Unit 2

LAN (Local Area Network)

• covers a small geographical area .
• located on a single site.
• all hardware for LAN owned by organisation that uses it.
• are wired or wireless.
• various devise can connet to a lan, e.g PCs, smart TV, printers.
• sharing files are easy.
• share same hardware.
• internet connection can be shared between all devices.
• install and update software on all computers at once.
• user account can be stored centally.

WAN (Wide Area Network)

• conects LANs that are in different geographical areas.
• more expencive than a LAN.
• may be connected using fiber or copper telephone lines, satellite links or radio links.
• the internet is an example.

Bandwidth

• amount of data that can be transfered at a single time.
• shared between users of a network and so if too many users or heavy use may cause congestion can cause a slow network connection.
• you can limit the use of bandwidth for each person in the network

wired connections

• are generally faster 
• more reliable 
• fiber optic cables can give much better performcance than copper cables 
• wireless singnal depends on signal quality 

Network Interface controller (NIC) 

• internal piece of hardware that allows a device to connect to a network
• wired and wireless 
• built into a motherboard

Switch

• connect devices on a LAN
• recieve and transmit data to the decixe on the network with correct MAC address

Router

• transmitting data between networks 
• connected to at least 2 different networks
• direct data packets to their destination 
• connect LAN to the internet

Ethernet

• twisted pair cables containing 4 pairs of copper wires which are twisted together to reduce internal interface

Coaxial

• single copper wire surrounded by a plastic lay of insulation and metallic mesh, provding a shield from outside interference

Fibre-optic 

• transmit data as light, high performance

• managed by a server
• devices connected to the server are clients 
• files and software stored centrally 
• the client sends requests to the server asking for data, the server processes the request and responds, which is known as the client-server relationship 
• stores user profiles, passwords, and access information.

pros

• easy to keep track of files
• easy to perform backups
• easy to install and update software
• easy to manage network security
• very reliable

cons

• expensive
• server dependence
• overloaded 

• all devices are equal 
• store files on individual devices
• may be used at home to share data/files

pros

• easy to maintain
• no dependence on server

cons

• no centralized management
• can create duplicate files, easy to lose track of what's stored where and which files are up to date
• less reliable and data may be lost if one fails
• slow down when other devices access them

• all devices are connected to the central switch or server that controls the network.
• a central switch allows many devices to access the server simultaneously. 

pros

• if the device fails or is disconnected then the rest of the network is unaffected.
• simple to add more devices 
• better performance than other setups

cons

• expensive
• if there is a problem with switch or server then the whole network affected 

• network devices are either directly or indirectly connected to every other one without need for a central switch or a server.
• work by sending data along the fastest route from one device to another
• no single point where it can fail
• if one device fails then data is sent along a different route so that it can reach its destination.
• wired mesh networks are more expensive but wireless ones are more practical. 
• full mesh topology is where all devices are connected together but a partial mesh topology is where not all devices are connected. 

•    Set of rules
•   How communication between 2 devices should start and end
•     How the data should be organized and what devices should do if data goes missing

•  Unique identifier
•    Assigned to all network-enabled devices
•    48 or 64-bit binary number into hexadecimal
  • E.g 10011000 10000001 01010101 11001101 11110010 00101111 =98-81-55-CD-F2-2F
•  the Ethernet protocol on LANs allow the switches to read MAC Address and direct them to a device

• Used when sending data between TCP/IP networks
• Aren’t linked to hardware – can be assigned manually or automatically before the device can access network
• STATIC – permanent addresses used to connect printers on a LAN and for hosting websites on the internet
• DYNAMIC – assigned every time it logs onto a network so could get a different one each time you connect.
• It may change if you take a laptop to a new country and connect to a network over there.It may change if you take a laptop to a new country and connect to a network over there. 

·       Broken into equal packet sizes

·       Given a header containing;

o   IP its going to

o   IP its come from

o   Sequence/order

o   Number of packets in sequence

o   Error checking data

·       Sent across internet separately following different routes

·       Reassembled once it has reached the destination/recipient

·       Any packets not received will be resent

·       HTTP (Hyper Text Transfer Protocol) – access to websites and communication with web server

·       HTTPS (Hyper Text Transfer Protocol Secure) – a secure version of HTTP, encrypts all information it sends and receives.

·       FTP (File Transfer Protocol) – edit and move files on a network

·       POP3 (Post Office Protocol – version 3) – retrieve emails from a server, server holds until you download it at which point it is deleted from the server

·       IMAP (Internet Message Access Protocol) – retrieve email from server, server hold until you delete it and you only download a copy

·       SMTP (Simple Mail Transfer Protocol) – Used to send emails, and used to transfer emails between servers

·       A layer is a group of protocols with similar functions

·       They are self contained – they do not need to know what is happening in other layers in order to function

·       Each layer serves the layer above it.

Layer 4 – Application layer

Layer 3 – Transport layer

Layer 2 – Network layer

Layer 1 – Link layer

              Advantages

·       Communication is in manageable pieces

·       Self contained – edit one and not affect the others

·       Makes compatible universal hardware

·       The internet is a network of networks

o   A WAN that connects devices and networks all over the world, it is based around the protocol TCP/IP.

·       The World Wide Web (WWW) is a collect on websites that are hosted on web servers using the HTTP protocol.

·       URLs are addressed used to access web servers and resources on them.

·       A Domain Name Server (DNS) translate a website’s domain name into its IP address. The internet has a network of DNSs meaning you don’t have to remember the IP Address to  access a website so you can use a domain name instead.

·       Hosting is when a business uses its servers to store files of another organisation.

Pros

• Users can access files from any connected device.
• Easy to increase storage availability
• No expensive hardware
• No IT staff needed to manage storage
• Cloud host provides security and backups for you
•  Cloud software will be updated automatically

Cons

• Need connection to internet to access files
•  Dependant on host for security and backups
• Vulnerable to hackers
• Unclear who has ownership of data
• Expensive

·       A network that is entirely software-based.

o   Created by partitioning off some of a physical network's bandwidth to form a separate network.

·       Several virtual networks exist on the same physical network. These networks all share the same hardware making virtual networks more efficient.

·       Has own security including its own firewall so can only be access with certain software or login details.

·       A VPN is a Virtual Privet Network that can be used to send data securely over a large network, like a WAN or the Internet.

·       A virtual LAN allows you to split up a network into several separate networks using the same hardware.

·       Passive attack – where someone monitors the data traveling on a network and intercepts any sensitive data that they find. Network monitoring software is used to see what each type of data is being transferred.

·       Active attack – someone attacks a network with malware or other planned attacks. These are easier to detect and can be stopped with a firewall.

·       Insider attack – someone within a network uses their access to steal information.

·       Bruit force attack – gaining information by cracking passwords using trial and error. Normally they are automated software that produces hundreds of likely password combinations. By locking accounts after a certain number of attempts and using strong passwords will stop or so down the process.

·       Dos attack – stopping a user from accessing a part of the network or website, by flooding with useless traffic making network really slow or making it crash.

·       People can give personal information in many ways:

o   Social engineering – influencing people and gaining personal information

o   Telephone – someone pretends to be a person from well known business requesting personal information.

o   Phishing – getting emails suggesting something bad will happen if you don’t click on the link.

·       Data base query language

·       One of the main coding languages used to access information in databases

·       SQL typed into a websites input box which then reveals sensitive data/information 

·       Will have:

o   Regular tests to find and fix security weaknesses and investigate any problems

o   Use passwords to prevent unauthorised access

o   User access levels to limit number of people who can access sensitive information

o   Install anti-malware and firewall software to prevent and destroy software attacks.

o   Encrypt sensitive data

·       Also known as pentesting is when organisations employ specialists to simulate potential attacks on their network

·       Used to identify possible weaknesses in a networks security

·       The results are then resulted back 

·       Investigations undertaken to find out the cause of attacks on networks

o   Need to have system of capturing data packets as they enter a network

·       After a network is attacked these packets can be analysed to discover how a network was attacked and decide how to prevent future attacks.

·       Prevent unauthorised users accessing a network

·       Passwords need to be strong in order to protect peoples sensitive data – should be a long consist of a range of letters and numbers, in both capital and lowercase 

·       Controls which group of people can access which information on a network

·       Helps to limit the number of people with access to important information

o    prevent insider attacks

·       Find and stop malware from damaging a network

·       Lots of different types like anti-virus softer, which isolate and destroy and infected data.

·       Companies use firewalls to block unauthorised

·       Data transferred into code, where someone with the encryption key and access

·       Text called cipher text is encrypted and plain text is the opposite

·       Essential for sending data over a network securely.