chapter 2 - internet

Question 1

yo connect to the internet you need

Answer 1

device
telephone line / mobile phone network connection
router / mode
ISP
web browser

Question 2

modem

Answer 2

modulator demodulator
converts digital to analogue (to be sent down a telephone wire) and vice versa (so a computer can process it)

Question 3

router

Answer 3

enables data packets to be routed between different networks eg join LANs to form a WAN

Question 4

ISP

Answer 4

company which allows the user to connect to the internet
- charge a monthly fee for this service
- provides the user with an IP address
- company has telecommunication lines to allow connection to the internet

Question 5

PSTN

Answer 5

• cables connect devices between towns
• now are fibre optic (faster)
• always open so can always be used
• remain active during a power cite
• use circuit switching - connection is maintained for whole call

Question 6

phone calls via internet

Answer 6

VoIP - converts sound to digital packets
- uses internet not telephone lines
- compresses data so it’s easier to transmit
- more efficient as the link only exists while data is being transmitted - peopel are talking
- need broadband

Question 7

phone calls via satellites

Answer 7

• always give complete coverage as don’t suffer attenuation
• prone to interference (weather)
• easier to resolve faults than in cables
• uses LEO

Question 8

www

Answer 8

• collection of web pages accessed by web browsers
• written in HTML
• URL specified the location of web pages
• use the infrastructure of the internet

Question 9

bit streaming

Answer 9

– contiguous sequence of digital bits sent over a network (one after another)
– needs good broadband
- data needs to be compressed
– needs buffering to ensure smooth playback

Question 10

buffers

Answer 10

– Holds some of the file in storage before it gets played, (so you don’t need to stream as you play and prevents gaps in playback)
– must have faster transmission to the buffer, than from the buffer to the media player, so it’s not behind.
– big buffer = higher a bit rate

Question 11

on demand but streaming

Answer 11

• files are converted to streaming format and uploaded to a server.
  – link is on a server to be downloaded by the user.
  – stream can be broadcasted when required.
  – can pause/rewind

Question 12

real time bit streaming

Answer 12

• captured by a camera and sent to computer a converted to a streaming file.
  – uploaded to a server
  – server sends video to the device.
  – can’t pause / rewind - live

Question 13

IPv4

Answer 13

• 32 bits - 2^32 addresses
• 4 groups 8b
• dotted decimal
• networks are split into classes (subnetting) so you can reuse the host id range for every different class and have more IPs

Question 14

class ranges

Answer 14

A - 0 to127 - 8b /24 - very large
B - 128 to 191 - 16b/ 16 - medium
C - 192 to 223 - 24b / 8 - small
D - 224 to 239 - multi cast
E –240 to 255 - experimental

Question 15

CIDR

Answer 15

classless inter domain routing
- IPv4 provides insufficient address range, but CDR fixes this
- Uses a suffix meaning 18 bits used for net ID and 14 for host ID, - increases the flexibility of bits used to represent the net ID and host ID
- means you don’t have to have 8 and 24 bits in class A as long as you have the same total (32)

Question 16

IPv6

Answer 16

• 128 b - allows for complex addressing structures
• hex not decimal - ; not .
• 8 groups of 16b
• uses zero compesssion

Question 17

zero compression

Answer 17

replace 0000:0000 by :: to shorten the address
however can only be used one

Question 18

IPv6 +

Answer 18

• no need for NATs (network address translation - converts public to private IP) - more address so don’t need to reuse addresses
• removes risk of private IP address collisions
• built in authentication
• allows for more efficient routing

Question 19

public IP address

Answer 19

• identifies the location of a device
• available to anyone on the internet
• used by DNS, routers, directly controlled comps

Question 20

private IP adress

Answer 20

• internal use behind a router or NAT
• allow for a separate set of addresses within a network - don’t take space of public IP
• private IP addresses can not be reached by internet users

Question 21

sub netting

Answer 21

• divides a LAN into two or more smaller networks
  + reduces traffic
  + makes less complex networks - allows extensions
  + improved security

Question 22

domain names

Answer 22

• direct use of an IP address is not sensible
• DNS allows use of URL instead
• provides a domain name when IP is supplied
• eliminates the need for users to memorise IP

Question 23

URLS

Answer 23

web browsers use uniform resource locators to access websites
protocol://web address/path/file name
web address is made of domain host, name, type and country code

Question 24

DNS server process

Answer 24

• open web browser type in URL - ask DNS for address
• can’t find URL in database so sends request to DNS2
• finds URL and can map it back to an IP which it sends to DNS1
• puts IP address in its database - sends back to user
• sets up communication with the website server and browser interprets HTML na displays to user

Question 25

bit streaming +/-

Answer 25

+ no need to wait for file to download + no need to store on device + on demand play back + no specialist software required to playback - video stops if slow - stops if inadequate buffering - no internet means no access to data - viruses

Question 26

bit streaming + / -

Answer 26

+ no need to wait for whole video to download + no need to store large files + allows files to be played on demand + no need for specialist hardware - can’t stream if broadband is lost - video will pause if insufficient buffer capacity - security risks downloading malware -

Question 27

satellite types

Answer 27

GEO - orbits over the equator and is geostationary - long distance telephone and computer network (35800km) MEO - GPS (5000-12000km) LEO - mobile ohoen network (500-1500km)

Question 28

WNIC

Answer 28

provides interface to wireless network as an antenna - recieved analogue converts to digital - checks incoming transmissions for MAC and ignore the ones without the correct MAC - takes digital and converts to analogue - sends as radio waves via antenna