Topic 4 - Networks Flashcards
what is a network?
a network connects two or more computers for the purpose of communication
stand alone computer
a computer NOT connected to a network
advantages of networks
- easily share files with other users
- share common hardware
- communicate via email or instant message
- user accounts stored centrally, anyone can access any computer
disadvantages of networks
- requires expensive additional hardware
- specialist technical staff to manage
- heavy reliance on server
- risk of viruses and hacking
LAN ( Local Area Network )
- covers a small geographical area on a single site
- all the hardware of a LAN is owned by organisation using it
WAN ( Wide Area Network )
- connects different LANs in a large geographical area
- hardware for WAN is leased by telecommunication companies making it expensive
Factors affecting network performance ( B,L,T,N )
- bandwidth
- latency
- type of network ( wired/wireless)
- number of devices ( shared bandwidth. )
bandwidth
amount of data transferred over a network in a given time
greater the bandwidth the better the performance of network
latency
how long it takes for a message to travel from one device to another
low latency = better performance
type of network
wired connection or wireless connection
number of devices
available bandwidth shared between devices on network can cause congestion and slow the network
NIC ( Network Interface Controller)
-internal piece of hardware that allows a device to connect to a network
- has a unique MAC address
switch
- switch connects devices on a LAN
- receives data in frames from one device and transmits it to the device with correct MAC address
router
- transmits data between networks
- direct data packets to their destination
- assigns IP address to devices
WAP ( Wireless Access Point )
allows devices to connect to each other wirelessly
wired networks
- more reliable : it isn’t affected by interference from other networks
- faster : data can be transferred with less latency
examples of wired ( ECF )
-ethernet
-coaxial cables
-fibre optic cables
wireless networks
- use radio waves to transmit data as compared to wires
- cheaper : less wires
- more convenient : can move around while connected
examples of wireless
- Bluetooth
- WiFi
ethernet cables
- 4 pairs of copper wires that are twisted together to reduce internal interference
coaxial cables
single copper wire surrounded by a plastic layer for insulation
- contains a metallic mesh to shield from outside interference
fibre optic cables
- transmit data as light
- high performance and don’t suffer interferences
bluetooth
- direct connection between 2 devices used to share data
- lower connection range and bandwidth than wifi
wifi
- can be used by multiple devices to connect to a LAN
client-server networks
- the server stores files+software centrally and manages the network
- the client sends request to the server asking for files/software
- the server either accepts the request or declines it
client-server Pros
- easier to keep track of files ( centrally )
- easier to perform back ups
- easier to install software all at once
- easier network security
client-server Cons
- server dependence : if server goes down all users lose access to work
- expensive to set up
- needs IT specialists to maintain
peer to peer networks
all devices are equal and connect directly to each other without a server
P2P Pros
- easy to maintain : no expensive hardware
- no dependence on server
P2P Cons
- peer machines are prone to slowing down when other devices access them
- devices need their updates installed individually
- creates duplicate files easy to lose track of what is stored where
star topology Pros
- simple to add more devices to network
- all devices can transmit data at once
- fewer data collisions as data goes straight to central device
star topology Cons
- heavy reliance on switch/server : if they are damaged then every device is affected
- every device needs a cable to connect which is expensive
mesh topology Pros
- no single point where the network can fail so more reliable
mesh topology Cons
- very expensive as you need lots of wires to directly/indirectly connect all devices together
MAC address
- a unique identifier that allows communication on the same network
- unique to the device, assigned manually and can’t be changed
IP address
- identifier that enables communication over different networks over the Internet
- assigned either manually or automatically
network protocol
set of rules for :
-how devices communicate &
-how data is transmitted across a network
TCP
sets rules for how devices connect on the network
- splits data into packets and reassembles packets back into data once received
- checks if data is correctly sent/delivered
IP
- directs packets to their destination across network
HTTPS
Hyper Text Transfer Protocol
used by web browsers to access websites and communicate with web servers
FTP
File Transfer Protocol
used to access/move/edit files between devices on a network
POP3
Post Office Protocol v3
- retrieves emails from a server
- server deletes email once downloaded
IMAP
Internet Message Access Protocol
- retrieve emails from a server
- server holds the email until you delete it
SMTP
Simple Mail Transfer Protocol
- used to send emails and transfer emails between servers
layer
division of network functionality
advantages of using layers
- they are self contained : can be changed without other layers affected
- standards for each layer forces companies to make compatible, universal hardware
- they can group protocols together
what is the Internet?
a big WAN that connects networks from all over the world and based around tcp/ip protocol
what is the WWW?
World Wide Web
- a collection of websites that are hosted on web servers and accessed through the https protocol
How do people access websites
( part 1 )
1) user types in URL containing a domain name which easier for user to remember
2) this represents an IP address
3) the computer sends a recursive DNS query to the network which is sent to ISP
How do people access websites
( part 2 )
4) The Domain Name Server has an address book which contains a list of URLs and their matching IP address, and can use this to translate the url to the IP address
How do people access websites
( part 3 )
5)The client send a request to the web server with the specific IP address, asking for access to the website
6)The web server either grants or denies access to the client, if the sever grants access the user can now access the website on their client computer
