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Networking - Coggle Diagram
Networking
4 layer model
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Network
This attaches the IP address of the sender so that computer that receives it knows where it has come from. It also attaches the address of the host and the destination IP address.
Application
This encodes the data that is being sent so that it will be understandably by the recipient. This might involve formatting data and adding a header according to the protocol such HTTP or FTP.
Link
This attaches the MAC addresses of the sender and the recipient allowing for the packet to be sent to a specific device on a LAN.
The design allows for developers to develop and adapt a protocol for specific layers without damaging another one
Encryption
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Terms
Plaintext- The original, unencrypted message
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Symmetric encryption
Symmetric encryption uses a key which can be a combination of letters, numbers and other characters.
A single key is used to encrypt and decrypt the message. The key is shared with the recipient so that they can decrypt it.
Asymmetric encryption
Symmetric encryption still has a number of risks attached to it especially if the encryption key, which is shared between the users, is intercepted. With this type of encryption a private and a public key is needed. In this type of encryption there is always one key that is kept by an individual user. A certificate authority sends the first user and public and a private key. If User B wants to send a encrypted message the public key is sent by user A. The private key, which user A has, is then used to decrypt the message.
The more secure version is to use Asymmetric encryption or as it is sometimes know Public Key Encryption (PKE).
Encryption does not prevent hacking but it does make the data unreadable unless the person receiving the information has the correct tools to decode it.
Wireless Networking
Wi-Fi is a family of protocols or rules.
In order to use a Wireless network a Wireless Access Point (WAP) is needed. This receives the data via a physical wired connection. The data is then converted into radio signals. Any device that has a Wireless Network Card can then access this data. The reverse happens to send data back over the internet.
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Using WiFi can also reduce the speed of transmission of data. A wireless connections is rarely as quicker as having a device wired into a network. Other factors that might affect the performance include:
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To manage the connections to WiFi installations there are two different band of frequencies that are used. These are 2.4Ghz and 5GHz bands. These frequencies are subdivided into channels. These channels overlap each of which has a central frequency and bandwidth. Most broadband providers send their routers out with the channel settings as Auto but it is possible to change the channel especially if you are experiencing issues with connections; this can happen if a neighbour is using the same channel on their router.
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Bluetooth
Designed for communication over short distances- usually up to 10 metres. This is used so as not to drain the power of the devices using the protocol. Common Bluetooth devices include, keyboard and mice, phones and speakers.
Network hardware
Router
A router is the device that we may most often recognise as most people have broadband. As mentioned before it is the connection between a Local Area Network and a Wide Area Network and is often has other components built into it.
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Hub
You will have come across the term hub when we looked at network topologies. It is often used as part of a star network.
Data on a Local Area Network is carried by a data type known as a frame (once ready for transmission on the internet this is transferred to packets).
When a hub receives a frame it amplifies it and then transfers it to a destination PC by broadcasting it to all other devices on the network.
This is the key difference between a hub and Switch. This broadcasting of data to all connections has the added problem of slowing a network down as there is so much traffic on the network.
A hub acts as a point that can connect all devices on a network together, in much the same way as a bike wheel has a hub to hold all the spokes in place.
Hubs are similar to another device that is now more commonly found on a network, a switch. A hub receives data from computers connected to it.
Switch
more expensive than hubs, as they perform an additional task
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As described above a switch performs a similar role as a hub. In a hub the data frames are broadcast to all devices.
Network Interface Card
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The NIC stores the information that identifies an individual device on a network, the MAC address.
Each NIC has it's own unique, and unchangeable MAC address (it is however possible to spoof a MAC address).
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Peer to peer
In order for a user to access the files or services from another computer on the network the computer has to be configured to share those resources.
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Protocols
Web protocols
HTTP- Hypertext transfer protocol. Requests that the web server transmits the requested web page to the viewer's web browser.
HTTPS- Hypertext transfer protocol secure. Works in a similar way to HTTP but as this data is transmitted it is encrypted. This is becoming the most common protocol on the world wide web as it gives users peace of mind when entering financial details such as banking or debit/credit card details.
Email protocols
POP- Post Office Protocol. POP receives and holds emails until they are picked up by a user. When the user checks their email it is downloaded from the server and then deletes it from the server. The email is then only available locally on the device which the user downloaded it to.
IMAP- Internet Messaging Access Protocol. This method of receiving emails is more suited to users who have multiple devices. This is because it maintains a copy of the email on the server until it is deleted by the user.
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SMTP
Simple Mail Transfer Protocol. This protocol allows for emails to be sent between email servers. This is particularly relevant when the server and recipient have different email providers .
TCP/IP- Transmission Control Protocol/ Internet Protocol. These are in fact two separate protocols. TCP is responsible for how messages are broken into packets and reassembled at the destination. TCP is also responsible for checking for errors and if necessary resends lost packets. The IP protocol allows for a device to be identified on the internet and allows for appropriate packet routing.
Topologies
Mesh
This provides a number of advantages including that if one cable fails only that workstation is affected and the performance is consistent even when being heavily used. Conversely it can be costly to install because of the extra hardware and cabling and also if the central switch or the server fails then the whole network is affected.
Full mesh networks are expensive to build as a result of the necessary hardware and cabling but in the event of one cable failing data finds an alternative route to get to the intended destination- the network self heals.
STAR
Switch in the center, all the devices are connected to it
This provides a number of advantages including that if one cable fails only that workstation is affected and the performance is consistent even when being heavily used. Conversely it can be costly to install because of the extra hardware and cabling and also if the central switch or the server fails then the whole network is affected.
Client-Sever networks
In school we use a client server network. This means that the computers that you are working at are clients and then in another part of the building there is a server.
Summary
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Email servers are used to distribute emails to users and can also be used to filter incoming emails for spam.
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Circuit
When you make a phone call on a landline a dedicated connection is set up between you and the person. This is called circuit switching- you are creating a circuit for the data to travel down.
Circuit switching is limited and there would be limit to the number of people who could be connected at any time. To get around this a process called packet switching is used.
Packet switching
To send large files across a network we can split into smaller data packets. Data packets are round 512 bytes in size.
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The advantage of using packet switching is that allows for packets to follow different routes to get to it's final destination
LAN AND WAN
Local Area networks usually cover a relatively small geographic area. They consist of a single site such as a school or home. The infrastructure of a Local Area Network is owned by the company or individual, they are responsible for the issues that occur on the network.
Wide Area Networks (WAN) cover a large geographical area, the most famous being the internet. Some large organisations will also make use of WANs. A WAN is a collection of computers and networks connected by a third party. This third party will be a company that owns the infrastructure such as BT. A WAN will make use of this companies cables, telephones lines, satellites and radio waves to transfer the data from one site to another.
Using a Wide Area network makes it possible for resources to be shared across a large area. These resources might be something like storage and it would enable employees working at different sites to access the same files or programs.
DNS and URLs
URL
Websites are stored on webpages that are connected to the internet. Each website has it's own IP address. As we have seen IP address are difficult to remember so web sites are given a domain name or a Uniform Resource Locator (URL)
When you type in a URL to the address bar this is sent as a request to the a domain name server. This is part of the Domain Name System and it controls how webpages are retrieved.
DNS
There are a large number of DNS servers around the world and they communicate with each other.
This is the process that happens to retrieve your webpage:
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If the IP address is not found it is passed up to the next level of Domain Name servers. If the IP address cannot at the top level (.com or co.uk etc) an error is returned to browser.
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Connection media
There are a number of different ways in which network hardware can be connected. They generally involve cabling but increasingly devices are becoming wireless. This section will look at the different types of cables and connections that are commonly used in the networking of computer.
MAC addressing
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A MAC address is a 48 bit address written in Hexadecimal. This makes it easier for humans to identify and communicate the devices addressing than a binary value.
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Try finding the MAC addresses on your mobile phone. You will probably find more than one. This is because there is likely to be a WiFi adapter and a Bluetooth adapter and both have different MAC addresses.
IP addressing
Every computer in the world has a unique IP address. This IP can be changed be the user or automatically depending on the situation in which it is being used; mobile devices tend to have dynamic IP addressing meaning that it can change.
The current system is known as IPv4. It takes an address that is made up of 4 values up to 255 (8 bits).
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It is anticipated that we will run out of possible combinations for IPv4 as there may be as many as 30 billion devices in the world. To deal with more devices a new system called IPv6 has been developed. IPv6 128 bits long which are arranged in eight groups of sixteen bits. Each group is four hexadecimal values.
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INTERNET
The internet started in the 1960s as a way for US government researchers to share information. In the 60s computers were large and immovable and the storage that was used was little better with huge magnetic tapes being used to store data.
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