tryhackme: OSI Model (summarized)

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Layer 1 - Physical

This Physical Layer is one of the easiest layers to grasp.

This layer references the physical components of the hardware used in networking and is the lowest layer.

Devices use electrical signals to transfer data between each other in a binary numbering 1s and 0s. 

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Layer 2 - Data Link

The data link layer focuses on the physical addressing of the transmission. 


It receives a packet from the network layer and adds in the physical MAC address of the receiving endpoint.


MAC: Media Access Control.

NIC: Network Interface Card. 


NIC comes with a unique MAC address to identify it.


MAC addresses can be spoofed. 


The job of the data link layer to present the data in a format suitable for transmission.


The physical address is used on this layer to identify where exactly to send the information.

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Layer 3 - Network


The third layer of the OSI model (network layer) is where the magic of routing & re-assembly of data takes place (from these small chunks to the larger chunk).

OSPF (Open Shortest Path First)

RIP (Routing Information Protocol)


At this layer, everything is dealt with via IP addresses

Devices such as routers capable of delivering packets using IP addresses are known as Layer 3 devices 

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Layer 4 - Transport


Layer 4 of the OSI model plays a vital part in transmitting data across a network and can be a little bit difficult to grasp.


it follows one of two different protocols that are decided based upon several factors:


TCP: Transmission Control Protocol

UDP: User Datagram Protocol


TCP:


-  Tthis protocol is designed with reliability and guarantee in mind. 


- This protocol reserves a constant connection between the two devices for the amount of time it takes for the data to be sent and received.


- TCP incorporates error checking into its design


- TCP can guarantee that data sent from the small chunks in the session layer (layer 5) has then been received and reassembled in the same order.


Advantages of TCP:


1.Guarantees the accuracy of data.


2.Capable of synchronizing two devices to prevent each other from being flooded with data.


3.Performs a lot more processes for reliability.


Disadvantages of TCP:


1. Requires a reliable connection between the two devices. If one small chunk of data is not received, then the entire chunk of data cannot be used.


2. A slow connection can bottleneck another device as the connection will be reserved on the receiving computer the whole time.


3. TCP is significantly slower than UDP because more work has to be done by the devices using this protocol.


UDP:


- This protocol is not nearly as advanced as its brother - the TCP protocol. 


- There is no synchronization between the two devices or guarantee; just hope for the best, and fingers crossed.


Advantages of UDP:


1. UDP is much faster than TCP.


2. UDP leaves the application layer (user software) to decide if there is any control over how quickly packets are sent.


3. UDP does not reserve a continuous connection on a device as TCP does.


Disadvantages of UDP:


1. UDP doesn't care if the data is received.


2. It is quite flexible to software developers in this sense.


3.  This means that unstable connections result in a terrible experience for the user.

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Layer 5 - Session

The session layer creates a connection to the other computer that the data is destined for.

The session layer synchronises the two computers to ensure that they are on the same page before data is sent and received.

The session layer will begin to divide up the data sent into smaller chunks of data and begin to send these chunks (packets) one at a time.

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Layer 6 - Presentation

Layer 6 of the OSI model is the layer in which standardization starts to take place.

his layer acts as a translator for data to and from the application layer (layer 7).

The receiving computer will also understand data sent to a computer in one format destined for in another format.

Security features such as data encryption (like HTTPS when visiting a secure site) occur at this layer.

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Layer 7 - application


the application layer is the layer in which protocols and rules are in place to determine how the user should interact with data sent or received.

DNS (Domain Name System)


FileZilla:
is a free and open-source, cross-platform FTP application, consisting of FileZilla Client and FileZilla Server.

Clients are available for Windows, Linux, and macOS, servers are available for Windows only. 

Both server and client support FTP and FTPS, while the client can in addition connect to SFTP servers.

FileZilla's source code is hosted on SourceForge and the project was featured as Project of the Month in November 2003.

FTP (File Transfer Protocol) 
FTPS (also known FTP-SSL, and FTP Secure)
SFTP (SSH File Transfer Protocol)
GUI Graphical User Interface

Thanks for reading! 👨‍💻
Roger

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