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Computer Science Cards Rewrite > Networks > Flashcards

Networks Flashcards

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
What is handshaking
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
26
What is the hardware required for a wireless network connection
A wireless router Wireless network card (or wireless adapter) for each device Although infraseingly wireless chips and antenna are built into devices
27
What are protocols
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
What is the TCP/IP protocol
Transmission control protocol/Internet protocol The protocol used for transferring information across the internet and around most modern local and wide area networks.
29
What is the UDP protocol
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
What is the HTTP protocol
Hyper-text transfer protocol Defines the standard for exchanging Web page information on the world-wide Web
31
What is the FTP protocol
File transfer protocol Defines the standard for transferring files across the Internet
32
What is the SMTP protocol
Simple mail transfer protocol Used for sending email, often in conjunction with POP (post office protocol)
33
What is the POP protocol
Downloads email from a mail server
34
What is the IMAP protocol
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
What is the DHCP protocol
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
What are the two types of data transmission
Serial transmission Parallel transmission
37
What is serial transmission
When data bits are sent in a sequence one after the other over a single wire (one communication channel)
38
What is parallel transmission
Several bits are sent at the same time over their own dedicated wires (multiple communication channels)
39
What are the advantages of parallel transmission
More data can be sent at the same time
40
What are the disadvantages of parallel
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
What are the three different ways data can be transmitted
Simplex Half duplex Full duplex
42
What will simplex data transmission do
One way data transmission only
43
What will half-duplex data transmission do
2 way data transmission but not at the same time
44
What will full duplex data transmission do
Data transmission 2 ways at the same time
45
What type of data transmission does wireless networks use
Half duplex
46
What type of data transmission does most modern wired networks use
Full duplex
47
What is multiplexing
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
What does switching do
Switching is required to ensure that lackers of data are only sent to the computers that require it This saves on bandwidth
49
What do hubs do
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
What is the difference between a router and a switch
They are very similar devices But switches link devices connected on a LAN And routers link different networks together
51
What is a collison
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
What is collision detection
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
Why don't modern wired networks require collision detection?
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
How does a router learn about the layout of the network?
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
What does a router do to understand where it needs to send data?
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
What does it mean by a data transfer rate?
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
How do you calculate data transfer rates
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
What speed does a typical wired Etherley network operate at
1Gbit/s
59
What is the internet
Global network of interconnected networks that communicate using a common standard of protocols
60
What data does Internet cabling carry
Email Streamed video and audio Online games
61
What protocol is Web pages based on
They are based on the HTML protocol
62
Whar are the advantages of HTML
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
What is an error checking method when data is transmitted through a network
Checksum
64
What is a token ring network
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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