Networks and the internet Flashcards
Network
an interconnected set of devices
Physical network topology
The actual architecture of a network i.e. how its laid out
Positives of Networks
- allows sharing of data
- allows collaberative working
- good for communication
- allows sharing of resources e.g. printers, storage and scanners
- easy to backup to a central point
Drawbacks of networks
- The user can become dependent on the network (If the network stops operating then it may not be possible to access various resources)
- Efficiency of a network can be very dependent on a network manager
- It is difficult to make a network of computer secure for hackers and outside threats
- As traffic increases on a network the performance can degrade
Protocol
A protocol is a set of rules relating to the communication between devices.
TCP
Transmission Control Protocol – used with IP to ensure error free transmission and package switching
IP
Internet Protocol – used to transfer all packets across the internet between routers
NIC
receive and send electrical signals in a network.
Router
devices which are used to connect networks. they receive data packets from one network and based on the address on the packet forward them of
Switches
devices used to connect devices on a network, they use the physical hardware MAC address to send data on to the required destination node.
MAC Address
identifier that is permanently added to a device by the manufacturer
Hubs
connects nodes together by broadcasting a signal to all possible destinations. The correct destination will accept the signal
WAP (wireless access point)
use wireless to connect a node to a WiFi network avoiding the need for lots of physical caballing
Transmission media
the wires that connect a network
Coacial Copper Cables
older, slower and cheaper
Fibre Optic Cables
newer, faster and high-capacity
Bus Topology
an arrangement where nodes are connected to a central communication channel. Each end of the backbone is connected to a terminator. Each node is passive and data is sent in one direction at a time only
Bus topology advantages
Inexpensive to set up
Devices can easily be added
Good for small networks
Bus Topology Disadvantages
Main cable is a single point of failure
Limited cable length
Performance degrades with heavy use
Poor security
Star Topology
an arrangement where a central node or hub provides a common connection point for all other nodes.
Star Topology advantages
Easy to isolate problems
Good performance
More secure is a switch is used a data is sent only to the recipient
Star topology disadvantages
Can be expensive to set up because of the length of cable required
Central device is a point of failure
Ring topology
an arrangement where on node is connect to two others to form and ring.
Mesh Topology
an arrangement where ever node is connected to every other node.
Client-Server Model:
one device (the client) requests services from another device (the server).
Peer-to-Peer Model:
all terminals have equal status and there is no powerful central server, each computer acts as both a client and a server.
advantages of Client-Server
- User IDs, passwords and access levels centrally controlled
- Backup is centralised and usually automated
- No access to other users’ files
disadvantages of Client-Server
- Can be expensive to set up and to manage
- Server is single point of failure
advantages of peer-to-peer
- cheap to set up and maintain
- easy sharing
disadvantages of peer-to-peer
- no central backing up
- slower performance
- bad security
client side processing
Client Processing is where webpages use JavaScript to validate data before it gets sent to the sever for further validation.
advantages of client side processing
- Allows for more interactivity by immediately responding to a users’ action
- Removes potentially unnecessary processing from the server
Disadvantages of client side processing
- Not all browsers support all script
- Because the scripts are processed by the client, they are dependent on the performance of the clients’ machine
Application Programming Interface (API)
a prewritten set of subroutines that provide access to the
companies data
Gateway
A gateway is a node on a network that serves as an entrance to another network.
Port
software construct serving as a communication endpoint. Each has a number used by protocols to specify what data is being sent.
Circuit Switching
Circuit Switching: a complete circuit or route between two nodes is established before transmission begins. Once the rout is established all data follows this route until transmission is complete.
Packet Switching
the data to be transmitted is broke up into individual packets at the source computer. each packet is labelled with an address and sequence number. The packet is then forwarded onto the network and follows its own individual route. Depending on network traffic each packet will take different routes at different times to reach their destination where is is then reassembled.
Proxies
A proxy ensures there is no direct physical connection between a single user and a remote source.
Encryption
A method of transforming data into an unintelligible way so that it cannot be read by unauthorised individuals.
Malicous Software
is software that annoys users or damages their data. For example, Worms, Viruses, Trojans, Spyware and ransomware.
Worm
A Worm is a standalone program that does not require a user to run it in order for it to spread.
Trojan
A Trojan is software that misleads the user of its true intent. Often, they serve to open up back doors in your computer.
Phishing
Phishing is using email to manipulate a victim into visiting a fake website and giving away personal information.
protecting agaisnt hacking:
- Packet snifferes
- User access logs
Layering
the principle of dividing a complex system into separate slices of functionality
Open Systems Interconnection 7 layer model
(7) Application Layer
(6) Presentation Layer
(5) Session Layer
(4) Transport Layer
(3) Networking Layer
(2) Data Link Layer
(1) Physical Layer
TCP/IP stack
Application Layer
Transport Layer
Internet layer
Link Layer
Transport Layer
(2) Makes and breaks connections with routers
Internet Layer
(3) provides links across different network types.
Link Layer
(4) Passes data to the physical network
application layer
(1) package data and passes it on
Domain Name System Server (DNS sever)
System thats stores names for IP addressees on a network
Local Area Network (LAN):
method of connecting computers together in a small geographical area. All the hardware and infrastructure is owned by the business/ organisation that uses it.
Wide Area Network (WAN):
a method of connecting remote computers or networks. Typically made up of smaller LANs which have been connected together.
relationship between the DNS server and IP addresses
a registered domain name is held on the DNS server. The corresponding IP address to a searched domain name is loaded on the users computer.
advantages of using an external css file
code only needed to be added to one file but the changes are applied to all the pages that use that css file
role of JavaScript
the code interactivity into webpages
Methods of sending data
- Electronic Data Interchange (EDI)
- Application Programming Interface (API)
- A URL to a file
EDI
is the computer-to-computer exchange of business documents in a standard electronic format between business partners.
script tag
the tag to include JavaScript code
<ul></ul>
unordered list
<ol></ol>
ordered list
<li>
</li>
The individual parts of the list <ol> <li> </li><li> </li><li> </li> </ol>
order of main HTML tags
html head /head body /body /html
title tag
The text that will appear in the tab heading
<h1></h1>
<h2></h2>
<h3></h3>
head text
full image tag
img scr=”” alt= “” height= “” width=””
div
/div
divides the page into segments allowing for improved styling
form tag
defines a form that is used to collect user input
how to use a form tag
form
input type=”” name=””
/form
how to do CSS in HTML
h1 style = “color:blue; … “
background colour CSS property
background-color
border colour CSS property
border-color
border style CSS property
border-style
border width CSS property
border-width
font CSS property
font-family
font size CSS property
font-size
height CSS property
height
width CSS property
width
changing the contents of an HTML element JavaScript
chosenElement = document.getElementById(“example”);
chosenElement.innerHTML = “Hello World”;
writing directly to a document JavaScript
document.write(“Hello World”);
Writing an alert box
alert(“Hello World”);
CSS identifiers vs classes
and identifier can only be used once on one element but classes can be used on multiple elements
styling of elements CSS
h1{
color:blue;
}
CSS class
DOT
.infoBox{
background-color: green;
}
CSS identifier
HASHTAG
#menu{
background-color: #A2441B;
}
Server side processing
used to interact with permanent storage like databases or files. It also renders the pages to the client
advantages of server side processing
- doesn’t require plugins or browser scripting technology
- more secure
- reduces loading time
disadvantage of server side processing
- can be slow
- pages have to be refreshed often to keep up to date
components of a packet
senders address, recievers address, packet contents, sequence number
what connects different networks?
routers and gateways
SAN
storage area network
MAN
metropolitan area network
Uses of the internet
communication, information, entertainment, education, financial transactions, controlling devices
portable document format, to display documents exactly as intened
JPEG
joint photographic experts group, losy compressed form of graphics storage
GIF
graphics interchange format, lossless compressed image file format
MPEG
motion picture experts group, a compression standard for audio visual and data files
Unicode
character set which displays over a million characters
XML
extensible markup language, text based means of describing data.
Flash
multimedia platform for creating and displaying graphics (replaced by HTML5)
tags
mark out elements on a web page to indicate to a browser how to display or process an element
Benefits of a LAN over a WAN
- Can share hardware/software
- Easy to maintain all computers
- Staff can work off any computer (meaning no need for each member to have their own computer).
- Easy for staff to share data.
- Central backup
How to protect a server
- Encrypt the information
- Set up user access controls
- Set up a firewall
- physical security measures e.g. locks in the server room
- keep logs of whose accessed the data
process and purpose of archiving
- copy original data to a new location then delete the original
- To free up storage space while still keeping them available
firewall
hardware or software which prevents unauthorized access.
reads packet data and determines if a threat.
characteristics of a LAN (3)
- small geographical area
- owned by organization (privately owned)
- more secure
characteristics of a WAN (3)
- covers a large geographical area
- use third party connections (not single ownership)
- less secure
advantages of using peer-to-peer networks when downloading off a server
- once its been downloaded there isn’t reliance on the server and can be seen from all devices on the network
- company doesn’t have to invest in hardware
- more fault tolerant
- frees up bandwidth
IP address
unique identifier for a device on a network, its logical so it can be changed.
difference between IP and MAC address
IP is logical so can be changed
MAC is physical so can’t be changed
why would companies store IP addresses
identify users so the company can track/ monitor the access
Difference between an ID and a class
ID is unique and can only be used once but a class can be assigned to many elements
What is at the end of all CSS lines
a semicolon ;
disadvantage of clientside
- the code may fetch the wrong data from the computer e.g. wrong time
- clientside can be edited by the user (they can remove validation)
- other people can view the code and copy it
- some browsers disable JavaScript to run
advantage to company of external CSS file
- saves time/money
- the file will be easier to read when checking for bugs
- easy to differentiate between content and formatting
- consistent throughout whole site
- can be used for different devices formatting
advantage to user of external CSS file
- the files are smaller so it will take a shorter time to process
why is it important to validate server side
javascript code can be amended/ disabled from running therefore the data must be validated server side to check this hasn’t happened
why is it important to validate client side
the data can be checked before reaching the server giving the user immediate feedback and preventing unnecessary load on the server
linking a css file
link rel=”stylesheet” href=”name.css”
linking another webpage
a href=”” link text /a
additional security as well as passwords
- memorable information
- double passwords/ entry
- smart access card
- biometric access
octet
a group of 8 bits used to designate IP addresses
benefits of layering
- each layer can be designed and maintained independently
- easier to maintain
what doees layering do
it abstracts the reality to make it simpler
