T3 - Client server network Flashcards
Client-server model:
One or more servers may be part of a LAN
there is a client computer and a server
server
- powerful computer which provides services or resources required by any of the clients
A client
- computer or device which requests the services or resources provided by the server
In a school network:
A file server
holds all the data files and databases and manages backups
In a school network:
A print server
may organise printing on different printers
In a school network:
An email server
may receive emails, detect and block spam, distribute emails to users
In a school network:
A web server
may host the school’s external website
In a school network:
A database server
may hold student records
In a school network: types of servers
-database
-printer
-web
-email
-file
Role of the client:
The client sends requests to the server
Waits for a reply
Receives the reply
Role of the server:
The server waits for requests from a client
Performs any processing required to fulfil the request
The requested data is sent back to the client
Advantages: client server network
- file servers, = one file server needs to be backed up + files can be accessed from any computer
- Email servers = a central place for email that is then accessed from different devices
- print server manages all files to be printed. + allows one printer to be shared by many computers
Peer to peer network:
Has no central server
Suitable for a small companies with fewer computers
No central server controls files or security
All computers can easily see files on all other computers
All computers can communicate with each other without going through a server
Peer to peer network: pros
Advantages:
Easier to set up – computers can simply be cabled together
No need for dedicated server equipment
Individual computers can share a printer, router, modem and other hardware
Users can communicate directly with each other and share each others’ files
Peer to peer network: cons
Disadvantages:
Viruses and malware are more easily transferred over this type of network as there is no central firewall
Data recovery and backup is not done centrally, so each computer has to have its own backup system
Files are not centrally organised, but stored on individual computers and may be hard to locate if the computer’s owner does not have a logical filing and naming system
If a computer is switched off, data on that machine cannot be retrieved from other machines
P2P servers: are used for
Used for illegal distribution of copyright materia as they are harder to shut down
P2P servers role and pro
allows each user to share parts of a file, rather than all downloads coming from one central server
This significantly reduces the amount of bandwidth required when trying to share a file
Hosting:
Web hosting
- a service offered by companies that will host web pages and files for websites
provide database servers
hosting service providers
Companies that provide more general hosting, such as backup servers
Hosting Advantages
Web hosts have far more bandwidth – so they can serve more users
Web hosts are able to monitor their equipment 24 hours a day
Web hosts will backup web sites remotely
The cloud:
used to refer to services that are delivered over the Internet
enables users connected to any Internet-enabled computer to access these services
cloud eg
Eg = Google Drive, OneDrive and Dropbox
Cloud-based servers enable
access to software on demand
cloud - pros
Advantages:
You can access your data and applications from anywhere at any time
You don’t need a powerful computer with a huge hard drive – everything is stored and run on a remote computer
Backing up data is no longer crucial – it is done by the service provider
cloud - cons
Disadvantages:
Personal data will be stored on another company’s servers
If the Internet connection is lost, often the service becomes unusable
Slow Internet connections may result in a poor quality of service
Factors that affect the performance of a network:
Bandwidth
Latency
Error rate/collisions
Bandwidth
- is the amount of data that can be carried through a connection at a time
Bandwidth is how many packets of information can travel through per second
Connection speeds -
are measured in Mbps (Megabits per Second)
Latency -
delay between the client and server or the length of time a packet of information takes to travel through the network
copper cable cons
signal affected by electric and magnetic fields
low bandwidth
heavy cables
Copper cable
(uses electricity) pros
tried and trusted technology
relatively inexpensive
Fibre optics
(uses light) pros
very fast data transmission
low loss of signal over distance
not affected by magnetic or electric fields
require very little power
more difficult to ‘tap into’ than copper cables
Fibre optics
(uses light) cons
high investment cost
need for expensive optical transmitters and receivers
Wireless transmission
(uses radio waves)
pros
no need for trailing wires (safer)
allows devices to be used anywhere provided there is a signal
easier to add devices to a network
Wireless transmission
(uses radio waves)
cons
data transmission rate less than wired systems
signal can be blocked by objects or walls
increased security issues
