5.1: networks Flashcards
network
a group of devices connected together so they can communicate with each other and share resources
communication systems examples
- text (SMS) message
central backup procedures
- A network allows data to be backed up centrally
- Networks allow important systems to be mirrored so that there is always a duplicate system with a copy of the live data
advantages of a network
- The ability to share expensive hardware devices between multiple users
- The ability to share files
- The ability to have multi-user systems
- The ability for the organisation to track what users are doing
- The ability to back up files centrally
- The ability to deploy and upgrade software centrally
disadvantages of a network
- Extra hardware costs (cabling and connection devices)
- The cost of having to have employ someone to look after the network
- Greater security risks
types of networks
- personal area network (PAN)
- local area network (LAN)
- wide are network (WAN)
personal area network
- PAN
- connected devices that are located within a few metres of each other
- example: bluetooth
local area network
- LAN
- a single network that is located in a small geographical area such as someone’s home, an office, or to cover a school site
- examples: network at home or school
wide area network
- WAN
- a network that connects two or more networks over a wider geographical area
- example: bank contacting all of its machines across the country
server
- a program on a computer that shares resources with, or provides services to, any authorised client
- usually work 24/7
types of servers
- file
- web
- database
client
- A client sends a request to the server and the server processes the request and then sends a response
peer-to-peer network
- no central servers
- peers communicate directly with each other.
- example: sharing files
comparing peer-to-peer and client-server
- setup cost peer-to-peer is cheaper as no additional hardware required
- security client to server is more secure as it can be easier to monitor
- backups in client to server files are stored on servers so its easier to make sure files are backed up
- points of failure in client to server if the server fails many users will be affected whereas in peer-to-peer it has less impact
wired networks
a range of devices that are connected through a network Switch by a UTP cable
wireless networks
based around a central communications device
called a wireless access point (WAP)
comparing wired and wireless
- speed wired is faster
- security wired is more secure as as cables are harder to intercept
- range wired has an infitite range and wireless only has a range of 50m
- setup wireless is easier to setup as devices can be wherever and there are no cables
- cost wired networks are more expensive as hardware and cables are needed
bit rate
the measure of the amount of data (in bits) that is transferred per second
HTTP
- Hypertext Transfer Protocol
- application
- Used to make a request for a webpage
HTTPS
- Hypertext Transfer Protocol Secure
- application
- Sends an encrypted request for a webpage
FTP
- File Transfer Protocol
- application
- Used to upload or download a file
SMTP
- Simple Mail Transfer Protocol
- application
- Used to send an email to an email server
POP
- Post Office Protocol
- application
- Used to request any new emails for a specific email account
IMAP
- Internet Message Access Protocol
- application
- Used to synchronise a client email account with an account on a mail server which allows a user to use multiple devices to access their email account
DHCP
- Dynamic Host Configuration Protocol
- application
- Used to assign IP addresses and other configuration options to devices in a network
TCP
- Transmission Control Protocol
- transport
- When data is to be sent the data is split into packets and each packet is given a sequence number. This is a reliable transmission protocol. At the receiving end, the packets are checked. If any packets go missing, they will be resent
UDP
- User Datagram Protocol
- transport
- Data is split into packets (as with TCP). UDP is suitable where data does not have to be 100% accurate but speed is important, e.g., with some video streaming services
IP
- Internet Protocol
- network
- Creates a new packet. Adds the source and destination IP addresses to allow the packet to be delivered.
ethernet and wifi protocols
- link
- Encapsulates the data from the previous layer into frames with a source and destination
bus network
On a bus network, all computers are connected to a single main cable. Terminators at the end of
the cable stop the signal.
bus network advantages and disadvantages
Advantages:
* Cheap to install
* Easy to install
Disadvantages:
* One point of failure (the main cable)
* the more devices on the cable the slower performance
* All devices see all the data (security risk)
ring network
All computers are connected in a circle. Each device is connected to two other devices. Data is
passed around the “ring” until the destination has been found.
ring network advantages and disadvantages
Advantages:
* Data can be transferred quickly
* No data collision (data only flows in one direction)
Disadvantages:
* If one device or one cable fails, the entire network is down
star network
All computers have their own link to a central network device (hub or switch).
star network advantages and disadvantages
Advantages:
* Very reliable (one device or cable fails, the rest of the network is still up)
* No data collision
Disadvantages:
* Expensive (you need a dedicated device + more cables)
* If entral device fails thee whole network goes down
mesh network
Each computer can connect to other computers.
mesh network advantages and disadvantages
Advantages:
* Multiple paths between devices
Disadvantages:
* Expensive (a lot of cables)
* Complicated to install
