networks Flashcards
what is a network
2 + computers connected together that can transmit data
what are the 2 types of networks
local area networks
wide area networks
what is a protocol
a set of rules defining hoow 2 computers communicate
they are standard
what are the 6 types of protocols
HTTP
TCP / IP
POP3 IMAP
FTP
what is HTTP (HyperText Transfer Protocol)
used for web page rendering
what is TCP (Transmission Control Protocol) and IP (Internet Protocol)
networking protocol used in the routing of packets through a network
what is POP3 (Post Office Protocol) and IMAP (Internet Message Access Protocol)
mailing protocols used for email access
what is FTP (File Transmission Protocol)
used for the transmission of files over networks
what is the order of the TCP/IP stack
application layer
transport layer
network layer
link layer
what does the application layer do
its based at the top of the stack
it specifies what protocol needs to be used to relate to the application that is being sent
what does the transport layer do
uses TCP to establish end - end connection between source and recipients computer
split data into packets label w packet number, how many packets the og data was split into and the port number being used for communication
if any packet gets lost the transport layer requests retransmissions
what does the network layer do
adds the source and destination IP addresses
routers operate on the network layer and uses IP addresses to forward packets
sockets are used to specify which device the packets are sent to and the application being used on that device
what does the link layer do
connection betweek the network devices
adds mac adress identifying the network interface cards of the source and destination computers for devices on same network
destination MAC address is the same of the recipients computer otherwise it would be of the router
what happens when the destination has been reached of the tcp
mac address is removed by link layer
ip addresses are removed by network layer
transport layers remove port numbers and reassemble the packets
application layer presents data into the form it was requested in
what is the DNS
the domain name system is used to name and organise internet resources
what are packets
segments of data
what information does the header packet contain
sender and recipients IP addresses
protocol being used
order of the packets
time toe live / hop limit (tells the packet when to expire)
what information does the payload packet contain
raw data to be transmitted
what information does the trailer packet contain
checksum or cyclic redundancy check
a code that detecs whether any errors occured during transmission
what is packet switching
communiccation method where data is sent in the most efficient route which can vary
packet switching advantages
multiple methods to ensure data arrives intact
multiple routess can be used so if 1 path breaks
packets can be transferred over very large networks to allow global communication
packet switching disadvantages
time is spent deconstructing and reconstructing data packets
must wait for all packets to arrive before data is recieved
what is circuit switching
method of communication direct link is created betweek 2 devices
maintained for entire conversation
requires devices to transfer and recieve data at the same time
circuit switching advantages
data arrives in logical order - quicker reconstruction
enables 2 users to hold a call without delay in speech
circuit switching disadvantages
bandwith is wasted when no data is being sent
electrical interferences may occur which can corrupt or destory data
what is a firewall
device designed to prevent unauthorised access to a network
how does a firewall work
consits of 2 network interface cards between the user and the internet
passes packets between the two NICS and compares then against firewall software rules (packet filters)
how does packet filtering work
limits network access in accordance to administrators rules
examines source IP, destination IP and protocols being used and ports being requested
what happens when firewall denies access
packet is either dropped or rejected
rejected packet sends an alert to sender
dropped doesnt
what does a proxy server do
collects and sends data on behalf of the user
benefits of using proxies
users privacy is protected
can cache frequently making data faster to load
reduce overwall web traffic
used by administrators to prevent access to sensitive / irrelevant info
what is encryption
way of keeping data secure when transmitting it over the internet
makes data unreadable if intercepted
can by decrypted and encrypted by using keys
network interface cards
card required to connect a device to a network
built into computer
assigns a unique MAC address to each device
switch
device used to direct flow of data across a network
wireless access point
device that allows device to connect to a network
commonly combined with a router to enable internet access
routers
connect 2+ networks together
allows privste, home networks to connect to the internet
gateway
used when protocols are not the same between networks
translates protocol so networks can communicate with each other
removes header from packets before adding data to packets using new protocol
what is a client - server network
terminals (clients) connected to server (powerful, central computer)
holds all important info and resources has greater processing power
clients can request usage
advantages of client - server
more secure datas stored in 1 location
data and resources can be shared between client
central bakup are carried out no need for individual
disadvantages of client - server
expensive
server fails performance fails
trained staff required
what is peer - peer network
computers are connected to eachother so they can share files
both can provide and request resources
used in piracy cause impossible to trace origin
advantages of peer - peer
cheaper to set up
easy to maintain
users can share resources
not dependant on central server
specialist staff are not required
disadvantages of peer - peer
impossible to trace origin
poor security
difficult to locate resources
backups must be performed seperately
