Networks Flashcards
LAN
Local Area Network
- covers a small area on a single site e.g. Businesses, schools, uni’s + homes
- all hardware personally owned + wireless/wired
WAN
Wide Area Network: e.g. Internet
- connects LANS in diff locations e.g. a business w offices in 3 diff countries
- infrastructure is HIRED as expensive, connected by tel lines, sat links/radio links
PAN
Personal Network
- very short range, centred around 1 user usually e.g. phones, watches, headphones
- can use wireless tech - BLUETOOTH
NIC
Network Interface Card - piece of hardware that allows a device to connect to networks
Switches
Connect devices on LAN
Routers
Transmit data between different networks, e.g. connect to the internet
Fibre optic cable
- data transmitted as light
- high performance + expensive
- don’t suffer interference, can transmit very large distances at high bandwidth w out loss of signal quality
Ethernet Cable (Cat 5e/Cat 6)
- pairs of twisted copper wires to reduce internal interference
- cheaper, decent bandwidth
- used in homes + offices to connect on LAN
Coaxial Cables
- Single copper wire surrounded by plastic layer for insulation
- metallic mesh to provide shielding from outside interference
- very cheap but low bandwidth
Networking computers advantages
- sharing files easier: can access same files, work on same time + copy between machines
- can share same hardware e.g. printers
- Install + update software on all computers at once
- communicate cheaply + easily (email)
- User accounts can be stored centrally so can be logged on any device on the network
Networking computers disads
- expensive as lots of extra hardware needed
- vulnerable to hacking, malware can spread easily between
- dependent on servers - if they go down = disruptive
- large networks are difficult to manage
- may need to employ specialist to maintain
WLAN’s
Local wireless networks (e.g. WiFi is a specific family of WLAN protocols)
How to set up a wireless network
with a WAP: wireless access point - a switch that allows devices to connect wirelessly
Benefits of wireless networks
- Convenient as automatic connection to network + good portability
- cheaper + better for environment due to lack of wires
- easy to add more users as no extra set up + wires
Drawbacks of wireless networks
- less secure as access points usually access points are visible to ALL devices so hackers can gain access
- distance from WAP, interference from other wireless networks + obstructions can reduce signal strength = limit on how far a wireless network can reach
- generally lower bandwidth + less reliable than wired networks
Star topology
- all devices connected to a central switch or server
- allows many devices to access the server simultaneously
- may be wired/wireless
star topology pros
- if a device/cable fails rest of the network is unaffected
- simple to add more devices
- better performance as data goes straight to central device so devices can TRANSMIT data at the same time
- fewer data collisions
star topology cons
- for wired, cable needed for each device = expensive
- switch is expensive + if it fails then whole network is affected
- max num of connections is determined by the switch so you may need to buy a new one for more connections
Bus topology
- single cable ‘backbone’ cable = bus, to connect all cables
- 2 terminators placed at the ends of the bus to stop data reflecting back along the bus otherwise reflected signals cause interference = network unusable
Bus topology pros
- network unaffected if a device fails
- aren’t dependent on a central switch
- relatively cheap as total length of wiring needed is much less + hardware (terminators + bus cable) is cheaper to buy AND maintain
Bus topology cons
- data collisions more common = slower network as data has to re sent
- more devices = more data collisions likely = UNSUITABLE FOR LARGE NETWORKS
- to avoid data collisions, devices must wait for the bus to available = slow network
- iF bus is broken = splits network and as these splits don’t have terminators = a lot of reflected signals = shut down entire network
protocol
set of rules for how devices communicate + how data is transmitted across a network
- covers how communication show start + end, how data should be organised + what to do is data goes missing
How is data sent between networks?
- split into equal sized packets
- packets all contain extra info like destination + source address + a CHECKSUM = to find errors
Advantages of using layers
- breaks network communication into manageable pieces = helps developers concentrate in 1 area of the network
- self-contained layers, so 1 layer can be changed independently
- Set of rules for each hardware = compatible + universal hardware + software so other brands can work w each other in the same way
Layer 4
Application layer
- provides networking services to applications
HTTP, FTP, SMTP
Layer 3
Transport layer
- sets up communication between 2 devices ; splits data into packets + checks that they are sent correctly
TCP, UDP
Layer 2
Internet layer (used by routers)
Adds IP addresses to data packets + directs them between devices + handles traffic
IP
Layer 1
Link Layer
Passes data over the physical network: responsible for how data is sent as electrical signals over cables, wireless + other hardware
- interprets signals using device drivers
WIFI , ETHERNET
