topic 3 - networks

network

more than one computer system connected together for communication and sharing of resources

LAN

computers are situated geographically close together, infrastructure is usually owned and managed by network owner

WAN

computers are situated geographically distant to each other, infrastructure usually owned by service provider

client server

network model where client sends request and server sends response

advantages of client server

easy to scale, easy to back up data and update software, hardware/software can be shared

disadvantages of client server

need to pay for IT technician, if server fails the whole network is down

p2p network

all computers are equal. a computer can send requests and responses

advantage of p2p

optimal for sharing files, not dependent on server

disadvantage of p2p

backups have to be performed individually on each computer, adding more devices slows the performance

what do data packets do

split large files into small pieces. send them to destination where they are reassembled

data packet order

header, payload, trailer

what does the header have

source and destination address, protocol , packet number

payload

the data

trailer

checksum - calculation to check for data errors or corruption in transmission

bandwidth

maximum amount of data that can be sent across a network at once

cloud storage

series of servers on the internet that you can upload files to via the internet

internet

global network of interconnected networks

advantages of star topology

easy to add new systems, security, speed

disadvantages of star topology

dependent on switch , extra hardware - expensive

full mesh advantages

multiple routes for data transfer, can withstand large traffic

full mesh disadvantages

redundant cabling, hard to set up, expensive

w.a.p

provides a link between wireless and wired networks

router

transfers data packets between networks

switch

connects devices on a LAN. sends data to exact computer using MAC address

NIC

hardware required to connect to a network. has a MAC address used to send data across a LAN

3 types of transmission media

ethernet cable , fibre optic, coaxial

DNS server process

type in domain name, query sent to local DNS server for corresponding IP address, finds the IP and sends it to the web browser, browser receives IP and displays website

what happens if the DNS server can’t find the IP

asks a larger DNS server

protocol

set of rules that allow devices to communicate

Transmission Control Protocol

allows data packets to be sent and received between computers. splits data into packets and reassembles them at destination

Internet Protocol

routes and addresses packets, gives devices an IP address

Hypertext transfer protocol

transfers web pages over the internet so users can view it on a web browser

HTTPs

encrypted and more secure versions of HTTP

File Transfer Protocol

transfers files across a network

Simple Mail transfer protocol

send email to a mail server and between mail servers

what do POP and IMAP do

recieve and store emails from a mail server

POP

deletes an email from sever once it has been downloaded to a device

IMAP

syncs the message with a mail server so it can be used on different devices

MAC address

unique hexadecimal number on a NIC. Can’t be changed. Used to identify devices in a LAN

IP address

address given to devices connected to a network. used to route packets in a WAN, can be changed

IPv4

32 bit address

IPv6

128 bit address in hex

4 layers

application, transport, network, data link

application

allows usage of the network - HTTP,HTTPS,SMTP,FTP

transport

TCP protocol

network

IP protocol

data link

ethernet/wifi sets out format of data packets and handles transmission errors

advantages of cloud storage

huge capacity and can easily upgrade storage

can access anywhere and at any time, on any device

can be more secure and encrypted than at home

disadvantages of cloud storage

requires internet to access data

not in control of security, data may be hacked/stolen

may cost monthly fee which could be more expensive