chapter 2 - internet Flashcards
yo connect to the internet you need
device
telephone line / mobile phone network connection
router / mode
ISP
web browser
modem
modulator demodulator
converts digital to analogue (to be sent down a telephone wire) and vice versa (so a computer can process it)
router
enables data packets to be routed between different networks eg join LANs to form a WAN
ISP
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
PSTN
- 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
phone calls via internet
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
phone calls via satellites
- always give complete coverage as don’t suffer attenuation
- prone to interference (weather)
- easier to resolve faults than in cables
- uses LEO
www
- collection of web pages accessed by web browsers
- written in HTML
- URL specified the location of web pages
- use the infrastructure of the internet
bit streaming
– 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
buffers
– 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
on demand but streaming
- 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
real time bit streaming
- 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
IPv4
- 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
class ranges
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
CIDR
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)
IPv6
- 128 b - allows for complex addressing structures
- hex not decimal - ; not .
- 8 groups of 16b
- uses zero compesssion
zero compression
replace 0000:0000 by :: to shorten the address
however can only be used one
IPv6 +
- 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
public IP address
- identifies the location of a device
- available to anyone on the internet
- used by DNS, routers, directly controlled comps
private IP adress
- 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
sub netting
- divides a LAN into two or more smaller networks
+ reduces traffic
+ makes less complex networks - allows extensions
+ improved security
domain names
- 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
URLS
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
DNS server process
- 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
bit streaming +/-
+ 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
bit streaming + / -
+ 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
-
satellite types
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)
WNIC
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
