Networks Flashcards
What does LAN stand for?
Local Area Networks
What do we call two or more computers connected together to share information and resources.
(this can involve physical or wireless connections, or both)
A computer network
What is a LAN (Local Area Networks)?
It is a connection of computers and devices.
Each device on a network is known as a node (e.g. computer, printer, etc.)
A LAN is confined to one site.
It’s therefore relatively small
All network infrastructure is the property of the organisation
What are the advantages of a LAN? (5 of them)
It enables digital communication between people
It enables the sharing of digital information
It enables the sharing of peripheral devices such as printers and scanners
It enables computers to be updated with the latest software from a central point
It enables distributed processing – the ability for a single program to be run simultaneously at various computers.
What are the two disadvantages of a LAN?
1) There requires a bit of ‘expertise’ to install and maintain a large network which can be costly.
2) There are a number of security issues from unauthorised access to data - measures to secure a network include:
• Passwords – strong passwords use a range of character types
• Not allowing users to install software
• With wireless access, use encryption
• Changing passwords frequently
What is needed to make a LAN?
At least two computers (Nodes)
Each having a NIC – network interface card (either wired or wireless)
The NICs convert the data signals from the nodes into data signals that can be transferred across the network.
For LAN you might need a Hub.
What is a Hub?
Hub
A device that connects
nodes together.
Makes all connected nodes
act as a single segment.
Not intelligent – data
packets are transmitted
across the whole of the
network.
Cheap devices – USB hubs
useful in home computer
installations.
For LAN you might need a Switch.
What is a Switch?
A device that connects nodes together.
An intelligent device that can create and connect to different segments of the network.
This reduces network traffic because data packets are sent to the nodes or segment where they are needed rather than being broadcast to the whole network.
Hardware needed for a LAN
If a LAN is to connect to the Internet then what is needed and what does it do?
If the LAN is to connect to the Internet, a Router is needed.
Routers manage the data packets enabling them to be sent between networks (e.g. over the internet)
Hardware needed for a LAN
A wireless access point has advantages and drawbacks.
What are they?
Wireless technology has many advantages over wired networks:
No need to do building work
Add new node with ease
General public can access network / internet if allowed.
But there are drawbacks:
There can be performance issues
…and security issues too!
What are the two types of Network in a LAN?
Peer - to - peer
Client - server
LAN Network - Peer - Peer
What are four key features of this type of network?
All computers have the same status.
Data transfer may be very slow because of
data collisions
shared processor power
Only really suitable for small and low traffic networks.
This is a very popular design for a home network
LAN Network - Client - Server
What are key features of this type of network?
At least one computer is designated as a server.
This usually needs to be high spec.
It offers services such as software and data to client PCs.
It manages the traffic on the network.
Records what people do.
Gives security.
Clients have to sign in and so their identification is known enabling certain rights to be given to certain people.
Large networks may have many servers to handle the increased network demand.
Different LANS can have different topologies. What are four topologies?
Bus
Ring
Mesh
Star
LAN - Bus topology
What are some pros and cons?
• It very cheap to set up due to little cabling
- Because data travels both ways along one cable, data collides which slows the network
- If the cable has a fault the whole network may suffer
- Only really useful over small areas
LAN - Ring topology
what is a pro and con?
• Only one cable -
data travels in only one direction which means no collisions
• If the cable breaks or a node breaks then the whole network may go down.
LAN - Mesh topology
what is a pro and a con?
• This is a fully connected network:
Every node is connected to all others, which means that if a cable breaks or if there is heavy traffic on one area, there are other routes for the data to take
•It can be a very expensive to set up due to the cabling required
LAN - Star topology
What is a pro and a con?
- All nodes connect to a hub or a switch and therefore data doesn’t share one cable this results in fewer data collisions and therefore a fast network
- It is an expensive topology as it requires a lot of cables
Networks
What does WAN stand for ?
Wide Area Network
A LAN is Local Area Network:
Located on one site
Owner of network owns the network devices (cables etc)
How is that different to a WAN?
WAN
Wide Area Network
Covers a large geographical area – may be worldwide
Devices may be provided by telecoms companies like phone lines and satellites.
What is the biggest WAN on the planet?
The Internet
How is the Internet a WAN?
The internet is a massive network of networks.
A ginormous collection of connected computers
Networking
What is a host?
A host is a computer on a network which offers to serve users from another location, using the internet.
Networking
What is a web host?
Web hosting, in particular, is a service provided by various companies.
These companies ‘host’ websites on their servers so that people around the world can access them 24/7.
They will often charge a small fee for the rental of hard drive space, site security and back up services.
What does IP address mean?
This means INTERNET PROTOCAL ADDRESS
It is a unique number given to every computer on the internet – no two computers can have the same address.
E.g. 324.45.321.23
Its just like a postal address – used to identify a house – no two houses have the same address!
A device’s IP address will not necessarily remain the same each time it joins a network or goes on-line
What does ISP mean?
This means INTERNET SERVICE PROVIDER
This is simply the company who provide you with your internet connection.
Data Transfer Media
All networks must enable computers to communicate with one another.
This can be done using two main data transfer mediums, which are?
Cables (wired)
Wifi (wireless)
Data Transfer Media
Cables (wired)
there are two main types, what are they?
Ethernet cables
Fibre Optic cables
Data Transfer Media
Cables (wired)
These are made up of copper wires with the data being transported via electrical signals. Because they carry electrical signals, they can suffer from interference.
What are they?
Ethernet cables
Data Transfer Media
Cables (wired)
These are made up of glass fibres with the data being transported via light signals.
What are they?
Fibre Optic cables
Data Transfer Media
Cables (wired) Comparing Ethernet and fibre optic cables.
Which is faster AND much more expensive?
Fibre optic
Data Transfer Media
Wi Fi (wireless)
Wi-Fi allows network access to portable devices by using radio waves to send data (not wires!).
Wi-Fi is a ‘standard’. This means that all Wi-Fi devices using the same standard technology.
How does wifi send and receive data?
Using standard radio frequency waves
Either 2.4 GHz band or 5 GHz band
(Each band is then split into smaller frequency ranges, or channels
Data Transfer Media Wi Fi (wireless)
why is each band split into frequency ranges of channels?
This is so that if two devices are sending signals using the same band (e.g. 2.4GHz)
…they can each use different channels and therefore slightly different frequencies (e.g. 2.41GHz and 2.45GHz)…
…so that they do not suffer from interference with one another.
When files are sent across the internet they are divided into ____
Data packets
When you send data on line and it gets into data packets. are the packets in a simple pattern?
No
Packets get sent by different routes according to availability.
When you send a file online, the parts of the file might travel one way around the world and the other parts may go in the opposite direction!
Packets are reassembled at receiving end.
Internet Protocols
MAC Addresses
What is a MAC address?
every network card in the world has a MAC address (MAC - Media Access Control).
A MAC address is hard coded into each and every network device and cannot change.
It is a 12-digit hexadecimal number, e.g.
56:b3:8f:90:64:ef
It is there so that data being sent over a network can be sent to the correct network card.
It is known as a PHYSICAL ADDRESS
Internet Protocols
The TCP / IP Protocol
this might be the most important of protocols.
It is made up of two protocols. What are they?
1) TCP – Transmission Control Protocol
2) IP – Internet Protocol
Internet Protocols
What is TCP – Transmission Control Protocol?
Data is split into packets before being sent across the internet. The TCP defines the rules for this.
It ensures all data is split up into data packets in the same way.
It ensures that these data packets are put back together when received by the destination device.
It also ensures that any data received is the same as that sent.
Internet Protocols
What is Packet Switching?
Packet switching ensures that data gets to its destination as fast as possible – this may not be the shortest distance however.
World Wide Web protocols
HTTP - what is it and what does it do?
HTTP = Hyper Text Transfer Protocol
HTTP – Hyper Text Transfer Protocol
This is the protocol which governs the way in which websites and web servers are accessed by web browsers. By conforming to the same standards it means that all browsers can access all websites on the WWW.
Internet Protocols
HTTPS – Hyper Text Transfer Protocol Secure
What is it?
This protocol is almost identical to HTTP. The only difference is that it ensures all data being sent is encrypted and so makes web data communication far more secure.
Internet protocols
What is FTP (File Transfer Protocol)?
This standard (FTP) ensure that all clients (computers) on a network can access files from a server in the same way.
Email Protocols
What are the protocols called?
POP – Post Office Protocol
IMAP – Internet Message Access Protocol
SMTP – Simple Mail Transfer Protocol
Email Protocols
What is POP?
This is the protocol that governs how emails are accessed from a server. Email clients will use this protocol to access emails from a server in the same way.
Email Protocols
What is IMAP?
This is similar to POP but with one important difference. With IMAP, the email will remain on the server once it has been downloaded by a mail client. This allows other devices to also access the emails which is important for users with multiple devices – they can synchronise their emails across all devices.
Email Protocols
What is SMTP?
This protocol governs how data is sent between mail servers. By conforming to the same standards, emails can be sent to and from all mail servers across the internet.
