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1.5 Network topologies, protocols and layers - Coggle Diagram
1.5 Network topologies, protocols and layers
Topologies
Mesh Topology
In a mesh topology, all the devices are connected. It is decentralised, which means that the networking devices are either directly or indirectly connected to every other one without the need for one central switch or server.
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Advantages - There is no single point where the network can fail. If one device fails then the data is sent along another route to get to its target.
Disadvantages - Mesh networks are very expensive, you need a lot of wire to connect so many devices. However now more people are using wireless technology, therefore mesh networks are the more practical option.
A full mesh topology is where every device is connected to every other device, but in a partial mesh topology, not all devices are fully connected.
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Star Topology
In a start topology all the devices are connected to a central switch or server that controls the network. The central switch allows many devices to access the server simultaneously.
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Advantages
- If a device fails or a cable is disconnected, the rest of the network is unaffected,
- It's simple to add more devices onto the network;
- It has better performance than other setups - data goes straight to the central device so all devices can transmit data at once and there are few data collisions.
Disadvantages
- In wired networks, every network needs a cable to connect to the central switch or server. This can be expensive;
- If there is a problem with the switch/server, then the whole network is affected.
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Wifi
Frequency and Channels
2.4 GHz (802.11b/g/n) wireless channels and frequencies:
- Adjacent channels can cause interference with each other, so only 3 or 4 channels are used as shown.
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The bands are split into numbered channels that each cover a samll frequency range. The channels in the 2.4 GHz band overlap.
Wi-Fi performance is affected by intereference between networks using adjacent channels. To avoid problems, only certain channels that are spaced apart tend to be used.
The frequency band that a network uses can also affect the Wi-Fi performance:
Pros of 2.4 GHz:
- Has a greater range, so can server devices across a wider area.
- Better at getting through solid objects/ walls.
Pros of 5 GHz:
- Much faster when communicating over a short distance.
- There are more non-overlapping channels, so there's less chance of interference from other devices.
Overview
Wi-Fi allows a device to wirelessly connect to a network with a WAP - that network would then need to be connected to a router in order for the device to be able to access the internet.
Encryption
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encryption software scrables - encrypts - the data to stop third-parties from accessing it. Encrypted data can be decrypted using a 'master key'.
Protocols
A protocol is a set of rules that governs the transmission of data. These determine how the communication is actually made and manage key factors like transmission speed, error checking andd methods of addressing.
Common protocols
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HTTP + HTTPS - Hypertext Transfer Protocol - governs communication between a web server and a client. HTTPS (Secure) includes secure encryption to allow transactions to be amde over the internet.
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SMTP - Simple Mail Transfer Protocol - governs the sending of email over a network to a mail server.
POP + IMAP - Post Office Protocol and Internet Message Access Protocol - govern retrieving emails from email servers. POP is an older implementation, largely replaced by IMAP
IP Addressing
IP addresses are used when sending data between TCP/IP networks over the networks. IP addresses are not linked to hardware; they are either assigned manually or automatically before the device can access the network.
Static IP addresses are permanent addresses, they're used to connect printers on a LAN, and for hosting websites on the internet - companies don't want teh IP addressof their website changing. Static IP addresses can be very expensive - businesses pay A LOT for them.
Dynamic IP addresses are assigned when a device logs onto a network, menaingn that it may have a different address every time it connects. Internet Service Providers (ISPs) commonly use dynamic IP addresses as they are more cost effective and can be reused.
An IP address can either be a 32-bit or 128-bit binary number, depending on the version of IP you're using. The longer 128-bit numbers are translated into eight hexadecimal numbers, while the 32-bit ones are converted into four denary numbers.
Mac addressing
Every device needs a unique identifier so it can be found on a network. Mac addresses aree assigned to all network-enabled devices by the manufacturer
