computer networks Flashcards
kernel
tells you where to find operating system
network
2 or more devices(nodes) connected by some type of communications channel
node
any device connected to the network
-user device
-switch -connect nodes to each other
-router-connect to internet
-service device - printer or server
types of communication channel
bounded or unbounded(wireless)
server
computer designed to act as central network computer that provides various resources (network security, hardware access, disk space, printer access.
has software which manages logins and user access to computers on network
area eg school.office buildings network name (limited )
LAN , local area network
network name city
metropolitan area network (MAN)
network name large company
wide area network (WAN)
worldwide WAN
global area netwok
network individual eg hot spot
personal area network pan
network name home
home are network
router
small electronic device
joins networks together through wired or wireless connections
types of networks
LAN,MAN,WAN,GAN,PAN,HAN
cloud computing
makes use of computing services like storage,databases,software,networking and over the internet “the cloud”
only pay for services you use
cloud competing
making use of competing services like storage, databases, software, networking + more over internet “the cloud”
types of nodes
devices that users use (laptop,desktop,mobile device)
devices to connect nodes to each other (switch)
device to connect to internet (router)
device to provide service (server or printer)
switch
connect nodes in network using communication media such as cables.
node connected to ports in switch
3 parts of communication media
- hardware - source or sender
- hardware- destination or receiver
- connection between source + destination
what is the connection between source and destination
communication channel or transmission medium
bandwidth
maximum amount of data that it can transfer per unit time (usually bits/sec)
what is the rate that data is transferred over communication channel measured in
thousands of bits per second (kilobits per second Kbps)
millions of bits per second (megabits per second Mbps)
billions of bits per second (gigabits per second Kbps)
what is bounded media
consist of physical cabling
commonly used for wired LANs
UTP
unshielded twisted pair
most common bounded media cabling in small LANs
several pairs of twisted pairs in an outer protective plastic cover
has RJ45 connector on each end (one end to port on device, one end on switch)
why are wires twisted
eliminate interference from signals on other wires and from other electrical devices
attenuation
signal loses strength over distance
electro-magnetic interference
signals from other sources (eg machinery) corrupt signals travelling in copper cables near by
eavesdropping
signals travelling along copper cables intercepted by outsiders
crosstalk
signals in adjacent wires interfere with each other
advantages of utp
inexpensive and easy to install
supports fast transmission rates
widely used and tested
can be used in many diff networks
disadvantages of UTP
susceptible to interference
crosstalk - signals
attenuation -distance limitations (repeater used to join 2 long lengths of cables- amplify signal on cable)
STP
shielded twisted pair
more expensive, bulkier
twisted pairs open enclosed in protective foil
less affected than UTP by interference
fibre optic cable
central glass/plastic core surrounded by several layers of protective materials.
cladding used to surround core + reflect light back into core
transmits light pulses rather than electronic signals—eliminating interference
connector of fibre optic cable
SC connector
advantages of fibre optic cable
supports much faster transmission rates - light travels faster than electronic signals
more secure than UTP- light signals cannot easily be tapped
can transmit longer distances than UTP —light signals dont weaken like electronic signals in copper wires
light signals not susceptible to interference unlike electronic signals
light signals immune to lightning + electrical surges
how is fibre optic cabling used as a backbone
used to join LAN segments in diff buildings together - not affected by lightning
unbounded media
no cables, carry signals
use air to transmit radio signals such as bluetooth, infrared beams, microwaves, satellites, laser light signals
how do wireless signals remain separate
each type of signal uses diff frequency ( Hertz or cycles/sec)
microwave transmissions
long distance
affected by weather conditions
main types of microwave transmissions
terrestrial
satellite
terrestrial microwaves
land based
use line of sight method for transmitting data between 2 anntea
can transmit over 50 km (no obstacle)
problem w/ copper cables
attenuation
electro magnetic interference
cross talk
eavesdropping
disadvantages of fibre optic cables
expensive to purchase and install
strict complex installation criteria
satellite transmissions
transponders receives signals
converts to different frequency
boosts signal
sends to stations on ground
types of satellites
geo stationary- fixed position above earth’s surface and rotate at same speed as earth
good for TV broadcasting
low orbit-nearer to earths surface,rotate every few hours
better for interactive communication
radio wave transmissions
short distance
can travel through walls and buildings
can travel long or short depending on frequency
radio,TV.phones - WiFi,bluetooth
router in the home
connects all nodes in network to other networks outside the home
how to get fibre into your home
fibre optic backbone cable connected from local distribution node to your street
fibre connected from distribution box into your home
Optical Network Terminal (ONT) connects fibre to router
firewall
system designed to prevent unauthorised access to/from private network
types of servers
file server-store files to be accessed by network users
print server- printers to be shared by computers on network
web server+accepts requests for web pages and sends to client machines
email server-stores mail and distributes to users
proxy server- all web content passes through- disallows access to unauthorised users
local vs cloud servers
local-servers located in organisation -company has physical control over set up , no need for internet to access BUT have to pay for setting up and managing
cloud- no expensive of continual upgrading. storage can be added,pay for what you use,backed up often BUT no access if no internet connection
NAC
network area control
can only access network if user login complies w/protocols
must authenticate by verifying login information
advantages of computer networks
communication
file sharing
printer and resource sharing
centralisation
data transfer
productivity
disadvantages of computer networks
security issues
spread of computer viruses
cost
dependancy on central servers
data transfer rate
amount of data that can be transferred between 2 points on a network in a given time
problems w copper wires
attenuation
electro-magnetic interference
eavesdropping
cross talk
