Computer networks, connections and protocols Flashcards
avantages netowrking
users can share files
users can share peripherals and connections to other netowrks e.g internet
users can access files from any comp on network
servers can control secuiry software updates and backup of data
communication w/ other ppl
two types of netowrk
LAN -Local area network
WAN - wide area network
LAN
covers small geogrpahic area
all hardware for lan owned by organisation useing it
LANs are wired w/ utp cable, fibre optic or wireless using wifi
WAN
large geographic area connecting lans together
infrastructure between lans leased from telecomunication companoes who own and manage it
wans connected by telephone lines, fire optic cables or satellite links
what are computers in lan connected to
a switch
what are computers in wan connected to
router
job of the router
personal home device for connecting to internet - multi function all in one device:
acts as router, switch and wireless access point
disavantage netowrking
increased secuiy risk to data
malware and viruses spead very easily between comps
if server fials comps connected to it may not work
computer may run more slowly if lots of data travelling over netowrk
how does bandwidth affect performance of netowrk
bandwidth is amount of data that can be sent and received successfuly in given time
not a measure of how fats data travels, but how much data can be sent on transmission media
mesaured in bits per sec (bit rate)
factors affecting erofrmace of netork
bandwidth
num of users
transmission media
latency
error rate
how does num of users affect netork performances
too mnay users slow down netowrk if insuffiencient bandwidth for data
how does transmission media affect performance of netowrk
wired connections have highhr bandwidth that wireless
fibre optic cables have higher bandwidth than copper cables
how does error rate affect netowrk performance
less relible connections increase num of erors occuring when data transfered
means data has to be resent until ariving correctly
signal quality of wirelss connections dpeendant on range of devics from wirelss access point and other envitonmental factors
signal quaity of copper cables determinded by grade of material used which reduces interference
length of cable also a factor
how does latency affect netowrk per4mance
latency is delay from transmitting data to receiving it
caused by bottlenecks in infrastructure of netowrk
eg by not using switches to apporpriately segment traffic on netowkr
hardware such as switches and transmission media may not operate on same spd
whats a server
special comp on netowrk not used as workstation
dedicated to serving files and managaing other services
both LAN and WAN can use servers
what is a netowrk using a server and what is a network not using a server
using server:
client server model
not using server:
peer to peer model
job of server
control access and security to one shared file store
manages access to internet
manages printing jobs
provides email services
runs a backup of data
makes reuqests to server for data and connections
avantages client server model
easier to manage security files
easier to take backups of all share ddata
easier to install software pdates to all computers
disavantages client server model
expensive to setup and maintain
requires it specilaists to maintain
server is single point of failure
users will lose access if server fails
what is a peer
comp on a network, is equal to other peers
how does peer-2-peer model work
peers serve own files to each other
each peer resposnsible for own security and backup
peers have own printers
can send print jobs to another peer to process but other peer must be switched on to communicate ith connected printer
avantge peer2pper model
very easy 2 maintain
specialist staff not reuqired
no dependency on single comp
cheaper to set up
no expensive hardware required
disavantage peer2p model
network less secure
users need to manage own backups
can be difficult to maintain well ordered file store
what does every comp need to connect to network
NIC - Netowrk interface card
every device on a network has a NIC
they are integrated into comp
use a protocol (a set of rules) to determine how connection should work
allw a device to conect to either wired or wireless netowrk
WAP
wireless access point
allowes wireless enabled devies to connect 2 network without cables
more convenient
less bandwidth than wired connection
secuirty more a concern with wirless connections
connection sometimes not as strong or relaiable as wired connections
a switch (hardware to connect to lan, in detail)
sends data between comps on a lan
segment network by forwardibg traffic to correct location
learn which devices are connected and understand how to forward traffic in intelligent way
uses NIC address on device to route traffic
a router (detailed)
sends data between networks
creates a wan from a number of lans
cannot connect to a wan withot router
uses IP address (internet protocol) to route traffic
transmission media - copper cables (utp)
wired connections assure max bandwidth security and reliability
with twisted pair cables wires are twisted around each other to reduce interference
there are normally a set of wires for transmission and 4 receiving
gradeof copper and insulating material aggects quality of overall cable and therefore the bandwidth
transmission media - fibre optic cables
uses light to transmit data
cover much longer distances and greater bandwidth than copper
backbone of internet uses fibre optic cables
def protocl
a set of rules that allow two devices to communicate
why are copper cables used
theyre cheap and fleible - easy to install
what is the internet
most widely known WAN
collection of interconnected networks
not the same as world wide web which is a service on internet
the internet detail
home network connected via wirelss router
home router connected to internet service provider
isp is connected to domain name server (dns) and other routers on backbone of internet
these routers further conencted to: their own lans, other routers, servers
web servers and clients
web servers carry out many functions - most common is:
hosting ebsites
dealing with client reuqests e.g http get requests for a page
the webpage stored as text is sent to browser which uses rules to render it correctly for user
example of web server functioning
url request sent by browser made from user
browser sneds domain name to DNS
DNS maps domian name to IP addres and returns it to browser
GET request for webpage is sent to web server using IP address
requested webpage returned to clients web browser
the cloud
servers can be used 2 store data and programs that can be accessed and used over the internet
this is the cloud
avantages of lcoud
access any time anywhere from any device
large storage capacity
autmoatic backup
ez online collaboration
how does a dns turn a url into an ip address
.com / google.com is example
url received by dns resolver server
server queries a dns root name server
root server responds w/ address of top level domain server for .com
resolver makes a reuqest to the .com TLD server
the TLD server responds w/ ip address of domains name server - google . com
recursive resolver sends query to domains name server
ip address google.com returned to resolver from name server
dns resolver then responds to web browser with ip addres of google.com
the two toplogies
star
mesh
def network topolgy
give arrangement of all elements needed for networking
star netowrk toplogy
most popular wired network type
has a central switch
all devices conenct to central switch
switch is intelligent and makes sure traffic only goes where intended
if a single cable breaks only that comp affected
swithc is still a serious point of failure
full mess network topology
every device connected t every other device
if a break in a connection you can still route traffic via another route
however lots more cabling and switch hardware required adding to cost for large networks
partial mesh netowrk tololgy
multiple routes exist between different devices
every device not connected to every single other device
is a compromise solution which lowers amount of hardware needed compared to full mesh network
what is the wired connection you should know in gcse spec
ethernet
wireless connection to know
wireless
bluetooth
what is chosen standard for implementing star network
ethernet.
with twisted pair cables, dublex communication is possible (sending and receiving data simultaneously)
CSMA/CD protocol is therefore not needed because frames dont collide
can you use ethernet for mesh toplogies
yes.
however additional protocols for route finding between switches will be needed.
ethernet
data is transmitted in frames which includes
preamble of bits used to synchronise transmission
start frame deliminator to signify start of data part of frame
source and destination of MAC address
actual data
error checking info (cyclic redundancy check - CRC)
wireless networks (wifi)
popular because avoids need to install cables
portable connection
bandwidth is lower than in wired connection
secuirty is more of a problem than with wired connextion
ideal as running lotsof cabling through home is undesirable
wireless networks (bluetoth)
ideal for connecting personal devices
very short range
ideal for connectig wireless keyboard to computer, or wireless headphones to a phone
wifi vs bluetooth
wifi range: 100m
wifi bandwidth: high
power consumption: high
bluetooth:
range: 10m
bandwidth: low
pwr consumption: low
encryption of wireless networks
wireless networks broadcast data so must be encrypted 2 b secure
done by scrambling data in cipher using ‘master key’ created from SSID of the netowrk and password
data is decrypted by receiver using same master key - key isnot transmitted
protocols used 4 wireless encryption
WEP, WPA, WPA2
a handshaking protocol used to ensure receiver has valid master key before transmission to device begins
do wired networks need encrption
though naturally more secure, it is still recommended to encrypt data on wired networks
what does every NIC have
a Media Access Control address (MAC address)
used to route frames on a LAN
what addressing method used for when LAN is connected to WAN
IP addressing - used to route frames on a WAN
frames on a WAN are called ‘packets’
Internet Protocol Address
a unique number used to identify a host computer or node which communicates over IP on the internet
twoversions:
IPv4, IPv6
IPv4 format
written as 4 numbers
seperated by periods
each number in the range 0-255
around 4bn addresses possible with IPv4
two parts to IPv4 address
network idenidier
host identifier
network identifier is 3 bytes (is at beginning)
host identifier is 1 byte at the end
Internet of Things
describes devices that connect and exchange data with other devices and systems over the Internet and other communication networks
IPv6 format
16 bytes in size
written as 8 groups
seperated by colons
each group made up of 4 hex values represntig 16 bits
around 340 trillion, triollion, trillion combs
standards in use
character sets: ascii, ex. ascii, unidcode
webpages and HTML
protocols to communicate on LANs and WANs
IEEE (standards for computer cables)
document image andsound standards (PDF, PNG, MP3)
what are standards
a set of specifications for: hardware and software
what do standards make possible
for manufacturers and producers to create products and services compatible ith each other
key protocols
TCP/IP
HTTP
HTTPS
FTP
POP
IMAP
SMTP
TCP/IP
transmission control protocol/internet protocol
used for communication over lans and wans.
TCP - provides error free transmission between 2 routers
IP - routes packets across a WAN
HTTP(S)
hypertext transfer protocol (secure)
used for webpage requests
HTTPS has encryption and authentication - used for websites dealing with senstive info e.g banking sites
FTP
file transfer protocl
used for file transfers, normally on a WAN
often ppl use ftp clients, software apps which sit on op of actual ftp protocl. you interact w/ program and it generates and sends appropriate FTP commands
POP, IMAP and SMTP
used for email
POP - Post office protocol
IMAP - Internet message access protocol
SMTP - simple mail transfer protocol
used in conjunction w/ mail servrs
mail servers act like online post office
SMTP - transfes outgoing emails from one server to another/ from email client to server
job of POP and IMAP
POP - retrieves emails from mail server. removes it from server and transfers it to your device
IMAP - same, but keeps emails on mail server to allow synchronicity beteen devices
complexity of networking (data transfer)
data transfer must be split into smaller packets and frames
packets must be sequenced on arrival
packets must be sent between routers on a wan
frames must be sent between devices on a LAN
packets and frames must be error checked on arrival, and requested to be resent if necessary
complexity of networking (transmission)
different cables used: fire obptic, twister pair, coaxial
wireless comms w/ frequencies and channels
simple and dublex transmissions
complexity of networking (others)
different applications for different tasks: web pages, email, file transfer
encryption, security and authentication of users and data
connexion to remote servers and maintinaing open connextions
peer2per and client server models
the concept of layering
to divide complex task of networking into smaller simpler tasks that work with eahc other
hardware and/or software for each layer has defined responsibility
each layer provides servcice tolayer above it
avantage layering
reducses compleinty of problem into manageable sub problms
devices can be manufactured to operate at a partuicualr layer
products from different vendors will work together
the layers
Application Layer
Transport Layer
Internet Layer
Link Layer
application layer
