local area networks Flashcards
what is a network
- 2 or more devices connected by some type of communications channels.
-exists to share hardware and software resources between devices
node
any device connected to a network
LAN
local area network
networking capabilities of computers near each other that share resources and connect to other LANS + the internet
what are the basic requirements of a network
hardware as source/sender
connection
hardware as destination/receiver
eg. of nodes
PCs, servers, printers
server
central network computer that provides various resources
eg. connecting devices
switches,bridges,routers
bounded connection media
signals are confined to the medium + dont leave it
cables carry signals between computers and peripheral devices
twisted pair cable
2 insulated strands of copper wire twisted around each other - prevents electrical interference
STP
shielded twisted pair
more expensive/bulkier - twisted pairs enclosed in protective foil
less affected by interference than UTP
UTP
unshielded twisted pair
most widely used network cable
easy to install,expand + trouble shoot
UTP variations
UTP Cat 1- traditional telephones
UTP Cat 5e- most popular
disadvantages of twisted pair
attenuation, cross talk, eavesdropping, electro magnetic interference
length cant exceed 100m
unbounded connection media
source +destination devices connected w/o physical connection
eg infrared,bluetooth,microwaves
advantages of twisted pair
low cost
easy to install
fibre optic cable
carry digital data pulses in the form of light
cable- extremely thin cylinder of glass surrounded by cladding
includes 2 strands in separate sheaths - 1 transmits and 1 receives
advantages of fibre optic cable
high speeds of data transmission
secure transmission over long distances
disadvantages of fibre optic cables
more expensive than UTP
expertise needed to install + connect
wireless technologies
allow for transfer of data over short + long distances
used mostly for long rage communications (radio + microwave communication, light, infrared)
bluetooth
wireless technology used to send data over short distances
uses short wavelength radio transmissions from 2400 - 2480MHz
inexpensive, automatic
versions of bluetooth
1.0 max transfer speed of 1Mbps
2.0 backwards compatible, max 3Mbps
3.0 24 Mbps
4.0 + 5.0 Bluetooth Low Energy (BLE) applications with lower power consumption
advantages of bluetooth
can handle data + voice transmissions simultaneously
NFC
near field communication
wireless connection between 2 devices in close proximity
2 way communication (used in contactless payment systems)
radio waves
electromagnetic wave used in communication technologies + data transfer
used in radio,TV and mobile phones
long wavelengths in EM spectrum(1mm to 100km +)
EM spectrum
electromagnetic spectrum
7 regions in order of decreasing wavelength + increasing energy + wavelengths (higher frequency =shorter distance)
broadcast
communication channel shared by all devices in a network
signal heard by multiple parties
eg radio stations
point to point communication
directly connects 2 nodes of a network
eg telephone call
topology
physical set up of a network and how nodes are connected
STAR topology
cable connected to NIC has other end in a port on a switch which boosts signals coming through it
UTP cable most commonly used for this
advantages of STAR topology
easy to set up + maintain as cables all connect to central device
a problem w one node/cable, adding or removing nodes will not disrupt network
most commonly used topology
easy to extend if free ports on switch
disadvantages of STAR topology
large amount of cabling required
switch adds to cost
if switch fails- whole network fails
BUS topology
all nodes connect to 1 backbone which has a terminator at the end to stop signals bouncing out
used in older LANS (no longer as popular)
advantages of BUS topology
requires less cabling than STAR topology
no switch needed- further reduced costs
easy to extend network
disadvantages of BUS topology
faults are difficult to trace (common cable)
one point of failure- whole network won’t work
can result in congestion (common cable)
ring topology
all nodes are connected in a closed loop
data signals travel around loop in one direction + pass through each computer
each computer boosts signal and sends it to next
Now- Fibre Distributed Data Interface (FDDI) - light transmits signals over 2 fibre optic cable rings
single ring topology
failure of 1 comp caused whole network to fail
double ring topology
1 ring fails, signals can still be sent on other
advantages of ring topology
orderly
little singal degradation
easy to create larger ring
disadvantages of ring topology
changes of devices can disrupt network
slower than STAR topology
one failure- failure of whole system
hybrid topology
aka tree
combo of 2 or more different network topologies
advantages of hybrid toplogies
reliable (error detection and troubleshooting easy)
flexible
scalable
effective
disadvantages of hybrid topology
complex design
costly
ethernet
connects nodes in LAN so they can share resources and communicate using a common protocol
protocol indicates how nodes transmit, receive,process and recognise data
fast data speed transfer
delivers consistent speed
data doesn’t need to be encrypted
lower latency
cable installation infrastructure required
IP Address
internet protocol address
numerical label assigned to each device so it can communicate on the internet
static or dynamic
IP Address versions
v4 - 32 binary bits create unique address (4 decimal numbers separated by .)
v6- 128 binary bits create unique address (8 groups of hexadecimal numbers separated by : )
MAC address
media access control address
hardware (static) identification number that uniquely identifies each device on a network
48 bit serial number- 6 2-digit hexadecimal numbers separated by :
protocols
define how data is transmitted between computing devices over network
determines how errors will be handled
stipulates if data will be compressed
determines how sending + receiving devices will communicate
ARP
address resolution protocol
allows for MAC address to link to an IP address using ARP table which is stored in RAM of NIC
also stores MAC address of other devices on network
DHCP
dynamic host configuration protocol
assigns each client a unique address
keeps record of used, available and assigned addresses
DNS
domain name servers
maintain directory of domain names and translates them to IP addresses
stored at Central Registry
TCP/IP protocol
communication protocol for internet
defines rules that computers must follow in order to communicate w each other
defines how data formatted, addressed,transmitted, routed and received
TCP
transmission control protocol
connection oriented protocol therefore no corruption while transferring messages
messages delivered in correct order
eg www, email, file transfer
UDP
user datagram protocol
type of transportation protocol
connection less protocol- may be corruption whilst transferring messages
no guarantee what order messages will arive
eg streaming media applications, online multiplayer games
fast
NIC
network interface card
physical connection between computer and network cable
repeater
connects network segments over long distances
strengthens all signals (has no intelligence)
bridge
connects similar networks (same protocol)
makes intelligent decisions
switch
connects nodes in STAR topology
is sent messages in form of frames
boosts incoming signals + sends to messages to intended nodes
reduces network traffic (only goes to node w/ matching MAC address)
router
determines best/shortest route to connect to internet boosts signals
determines best routes for data data packets to travel
routing table stores info about all networks router is connected to
connect diff networks using the same protocol
packet
allows for info to be exchanged between diff LANS
allows router to send + receive data across internet using IP addresses
Header (instructions abt data)
payload (actual data)
trailer/footer (error or acknowledgement- Cyclic Redundancy Check)
Frame
created by datalink layer
encapsulates packet from network layer as frame’s payload
802.3 - telephone, 802.11- wireless
FCS
frame check sequence
used to detect if errors occurred in data transmission
VLAN
A logical subdivision of a network’s devices to isolate traffic or for security reasons based on function and security requirements
allows multiple networks to share the same physical infrastructure without interfering
VLAN TAGS
allow LAN switches to distinguish between logical + physical groups of LAN ports
4 byte field
WLAN
wireless lan
consists of wireless components communicating w network that use’s cabling
provides portability
provides backup to an existing network
extends networks beyond limits of cable connectivity
useful for mobile devices and isolated areas
consists of microcell- wireless transceiver in fixed position that broadcasts signal w/in an area
WAP
wireless access point
provides access to wired ethernet network
access point plugs into switch + sends out wireless signals
hotspots
site that offers internet access over WLAN
uses router/wireless access point connected to an ISP
wireless bridge
provides data path between 2 network segments
wifi router
allows multiple computers to join same network
provides access to internet
can function as switch , internet router or access point
WMN
wireless mesh network
many wireless nodes w/ access points spread out among wireless mesh nodes
share network
each node acts as a router
only requires one node to be physically connected to switch
more nodes- further connection
advantages of WMN
reduced cable cost
robust can “self heal”
easy to extend
disadvantages of WMN
increased workload for each node
initial set up is complicated
