraseingly wireless chips and antenna are built into devices

27
Q

What are protocols

A

Standards or rules

Data formats specified to allow communication

Networking software and equipment need to follow protocols in order to be able to communicate

28
Q

What is the TCP/IP protocol

A

Transmission control protocol/Internet protocol

The protocol used for transferring information across the internet and around most modern local and wide area networks.

29
Q

What is the UDP protocol

A

User Datagram Protocol

An alternative to TCP/IP

much less sophisticated

Used to broadcast data across a network without error correction or handshaking. Used for very simple data transfer.

30
Q

What is the HTTP protocol

A

Hyper-text transfer protocol

Defines the standard for exchanging Web page information on the world-wide Web

31
Q

What is the FTP protocol

A

File transfer protocol

Defines the standard for transferring files across the Internet

32
Q

What is the SMTP protocol

A

Simple mail transfer protocol

Used for sending email, often in conjunction with POP (post office protocol)

33
Q

What is the POP protocol

A

Downloads email from a mail server

34
Q

What is the IMAP protocol

A

Internet message access protocol

A better alternative to POP

Allowed email to be accessed from a mail server but stays connected to a server over longer periods rather than downloading the email and disconnecting

35
Q

What is the DHCP protocol

A

Dynamic Host Configuration Protocol

A computer or another device attached to a network can request an IP address from a DHCP server on a network

Helps to ensure the address used is unique and simplifies the job of the network manager so they don’t have to manually allocate IP addresses to network devices

36
Q

What are the two types of data transmission

A

Serial transmission

Parallel transmission

37
Q

What is serial transmission

A

When data bits are sent in a sequence one after the other over a single wire (one communication channel)

38
Q

What is parallel transmission

A

Several bits are sent at the same time over their own dedicated wires (multiple communication channels)

39
Q

What are the advantages of parallel transmission

A

More data can be sent at the same time

40
Q

What are the disadvantages of parallel

A

Over longer distances the bits can get out of sequence

Parallel wiring is more expensive, therefore parallel transmission tends to only be used over short distances

41
Q

What are the three different ways data can be transmitted

A

Simplex
Half duplex
Full duplex

42
Q

What will simplex data transmission do

A

One way data transmission only

43
Q

What will half-duplex data transmission do

A

2 way data transmission but not at the same time

44
Q

What will full duplex data transmission do

A

Data transmission 2 ways at the same time

45
Q

What type of data transmission does wireless networks use

A

Half duplex

46
Q

What type of data transmission does most modern wired networks use

A

Full duplex

47
Q

What is multiplexing

A

Allows several signals from different sources to be combined for transmission over a shared medium

The signals are combined at the multiplexor (mux) and split at receiver using a demultiplexor (de-mux)

48
Q

What does switching do

A

Switching is required to ensure that lackers of data are only sent to the computers that require it

This saves on bandwidth

49
Q

What do hubs do

A

Network devices and segments are connected to a hub

The hub broadcasts the information received from one of their connections to all those attached to ensure wherever the receiving device is, it got the data.

50
Q

What is the difference between a router and a switch

A

They are very similar devices

But switches link devices connected on a LAN

And routers link different networks together

51
Q

What is a collison

A

If two or more computers find the line is free and start to send packets at the same time the packets will be corrupted

52
Q

What is collision detection

A

The computer sending the packets will detect a collision has taken place and stop sending

Each computer then waits a small random amount of time before checking the line is free again and attempting to send

Meaning that one of them gets to send the packet before the other, avoiding a collision

53
Q

Why don’t modern wired networks require collision detection?

A

Lines only connect between 2 end points (e.g. network routers and computers) and full-duplex lines allow packets to be sent in both directions without collision

54
Q

How does a router learn about the layout of the network?

A

Initially configured to only know networks attached to it directly

Routing protocol shares this information among neighbors, then throughout the network

This way, routers gain knowledge of the topology of the network

55
Q

What does a router do to understand where it needs to send data?

A

It builds a routing map/graph in its memory so that it understands to which connected router it needs to send data

This allows a router to calculate the shortest path to a destination using the ‘hop count’

56
Q

What does it mean by a data transfer rate?

A

The speed thst fats can be transmitted around a network

Usually measured using Bits per second (bit/s) or sometimes Bytes per second (B/sec)

57
Q

How do you calculate data transfer rates

A

First make sure thst the rate is converted to ‘per second’

So divide 3 GB by 2 * 60 (120 seconds) = 0.025 GB per second (0 025 GB/s)

Then to convert to bits per second multiply by 8

58
Q

What speed does a typical wired Etherley network operate at

A

1Gbit/s

59
Q

What is the internet

A

Global network of interconnected networks that communicate using a common standard of protocols

60
Q

What data does Internet cabling carry

A

Email

Streamed video and audio

Online games

61
Q

What protocol is Web pages based on

A

They are based on the HTML protocol

62
Q

Whar are the advantages of HTML

A

Entirely text based - meaning it can be loaded into just about any computer in the world.

Takes up very little space and is therefore quick to download

63
Q

What is an error checking method when data is transmitted through a network

A

Checksum

64
Q

What is a token ring network

A

Carry a single circulating token to which devices will attach a message for transmission

Only one message can be transmitted at a time, meaning no collisions

Computer Science Cards Rewrite (18 decks)

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