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Topic 1.3 network - Coggle Diagram
Topic 1.3 network
what is the 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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HTML- hypertext markup language. All web pages are based on a version of HTML, it is a standard format for webpages
URI- perhaps more commonly known as URL- Uniform Resource Locator. This is a unique address for each website.
HTTP- Hypertext Transfer Protocol. This allows for a common way of retrieving information across the web- now succeeded by HTTPS, the S standing for secure as it uses encryption to transfer the data.
Network Hardware
Too create a network certain pieces of hardware are required for the devices to be connected and for these to be able to access the internet. You do not need to know all of these devices for your GCSE but you should be aware of them.
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. It is responsible for forwarding data packets (more on this later) between different computer networks. Each of the devices connected to your router will most likely have a dynamic IP address that changes, your devices will be assigned these by your router which recognises the device by it's MAC address.
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You will have come across the term hub when we looked at network topologies. It is often used as part of a star 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
As described above a switch performs a similar role as a hub. However switches tend to be more expensive as they perform an additional task. In a hub the data frames are broadcast to all devices. A switch 'learns' the MAC addresses of the devices attached to it and creates a routing table. Once it has learnt the addresses it only sends data to the device that it needs to; this means that there is less data on a network meaning that transfer of data is significantly faster.
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Network Interface card
All devices that connect to a network require a Network Interface Card (NIC). 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). NIC can be wired or wireless.
4 layer model
Application layer
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
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Network/Internet layer
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
Link layer
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
DNS and URLs
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.
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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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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.
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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.
MAC addressing
Each device that connects to a network has a Network Interface Card (NIC). Each NIC has it's own Media Access Control address (MAC address). This is give to the device by the manufacturer. A MAC address cannot be changed, it is unique to that device.
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. Each MAC address can identify the manufacturer and then the individual device.
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
